Phụ gia dinh dưỡng-Tuyet Anh 06H2A

8/8/2019 Ph gia dinh dng-Tuyet Anh 06H2A

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n: Ph gia lm tng gi tr dinh dng thc phm-GVHDTs. Trng Th Minh Hnh

LI NI U

Cng vi s pht trin khng ngng v khoa hc, k thut ca x hi, mc sngcng nh nhng nhu cu ca con ngi ngy cng tng ln. Trong nhng nhu cu ,s dng thc phm khng l mt ngoi l v v th, yu cu v cht lng thc phm,

bao gm c cht lng dinh dng v cht lng cm quan tr thnh nhng yu thng u c ngi tiu dng v cc nh sn xut lu tm.

S cn bng v y v mt dinh dng quyt nh trc tip n cht lngba n, cng nh n sc khe con ngi. Khi khng c cung cp y mt hayvi cht dinh dng no , cc hot ng sng bnh thng ca c th, v d nh sinhtrng, pht trin, khng s b gin on v ngng tr. Tuy nhin, khng mt loithc phm no c th cha y tt c cc loi cht dinh dng cn thit cho conngi. V th, ngoi kt hp cc mn n t nhiu ngun thc phm, vic b sung cccht dinh dng vo thc phm mt cch hp l cng l mt trong nhng gii php chiu qu rt cao v l mi quan tm c u tin nht ca cc nh thc phm.

Cc cht ph gia lm tng gi tr dinh dng ca thc phm (nutrient additive) lcc cht dinh dng c nghin cu v b sung vo thc phm . Vic b sung phgia dinh dng vo thc phm cn c s nghin cu k lng, khng nhng v chcnng v tc dng ca chng, m cn v nhu cu ca c th cng nh nhng tc hi khi

s dng qu liu lng hoc nhng tng tc c li v bt li gia chng vi cc thnhphn khc trong c th. V v th, ph gia lm tng gi tr dinh dng ca thc phmcng chnh l i tng nghin cu ca em trong n ny.

ti s 1: Ph gia thc phm: cc ph gia lm tng gi tr dinh dng ca thcphm (nutritional additive)

SVTH: Trnh Th Tuyt Anh Lp 06H2A i


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n:Ph gia lm tng gi tr dinh dng thc phm GVHD Ts.Trng Th MinhHnh

MC LCPhn A: GII THIU CHUNG....3Phn B: NI DUNG CHNH...4

1. GII THIU CHUNG PH GIA THCPHM.41.1 nh ngha ph gia thc phm41.2 Lch s s dng PGTP Vit Nam v trn th gii.......51.3 C s cho php mt cht tr thnh ph gia thc phm...51.4 Cc vn bn php lut ca nh nc Vit Nam v ca nc ngoi v

s dng PGTP..51.5 Cc l do s dng PGTP.61.6 Tm quan trng ca vic s dng PGTP.71.7 Phn loi PGTP...7

1.8 H thng k hiu v cc thut ng c bn..81.8.1 H thng khiu...91.8.2 Cc thut ng c

bn.92. PH GIA THC PHM TNG GI TR DINHDNG..102.1Tng quan v ph gia thc phm tng gi tr dinh dng.102.2 Phn loi ph gia thc phm tng gi tr dinh dng...112.3 Mt s ph gia thc phm tng gi tr dinh dng...12

2.3.1 Vitamin122.3.1.1 Tng quan v vitamin... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 152.3.1.2 Phn loi vitamin...........................................................152.3.1.3 Vitamin A..... ..152.3.1.4 Vitamin D..212.3.1.5 Vitamin E.. .. .. .. 272.3.1.6 Vitamin B1332.3.1.7 Vitamin B2 372.3.1.8 Vitamin C. .40

2.3.2 Cc cht khong.42

2.3.2.1 St (Fe)...432.3.2.2 Calcium (Ca)..45

2.3.3 Cc acid amin..482.3.3.1 Alanine.512.3.3.2 Lysine..532.3.3.3 Iso- leucine..54

SVTH: Trnh Th Tuyt Anh Lp 06H2A 2


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2.3.3.4 Leucine562.3.3.5 Methionine...58

Phn C: KT LUN..............................................................................59Ti liu tham kho.................................................................................60

Phn A: GII THIU CHUNG

Ba n, c lc khng phi l mt nhu cu, l s cn thit, m l mt s gii tr,hoc bt buc. Do chng ta cn cc mn n c mu v hnh dng tht hp dn,hng v tht kch thch, v khu v c th thch hp vi mi ngi trong tt c cc iukin. Trong ch bin thc phm, do nhiu tc nhn c, l, ho, hng v t nhin ca

thc phm s b gim, v chng ta khng th khng tm cch a thm cc cht c tcdng tng v vo thc phm.

Vic sn xut nhiu loi thc phm mi, thay th cho cc sn phm ng vt,thc vt t nhin, cn rt nhiu cc cht ph gia. Th d ch bin gi tht b, ln, g,xc xch ... T u tng hoc men l-vuya c sinh tng hp t parafine du ho,vi mt s cht ph gia c tc dng kt dnh c tng thm mu v hng v. Tronglnh vc cc cht ph gia v hng liu, cc nh khoa hc c thnh cng ng k.

Ngi ta chit tch c c f c ti trn 300 thnh phn hng liu khc nhau.Ti nay ring cc loi bnh, b, fomat, ru, qu, ngi ta pht hin c trn 800loi hng liu, c mi c trng v vic lm gi cc sn phm ging nh thin nhin,khng phi ch b hp trong phm vi sn xut nh na.

Ph gia dinh dng ngy nay ng mt vai tr ht sc quan trng trong cucsng hin i. N khng nhng gii quyt tnh trng thiu dinh dng dn n mc

phi cc bnh tt nguy him cho sc khe v tnh mng con ngi, m cn gp phnlm tng cht lng cuc sng ca con ngi thng qua cc loi thc phm b sungcht dinh dng. [34]



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Phn B: NI DUNG CHNH

1. GII THIU CHUNG PH GIA THC PHM1.1 nh ngha ph gia thc phm (PGTP): Theo FAO: Ph gia l cht khng dinh dng c thm vo cc sn phm vi

cc nh khc nhau. Thng thng cc cht ny c hm lng thp dng cithin tnh cht cm quan, cu trc, mi v cng nh bo qun sn phm.

Theo y ban Tiu chun ha thc phm quc t (Codex AlimentariusCommisson - CAC): Ph gia l mt cht c hay khng c gi tr dinh dng,khng c tiu th thng thng nh mt thc phm v cng khng c sdng nh mt thnh phn ca thc phm. Vic b sung chng vo thc phm l gii quyt mc ch cng ngh trong sn xut, ch bin, bao gi, bo qun,

vn chuyn thc phm, nhm ci thin cu kt hoc c tnh k thut ca thcphm . Ph gia thc phm khng bao gm cc cht nhim hoc cc cht cb sung vo thc phm nhm duy tr hay ci thin thnh phn dinh dng cathc phm.

Theo TCVN: Ph gia thc phm l nhng cht khng c coi l thc phm haymt thnh phn ch yu ca thc phm, c hoc khng c gi tr dinh dng, m

bo an ton cho sc khe, c ch ng cho vo thc phm vi mt lng nhnhm duy tr cht lng, hnh dng, mi v, kim hoc axt ca thc phm, png v yu cu cng ngh trong ch bin, ng gi, vn chuyn v bo qun thc

phm. [3]

1.2 Lch s s dng cht ph gia thc phm Vit nam v trn th gii:Ngi xa bit dng cc cht ph gia t lu, tuy cha bit r tc dng cachng.

V d nc ta, ngi dn t n du ho lm chui mau chn, mc ducha bit trong qu trnh t chy du ho sinh ra 2 tc nhn lm mau chn hoa qul etylene v propylene.

n u th k 19, khi bt u c ngnh cng nghip ho hc, ngi ta mi btu tng hp cht mu aniline (1856). Sau rt nhiu cht mu tng hp khc ra i.i vi cc hng liu cng th, u tin ngi ta chit xut t thc vt, ri em phntch v tng hp li bng ho hc. Ti nm 1990 tr vanille, tinh du chanh, cam, bch c chit xut t thc vt, cn cc cht hng liu khc em s dng trong thc

phm u c tng hp.Vic sn xut thc phm quy m cng nghip v hin , i hi phi c

nhiu cht ph gia, lm d dng cho ch bin thc phm. Do s dng cc cht phgia bo qun, trnh cho bt m mc, khi cho thm cht lindane hoc chomalathion vo bt m, cc cht bo khng b i kht khi cho thm cc cht chng oxyho, khoai ty c th bo qun chc chn qua ma h nu cho thm propane. Trong cc



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nc nhit i, vn bo qun thc phm li cng tr thnh mt vn ln. Theo Tchc Y t th gii hin nay khong trn 20% ngun thc phm b hao ht trong qutrnh bo qun. Vic giao lu cc sn phm trong thi gian gn y v sau ny s trthnh vn quc t c ngha rt ln. Khong cch v thi gian thu hoch theo ma,khng cn l tr ngi chnh na. Ngi ta c th n c chua ti quanh nm, cam c tha i tt c cc lc a. chng mc cho loi qu ny, ngi ta dng diphenyl, vthy c kt qu rt tt.

Phong cch sng thay i, lm thay i cch n ca nhiu nc. Php, nm1962 ch mi s dng 55.0000 tn thc phm ch bin sn, ti nm 1969 ln ti150.000 tn v sau nm 1975 tng ln trn 400.000 tn.

Khi cc cht ph gia m bo vic ko di thi gian bo qun thc phm trn 6thng th cc sn phm ch bin trong lnh vc thc phm, s cn tng hn na. ngthi, khu v cng c thay i nhanh chng, cng vi s tin b vt bc ca khoahc k thut. [3]

1.3 C s cho php mt cht tr thnh PGTP: Cc cht ph gia (CPG) c php s dng trong thc phmcn c 3 iu kin:1)- C y ti liu nghin cu v k thut v cng ngh s dng CPG

Cn phi a ra nhng ti liu nghin cu v nhng tnh cht ho hc, l hc vkh nng ng dng ca CPG

2)- C y ti liu nghin cu v c t hcMun c kt lun r rng cn phi tin hnh nghin cu :- Cc cht ph gia phi c th c t nht trn 2 loi sinh vt, trong c mtloi khng phi l loi gm nhm, c th sinh vt cn c cc chc nngchuyn ho gn ging nh ngi.- Liu th c phi ln hn liu m ngi c th hp th cht ph gia vo cth khi s dng thc phm (tnh cho khi lng mt ngi ti thiu l 50-100kg).

3)- C y ti liu nghin cu v cc phng php phn tchCn phi c cc phng php phn tch chnh xc v thch hp xc nhhm lng CPG c trong thc phm.

Khi mun s dng cht ph gia mi trong sn xut thc phm,phi trnh cho Hi ng V sinh an ton thc phm ti cao Quc gia thuc By t cc th tc sau:1)- Tn cht ph gia, cc tnh cht l hc, ho hc v sinh vt hc 2)- Tc dng v k thut, nng cn thit, liu ti a3)- Kh nng gy c cho c th ngi (ung th, qui thai, gy t bin...) th trnvi sinh vt v theo di trn ngi.4)- Phng php th c v nh lng cht ph gia trong thc phm.



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1.4 Cc vn bn php lut ca Nh nc Vit nam v ca nc ngoi v sdng PGTP:

Khi s dng cht ph gia trong thc phm phi c cc c quan qun l chophp.

Vit NamDo B Y t v Tng cc Tiu chun o lng v Cht lng qun liu 10 v Tiu chun tm thi v sinh 505/BYT-Q ca B Y t quyt nhv vic s dng ph gia trong ch bin lng thc thc phm nh sau:a.. Khng c php s dng cc loi ph gia khng r ngun gc, mt nhn, baob hng. Khng c php s dng cc loi ph gia ngoi danh mc cho php caB Y t.b.. i vi cc ph gia mi, ho cht mi, nguyn liu mi, mun a vo s dngtrong ch bin, bo qun lng thc thc phm, cc loi nc ung, ru v snxut cc loi bao b thc phm th phi xin php B Y t. Trn th gii- FAO : Food and Agriculture Organization of the United Notions tr s Rm- OMS : Organizotion Mondial de la Sant Tr s GenevFAO v OMS l thnh phn ca lin hp quc tp hp 121 nc thnh vin- EU: Eropenne Union kim tra hm lng cht ph gia c trong thc phm, cquan tiu chun ho quc t v ca cc quc gia xy dng nhng phng php

phn tch- ISO Internationnal Stadadisation Organisation- AFNOR- Association Francaise de Normalisation, ca Cng ho Php

- DIN - Deutsches Institut pr Normung, ca CHLB c- BS British Standard, ca Vng quc Anh- ASTM American Society for Testing and Materials, ca M- TCVN Tiu chun Vit nam, ca CHXHCN Vit nam [3]

1.5 Cc l do s dng ph gia thc phm:- Duy tr ng nht ca sn phm: cc cht nh ha to s ng nht cho kt

cu ca thc phm v ngn nga s phn tch. Cht n nh v cht lm c to cutrc nhuyn mn. Cht chng vn gip nhng thc phm dng bt duy tr c trngthi ti ri.

- Ci thin hoc duy tr gi tr dinh dng ca thc phm: Cc vitamin v

khong cht c b sung vo cc thc phm thit yu nh bt m, ng cc, b thcvt, sa b p nhng thiu ht trong khu phn n cng nh s tht thot trongqu trnh ch bin. S b sung ny gip gim tnh trng suy dinh dng trong cngng dn c. Tt c cc sn phm c cha thm cht dinh dng phi c dn nhn.

- Duy tr s cht lng ca sn phm thc phm: cht bo qun lm chm s hhng ca thc phm gy ra bi nm men, mc, vi khun v khng kh. Cht oxy ha



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gip cht du m trong cc thc phm khng b i hoc to mi l. Cht chng oxy hacng gip cho tri cy ti, khi b bin sang mu nu en khi tip xc vi khng kh.

- To n hoc kim sot kim, acid ca thc phm: cc cht bt n giiphng ra nhng cht kh khi b un nng gip bnh n ra khi nng. Cc cht ph giakhc gip iu chnh acid v kim ca thc phm, to hng v v mu sc thchhp.

- Tng cng hng v hoc to mu mong mun cho thc phm: nhiu loi giav v nhng cht hng tng hp hoc t nhin lm tng cng v ca thc phm.

Nhng cht mu lm tng cng s hp dn ca mt s thc phm p ng mongi ca khch hng.[3]1.6 Tm quan trng ca vic s dng ph gia:

S pht trin ca khoa hc cng ngh gip cho ph gia thc phm ngy cnghon thin v a dng hn, hn 2500 ph gia c s dng trong cng ngh thc

phm gp phn quan trng trong vic bo qun v ch bin thc phm. Ph gia c vai

tr quan trng trong lnh vc cng ngh thc phm c th l:- Gp phn iu ha ngun nguyn liu cho cc nh my sn xut thc phm,

gip nh my c th hot ng quanh nm, gip sn phm c phn phi trn ton thgii.

- Ci thin c tnh cht ca sn phm: cht ph gia c b sung thc phmlm thay i tnh cht cm quan nh cu trc, mu sc, ng u,.ca sn phm.

- Lm tha mn th hiu ngy cng cao ca ngi tiu dng. Do nhu cu nking ca con ngi t ra i cng nghip sn xut cc thc phm t nng lng.

Nhiu cht to nh v keo t, cc este ca acid bo v cc loi ng gip lm gimmt lng ln cc lipid c trong thc phm

- Gp phn lm a dng ha cc sn phm thc phm. Cng vi s xut hin caph gia thc phm, thc n nhanh, thc n t nng lng, cc thc phm thay th khccng ra i v pht trin p ng nhu cu n ung ngy cng a dng ca con ngi.

- Nng cao cht lng thc phm. Cc cht mu, cht mi, cht to v lm giatng tnh hp dn ca sn phm.

- n gin ha cc cng on sn xut. Vic s dng cc hp cht bc v trongch bin cc loi c gip rt ngn c thi gian bc v trong ch bin.

- Gim ph liu cho cc cng on sn xut v bo v b mt ca nh my.[2]1.7 Phn loi ph gia thc phm:

Cc ph gia thc phm c th phn chia thnh 4 nhm, mc d c mt s phn

chng ln gia cc th loi ny: Ph gia dinh dng. Ph gia bo qun thc phm: cht chng vi sinh vt, cc cht chng nm mc,

nm men, cc cht chng oxi ha. Ph gia tng gi tr cm quan ca thc phm: cht to mu, to mi, to v.



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Ph gia s dng ch bin c bit (ci to cu trc ca thc phm): cc chtlm n nh, cc cht lm nh tng ha.

1.8 H thng k hiu v cc thut ng c bn:Bng 1.1: Phn loi ph gia thc phm theo khong s [25]

100199To mu

100 - 109 Vng110 - 119 Vng cam120 - 129 130 - 139 Lam v tm140 -149 Lc150 - 159 Nu v en160 199 Khc

200299

Cht bo qun

200 -209 Cc sorbat

210 219 Cc benzoat220 229 Cc sulfit230 239 Cc phenol v format

200299Cht bo qun

240 259 Cc nitrat260 269 Cc axetat (etanoat)270 279 Cc lactat280 289 Cc propionate (propanoat)290 299 Khc

300399

Cht chng xi ha v cht iuchnh chua

300 305 Cc ascorbat (vitamin C)

306 309 Tocopherol (vitamin E)310 319 Cc gallat v erythorbat320 329 Cc lactat330 339 Cc citrat v tartrat340 349 Cc phosphate350 359 Cc malat v adipat360 369 Cc succinat v fumarat370 399 Khc

400499

Cht to c, cht n nh &cht to th sa

400 409 Cc alginat

410 419 Cc gm t nhin420 429 Cc tc nhn t nhin khc430 439 Cc hp cht polyoxyethen440 449 Cc cht to th sa t nhin450 459 Cc phosphat

400499 460 469 Cc hp cht cellulose



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Cht to c, cht n nh &cht to th sa

470 489 Cc acid bo v hp cht490 499 Khc

500599Cht iu chnh pH & cht chngvn

500 509 Cc acid khong v base510 519 Cc chlorua v sulfat520 529 Cc sulfat v hidroxit530 549 Cc hp cht kim loi kim550 559 Cc silicat570 579 Cc stearat v gluconat580 599 Khc

600699Cht iu v

620 629 Cc glutanat630 639 Cc inosinat640 649 Khc

700799 Cht khng sinh 710 713

900999Linh tinh 900 909 Cc loi sp910 919 Men bng tng hp920 929 Cht hon thin930 949 Cc kh ng gi950 969 Cc cht to ngt990 999 Cc cht to bt

11001599Cc ha cht b sung

Cc ha cht mi khng thuc s phn loitiu chun

1.8.1 K hiu: qun l cc ph gia ny v thng tin v chng cho ngi tiu dng th mi

loi ph gia u c gn vi mt s duy nht. Ban u cc s ny l cc "s E" cs dng chu u cho tt c cc ph gia c chp nhn. H thng nh s nyhin c y ban m thc phm (Codex Alimentarius Committee) chp nhn v mrng xc nh trn bnh din quc t tt c cc ph gia thc phm m khng linquan n vic chng c c chp nhn s dng hay khng.1.8.2 Cc thut ng c bn:

H thng nh s quc t (International Numbering System - INS) l k hiuc y ban Codex v thc phm xc nh cho mi cht ph gia khi xp chngvo danh mc cc cht ph gia thc phm.

Lng n vo hng ngy chp nhn c (Acceptable Daily Intake - ADI) l

lng xc nh ca mi cht ph gia thc phm c c th n vo hng ngythng qua thc phm hoc nc ung m khng gy nh hng c hi ti sckho. ADI c tnh theo mg/kg trng lng c th/ngy.ADI c th c biu din di dng:- Gi tr xc nh- Cha qui nh (CQ)- Cha xc nh (CX)



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Lng ti a n vo hng ngy (Maximum Tolerable Daily Intake - MTDI) llng ti a cc cht m c th nhn c thng qua thc phm hoc nc unghng ngy. MTDI c tnh theo mg/ngi/ngy.

Gii hn ti a trong thc phm (Maximum level - ML ) l mc gi hn ti aca mi cht ph gia s dng trong qu trnh sn xut, ch bin, x l, bo qun,

bao gi v vn chuyn thc phm. Thc hnh sn xut tt (Good Manufacturing Practices - GMP) l vic p

ng cc yu cu s dng ph gia trong qu trnh sn xut, x l, ch bin, boqun, bao gi, vn chuyn thc phm [30]

RDA* (Recommended Dietary Allowances) khuyn ngh mc tiu th trungbnh hng ngy trong ch n ung p ng yu cu dinh dng ca gnnh tt c (97% n 98%) ngi khe mnh trong mi nhm tui v giitnh.Tuy nhin RDA trn ch l mc ti thiu c th cn mi ngy trnh khivic thiu ht nghim trng vitamin A.

UL: (Upper level) lng cht dinh dng ti a n vo m khng gy nhng tcng xu hoc nguy him cho c th. Tr nhng trng hp iu tr c ch nhUL bao gm tng lng cht dinh dng c th nhn c t thc n, ncung v cc thc phm b sung.

AI (Adequate Intake) [7]2. PH GIA THC PHM TNG GI TR DINH DNG

2.1 Tng quan v ph gia thc phm tng gi tr dinh dng:

Vo u th k trc, con ngi mc phi rt nhiu loi bnh him ngho chv thiu cht dinh dng nh bnh bu tuyn gip v thiu iod cn thit cho s to ra

hormon ca tuyn ny; bnh ci xng tr em v thiu vitamin D, khng hp th ccalci nn xng mm v bin dng; bnh scurvy gy sng, chy mu nu rng, lulnh vt thng v c th dn n t vong nu ko di, ch l do thiu sinh t C khikhng dng rau tri ti.

Ngy nay, nh cc cht dinh dng cn thit ny c b sung vo thc phmtrong qu trnh ch bin m cc bnh va k him khi xy ra, ta gi l cc cht

ph gia dinh dng (nutritional additives). Thc phm b sung dinh dng tr thnhmt khi nim rng hn, v c th c sn xut bi nhiu l do. u tin l khi

phc li cc cht dinh dng b mt trong qu trnh ch bin thc phm, c gi llm giu cht dinh dng (enrichment). Trong trng hp ny, lng cht dinh dngc thm vo l xp x lng t nhin trong thc phm trc khi ch bin. L do thhai l thm vo nhng cht dinh dng m c th khng c mt trong thc phm tnhin, c gi l tng cng cht dinh dng (fortification).Trong trng hpny, hm lng cht dinh dng b sung c th cao hn so vi hm lng trc khich bin. [2]



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V vy, da vo cc l do trn, muc ch cui cng ca vic b sung ph giadinh dng l: duy tr cht lng dinh dng ca thc phm, gi mc dinh dngy ci thin hoc ngn nga s thiu ht dinh dng trong mt cng ng hoctrong cc nhm ngi c nguy c b thiu ht mt s loi cht dinh dng nht nh (vd, ph n ngi cao tui, ngi n chay, mang thai, vv); ng thi tng gi tr giatng dinh dng ca mt sn phm thng mi; v b tr cho nhng chc nng cngngh nht nh trong ch bin thc phm.Tuy nhin, vic b sung cht dinh dngtrong thc phm cng c tiu chun ha bng nhng quy nh v hm lng vthnh phn cht dinh dng c th, v nhng cht c dng thm vo thc phmtrong khi ch bin c gi chung l ph gia dinh dng (nutritional additives).[2]

Bng 2.1 : Thc phm b sung dinh dng: [34]

Bng 2.2 bn ca ph gia di cc iu kin khc nhau:[5]

pH 7 pH 7 Khngkh/O2

nhsng

Nhit

Lng mt mtti a (%)

Vitamin C U S U U U U 100Folic acid U U S U U U 100Vitamin A S U S U U U 40

Niacin S S S S S S 75Cobalamine S S S U U S 10

Mui khong S S S S S S 3

S = stable (bn) ; U = unstable (khng bn)2.2 Phn loi ph gia thc phm tng gi tr dinh dng:

Cc nhm ph gia thc phm tng gi tr dinh dng:- Cc vitamin: bao gm

+ Cc vitamin tan trong du: A, D, E, K+ Cc vitamin tan trong nc: cc vitamin cn li, bao gm B, C, H .

SVTH: Trnh Th Tuyt Anh Lp 06H2A

Mui I t, st

Bt, bnh m, go Vitamin B1,B2, niacin, stSa, magarine Vitamin A, D

ng, bt ngt, tr Vitamin A

Sa u nnh, nc cam Calcium

Bnh quy, thc phm cho tr em St

Bt ng cc n lin Vitamin, khong cht

ung dnh cho ngi n king Vitamin, khong cht

Protein, amino acid thc vt Vitamin, khong cht

11


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- Cc cht khong: bao gm+ Cc nguyn t a lng+ Cc nguyn t vi lng

- Cc acid amin:+ Cc acid amin khng thay th+ Cc acid amin thay th

2.3 Mt s ph gia thc phm tng gi tr dinh dng:2.3.1 Cc vitamin:2.2.1.1 Tng quan v vitamin:

Khi nim: Vitamin l nhm cht (bt buc) cn thit cho hot ng sinh sngca bt k c th no v chng c kh nng nng thp hon thnh chc nng xctc c th sinh vt. [4]

Trong khi thc vt v vi sinh vt c kh nng sn xut ra cc vitamin cn thitcho s trao i cht ca mnh, con ngi v ng vt, tht khng may, mt i khnng ny trong qu trnh tin ha. Do thiu enzyme c bit tng hp, vitamin trthnh nhng cht dinh dng thit yu cho con ngi v c cung cp thng qua ccloi thc phm hng ngy. Mt khc, hm lng vitamin c mt trong thc phm l rtnh so vi cc loi hp cht dinh dng cao phn t nh protein, cacbohydrat v cht

bo; khi lng cht kh mt ngi ln n vo trong mt ngy cc nc cng nghipl khong 600g, trong ch c cha n 1g l vitamin. V th vic bo v cc vitamintrong qu trnh ch bin v bo qun thc phm l rt cn thit. Hin tng mt vitaminc th xut hin do cc phn ng ha hc gy mt hot tnh ca vitamin, do b tch rahay r r khi thc phm (nh cc vitamin tan trong nc b mt i trong qu trnh nu,

chn), theo , ngi ta b sung cc loi vitamin trong qu trnh ch bin nh mt loiph gia, gip lm duy tr v tng gi tr dinh dng ca thc phm. [7]

Bng 2.2. Tht thot vitamin trong qu trnh ch bin v bao gi rau c [1]

Sn phm chbin, ng hp

Tht thot vitamin (%) (So vi rau c mi nu xong v x nc)

Vitamin A Vitamin B1 Vitamin B2 Niacin Vitamin CSn phm ng

lnh(a)12(c)

0-50(d)20

0-6124

0-4524

0-5626

0-78Sn phm tit

trng(b)

10

0-32

67

56-83

42

14-50

49

31-65

51

28-67aGm mng ty, u lima, u xanh, sp l, bp ci, u H lan, khoai ty, rau

spinach, gi , li ng non.b Ging th nghim a, ngoi tr sp l, bp ci, gi .c Gi tr trung bnh.



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d Khong bin ng (ca gi tr o c).

Bng 2.3. Tht thot vitamin trong qu trnh ch bin v bao gi tri cy [1]

Sn phm ch bin, ng hpTht thot vitamin (%)

(so vi qu ti)A B1 B2 Niacin C

Sn phm ng lnh(cha tan gi)

37(c)

0-78(d)29

0-6617

0-6716

0-3318

0-50

Sn phm tit trng(b)39

0-6847

22-6757

33-8342

25-6056

11-86

aGm to, m, qu vit qut, s ri chua, nc p c c, o, qu mm xi vdu ty.

bGing th nghim (a) nhng s dng nc p thng thay cho dng nc p cc.cGi tr trung bnhdKhong bin ng (ca gi tr o c).

Trong lch s, tc dng u tin c ghi nhn ca vic s dng cc nhm thcphm c bit - m chng ta ngy nay gi l thc phm vitamin - l kh nng phngchng bnh qung g ca vitamin A trong gan ng vt. Tuy nhin, phi n hn 3000nm sau, nhng triu chng ca vic thiu ht cc cht dinh dng c bit mi cghi nhn v thit lp. Nhng v d in hnh l bnh sco-bt (do thiu vitamin C), bnht ph (do thiu vitamin B1) v bnh ci xng (do thiu vitamin D). V phi mt thm400 nm sau con ngi c th tm c mi quan h gia cc bnh tt ni trnvi cc hot cht c mt trong thc phm, m sau c t tn l vitamin. Mc dngy nay chng ta bit rng vitamin khng phi l mt nhm cc hp cht ha hcthng nht bao gm cc protein, carbohydrate v lipid, tuy nhin cm t ny vn cs dng chung cho tt c cc loi sinh t ni trn.

T u th k 20, kin thc ca con ngi v cc chc nng sinh hc cavitamin cp phn t v t bo tng ln ng k, vi vic 20 nh khoa hc otc gii thng Nobel trong lnh vc ny t nm 1928 n nm 1967. Tuy nhin, bt

chp nhng n lc nghin cu chuyn su sau , khng c thm mt loi vitamin noc tm thy v thm vo danh sch 13 vitamin (c thit lp t nm 1897 n nm1941).

Bng 2.4. Lch s ca vitamin [7]



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Vitamin Pht hin Phn lpTm ra

cu trcTng hpnhn to

Vitamin A 1909 1931 1931 1947Provitamin A 1831 1930 1950 1950

Vitamin D 1922 1932 1936 1959Vitamin E 1922 1936 1938 1938Vitamin K 1929 1939 1939 1939Vitamin B1 1897 1926 1936 1936Vitamin B2 1920 1933 1935 1935

Niacin 1936 1935 1937 1894Vitamin B6 1934 1938 1938 1939Vitamin B12 1926 1948 1956 1972Folic Acid 1941 1941 1946 1946

Pantothenic 1931 1938 1940 1940Biotin 1931 1935 1942 1943Vitamin C 1912 1928 1933 1933

Trong khi trc y cc nh khoa hc ch ch yu quan tm n vai tr cavitamin trong vic phng chng bnh tt v nhng chc nng sinh hc ca chng, ngynay, vitamin c ghi nhn l c vai tr quan trng n sc khe v hnh phc ca conngi. Kha cnh ny ca vitamin da trn nhiu dn liu chng minh rng chngkhng nhng l cc coenzyme tham gia vo cc qu trnh chuyn ha trong c th mcn ng vai tr nh cc hormone, m dn chng r rng nht l vai tr thit yu trongvic chuyn ha xng ca vitamin D. V th, vitamin gi y khng ch n gin cchia thnh hai nhm da vo nhng tnh cht ha l ca chng - nh l tan trong nc,tan trong du m cn c chia nhm da vo chc nng sinh hc ca chng trong cth: chc nng coenzyme, hormone v chng oxy ha

Nhng cuc tranh lun v lng vitamin ti u v lng vitamin cao nht c thngi c th chu c vn tip tc, v vn a ra mt nn tng php l c bn v sdng v b sung vitamin vo thc phm l mt thc s cn thit, khng ch da vohm lng cung cp cho c th, m cn da vo c im ni sinh sng, cc yu t mitrng nh hng n trng thi v nhu cu vitamin ca con ngi.

2.2.1.2 Phn loi vitamin:



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Theo tnh cht vt l:

- Vitamin tan trong cht bo: A, D, E, K. Cc vitamin ny c c th d trtrong gan v cc m m v s dng khi cn thit, iu ny c ngha l c th lun cn

mt lng cht bo ha tan cc vitamin ny khi s dng chng.- Vitamin tan trong nc: cc vitamin cn li, bao gm B 1 (thiamine), B2

(riboflavin), PPF (niacin), pantothenic acid, B6 (pyridoxine), B12 Xianocobanoxine, BcFolic acid, H (biotin), C (ascorbic acid). C th ng vt khng th d tr c loivitamin ny, v th khi lng cung cp nhiu hn nhu cu ca c th, chng s cthi ra ngoi c th theo nc tiu. y l nhng vitamin d b mt mt nht trong qutrnh ch bin thc phm.

Theo chc nng sinh hc:

- Vitamin chng oxy ha

- Vitamin c vai tr hormone

- Vitamin c vai tr coenzyme

2.2.1.3Vitamin A:

Tn gi khc: Retinol, axerophthol

Tn IUPAC: (all-E)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ol

Khi lng phn t: 286.45 [26]

Tnh cht ha hc: Retinol l hp cht c to thnh bi 4 nhm isoprenoidni tip nhau v cha 5 lin kt i lin hp. Chng thng tn ti dng ruretinol, aldehyde (retinal) hoc acid ( retinoic acid).

Hnh 2.1 : Cng thc phn t ca Vitamin A (retinol) [26]



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Hnh 2.2 : Tinh th vitamin A di nh sng phn cc [7]

Gii thiu:

Vitamin A l mt thut ng chung cho mt nhm cc hp cht ha tan trong chtbo thuc h trans-retinol. Vitamin A ch c trong cc t bo ng vt, nh trong dugan c, gan ng vt, cht bo ca sa, lng trng. Thc vt khng cha vitamin A

nhng cha cc carotenoid c th chuyn thnh viatmin A nh phn ct mt ni i trung tm. Carotenoid c nhiu trong cc loi rau c c mu xanh m v mu vngnh c rt, ci b xi, t, c chua, v c bit nhiu trong b ng, m, cam, du cCc loi carotenoid trong ng vt u c ngui gc t thc vt do ng vt nhn ct ngun thc phm hng ngy, thng gp nht l beta caroten.[1]

Chc nng:

Retinal, dng oxi ha ca retinol, cn thit cho cc hot ng th gic. Acid retinoic,mt dng chuyn ha khc ca vitamin A c xem nh l cht ng vai tr chnh chott c cc chc nng cn li ca vitamin A. Acid retinoic lin kt vi cc protein hp

th nhn c hiu, c chc nng nh vo DNA v iu tit cc biu hin gene, t nh hng n nhiu qu trnh sinh l, do c coi nh l mt hormone.

+ Th gic: Cc t bo hnh que trong vng mc mt cha mt loi sc t rt nhycm vi nh sng gi l rhodopsin, mt dng phc ca protein opsin v retinal. Vngmc nm pha sau mt. Khi nh sng vo mt, n kch thch vng mc, chuyn ithnh mt xung thn kinh v c no gii m. Retinol c vn chuyn n vng mcthng qua cc mch mu v tch ly trong cc biu m t bo sc t. y, retinol s beste ha to thnh dng retinyl ester, c th lu tr c. Khi cn thit, retinyl este

b thy phn v chuyn thnh ng phn 11-cis-retinol - cht c th b oxy ha tothnh 11-cis-retinal. 11-cis-retinal s chuyn ng ngang qua mt ma trn cc t bo

nhn kch thch nh sng n cc t bo hnh que, ni n hnh thnh lin kt vi proteinopsin hnh thnh sc t th gic rhodopsin. Cc t bo hnh que v rhodopsin c thnhn bit nhng tia sng c cng rt yu, v th chng rt quan trng cho vic nhnvo ban m. S hp th photon nh sng lm xc tc qu trnh chuyn 11-cis-retinalthnh dng ng phn trans-retinal, cc ng phn ny s phng ra to thnh mt chuicc tn hiu in truyn n cc t bo thn kinh th gic. Xung ng thn kinh to ra



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bi cc t bo thn kinh th gic c truyn t ln no v c no phn tch. Sau khiphng ra, tt c cc trans-retinal li chuyn i tr v dng trans-retinol, li c thchuyn ng qua ma trn tip nhn nh sng, ti cc biu m t bo vng mc, qua hon thnh chu k thu nhn hnh nh. Hin tng thiu retinol a hnh nh nvng mc nhng ngi khim th c gi l hin tng qung g. [20]

+ Bit ha t bo: trong c th, mi loi t bo khc nhau m nhim nhng chcnng khc nhau. Qu trnh trong cc t bo v biu m c lp trnh thc hincc chc nng c bit c gi l qu trnh bit ha. Thng qua qu trnh iu chnh

biu hin gene, acid retinol ng vai tr ch o trong qu trnh bit ha t bo. Phttrin v bit ha t bo xng l mt v d in hnh v vai tro ca vitamin A. Nhiu

bt thng v thay i cu trc v bit ha t bo, m do thiu vitamin A c bit nt lu: sng ha cc t bo biu m, cc t bo b kh cng li. Nhng m nhy cmnht vi vitamin A l da, ng h hp, tuyn nc bt, mt v tinh hon. Sng ha

biu m gic mc c th gy lot v dn n kh mt. Acid retinoic tham gia vo qutrnh bit ha t bo phi thai, t nhng t bo mm thnh nhng m khc nhau ca cth nh c, da v cc t bo thn kinh. Qu trnh ny thng qua nhng bin i cagene. Hin nay, khoa hc pht hin khong trn 1000 gene c tng tc vi vitaminA, trong bao gm hormone tng trng, osteopontin, hormone iu ha pht trin,trao i ca xng.

+ Tng trng v pht trin: retinol ng vai tr quan trng trong qa trnh sinh snv pht trin phi thai, c bit l pht trin ty sng, t sng, tay chn, tim, mt vtai. Khi b thiu vitamin A, qu trnh pht trin b ngng li, gim tch ly protein gan. Nhng du hiu sm ca thiu vitamin A l mt ngon ming, gim trng lng.

Thiu vitamin A lm xng mm v mnh hn bnh thng, qu trnh vi ha b rilon.

+ Min dch: Vitamin A cn thit cho qu trnh chc nng bnh thng ca h mindch v do , gip bo v chng li cc bnh do nhim trng. N ng vai tr quantrng trong vic duy tr tnh ton vn v chc nng ca da v mng nhy t bo, ngthi cng l ro cn bo v c th chng nhim trng. Thiu vitamin A, kch thc cat chc lympho thay i. -caroten lm tng hot ng ca t bo dit (Killer cell), tngs nhn ln ca t bo lympho B v T. Vitamin A cng l nhn t trung tm trong qutrnh pht trin v bit ha ca t bo bch huyt nh t bo lympho, thc bo v bchhuyt cu,gip c th chng li cc mm bnh.

Ngun thc phm:

Cc thc phm giu vitamin A nht c k n l gan, lng trng, sanguyn cht, b v pho mt. Tin t vitamin A carotenoid c tm thy nhiu trong crt, cc loi rau l sm mu (ci b xi, bng ci xanh), b , m v b ao. Ngoi rangi ta cn tng hp vitamin A t cc nguyn liu du c cha vng -ionone, v d



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t du cy Coriandrum sativum. Gn y, hm lng vitamin A trong thc phm vph gia thng c biu din bng n v quc t IU. Nhm tiu chun ha i lngo lng cho vitamin A, mt n v quc t mi ra i, gi l ng lngretinol, hay RE, biu th mi tng quan chuyn i gia carotenoid v retinol.

1 g RE = 1 g retinol

= 1,78 g retinyl palmitate

= 6 g -carotene

= 12 g cc carotenoid khc

= 3.33 IU vitamin A hot ng t retinol [6]

Bng 2.5: Hm lng vitamin A trong thc phm [7]

Thc phmVitamin A (retinol)

g/100g RE g/100gGan b 28000 28000C rt - 1500Ci b xi - 795B ao - 784B 590 653Pho mt 390 440Trng 276 272Bng ci xanh - 146

C hi 41 41Sa nguyn cht 35 35

S hng vitamin A trong thc phm:

Cc qu trnh ch bin v bo qun thc phm c th lm mt t 5-40% vitamin Av carotenoid. Khi khng c mt oxy v nhit cao (nh trong qu trnh tit trnghay nu), cc phn ng c bn xy ra l s isomerase ha v s phn hy vitamin. Khic mt oxy, phn ng oxy ha c th to ra cc hp cht bay hi hoc khng bay hi.Qu trnh ny thng xy ra song song vi phn ng oxy ha cht bo ( ng oxy ha).Tc ca phn ng oxy ha ph thuc vo p sut oxy ring phn, hot nc,nhit Thc phm sy kh (dehydrat ha) thng rt nhy cm vi qu trnh oxyha cht bo v vitamin A.

Chuyn ha vitamin A

T rut, vitamin A c hp thu vo mu di dng rtinol: 40% c a n cct chc s dng v 60% c d tr gan di dng palmitate retinol. Gan d tr90% vitamin A ca c th v sn sng cung cp vo mu, gi mc vitamin A trong



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mu lun lun n nh trn 20 microgam%. Mun c gii phng vo mu, rtinolphi c gn vi mt protein c hiu do gan sn xut, cn c gi l RBP (RtinolBinding Protine). Nu tr b suy dinh dng hoc suy gan, lng RBP gim v s gythiu vitamin A trong mu, 20 microgam% l ngng cho php v di mc s ctriu chng thiu vitamin A trn lm sng. D tr vitamin A c coi nh cn, nunng trong mu di 10 microgam%. y l giai on gy tn thng trm trng,kh hi phc. V vy, trong iu tr bnh thiu vitamin A, WHO ngh nhanh chnghi phc d tr gan, cc tn thng khng tin trin thm v sm c ci thin.

Hin tng thiu vitamin A:

cc nc phng ty,thiu vitamin A l mt hin tng rt him gp, tuy nhinvi nhng nc ang pht trin, n thc s l mt trong nhng nguyn nhn ph binnht gy gim th lc v m mt m cha th phng nga c .Cc triu chng smnht ca vic thiu vitamin A l hin tng gim thch ng vi bng ti, hay cn gi l

bnh qung g. Thiu vitamin A trm trng cn gy kh mt, c c trng bi sbin i cc t bo ca gic mc m kt qu cui cng l so v m mt.

Ngoi ra, tn thng da ( tng sng ha nang da) cng l mt cnh bo sm cavic thiu ht vitamin A. Chm pht trin tr em cng l mt biu hin thng gp,

bi v vitamin A l yu t cn thit cho nhng hot ng chc nng bnh thng ca hthng min dch, ngay c nhng tr em ch thiu vitamin A mc nh cng cnguy c mc cc chng bnh v h hp v tiu chy, cng nh t l t vong do cc

bnh truyn nhim cao hn nhng tr em c cung cp y vitamin A. Kh nng khng cng km khi lng vitamin A trong c th cng thp.

Mt s bnh tt v gan v ng tiu ha cng c th dn n vic gim hp th vd tr vitamin A trong c th. cc b m mang thai, thiu vitamin A cn dn nnhng d tt trong qu trnh pht trin ca thai nhi. Thiu vitamin A c th dn n suyhp th st v gim kh nng tng hp hng cu. V th c kh nng tng nguy c thiumu do thiu st. [7]

Tng tc dinh dng:

- Vitamin E bo v vitamin A khi b oxi ha, v vy, cung cp vitamin E s boton trng thi ca vitamin A trong c th.

- Nghin ru mn tnh nh hng n chc nng d tr vitamin A ca gan.

- Thiu ht cp tnh protein nh hng n qu trnh chuyn ha vitamin A; tngt, n qu t cht bo cng nh hng n s hp th ca c vitamin A v carotenoid.

- Thiu km c cho l c nh hng xu n qu trnh chuyn ha vitamin A,gim tng hp RBP - mt loi protein c nhim v vn chuyn retinol thng qua mchmu n cc m ( v d: vng mc) v chc nng bo v cc b phn ca c th chng



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li c tnh ca retinol. Thiu km cn gy ra hin tng gim hot ca cc enzymec nhim v gii phng retinol ra khi dng lu tr trong gan ca n retinyl palmitateng thi lm gim chuyn ha ca retinol t dng ru sang dng aldehyde.

- Ri lon tha vitamin A c th lm gim d tr vitamin C trong cc m, ng thingn cn chc nng lm ng mu ca vitamin K v nh hng n hot ng catuyn gip

- Vitamin A lm tng huyt p ni s khi c dng kt hp vi cc loi thuckhng sinh nh tetracyline v minocyline. [7]

Hp th v d tr trong c th:

Trn 90% retinol trong khu phn n di dng retinolpalmitat phn trn rutnon. Nh enzym lipase ca ty ester ny b thu phn gii phng retinol hp thu.Retinol c hp thu hon ton rut nh protein m ang retinol CRBP (cellular retinol

binding protein). Trong mu retinol gn vo protein i vo cc t chc v c d tr gan, gii phng ra protein mang retinol.Vitamin A c lu tr trong gan di dngretinyl ester, lng d tr cung cp cho mt c th ngi ln trong vng t 1 n2 nm. Vitamin A thi qua mt di dng lin hp vi acid glucuronic v c chu k gan- rut. Khng thy dng cha chuyn ha trong nc tiu. [15]

bn:

Vitamin A rt nhy cm vi qu trnh oxy ha trong khng kh. ng thi, hot ng ca n cng gim khi tip xc vi nhit v nh sng. Qu trnh oxy ha cht

bo v du (v d: b, b thc vt, du n) c th ph hy cc vitamin tan trong bo,

bao gm c vitamin A. V vy, s hin din ca cc cht chng oxy ha nh vitamin Egp phn rt ln vo vic bo v vitamin A.

Ngun sn xut ph gia vitamin A: chit xut t gan c hoc tng hp nhn to taceton, t cc nguyn liu du c cha vng -ionone.

Liu lng s dng:

Thiu ht hay d tha vitamin A u em n nhng vn khng tt cho sckhe ca con ngi. V th, nhiu nghin cu c tin hnh, v kt qu ca chngl nhng quy nh v khuyn co v hm lng vitamin A cho php c b sung vothc phm cng nh lng vitamin A gii hn cao nht cung cp cho tng i tng s

dng trong 1 ngy.1 RAE =1 g retinol

=12 g -carotene

= 24 g -carotene



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= 24 g -cryptoxanthinIncludes provitamin A

=1 RE [6]

Bng 2.6: RDA ca vitamin A cho tng i tng [17]

Nhm tui RDA g/ngy UL g/ngyTr s sinh 0 -6 thng tui 400 600Tr s sinh 7 -12 thng tui 500 600Tr em 1 3 tui 300 600Tr em 4-8 tui 400 900B trai 9-13 tui 600 1700

Nam gii 14 -18 tui 900 2800

Nam gii 19-30 tui 900 3000Nam gii 31-50 tui 900 3000Nam gii 50-70 tui 900 3000Nam gii trn 70 tui 900 3000B gi 9-13 tui 600 1700Ph n 14 -18 tui 700 2800Ph n 19-30 tui 700 3000Ph n 31-50 tui 700 3000Ph n 50-70 tui 700 3000

Ph n trn 70 tui 700 3000Ph n mang thai 18 tui 750 2800Ph n mang thai 19-30 tui 770 3000Ph n mang thai 31-50 tui 770 3000

2.2.1.4 Vitamin D:

Hnh 2.3: Tinh th vitamin D di nh sng phn cc [7]

Tn gi khc: Calciferol; nhn t chng ci xng; sunshine vitamin



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Thut ng vitamin D dng ch mt nhm cc vitamin c bn cht sterol tan trongcht bo v cc dung mi ca cht bo c mt trong rt t loi thc phm v hu nhc b sung vo ch dinh dng ca con ngi di dng cc ph gia dinh dng.Vitamin D cng bao gm mt s dng c cu trc gn ging nhau nh vitamin D2, D3,D4, D5, D6 Tuy nhin ch hai dng D2 v D3 l ph bin v c ngha hn c.

Vitamin D2: (Ergocalciferol )

Tn IUPAC (3,5Z,7E,22E)-9,10-secoergosta-5,7,10(19),22-tetraen-3-ol

Cng thc phn t: C28H44O

Khi lng phn t: 396.65 g/mol

Nhit nng chy: 114-118 C

Hnh 2.4: Vitamin D2 [9]Vitamin D3: (Cholecalciferol)

Tn IUPAC: (3,5Z,7E)-9,10-secocholesta-5,7,10(19)-trien-3-ol

Cng thc phn t: C27H44O


Nhit nng chy: 114-118 C

Mu trng, tinh th hnh kim.Hnh 2.5: Vitamin D3 [9]

Cu to ca chng cho thy, vitamin D2 v D3 l cc dn xut ca ergoterol vcolesterol. Khi chiu tia t ngoi vo ergoterol v colesterol s thu c cc vitamin D.

Hp th v chuyn ha vitamin D:

Vitamin D c hp thu tt qua ng tiu ha. C vitamin D2 v D3 u chp thu t rut non, vitamin D3 c th c hp thu tt hn. Phn chnh xc rut hpthu nhiu vitamin D ty thuc vo mi trng m vitamin D c ha tan. Mt cnthit cho hp thu vitamin D rut. V vitamin D tan trong lipid nn c tp trungtrong vi th dng chp v c hp thu theo h bch huyt; xp x 80% lng vitaminD dng theo ng ung c hp thu theo c ch ny. Vitamin D v cc cht chuynha ca n lun chuyn trong mu lin kt vi alpha globulin c hiu. Na i tronghuyt tng ca vitamin D l 19 - 25 gi, nhng thuc c lu gi thi gian di trongcc m m.

http://en.wikipedia.org/wiki/Ergocalciferolhttp://en.wikipedia.org/wiki/Cholecalciferolhttp://en.wikipedia.org/wiki/Ergocalciferolhttp://en.wikipedia.org/wiki/Cholecalciferol


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Cholecalciferol (D3) v ergocalciferol (D3) c hydroxyl ha gan to thnh25 - hydroxycholecalciferol v 25 - hydroxyergocalciferol tng ng. Nhng cht nytip tc c hydroxyl ha thn to thnh nhng cht chuyn ha hot ng 1,25 -dihydroxycholecalciferol v 1,25 - dihydroxyergocalciferol tng ng v nhng dncht 1,24,25 - trihydroxy.

Gan l ni chuyn vitamin D thnh 25 - OHD, cht ny lin kt vi protein vlun chuyn trong mu. Thc t, 25 - OHD c i lc cao vi protein hn hp cht m.Dn cht 25 - hydroxy c na i l 19 ngy v l dng ch yu ca vitamin D trongmu. Nng trng thi n nh ca 25 - OHD l 15 - 50 nanogam/ml. Na i cacalcitriol khong 3 - 5 ngy v 40% liu iu tr c o thi trong vng 10 ngy.Calcitriol c hydroxyl ha bi men hydroxylase thn thnh 1,24,25 - (OH)3D3,men ny cn hydroxyl ha 25 - OHD3 to thnh 24,25 - (OH)2D3. C 2 hp cht 24- hydroxy ny c t hot tnh hn calcitriol v c th l sn phm bi xut.

Vitamin D v cc cht chuyn ha ca n c bi xut ch yu qua mt vphn, ch c mt lng nh xut hin trong nc tiu. Mt vi loi vitamin D c thc tit vo sa.

Chc nng:

- Hot ha vitamin D: Vitamin D tn ti dng bt hot v phi c chuynha thnh cc dng hot ng sinh hc. Sau khi c hp th vo c th t thc nhoc c tng hp t cc lp biu b da, vitamin D i vo h thng tun hon v cvn chuyn n gan. gan, vitamin D b hydroxyl ha thnh dng 25-hydroxyvitaminD (calcidiol; 25-hydroxyvitamin D, dng tham gia tun hon chnh trong c th. Tng

cng tip xc vi nh sng mt tri hoc tng lng vitamin D trong thc phm slm tng lng 25-hydroxyvitamin D trong huyt thanh, v vy nng 25-hydroxyvitamin D l mt ch s v tnh trng dinh dng ca vitamin D. Trong thn,enzyme 25-hydroxyvitamin D3-1-hydroxylase tip tc hydroxyl ha ln th hai v tothnh 1,25-dihydroxyvitamin D (calcitriol, 1alpha,25-dihydroxyvitamin D) dng hotng nht ca vitamin D. Hu ht cc tc ng sinh l ca vitamin D ln c th u linquan n hot ng ca 1,25-dihydroxyvitamin D .

C ch ca qu trnh: rt nhiu hiu ng sinh hc ca 1,25-dihydroxyvitamin Dc thc hin thng qua mt yu t phin m nhn c gi l th th vitamin D(VDR). Khi c chuyn vo nhn t bo, 1,25-dihydroxyvitamin D lin kt vi VDR

v xc tc lin kt vi cc th th X ca acid retinoic (RXR). Nh s c mt ca 1,25-dihydroxyvitamin D, cc phc VDR/RXR s lin kt vi cc chui AND nh gi l ccyu t hng ng vitamin D (VDREs) v bt u mt chui cc tng tc lin phn tc chc nng iu chnh s sao m ca cc gene c th. Trn 50 gen ca cc m khpc th c iu chnh bi 1,25-dihydroxyvitamin D

http://tusach.thuvienkhoahoc.com/w/index.php?title=Cholecalciferol&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Ergocalciferol&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Cholecalciferol&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Ergocalciferol&action=edit


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Vitamin D2 v D3 c gi nh cho hiu qu ngi l nh nhau, tuy nhingn y, nhiu s liu cho thy rng vitamin D3 c th c hiu qu hn trong vic tnghm lng 25-hydroxyvitamin D trong huyt thanh.[6]

- Kim sot lng calcium trong c th: Duy tr mc calcium trong huyt thanhtrong mt gii hn tng i hp l rt quan trng cho cc hot ng chc nng bnhthng ca h thn kinh, cng nh cho s pht trin v duy tr mt xng. VitaminD rt cn thit cho c th trong vic s dng calcium mt cch hiu qu. Cc tuyn cngic da vo mc calcium trong huyt thanh iu tit loi hormone ny (parathyroidhormone, PTH). Tng tit PTH lm tng hot ng ca enzyme 25-hydroxyvitaminD3-1-hydroxylase thn, dn n tng sn xut 1,25-dihydroxyvitamin D. Tng 1,25-dihydroxyvitamin D lm thay i biu hin gen iu chnh lng calcium trong huytthanh bng cch tng hp thu calcium t thc phm rut, tng ti hp thu calcium thn v huy ng calcium t xng khi ch n ung khng cung cp calcium

duy tr mc calcium bnh thng trong huyt thanh.- Bit ha t bo: Qu trnh phn chia nhanh chng ca t bo c gi l qu

trnh tng sinh. S bit ha t bo to ra cc loi t bo vi nhng chc nng khc nhau.Nhn chung, s bit ha t bo lm gim s tng sinh. Trong khi tng sinh t bo l cnthit cho s sinh trng v lm lnh vt thng, s tng sinh t bin mt kim sotca t bo c th dn n cc bnh nh ung th. Dng hot ng ca vitamin D, 1,25-dihydroxyvitamin D, c th c ch s tng sinh v kch thch qu trnh bit ha t bo.

- Min dch: 1,25-dihydroxyvitamin D l mt tc nhn iu bin mnh m hthng min dch. Th th vitamin D (VDR) c biu hin bi hu ht cc t bo cah thng min dch, bao gm c t bo T, t bo khng nguyn nh t bo ui gai vcc i thc bo. Trong mt s trng hp, cc i thc bo cng sn xut ra enzyme25-hydroxyvitamin D3-1-hydroxylase, l enzyme c th chuyn ha 25-hydroxyvitaminD thnh 1,25-dihydroxyvitamin D. c nhng bng chng khoa hc ng k v hiung ca 1,25-dihydroxyvitamin D i vi h min dch: tng cng min dch bm sinhv c ch s pht trin ca min dch t do.

- iu tit insulin: Theo kt qu nghin cu trn ng vt cho thy, 1,25-dihydroxyvitamin D ng mt vai tr quan trng trong iu tit insulin khi nhu cuinsulin ca c th tng ln. Mt s bng chng cho thy rng thiu ht vitamin D c tcdng xu n mc chu ng glucose bnh tiu ng type 2.

- iu ha huyt p: H thng renin-angiotensin ng vai tr quan trng trongvic iu ha huyt p. Renin l enzyme phn ct mt on peptide nh (angiotensin I)t mt loi protein hnh thnh trong gan tn l Angiotensinogen. Sau , enzymechuyn i angiotensin ACE (Angiotensin Converting Enzyme) c trch nhim xc tcqu trnh phn ct angiotensin I thnh dng angiotensin II, mt loi peptide lm tnghuyt p bng cch gy ra s co tht cc ng mch nh, tng nng natri v gi



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nc. Lng angiotensin II tng hp c ph thuc vo enzyme renin. Nghin cutrn chut b thiu ht gene m ha cc VDR cho thy 1,25-dihydroxylvitamin D lmgim biu hin gene ca cc gene m ha renin thng qua s tng tc ca n viVDR. V th, s kch hot khng hp l h thng renin-angiotensin c cho l ngvai tr quan trng trong vic gy tng huyt p ngi, ni mt cch khc, cung cpy vitamin D c th gp phn lm gim nguy c cao huyt p. [22]

Ngun vitamin D:

- nh sng mt tri: Bc x cc tm B (UVB: Ultraviolet-B, bc sng 290-315nanomet) kch thch sn xut vitamin D3 trong lp biu b ca da. Tip xc vi nhsng mt tri c th cung cp nhu cu vitamin D ca hu ht chng ta. Tr em vngi ln, ni chung ch cn ng di nh nng mt tri trong mt khong thi gianngn 2 n 3 ln trong tun l c th tng hp c lng vitamin D cn thit choc th ngn chn nguy c thiu ht loi vitamin ny. Mt nghin cu bo co rng

nng vitamin D trong huyt thanh sau khi tip xc vi nh sng mt tri trongkhong thi gian nh nht c th lm da ng l tng ng vi 20000 IUvitamin D2 n vo. Nhng ngi c da sm mu tng hp c t vitamin D mt cchr rt so vi nhng ngi da mu sng. NgoI ra, ngi cao tui, kh nng tng hpvitamin D t nh sng mt tri gim i ng k.

- Thc phm: vitamin D c tm thy trong cc thc phm t nhin vi hmlng rt t. Thc phm c cha vitamin D bao gm mt s loi c nh c thu, c hi,c mi, du gan c v t trng ca g mi c cho n b sung vitamin D. TiM, sa v thc phm dnh cho tr s sinh c b sung vitamin D n hm lng 400IU/lt. Tuy nhin, cc sn phm khc ca sa nh sa chua, phomat, khohong phi lcno cng c b sung vitamin D. [22] Mt s loi thc phm b sung vitamin D ccho bng sau:

Bng 2.7: Hm lng vitamin D trong mt s loi thc phm

Thc phm Khi lng Vitamin D (IU)Vitamin D

(mcg)

C hi ng hp 3 ounces 530 13.3

C thu ng hp 3 ounces 213 5.3

Sa b b sung vitamin D 8 ounces 98 2.5

Nc cam b sung vitamin D 8 ounces 100 2.5

Lng trng 1 large 21 0.53

1 ounces = 28,35g



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Ngun sn xut ph gia vitamin D: Dng vitamin D c dng b sung vothc phm l dng vitamin D3. Ngi ta tm ra cch tng hp nhn to vo nm1907, da vo hai thnh phn l 7-dehydrocholesterol hoc cholesterol. 7-dehydrocholesterol c ly t dch chit hu c t da ng vt ( b, ln, cu...)cn cholesterol li c chit xut t m lng cu, sau qu trnh tinh ch, nhvo chui cc phn ng tng hp ha hc, n c chuyn thnh dng 7-dehydrocholesterol.

Bng 2.8: Adequate Intake (AI) ca vitamin D [22]

Nhm tui Nam giimcg/ngy(IU/ngy)

Ph nmcg/day(IU/ngy)

Tr s sinh 0-6 thng tui 5 mcg (200 IU) 5 mcg (200 IU)

Tr s sinh 7-12 thng tui 5 mcg (200 IU) 5 mcg (200 IU)Tr em 1-3 tui 5 mcg (200 IU) 5 mcg (200 IU)

Tr em 4-8 tui 5 mcg (200 IU) 5 mcg (200 IU)

Tr em 9-13 tui 5 mcg (200 IU) 5 mcg (200 IU)

V thnh nin 14-18 tui 5 mcg (200 IU) 5 mcg (200 IU)

Ngi trng thnh 19-50 tui 5 mcg (200 IU) 5 mcg (200 IU)

Ngi trng thnh 51-70 tui 10 mcg (400 IU) 10 mcg (400 IU)

Ngi trng thnh Trn 71 tui 15 mcg (600 IU) 15 mcg (600 IU)

Ph n mang thai Mi la tui - 5 mcg (200 IU)

Ph n ang cho conb

Mi la tui - 5 mcg (200 IU)

Nhn chung, ty thuc tng la tui, tnh trng sc khe v c im kh hu nisinh sng m nhu cu vitamin D ca tng ngi l hon ton khc nhau. Nm 1997,Ban thc phm v dinh dng (Food and nutritional Board) thuc vin Y hc Hoa K nhn thy rng, kh nng tip xc vi nh sng mt tri ca tng c nhn nh hngrt ln n nhu cu vitamin D trong thc phm, v th khng th tnh ton mt cch

chnh xc cc ch s RDA. Thay vo , ngi ta thit lp ch tiu AI, l hm lngvitamin D nhn c t thc phm cung cp y cho nhu cu ca c th nu gis khng c lng vitamin D no c tng hp trong da nh tip xc vi nh sngmt tri. cc gi tr bng di phn nh lng vitamin D n vo duy tr nng 25-hydroxylvitamin D trong huyt thanh t mc thp nht khng nguy hi cho sckhe: 37,5 nmol/l.



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Bng 2.9:Tolerable Upper Intake Level(UL) ca vitamin D (Vin Y hc Hoa K)

La tui mcg/ngy (IU/ngy)

Tr s sinh 0-12 thng tui 25 mcg (1,000 IU)

Tr em 1-18 tui 50 mcg (2,000 IU)

Ngi trng thnh trn 19 tui 50 mcg (2,000 IU)

bn ca vitamin D:

Vitamin D tng i n nh trong thc phm. Bo qun, ch bin thc phm t nhhng n hm lng ca n. Tuy nhin, Vitamin D d b phn hy khi c mt cc chtoxy ha v axit v c. S phn hy xy ra ni i c trong vng B ca phn tvitamin. V vy, phi lu n thnh phn ca thc phm khi quyt nh b sungvitamin D vo thc phm . [7]

Hin tng thiu vitamin D:

Mt trong nhng triu chng u tin ca vic tiu ht vitamin D l gim mccalcium trong huyt thanh v gia tng hormone tuyn cn gip (PTH), suy nhc c

bp v un vn, cng nh gia tng nguy c nhim trng. Tr em c mt s biu hinnh bng chn, kh chu, tit m hi nhiu v n khng ngon. Thiu vitamin D gp

phn gy long v dn xng ngi cao tui v ci xng tr em, m nguyn nhnl do xng b mt i khong cht. Cc khp xng khuu tay, khuu chn b nhhng v do qu trnh pht trin b chm li. ng thi, ci xng cn gy tc dng

xu n vic hnh thnh rng v men rng.[7]

Nhng nhm i tng c nguy c thiu vitamin D cao:

Tr s sinh ch b sa m: v sa m l ngun rt ngho vitamin D, ngoi ra chcnng chuyn ha vitamin D gan v thn ca tr s sinh l rt km

Ngi cao tui: do gim tng hp vitamin D khi tip xc vi nh sng mt tri

Nhng ngi c cc bnh nh hng n gan, thn, tuyn gip hoc kh nng hpth cht bo, cng nh nhng ngi nghin ru, n chay

Nhng ngi c mu da sm

Nhng ngi sng cc khu vc xa xch o, c bit l vo ma ng.[7]

2.2.1.5 Vitamin E:

Vitamin E l nhm vi cht ng vai tr thit yu trong cc qu trnh trao i chttrong c th m ng vt khng th t tng hp c. Vitamin E c bit n l cht



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cn thit cho qu trnh sinh sn bnh thng, cht c kh nng chng oxy ha, gip bov t bo, bao gm c cc cht bo khng bo ha khi s oxy ha ca oxy v cc gct do.

Vitamin E bao gm 8 cht chng oxy ha: 4 loi tocopherol l (alpha-, beta-,gamma-, v delta- tocopherol), 4 tocotrienol (alpha-, beta-, gamma-, v delta-tocotrienol). Alpha tocopherol l dng hot ng duy nht ca vitamin E trong c thngi. Tn gi tocopherol bt ngui t ting Hy Lp tocos c ngha l sinh con.Tn gi ny c t nu bt vai tr quan trng ca i vi qu trnh sinh sn cang vt. ui ol xc nh y l cc ru.

Hnh 2.6: alpha tocopherol [23]Tt c cc tocopherol u c nhnh bn ging nhau tng ng vi gc ru

phyton (C16H33). S khc nhau gia chng l do s sp xp khc nhau ca cc gcmetyl phn vng benzopiran. Cc loi tocopherol khc mi c tch ra vo thi giangn y cng kh nhau bi s sp xp v s lng ca cc nhm CH3 cc v tr 5, 7v 9 ca vng benzen.

Tnh cht:

Tocopherol l cht du lng khng mu, ha tan rt tt trong du thc vt, ruetylic, ete etylic v ete du ha. Alpha tocopherol thin nhin c th kt tinh chm trong

ru metylic nu gi nhit thp ti -35 oC. Khi s thu c tinh th hnh kimvi nhit nng chy 2,5-3,5oC (hnh 2.6).

Hnh 2.7: Tinh th vitamin E di nh sng phn cc

Trong s cc tnh cht ha hc ca tocopherol, tnh cht quan trng hn c lkh nng b oxy ha bi cc cht oxy ha khc nhau nh st III hoc acid nitric. Khi s to nn cc sn phm oxy ha khc nhau, trong c tocopherylquinon. Cht ny ccu trc ha hc gn ging vi cu trc ca cc vitamin K v Q, do cc loi vitamin



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E, K v Q c th c vai tr ging nhau trong qu trnh oxy ha km theo d tr nnglng trong c th.

Ngun vitamin E:

Ngun vitamin E ch yu l du thc vt, rau x lch, rau ci. Vitamin c mtnhiu trong du mm ht ha tho ( mm la m, la, ng), trong du p ca mt s htc du (lc, hng dng) hoc mt s qu. ng vt, vitamin E c trong m ngvt nh m b, m c, nhng hm lng thp hn nhiu so vi du thc vt. Du htcy hng dng cha ch yu alpha tocopherol, cn du u tng v du ng licha cc dng khc nhiu hn v bo v c cc vitamin ha tan trong m nhvitamin A, D cng nh cc cht bo cha no khi b oxy ha.

Hm lng vitamin E trong thc phm c biu din bng n v ng lng tocopherol (-TE). Thut ng ny c lp ra trn c s s khc bit gia cc hnh

thc hot ng khc nhau ca vitamin E. [7]1mg -tocopherol =1TE

1 mg -tocopherol = 0.5 TE;

1 mg -tocopherol = 0.1 TE; 1 mg

-tocopherol = 0.03 TE; 1 mg

-tocotrienol = 0.3 TE; 1 mg

-tocotrienol = 0.05 TE. [7]

Bng 2.10 : Hm lng vitamin E trong mt s loi thc phm [7]Thc phm Vitamin E(mg -TE/100g)

Du mm la m 174

Du ht hng dng 63

Ht cy ph 26

Du u nnh 17

Du liu 12

Du u phng 11

Du ht c ch 6

B 2

Ci b xi 1.4

Khoai ty 0.8



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To 0.5

Sa nguyn cht 0.14

bn ca vitamin E:Tocopherol kh bn vi nhit, n c th chu c ti nhit 170oC khi ung

nng trong khng kh, nhng tia t ngoi s ph hy nhanh tocopherol.

Tuy nhin, nh sng, oxy v nhit l nhng yu t gy hi n qu trnh boqun lu di v ch bin thc phm v lm gim lng vitamin E cha trong . Mt sloi thc phm, hm lng vitamin E c th gim n 50% ch sau hai tun bo qun nhit phng.

Hp th v chuyn ha vitamin E:

Vitamin E c hp th cng vi lipid trong rut non. vitamin E hp th quang tiu ha, mt v tuyn ty phi hot ng bnh thng. Vitamin E vo mu quavi th dng chp trong bch huyt, ri c phn b rng ri vo tt c cc m v tchli m m. tocopherol l dng vitamin E chim u th trong mu v m. l dotc ng ca mt protein trong gan (protein chuyn ha -tocopherol) u tin gn -tocopherol vo mt lipoprotein chuyn n cc m trong c th. M m, gan, c bpl ni cha nhiu vitamin E nht.

Mt t vitamin E chuyn ha gan thnh cc glucuronid ca acidtocopheronic v gamma - lacton ca acid ny, ri thi qua nc tiu, cn hu ht thitr chm vo mt. Vitamin E c tit qua sa m, nhng truyn rt t qua nhau thai.

Tng tc dinh dng:Tng hp thu vitamin A qua rut khi c vitamin E; vitamin E bo v vitamin A khi

b thoi ha do oxy ha lm cho nng vitamin A trong t bo tng ln; vitamin Ecng bo v chng li tc dng ca chng tha vitamin

Vitamin E i khng vi tc dng ca vitamin K, nn lm tng thi gian ng mu.

St lm gim lng vitamin E trong c th. [7]

Chc nng:

- Alpha-tocopherol: chc nng chnh ca alpha-tocopherol trong c th ngi lmt cht chng oxy ha. Cc gc t do c hnh thnh ch yu trong c th trong qutrnh trao i cht bnh thng, hoc cng c th trong khi tip xc vi cc yu t mitrng nh khi thuc l hoc cc cht nhim. Cht bo l thnh phn ca tt c ccmng t bo, chng rt d b ph hy thng qua qu trnh oxy ha bi cc gc t do.

Cc vitamin tan trong cht bo, alpha-tocopherol, l duy nht thch hp chngli cc gc t do, v do ngn chn mt phn ng dy chuyn ca s ph hy lipid.

http://tusach.thuvienkhoahoc.com/w/index.php?title=Glucuronid&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Acid_tocopheronic&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Acid_tocopheronic&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Vitamin_K&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Glucuronid&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Acid_tocopheronic&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Acid_tocopheronic&action=edithttp://tusach.thuvienkhoahoc.com/w/index.php?title=Vitamin_K&action=edit


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Bn cnh vic duy tr tnh ton vn mng t bo xuyn sut c th, alpha-tocopherolcn bo v cc cht bo trong cc lipoprotein t trng thp (LDLs) khi s oxy ha.Lipoprotein bao gm cc ht lipid v protein vn chuyn cht bo trong mu. C th,LDLs vn chuyn cholesterol t gan n cc m trong c th. LDLs b oxy ha ccho l c lin quan n s pht trin ca cc bnh tim mch. Khi mt phn t alpha-tocopherol v hiu ha c mt gc t do, kh nng chng oxy ha ca n cng bmt. Tuy nhin, nhng cht chng oxy ha khc li c kh nng lm ti sinh nng lcchng oxy ha ca alpha-tocopherol. Ngoi kh nng chng oxy ha, alpha-tocopherolcn c nhng chc nng khc nh l c ch hot ng ca proteinkinase C, mt phnt truyn tn hiu lin t bo quan trng. Alpha-tocopherol cng nh hng n hotng ca cc phn t v enzyme trong c t bo b vim v cc t bo min dch. Thmvo , n cng c ch ra l c tc dng c ch kt t tiu cu v tng hin tnggin mch.

Cc dng ng phn ca alpha-tocopherol c tm thy trong thc phm lRRR- alpha-tocopherol (hay cn gi l tocopherol t nhin hay d- alpha-tocopherol).Thng thng cc loi thc phm b sung vitamin E cha alpha-tocopherol tng hpv hm lng c a ra l t l phn trm ca gi tr hng ngy 30 IU.

- Gamma-tocopherol: chc nng ca gamma-tocopherol hin nay cha c xcnh r rng. Mc d hnh thc ph bin nht ca vitamin E trong ch n ung lgamma-tocopherol, tuy nhin nng trong mu ca n thp hn ca alpha-tocopherol10 ln. Hin tng ny c xc nh l do hai c ch. 1) alpha-tocopherol l cht cu tin gi li trong c th do tc ng ca cc protein chuyn ha alpha-tocopherol (-TTP) trong gan, theo u tin kt hp alpha-tocopherol vi lipoprotein trong mu v

2) Cc dng khc ca vitamin E c tch cc chuyn ha. Bi v gamma-tocopherolban u cng c hp th theo cch thc ging nh alpha-tocopherol, nhng ch cmt lng nh gamma-tocopherol c pht hin trogn mu v m. V nhng sn

phm do chuyn ha gamma-tocopherol th li c tm thy trong nc tiu, v lngny nhiu hn ca alpha-tocopherol rt nhiu, chng t rng gamma-tocopherol l tcn thit hn cho vic s dng vitamin E ca cc c quan. [23]

Thc phm b sung vitamin E:

M, lng alpha-tocopherol trung bnh n vo hng ngy l khong 8mg/ngy i vi nam v 6mg/ngy i vi n. Mc ny thp hn mc RDA l 15mg

RRR-alpha-tocopherol/ngy rt nhiu. Nhiu nh khoa hc cho rng rt kh cho mtngi c th tiu th hn 15mg alpha-tocopherol t thc n trong mt ngy m khngcn tng lng cht bo ln trn mc khuyn co. Tt c lng alpha-tocopherol trongthc phm u tn ti di dngRRR-alpha-tocopherol. Tuy nhin n khng lun lunng cho cc ph gia dinh dng. Thc phm b sung vitamin E thng cha t 100n 1000 IU alpha-tocopherol. Cc ph gia c ngun gc hon ton t t nhin chchaRRR-alpha-tocopherol. l dng ng phn c c th a thch s dng, lm



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n tr thnh dng ti u sinh hc nht ca alpha-tocopherol. Alpha-tocopherol tng hpch c tm thy cc loi thc phm b sung dinh dng v cc ph gia thc phmthng c ghi nhn l all-rac-alpha-tocopherol hoc dl-alpha-tocopherol, c ngha lton b 8 ng phn u hin din trong hn hp. V mt na trong s cc ng phnca alpha-tocopherol c mt trong all-rac-alpha-tocopherol khng c kh nng s dngc trong c th, nn alpha-tocopherol tng hp t ti thch sinh hc hn.

tnh s mg alpha-tocopherol c th s dng c c mt trong ph gia, ngi tas dng cng thc sau:

+ RRR-alpha-tocopherol (dng t nhin hoc alpha-tocopherol):IU x 0.67 = mgRRR-alpha-tocopherol.

V d: 100 IU = 67 mg+ all-rac-alpha-tocopherol (dng tng hp hoc dl-alpha-tocopherol):IU x 0.45 = mgRRR-alpha-tocopherol.V d: 100 IU = 45 mg

Thiu vitamin E:

S thiu ht vitamin E c quan st trn cc c th b suy dinh dng nng,b d tt di truyn nh hng n protein chuyn ha alpha-tocopherol v hi chngkm hp th cht bo. Thiu ht vitamin E trm trng thng gy ra nhng triu chnglin quan n thn kinh, bao gm cn bng km v mt iu ha, tn thng n cc

dy thn kinh cm gic (thn kinh ngoi bin), suy nhc c v tn hi vng mc mt(sc t vng mc). V l do ny, nhng ngi mc cc bnh v thn kinh ngoi vi, mtiu ha hoc gim sc t vng mc c chn on l do thiu vitamin E. V d, trem nu thiu ht trm trng vitamin E t khi sinh ra v khng c iu tr bngvitamin E th s nhanh chng pht trin cc triu chng thn kinh

Mc d thiu ht vitamin E l rt him nhng Vin y hc Hoa K vn a rakhuyn ngh RDA cho ngi trng thnh l 15mg/ngy. V trn thc t c n 90%ngi M khng p ng khuyn ngh ny.

Bng 2.11 : Recommended Dietary Allowance (RDA) ca RRR-alpha-tocopherol

(d-alpha-tocopherol) [23]Nhm ngi tui Nam gii;

mg/ngy (IU/ngy)Ph n;

mg/ngy (IU/ngy)

Tr s sinh (AI) 0-6 thng tui 4 mg (6 IU) 4 mg (6 IU)

Tr s sinh (AI) 7-12 tui 5 mg (7.5 IU) 5 mg (7.5 IU)

http://lpi.oregonstate.edu/infocenter/glossary.html#aihttp://lpi.oregonstate.edu/infocenter/glossary.html#ai


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Tr em 1-3 tui 6 mg (9 IU) 6 mg (9 IU)

Tr em 4-8 tui 7 mg (10.5 IU) 7 mg (10.5 IU)

Tr em 9-13 tui 11 mg (16.5 IU) 11 mg (16.5 IU)

V thnh nin 14-18 tui 15 mg (22.5 IU) 15 mg (22.5 IU)

Ngi trng thnh Trn 19 tui 15 mg (22.5 IU) 15 mg (22.5 IU)

Ph n c thai Mi la tui - 15 mg (22.5 IU)

Ph n cho con b Mi la tui - 19 mg (28.5 IU)

Bng 2.12: Upper Intake Level (UL) ca Alpha-Tocopherol [20]

Nhm tui mg/ngy (IU/ngy d-alpha-tocopherol)

Tr s sinh 0-12 thng tui Khng th thit lp*

Tr em 1-3 tui 200 mg (300 IU)

Tr em 4-8 tui 300 mg (450 IU)

Tr em 9-13 tui 600 mg (900 IU)

V thnh nin 14-18 tui 800 mg (1,200 IU)

Ngi trng thnh trn 19 tui 1,000 mg (1,500 IU)

2.2.1.6 Vitamin B1:

Tn gi khc: Thiamin, aneurine hydrochloride

Tn IUPAC: 2-[3-[(4-amino- 2-methyl- pyrimidin- 5-yl) methyl]- 4-methyl-thiazol- 5-yl] ethanol

Cng thc cu to:

Cng thc phn t: C12H17N4OS+Cl-.HCl

Khi lng phn t: 337.27

Nhit nng chy: 248-260 C (muihydrochloride )

Hnh 2.8: Vitamin B1 [19]Vitamin B1 l loi vitamin ph bin trong t nhin, c bit nhiu trong nm

men, mm la m, cm go v.v ng vt c nhiu trong gan, thn, tim l loivitamin c tch ra dng tinh th u tin bi Casimir Funk nm 1912. a s tn ti



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dng t do cn mt phn dng Thiaminpirophosphat. Trong thc t, thiamin thngtn ti dng mui thiaminclorit.

Hnh 2.9: Tinh th vitamin B1 di nh sng phn cc. [7] Tnh cht ha hc:

Vitamin B1 ch bn trong mi trng acid cn mi trng kim n b ph hynhanh chng khi un nng. Vitamin B1 l nhng tinh th ha tan tt trong nc v chuc cc qu trnh gia nhit thng thng. Khi oxy ha vitamin B1 s chuyn thnhmt hp cht gi l thiocrom pht hunh quang. Tnh cht ny c ng dng ph bin nh lng vitamin B1 trong cc thc phm khc nhau. Vitamin B1 c tng hpd dng bi thc vt, mt s vi sinh vt, c bit l vi sinh vt rut cc ng vt nhaili.

Ngun vitamin B1:C th ngi v a s ng vt khng c kh nng nn phi ly t cc thc

phm. Nm men cung cp mt lng vitamin B1 rt ln nn thng c dng vo ccmc ch cha bnh khi thiu vitamin nhm B. Trong tht ca mt s c nc ngt hocmt s nhuyn th c cha cc cht chng tc dng ca thiamin do chng c kh nnglm phn gii thiamin.

Bng 2.13: Hm lng vitamin B1 trong mt s loi thc phm. [7]

Thc phm Vitamin B1 (mg/100g)

Nm men bia 12Mm la mch 2

Ht hng dng 1.5

Qu hch Brasil 1

Tht heo 0.9

u 0.8

Bt yn mch 0.59

Tht b 0.23

bn ca vitamin B1:

Vitamin B1 khng bn khi tip xc vi nhit, kim, oxy v nh sng. S ha tantrong nc cng l mt yu t quan trng trong vic mt mt vitamin B1 trong thc

phm. Khong 25% lng vitamin B1 trong thc phm b mt i trong qu trnh nunng thng thng. Mt lng ng k cn c th b mt mt trong qu trnh r ng



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cc loi tht ng lnh v rau qu nu. bo ton thiamin, thc phm cn c nuchn trong thi gian ngn nht c th v khng nn ngm trong nc nng qu lu.

Chc nng:

Da vo c ch tc dng ca thiamin, ngi ta bit r rng thiaminpirophosphat l coenzyme ca cc enzyme piruvat T decarboxylase hoc alpha-xetoglutarat decarboxylase. Cc axit piruvic v cc axit alpha-xetoglutaric chnh l ccsn phm ca qu trnh trao i gluxit. Chnh v vy khi thiu vitamin B1 th s trao igluxit s ngng tr. Trong c th ngi v ng vt, thiamin chuyn thnh

pirophosphat. Di dng ny ni tham gia phn gii acid piruvic to ra sn phm cuicng l oxyetylpirophosphat.

Thiamin pyrophosphate (TPP) l mt coenzyme cn thit cho mt lng nhcc enzyme rt quan trng.

S tng hp TPP t thiamin i hi s c mt ca magnesium, adenosinetriphosphate (ATP) v enzyme thiamin pyrophosphokinase. Pyruvate dehydrogenase,ketoglutarate dehydrogenase v enzyme dehydrogenase ca chui phn nhnh ketoacid.Mi enzyme trn u c tm thy trong ti th ca t bo. Chng xc tc cc qu trnhdecarboxylate ca pyruvate, ketogluatarate v cc amino acid c mch phn nhnh to thnh acetyl coenzyme A,succinyl coenzyme A v cc dn xut ca amino acid cmch phn nhnh tng ng. Tt c cc sn phm ca qu trnh ny u ng vai tr

ht sc quan trng trong vic gii phng nng lng t thc n. Ngoi ra trong ccTPP, mi phc h enzyme dehydrogenase u cn niacin-cht cha coenzyme NAD vlipoic acid thiamin pyrophosphokinase.

Transketolase xc tc nhng phn ng quan trng trong qu trnh trao i chtkhc nh l con ng pentose phosphate. M mt trong nhng bc trung gian quantrng nht ca con ng nu l ribose-5-phosphate, mt ng 5 carbon lin quan nqu trnh phosphoryl ha cn thit cho s tng hp ATP v GTP. N cng cn thit choqa trnh tng hp cc axit nucleic, DNA v RNA, v coenzyme cha niacin

NADPH, cht cn thit cho rt nhiu cc phn ng tng hp sinh hc. V transketolases b gim rt nhanh trong cc trng hp thiu thianin, vic nh gi hot ng ca

n trong t bo hng cu cng c s dng nh gi tnh trng dinh dng cathiamin.

Di dng thiaminpirophosphat, vitamin B1 tham gia vo h ezyme decarboxyloxy ha cc xeto acid nh acid piruvic hoc acid alpha-xetoglutaric. V vy khi c th

b thiu vitamin B1 s dn ti tch ly cc xeto acid lm hn lon trao i cht km theohin tng bnh l trm trng, v d gim xut tit dch v, t ph Ngoi ra vitamin



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B1 cng vi acid pantotenic cn tham gia to nn cht axetylcholin, l cht gi vai trquan trng trong vic truyn xung ng thn kinh. Chnh v vy m khi thiu vitaminB1, h thn kinh, ni xy ra trao i mnh gluxit, s b nh hng nhiu hn c. [19]

Tng tc dinh dng:

S tn ti ca cc loi vitamin B khc, v d nh vitamin B6, B12, niacin v acidpantothenic h tr thm cc hot ng ca thianin. Cc vitamin chng oxy ha, v dnh vitamin E v C s bo v thiamin bng cch ngn cn qu trnh oxy ha thnh dngkhng hot ng ca n.

Mt s loi thc phm, chng hn nh c ph, ch, tru (ng Nam ) v mt s

loi ng cc khc c phn ng i khng vi vitamin. Acid chlorogenic v polyphenolthc vt khc c th l nguyn nhn ca vic ny.

Thiu ht vitamin B1:

Thiu ht thiamin c th biu hin thng qua cc triu chng nh mt mi, mtng, kh chu v thiu tp trung, chn n v to bn. Khi khng thiamin, cc qutrnh tng hp cc carbohydrate v amino acid gim, gy ra cc hu qu rt nghimtrng. Hai bnh c coi l hu qu tiu biu ca vic thiu ht thiamin l beriberi vhi chng Wernicke-Korsakoff.

Beriberi c ngha l ti khng th, ti khng th. Biu hin ch yu l ri lon

h thn kinh v tim mch. Tht khng may, y vn l bnh kh ph bin ng Nam, ni vic xay xt v nh bng go vn lm mt i mt phn rt ln thiamin.

Hi chng Wernicke-Korsakoff thng gi l bi no, l bnh do thiu htthiamin gy ra thng thy nht cc nc phng ty. Triu chng ca n bao gmnhm ln, t lit dy thn kinh c ng mt, tm thn v tr nh.

Nguyn nhn ca tnh trng thiu thiamin:Thiu ht vitamin B1 c th l dokhng thiamin, tng nhu cu thiamin, c th mt qu nhiu thiamin, hp th qunhiu cht chng thiamin t thc phm hoc kt hp ca cc yu t trn.

-Hp th thiamin khng : khng c cung cp thiamin t thc phm l

nguyn nhn chnh ca tnh trng thiu ht vitamin ny nhng nc km pht trin.Thiu thiamin ph bin trong cc cng ng dn c c thu nhp thp, c ch nnhiu carbohydrate v t thiamin (v d: go qua xay xt v nh bng qu k) hoc nhng ngi nghin ru.Tr s sinh b sa m t ngi m thiu thaimine s d bmc chng beriberi.



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- Tng nhu cu vitamin B1: nhng iu kin dn n tng nhu cu thiamine l slao lc v th cht, st, mang thai, cho con b v tng trng tui v thnh nin.

- C th mt mt qu nhiu thiamine: bng cch tng lu lng nc tiu, thuc

li tiu c th ngn cn qu trnh ti hp th thiamine ca thn v tng bi tit thiaminetrong nc tiu. C nhn b suy thn ph lc mu mt thiamine vi tc rt cao v cnguy c thiu ht thiamine.

- Cc anti-thiamine (ATF): s hin din ca cc cht chng thiamine trong thcphm cng gp phn vo nguy c thiu ht thiamin. Mt s loai thc phm c chaATF, cht s phn ng vi thiamin to thnh oxy ha bt hot. Tiu th qu nhiutr v c ph (bao gm c nhng loi gim lng caffe), l ch v tru, mt s loic nc ngt u gy ra s suy gim thiamin ngi. Thiaminases l enzyme phn hythiamin trong thc phm. [19]

Lng RDA ngh:Bng 2.14 : RDA ca thiamin

Nhm ngi tui Nam gii (mg/day) Ph n (mg/day)

Tr s sinh 0-6 thng tui 0.2 (AI) 0.2 (AI)

Tr s sinh 7-12 thng tui 0.3 (AI) 0.3 (AI)

Tr em 1-3 tui 0.5 0.5

Tr em 4-8 tui 0.6 0.6

Tr em 9-13 tui 0.9 0.9

V thnh nin 14-18 tui 1.2 1.0

Ngi trng thnh Trn 19 tui 1.2 1.1

Ph n mang thai Mi la tui - 1.4

Ph n cho con b Mi la tui - 1.4

2.2.1.7 Vitamin B2

Tn gi khc: Riboflavin, riboflavine, vitamin B2, lactoflavin,ovoflavin

Tn IUPAC: 7,8-dimethyl- 10-((2R,3R,4S)- 2,3,4,5-tetrahydroxypentyl) benzo [g]pteridine- 2,4 (3H,10H)- dione

Cng thc phn t: C17H20N4O6

http://lpi.oregonstate.edu/infocenter/glossary.html#aihttp://lpi.oregonstate.edu/infocenter/glossary.html#ai


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Nhit nng chy: 290 C

Hnh 2.10: Cu to phn t riboflavin [18]

Hnh 2.11: Tinh th riboflavin di nh sng phn cc [7]

Vitamin B2 l loi vitamin tan trong nc c phn b rng ri nht. v trongcu to ca vitamin B2 c hp cht riboza nn ngi ta gi tn l riboflavin.

Tinh th vitamin B2 mu vng, ha tan tt trong nc v ru, khng ha tantrong cc dung mi ca cht bo. Tinh th kh bn vi nhit v dung dch axit.

Trong c th, vitamin B2 d b phosphorin ha to nn nhm hot ng ca cc enzymexc tc cho cc qu trnh oxy ha kh, cc coenzyme thng gp l riboflavinmononucleotit hoc riboflavin-adenin-dinucleotit. Khi gn vo cc protein s to nncc enzyme nh cc loi dehydrogenaza khc nhau, men vng Vacbua, oxydaza D-axitamin, reductase Vitamin B2 tham gia vn chuyn hydro nhiu enzyme, trong n tn ti dng flavin adenin dinucleotit. Qu trnh vn chuyn hydro ca vitaminB2 c thc hin nh kh nng gn hydro vo cc nguyn t nito cc v tr 1 v 10.Khi vitamin B2 s chuyn t dng c mu sang dng khng mu.

Ngun vitamin B2:

Vitamin B2 c nhiu trong cc sn phm thin nhin: nm men bnh m, nmmen bia, u, tht, gan, thn, tim, sa, trng v c sn phm t c. Trong rau xanh cngcha nhiu vitamin B2. N c tng hp bi cc t bo thc vt v vi sinh vt. Ccng vt c sng khng cn ti riboflavin v rut ca chng, cc vi sinh vt tng hpc riboflavin v cung cp cho ng vt ch.

sn xut vitamin B2 t cc nguyn liu thin nhin c th da vo kh nngsinh tng hp riboflavin t cc vi sinh vt nh cc loi nm mc Eremothecium



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ashbyii. Khi to iu kin nui cy thch hp, cc vi sinh vt ny s tng hp v tit rami trng mt lng riboflavin kh cao (1.8 mg riboflavin/1 ml). T cc mi trngnui cy c th tin hnh kt tinh riboflavin.

bn:

Riboflavin d b phn gii khi un si v ngoi nh sng. Trong trng hpun si v gi riboflavin mi trng kim, n s chuyn thnh lumiflavin cn trongmi trng trung tnh hoc axit yu th s thu c dn xut lumicrom.

Trong qu trnh bo qun go v cc loi ht khc, ngi ta nhn thy rng ngc vi

vitamin B1, vitamin B2 c xu hng tng ln r rt nht l khi bo qun dng baoci, bao ti, bao PP, ngha l c s xm nhp d dng ca oxy khng kh.

i vi trng g, vitamin B2 trong lng trng khng bin i trong qu trnh bo qun,cn lng , c l do n tn ti dng t do nhiu hn nn vitamin B2 d b bin ihn. [3]

Hp th v chuyn ha:

Hu ht cc riboflavin c trong ch n ung c hp th trong protein thcphm vi FMN v FAD. Cc riboflavin c tch ra trong d dy ca qu trnh axit hav hp thu nhanh phn trn ca rut non, c ch vn chuyn bo ha. T l hp tht l thun vi lng riboflavin c tiu th cng vi cc loi thc phm khc. V vy,khong 15% c hp th nu thc hin mt mnh v hp th 60% so vi khi dngcng vi thc n. S khuyt tn th ng ch ng mt vai tr nh liu sinh l tiuha trong ch n ung.

Trong cc t bo mng nhy ca rut non ,riboflavin c chuyn nmononucleotide Flavin coenzyme mu (FMN). Trong h thng cng Roboflavin docgii hn vi albumin huyt tng hoc vi cc protein khc, ch yu l globulin mindch, v vn chuyn n gan, ti n c chuyn ha thnh dng coenzyme khc,FAD, v oc quy nh gii hn vi protein c th nh flavoproteins.

Riboflavin, ch yu l FAD, c phn b trong tt c cc m, nhng nng thp v t c lu gi. Gan v cc m vng mc l nhng ni lu tr chnh.Riboflavin c bi tit ch yu l trong nc tiu v n gp phn lm cho nc tiuc mu vng. Mt lng nh oc bi tit qua m hi v bi tit qua mt. Trong thigian cho con b, khong 10% riboflavin hp thu qua ngun sa m.

Tng tc dinh dng:



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- Thyroxine v triiodothyroxine kch thch tng hp cc flavin ononucleotide(FMN) v flavin adenine dinucleotide (FAD) cc ng vt c v.. Cc thuc chngtitsacetylcholine lm tng s hp th riboflavin bng cch cho php n tn ti lu hntrn cc b mt hp th.

- Mt s thuc c nh hng tiu cc n s hp th v chuyn ha riboflavin.Penicillin th ch ca riboflavin khi cc protein lin ht ca n, v th ngn cn qutrnh vn chuyn riboflavin ln h thng thn kinh trung ng, probeecid c ch s hpthu ng tiu ha v iu tit ng thn riboflavin.

- Cc vitamin B-complex:Bi v cc flavoprotein u tham gia vo qu trnhchuyn ha mt s vitamin khc (vitamin b6, niacin, v acid folic), s thiu ht trmtrng riboflavin c th nh hng n nhiu h thng enzyme. S chuyn i t dngt nhin thnh dng coenzyme ca vitamin B6 pyridoxal 5-phosphate (PLP), lun ihi s c mt ca cc enzyme ph thuc FMN pyridoxine 5-phosphate oxidase

(PPO). Cc nghin cu ngi ln tui ch ra nhng tchr s v tng tc giavitamin B6 v tnh trng dinh dng ca riboflavin. S tng hp ca cc enzyme ccha niacin, NAD v NADP, t cc amino acid, tryptophan, i hi s c mt caenzyme ph thuc FAD. S thiu ht nghim trng riboflavin c th lm gim schuyn ha tryptophan thnh NAD v NADP, lm tng nguy c thiu ht niacin.

- Mehtylene tetrahydrofolate reductase (MTHFR) l mt enzyme ph thucFAD, ng vai tr quan trng trong vic duy tr coenzyme folate c hiu tomethionine t homocysteine. Cng vi cc vitamin B khc, lng riboflavin n votng s gn lin vi mc homocysteine trong huyt tng gim.

- S thiu ht riboflavin lm thay i qu trnh trao i st ca c th. Mc d cch ny cn cha r rng, cc nghin cu trn ng vt cho thy rng thiu htriboflavin c th lm gim s hp th st, tng s tht thot st rut v gim vic sdng st tng hp hemoglobin. ngi, ngi ta thy rng, tng hm lngriboflavin trong ch dinh dng lm tng mc lu thng ca hemoglobin, v vyci thin c tnh trng ca nhng ngi mc chng thiu mu do thiu st.[18]

2.2.1.8 Vitamin C:

Vitamin C l mt thut ng chung c s dng cho tt c cc hp cht c hotng sinh hc ca acid ascorbic, l mt hp cht n gin, cha 6 nguyn t cacbon,

gn vi ng glucose, n nh trong mi trng acid, d b ph hu bi qu trnh oxyho, nh sng, kim, nhit , c bit vi s c mt ca st hoc ng. Dng oxy hoca vitamin C c bit n l dehydroascorbic acid (DHAA), cng c tnh hot ngca vitamin C.



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ferritin d tr trong gan, cng nh gii phng st t ferritin khi cn. Vitamin C cngh tr hp thu calci bng cch ngn calci b kt hp thnh phc hp khng ho tan.

S chuyn i t dng khng hot ng ca acid folic thnh dng hot ng l

acid hydrofolic v acid tetrahydrofolic cng c h tr nh vitamin C. Ngoi vic htr cho qu trnh hnh thnh, Vitamin C c th lm n nh cc dng hot ng ca acidfolic.

Hp th v chuyn ho

ngi, vitamin C c hp thu hng trng, ch yu theo c ch vn chuynch ng ph thuc vo natri. Khi tiu th lng nh di 100 mg, 80-90% lngvitamin C n vo c hp thu. Khi khu phn tng, hp thu gim xung 49% khu

phn 1,5g, 36% khu phn 3 g, v 16% khu phn 12g.

Hm lng vitamin C trong mu ti a l 1,2 n 1,5 mg/100mL vi khu phn

n 100 mg/ngy v gim xung 0,2-0,1 mg/100mL khi khu phn n di 10 mg/ngy.Nu tiu ho trn 100mg/ngy, hm lng vitamin C tng cao, lng tha nhanh chngc cc t bo m nm bt hoc bi tit ra nc tiu. Hm lng vitamin C cao trong cc m tuyn yn v tuyn thng thn, cao hn 50 ln so vi trong huyt thanh. cc m khc nh mt, no, thn, phi v gan cao hn t 5 n 30 ln so vi tronghuyt thanh. Lng vitamin C trong m c tng i thp, nhng do c chim mtkhi lng ln trong c th, nn c ti 600 mg vitamin C c d tr trong c ca mtngi c trng lng 70 kg.

Nhu cu khuyn ngh:

Nhu cu khuyn ngh cho vitamin C cn cha c thng nht. Mt s cho rngkhng nn cao hn liu phng bnh scorbut (10-12 mg/ngy). Mt s khc ngh 60mg/ngy hoc hn m bo cho cc m c bo ho vitamin C m khng gy ranguy c qu liu. Con s 60 mg/ngy nm trn ngng bi tit ra nc tiu 60-80mg/ngy, v lng vitamin C s dng vt ngng u b bi tit ra nc tiu.

Vi ph n c thai, cn thm 10 mg vitamin C/ngy so vi ngi trng thnh.B m cho con b trong 6 thng u cn thm 35 mg/ngy v thm 10 mg/ngy phn c thai.

B Y T 1997 a ra nhu cu khuyn ngh cho ngi Vit nam: tr


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C trong 10 pht un nu, trong khi phn l ch cn li 60%. Rau thn mm c chanhiu vitamin C hn rau thn cng. Rau b ho mt nhiu vitamin C trong qu trnh dtr hn rau ti.

2.3.2 Cc cht khong:Cc cht khong l nhng mi la cho cuc sng. Khng c chng, n gin l

chng ta s khng sng c. Khong cht l nhng thnh phn c bn ca tt c vtcht. N cng h tr cho mi kha cnh ca cuc sng t vic sn xut hormone vnng lng, tiu ha, truyn dn thn kinh v phn ng co c, cc iu chnh v pHchuyn ha, cholesterol v lng ng trong mu.

Cht khong a lng v vi lng khng cung cp nng lng cng nh khngphi l ngun nhin liu t chy ca c th, m l nhng cng c s dng cc chthu c v to ra nng lng. Cng vi vitamin v protein, cc cht khong c mt

trong enzyme v ng vai tr quan trng hon thnh chc nng sinh hc ca chtxc tc sinh hc ny.

C trn 100 loi nguyn t khong c tm thy trn tri t. 4 trong s , baogm oxy, hydro, carbon v nitrogen, to ng n 96% c th. 4 % cn li l cckhong cht khc. Lng khong cht c th ngi hp th vo mi ngy trung bnhkhong 1-5 gram, cn tng lng carbohydrate, protein v lipid l khong trn 500gram. Tc l cc cht khong ch chim trn 0,3% trn tng lng cht dinh dng, tuynhin li ng vai tr quan trng n mc, nu thiu chng, c th ngi s khng sdng c 99,7 % cn li. [ 24]

2.3.2.1 St(Fe)

L cht nhiu th 4 ca tri t,chim 4,7% lp v tri t.C th con ngichim khong 2,5-4g st,ph thuc vo gii,ging tui v kch thc c th,tnh trngdinh dng,mc d tr st

Chc nng

- Vn chuyn v lu tr oxy: St(Fe2+) trong cc Hemoglobin (Hb) v myoglobinc th gn vi oxi phn t(O2), ri chuyn chng vo trong mu v d tr trong c.St khng gn trc tip vi cc protein ny m thong qua nhn Hem.Mi phn t Hbgn vi 4 phn t oxi.Hb c trong t bo hng cu v lm hng cu c mu ,khi hng

cu ln phi s nh kh CO2 v nhn O2,ri cung cp O2 cho cc m ca c th.Myoglobin ch c mt cc gn vi O2,v nh vy mi phn t myogobin ch gn vimt phn t oxy.Myoglobin c trong c vn;chng c tc dng nh ni d tr oxycho hot ng.Chng s kt hp vi cc cht dinh dng gii phng nng lng choco c.



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- Cofactor ca cc enzyme v cc protein: St Hem tham gia vo mt sprotein,c vai tr trong qu trnh gii phng nng lng trong qu trnh oxy ha cccht dinh dng v ATP. St cng gn vi mt s enzyme khng Hem, cn cho hotng ca t bo.

- To t bo hng cu: Hb ca hng cu cha st,mt thnh phn quan trng chothc hin chc nng hng cu. Qa trnh bit ha t t bo non trong ty xng nhng cu trng thnh cn c st.Cn khong thi gian t 24 n 36 gi cho t bo rit h lin vng n hng cu trng thnh. Do hng cu khng c nhn nn chngkhng th sn xut nhng enzyme v cht hot ng cn thit cho ko di thi giansng.Chng ch c th sng c 120 ngy(4 thng). Khi hng cu cht,chng cchuyn n gan ty xng, lch, gi l h lin vng ni mc(reticuloendothelialsystem). Ti lch, st v protein ca hng cu st c ti s dng. St c gi ferritin v hemosiderin gan v lch c chuyn n ty xng to hng cu mi.

Phn cn li ca Hb c s dng to bilirubin,chuyn n gan v bi tit qua mt. Hp thu v chuyn ha:

c xy ra ch yu phn hng hi trng ca rut non. C hai dng st c thc hp thu theo nhng c ch khc nhau. Ngun ln nht l st khng Hem, chngkhng c gn vi phn Hem, c mt ch yu (chim 85%) trong cc thc phm cngun gc thc vt, dng Fe2+ hoc Fe3+. Dng st th hai l Hem, chng gn vi nhnHem,c trong thc phm ngun ng vt hemoglobin v myoglobin.

c hp thu,ngun st khng Hem phi c di khi thc n phn trnrut non thnh dng ha tan,sau chng c gn vi mt protein vn chuyn ging

nh Transferrin, i qua mng t bo thnh rut. Qu trnh gii phng st t do trongrut trc khi c hp th ph thuc rt nhiu vo cc yu t c th c ch hoc tngcng c mt trong thc n.

T l hp thu st khng Hem c th t 1% n 50%,t l nghch vi lng sttrong khu phn: v d hp thu gim t 16% xung 6,4% khi lng st khu phn tngt 1,5 mg ln 5,7 mg. Hp thu c hi qu hn vi nhng ngi b thiu st.St Hemc chuyn qua t bo thnh rut vn cn dng Hem. C nhng th th c bit t

bo thnh rut gip cho qu trnh hp thu ny.Khi st Hem vo t bo thnh rut sc chuyn ha nhanh chng vi s tham gia ca men Hem oxygenaza.St cchuyn vo ni d tr chung trong t bo. Do st c gn vi Hem trc khi c hp

thu vo thnh rut nn qu trnh hp thu ca st Hem khng ph thuc vo cc yu tnh hng c mt trong ba n. Duy c protein ngun ng vt blm tng hp thu stHem. Calci lm gim chuyn st hp thu t rut vo mu do c ch qu trnh vnchuyn ca st qua t bo thnh rut hn l vic c ch hp thu st vo trong t bo.Lng st Hem trong ch n t nh hng ti t l hp thu, lun trong khong 20-25%.



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Nhu cu khuyn ngh:

Lng st cn thit hng ngy b lng mt i, cho pht trin c nu bng sau:

Bng 2.16: Nhu cu st c hp thu (mg/ngy)

Nhmtui

Mt quaphn

Mt quanctiu,th, da

Mt quakinhnguyt

Cho phttrin

Cho cthai

Tng scn*

Nam trngthnh

N trngthnh

N c thai

0.7

0.7

0.7

0.2-0.5

0.2-0.5

0.2-0.5

0.5-1.0

1.9-2.2

0.9-1.2

1.4-2.2

2.8-3.2

Tr emN v thnh

nin

0.70.7

0.2-0.50.2-0.5 0.5-

1.4

0.60.5-1.0

1.5-1.81.9-3.7

*ch n cn 3-10 ln cao hn,ph thuc ngun v dng st s dng

2.3.2.2 Calci (Ca)

Calcium l khong cht c hm lng cao nht trong c th ngi. Trn 99%lng calcium trong c th c tm thy xng v rng, trong khi 1% cn li ctm thy trong mu v cc m mm. Mc calcium trong mu v dch ngoi bo phi

c gi trong mt gii hn nng rt hp m bo cc chc nng sinh l bnhthng. Cc chc nng sinh l ny l ti cn thit cho s sinh tn ca c th khi lngcalcium trong mu b gim thp nh vic ly i calcium t xng chuyn vo mu. Vth, ch n ung y calcium l yu t cn thit duy tr mt b xng khemnh.

Chc nng:



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- To xng: S hnh thnh xng c bt u t rt sm ngay t khi th thai vl mt hnh ng chc dn, to nn mt khun mu linh ng cc xng khc tp hpli. Khun ny chim 1/3 cu trc ca xng v cn rt mm mi cho n khi sinh ra,to iu kin d dng cho tr v m trong khi sinh. Khun xng ny bao gm cht xca mt loi protein c gi l collgen, n c bao ph bi phc hp gelatin gm

protein v polysaccaride c gi l cht nn. Sau khi sinh b xng tr ln di vrng ra v nhanh chng rn chc do s lng ng ca cc cht khong vo trong xng.Qu trnh ny c gi l calci hoc xng ho do cht to cng rn v cht khong cmt nhiu nht trong phc hp l calci. Vo thi im tr c th bc i c, bxng c calci ho nng trng lng c th.

Nhng tinh th khong c lng ng dn trong qu trnh xng ho l calciphosphate Ca3(PO4)2, c gi l apatie; hoc hn hp calci phosphate v Ca(OH) 2 -hydroxyapatite. V calci v P l nhng cht khong ch yu trong xng, nn vic cung

cp y 2 cht khong ny trong thi gian pht trin l cn thit.- To rng: Phn ngoi v gia ca rng c gi l men v xng rng c cha

mt lng rt ln hydoxyappatite, cht ny c mt dc theo chiu di cht proteinkeratin (trong xng l collagen). Qu trnh calci ho cc rng sa c bt u t thik bo thai khong 20 tun tui) v ch hon thin trc khi mc (khi tr c 6 thngtui). Rng vnh vin bt u c calcium ho khi tr t 3 thng tui n 3 nm tui,ngay t khi cn ang giai on to rng sa.C mt s trao i calci chm chp giamu v thn rng, c th c trao i gia calci nc bt v calci ca men rng. Thiuht calci trong qu trnh to rng c th dn n nguy c su rng. Mc d calci lthnh phn quan trng nht trong to rng, cng cn phi ch rng cht lng ca

rng ph thuc vo rt nhiu cc yu t khc.- Pht trin: Calci cn cn cho nhng chc nng khc ca t bo. Mt s nghin

cu Nht cho thy rng khu phn n ngho calci thng kt hp vi chiu cao thp.Mt khu phn ngho calci thng kt hp vi thp protein, mt yu t quan trng cho

pht trin c th v pht trin xng.

- Tham gia cc phn ng sinh ho khc: Vai tr ca calci trong qu trnh ng mul mt chc nng c bit r, qu trnh hnh thnh thromboplastin, thrombin, fibrin tini tn thng to cc mu ng cn s c mt ca calci. Nhng vai tr khc l vai trcalci trong vic dn truyn xung ng thn kinh, vo hp thu vitamin B12; vo hot

ng ca enzyme tu trong tiu ho m; vo qu trnh co c. Calci c n hng chcchc nng quan trng khc nhau, tuy nhin s thay i calci trong ch n thng tthy hiu qu sm do vic duy tr cn bng calci ca xng.

Hp thu, chuyn ho:

Hiu qu ca hp thu calci trong c th dao ng t 10 n 60%. Tr em angpht trin c th hp thu calci t 75%. Qu trnh hp thu calci phc tp v ph thuc



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nhiu yu t khc nhau: lng calci trong khu phn, nhu cu ca c th, la tui, gii,mt s thuc cng nh mt s cht dinh dng khc trong khu phn: lactose, protein,vitamin D. T l hp thu calci t l nghch vi lng calci trong khu phn. Ph nthng hp thu calci km hn nam gii, hp thu calci gim dn theo tui.

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Phụ gia dinh dưỡng-Tuyet Anh 06H2A