View
214
Download
0
Category
Preview:
Citation preview
OODSIM'2010 BRAGANÇA, PORTUGAL· JUNE 24-26, 2010
JUNE 24-26, 2010
CIMO RESEARCH CENTRE BRAGANÇA, PORTUGAL
ORGANIZED BY
EU'Dpron r«h".I~I1I"HI.""
lN COOPERATION WITH
.AiL
1TiiIT UNIVERSITEIT
GENT
6TH INTERNATIONAL CONFERENCE
ON
SIMULATION ANO MOOELLlNG
lN THE
FOOO ANO BIO-INOUSTRY
2010
FOODSIM'2010
EDITED BY
Vasco Cadavez
and
Daniel Thiel
JUNE 24-26, 2010
BRAGANÇA,PORTUGAL
A Publication of EUROSIS-ETI
Printed in Ghent, Belgium
6th International Conference on Simulation and Modelling
ln the Food and Bio-Industry
BRAGANÇA, PORTUGAL
JUNE 24-26, 2010
Organised by
ETI The European Technology Institute
CIMO Mountain Research Centre, Bragança
Sponsored by
Cámara Municipal Bragança
CoraNE
CVRTM
EUROSIS The European Simulation Society
Ghent University
INATEL Fundação
IPB Instituto Politécnico de Bragança
Escola Superior Agraria
Mirandela Municipio
Hosted by
CIMO
Bragança, Portugal
III
EXECUTIVE EDITOR
PHILIPPE GERIL (BELGIUM)
EDITORS
General Conference Chair
Vasco Cadavez Mountain Research Centre (CIMO)
ESA - Instituto Politécnico de Bragança, Campus de Santa Apolónia, Apartado 1172, 5301-855 Bragança,
Portugal
General Program Chair Daniel Thiel , University of Paris 13, Sciences Economiques
et Gestion , Paris, France
Local Programme Committee Joana Amaral, ESTiG-IPB, Bragança, Portugal Vasco Cadavez, ESA-IPB, Bragança, Portugal Elsa Ramalhosa, ESA-IPB, Bragança, Portugal
International Programme Committee
Simulation in Food Engineering and Processing Lionel Boillereaux, ONIRIS, Nantes, France
Cedric Brandam, INPT-ENSIACET, Toulouse, France Matthew de Roode, NIZO, The Netherlands
Jean-Yves Monteau, ONIRIS, Nantes, France Alcina Morais, ESBUCP, Porto, Portugal Cristina Silva, ESBUCP, Porto, Portugal
Olivier Vitrac, INRA-UMR FARE, Reims, France
Simulation in Food Sciences and Biotechnology Francis Buller, UCD, Dublin , Ireland
Enda Cummins, UCD, Dublin, Ireland Ricardo Dias, ESTiG-IPB , Bragança, Portugal
Carla Fernandes, ESTiG-IPB , Bragança, Portugal António Peres, ESA-IPB, Bragança , Portugal
José Teixeira, UM, Braga, Portugal
Methods and Tools Applied to Food and Bio-Industries Kristel Bernaerts, Katholieke Universiteit, Leuven, Belgium
Paulo Cortez, UM, Guimarães, Portugal Pierre-Sylvain Mirade, INRA-Theix, St Genes Champanel le, France
LeQn Rothkrantz, Delft University of Technology, Delft, The Netherlands Xavier Serra, IRTA, Girona, Spain
IV
International Programme Committee
Methods and tools applied to Food Quality and Safety Evaluation Manuel Rui Alves, IPV, Viana Castelo, Portugal Joana Amara!, ESTiG-IPB, Bragança, Portugal
Ursula Gonzales Barron, University College Dublin, Food Science and Veterinary Medicine, Ireland
Vasco Cadavez, ESA-IPB, Bragança, Portugal Luis Dias, ESA-IPB, Bragança, Portugal
Isabel Ferreira, ESA-IPB, Bragança, Portugal Isabel Mafra, REQUIMTE, Porto, Portugal Beatriz Olivei ra, FF-UP, Porto, Portugal
José Alberto Pereira, ESA-IPB, Bragança, Portugal Isabel M. Vica riao, University of Sevilla, Spain
Miguel Vilas-Boas, ESA-IPB, Bragança, Portugal
Simulation in Functional Foods Lourdes Amigo Garrido, CSIC, Madrid, Spain
Gianpaolo Ruocco, University of Basilicata, Potenza, Italy
Simulation in Food Production Management, Economics and Traceability Martin Cloutier, UQAM, Montreal, Canada
Magda Aguiar Fontes, Faculdade de Medicina Veterinária , UTL, Lisboa, Portugal Martin Grunow, Technical University of Denmark, Lyngby, Denmark
Vincent Hovelaque, INRA, Rennes, France
Sustainable Food Production Albino Bento, ESA-IPB, Bragança, Portugal
Cesar de Prada, University of Valladolid, Spain Federico Ferreres, Cebas-CSIC, Murcia, Spain
Bjórn Johansson, Chalmers University of Technology, Sweden Jaime Pires, ESA-IPB, Bragança, Portugal
Manuel Ângelo Rodrigues, ESA-IPB, Bragança , Portugal
Innovation in Traditional Food Products Maria J. Alcaide , University of Sevilla, Spain
Leticia Estevinho, ESA-IPB, Bragança, Portugal Dietrich Knorr, Technische Universitat, Berlin , Germany
Toomas Paalme, Tall inn University of Technology, Tallinn, Estonia Elsa Ramalhosa, ESA-IPB, Bragança, Portugal
v
© 2010 EUROSIS-ETI
Responsibility for the accuracy of ali statements in each peer-referenced paper rests solely with the author(s). Statements are not necessarily representative of nor endorsed by the European Simulation Society. Permission is granted to photocopy portions of the publication for personal use and for the use of students providing credit is given to the conference and publication. Permission does not extend to other types of reproduction nor to copying for incorporation into commercial advertising nor for any other profi t-making purpose. Other publications are encouraged to include 300- to 500-word abstracts ar excerpts from any paper contained in thi s book, provided credits are given to the author and the conference.
Ali author contact information provided in this Proceedings falis under the European Privacy Law and may not be used in any form , written or electronic, without the written permission of the author and th e publisher. Infringements of any of the above rights will be liable for prosecution under Belgian civil or criminal law.
Ali articles published in these Proceedings have been peer reviewed
EUROSIS-ETI Publications are ISI-Thomson and INSPEC referenced
For permission to publish a complete pape r write EUROS IS, elo Philippe Geri!, ETI Executive Director, Greenbridge NV, Wetenschapspark 1, Plassendale 1, B-8400 Ostend Belgium
EUROSIS is a Division of ETI Bvba, The European Technology Institute , Torhoutsesteenweg 162, Box 4,8-8400 Ostend , Belgium
Printed in Belgium by Reproduct NV, Ghent, Belgium Cover Design by Grafisch Bedrijf Lammaing , Ostend, Belgium
EUROSIS-ETI Publication
ISBN: 978-90-77381-56-1 EAN: 978-90-77381-56-1
VI
r(s). ·n is it is ling are ded
t be 1er.
00
PREFACE
Dear colleagues,
Welcome to the 6th Inlernational Conference on Sirnulation and Modelling in Food and Bio Industries (FOODSIM'2010), which is held in Bragança, Portugal from 24 to 26 June 2010.
The FOODSIM'2010 brings together researchers, food experts and industrial users to present the state-of-art sirnu lation research in the food industry, new research results and lo exchange ideas and experiences about the modeling and simulation tools used in the food industry.
The main theme of FOODSIM'201 O is: "Sirnulation applied to food processes, quality, safety, and suslainability", and the success of the conference is already assured, as can be witnessed by the quality and scientific rigor of the 47 published papers. We also take Ihis opportunity to challenge the researchers altending lhe FOODSIM'20 10 to produce a seed for a FP7 project to be submilted at the nexl call for pro posais, which is expected to open nexl July.
We present our recognition for the inestimable collaboration that we had in the FOODSIM'2010 organisation by Prof. Joana Amaral and Prof. Elsa Ramalhosa , and io ali the reviewers for their professional work in the papers evaluation. We also presenl our recognition to ali Institutions Ihat contributed to prepare a pleasant social programme for FOODSIM'2010.
Finally, we wish you ali a pleasant staying in Bragança and we are sure thal you will have the opportunity to be delighted by the Portuguese hospitality.
Prof. Vasco Cada vez, Moutain Research Centre (CIMO), ESA - Instituto Politécnico de Bragança , Bragança, Portugal
Prof. Daniel Thiel , Universite de Paris 13, UFR Sciences Economiques et Gestion, Paris, France
VII
PHYSICAL CHARACTERiSTlCS AND DRYI NG KlNETiCS OF PORTUCUES E 'Longal' CHESTNUT
Elsa Ramalhosa Hugo Lamas
Jose Albe rto Pereira
C IM O, Escola Superior Agrária, Instituto Politécnico de Bragança,
Campus de Santa Apolónia, Apartado 1172, 5301-855 Bragança, Portugal
E-mail : e lsa@ipb.pt; aI9759@alunos.ipb.pt; jpereira@ ipb.pt
KEYWORDS Chestnut, Physical charactcristics, Drying kinetics, Fick's second law, Apparent diffusivity.
ABSTRACT
Chestl1ut is a fruit of great impOItance in Portugal, being generally sold fresh or frozcn. Alternative products may be obtained by hot air drying. The presem work is 00 lhe dehydrati on behavior af Portuguese <Longal' chestnul, lhat is the 1110s1 used in industry, Diffcrent models for representing the variations af \Valer content anel drying rate along time were tested successfully. As expectecl, higher temperalures corrcspond to faster drying processes. lhe apparcnt diffusivity was predicted by Fick ' s second law equalion, and ii ranged from 1.25x I O-II n,';s, at 20"C, to 8.42x I O-III m' /s, at 100'C.
INTROO UCT ION
Chestnut (Casfal1ea sativa) has always becn used in human
feeding. Nowadays, chcstlluts have high eCOnOl11lC
importance in Portugal because this country is a11 important
exporter of th is fmit , contribllting significant ly to lhe
cqui librium of Ponugucsc commercia l balance. CheSllll1t
production is more significant in the North of Portugal,
namely in Trás-os-Montes and Beiras regions, reaching the
highest commercial values and representing 86% of the
national product ion (INE 2008). ln 2007, for example, 7
774 ton ofchestnut wcre exported, originating € 14 844 000.
Portuguese variet ies of chestnut are of excel!ent quality.
Three Protected Origin Dcnominations have been
identified, namcly ChestnuI of lcrm Fria, Chestllut of
Soutos da Lapa and C hestnu t of Padre ia. Bcing a seasonal
product, lhe chestnut needs to be prescrved in order to be
sold as a fresh produce, 01' to be further processed.
Traditionally, chestnuts are left in warehollses at room
84
Alcina 1VI .IVI.Bernardo 1VI0rai s
CBQF/ Escola Superior de Biotecnologia, Univers idade Católica Portuguesa,
Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal
E-mail: abmorais@esb.ucp.pt
temperature, being cons1I111ed along lhe year by lhc local
families. This chestnut is known as '"castanha pilada"', being
dehydrated anel extreme ly sweet. On the contrary, in
industry chestnuts are stored under refrigeration until lhcir
salc as fresh producc, or they are frozen after pee ling.
ln industrial chestnut prescrvation, two main problems have
been detected. These are related to weight losses (duc to
dehydration of the Iresh ehestnut) and to the dcvelopment
of microrganisllls, namely fungi produccrs af micotoxins,
such as aflatoxins: which present an eminent dangcr for
public health, as the latter are considcred can.:inogenic,
hepatotoxic, and tcratogenic. Besides, there is a need of
finding altcrnatives for chestnuts with low quali ty to the
fina l cons u111ers, such as sll1all fruits, tha t are OftC Il
discarded, and of developing innovative produets based on
chestnut, allowing the diversification of products and the
developrnent of others able to be incorporated imo a wide
var iety of food stuff.'i, sllch as chestnllt fiour. T herefore, ii is
Df great importance to find alternative prcservalio ll and
processing technologies.
laking imo account lhe popular knowledge, the
dehydralion of chestl111t seems to be a promising
technology, as chestnll ts cOllld bc storcd fo r longe r periods
withollt the problem of [ungi development. Rccently, some
illtcrcsting stlldies on drying of chestnut have been
perfomled, involving Ncw Zealand (Cletus anel Carson
2008), Italian (Attanasio ct aI. 2004), Turkish (Koyuncu et
aI. 2004) and evell Portuguese (Guiné and Fernandes 2006)
varieties. ln relation 10 this last work, three Portllguese
varieties were analyzed, namely ' Longal', 'Martainha' and
·Viana·. which were subjected to thl'ce drying temperaturcs;
70, 80 and 90°C. The firs l lwo variet ies showed better
drying features than the last. Nevcrtheless, the use of lower
temperatures may also be promising. Moreover, variability
of the characteristics af chestnuts harvestcd in different
l
years might have an impol1ant role on Iheir drying
behaviour a nd be a factor thm musl be taken into account.
ln fact ~ chestnut prodm:ers refer that the yea r 2009 was not
a good year fo r chestnut production. due to the lack of
waler during the maturat ion stage, orig inating sma!! fru its .
Taking into account these aspects, the aims of thi s work \Ve re : i) lO determine some physical properties of ' Long:1l' chestnuts , which is one af lhe mosl used in industry (due to the eas iness of peeling and to the pu lp not bcing too sectioned). collcered in the year 2009: ii) to s tudy and finei e mpirical 1l10dels lhat \Vi II a llow lhe est imation of lhe drying rates Df these chestnuts when subjected to different drying tcmperatures (20, 40, 50, 65 , X5 and 100°C); iii ) to evaluate the eftect of drying 011 chestnuts dimcns ions; iv) to evaluate the aelequacy of the Fick 's second law to express lhe dry ing process; v) to estimale lhe apparem diffusivity of water in this Portuguese chcslnul variely.
MATERIALS ANO METHOOS
P0I1uguese <Longal' cheslnuts \Vere supplied by a local producer of Trús-os-Montes regian, North of POrlugaJ , being harvestcd in Nove mber 2009. When aniving 10 the laboratory, chestlluts were carefully observed and the ones lha! were rotten were discarded.
Chestnuts were individu"lI y weighcd "mi their elli psoid axis dimensions ((I: length; h: width; c: thickncss) determined. To perfonn lhe drying exper iments, chestnuts \Vere placed in a convection oven (Binder, Germany) at 40, 50 , 65, 85 aml 100°C. To perform the assay aI 20"C, chestnuIS were left ai room tempera ture. ln each experiment, chestnuts \Vere put insidc the oven in several Petri di shes. Each Petri dish cantained 5 c hestnu ts. One Petri dish was removed ai defined time moments, the fru its being ana lyzed aga in (weighl anel e llipsoid aX IS
d imensions) \V ith and w ithout outer pceI, in order to evaluate the shrinkage.
At the beginning of each experiment, the dry matter content o f the chestnuts used in lhe assay was dctermined by drying fi ve e hesl llll ts ai 105°C 1I1lli l lhe samplc weight reached a steady value. The dry-basis moisture conlcnt (W, kg af \Vater! kg of dry matter) was determined for eaeh chestnut. At each time moment , the ave rage , sta ndard deviation anel cocffic ient of variation we re detc rmined for lhe fi ve chestnuls removed.
ln order 10 evaluate lhe sui'tability of approaching the chestnuts to sphercs in lhe diffusion eq uation, the diameter of chestn uts \Vas dc rcrmined a ftcr immersion of twenly ehestnuts in \Vater and measure ment o f the vo lume of \Vate r disp laced. These values \Ve re late r compared with lhe arilhmetic (Da) aml geometric (D.IJ average di amcters detennined by equat ions ( I ) and (2), respectively (M ohseni n 1970; Güner 2007; KJ!lçkan and Gliner 2(08 ):
85
a+b+ c Do = , -,
( I )
Dg = Va X b X C (2)
ChestnuI sphericily (CP) was a lso evalualcd by equation (3) (Mo hsenin 1970; Güner 2007; Klhçkan and Güncr 2(08):
Vax b xc (/) = (3) b
, considering h lhe biggest dimensiono
ORYING CURVES COMPUTER FITTINC
For a li lhe assays, lhe drying curves (W versus lime)
fa ll owed a s imi lar partem, expressed by í.ln exponemial
function ofthe forl11 :
W = y+ A x eH n (4)
whcrc y , A anel k were parameters of the mode!.
ln o rde r lO determine the d rying rales ( a;~ ). the method
of lhe approximatiol1 of the derivat ive to ti nite differences was used (Guiné and Fernandes 2006) :
For t = I {)
(a; )= (first -order forward finitc
diffe rcnces) (5)
For / = / , (i = I . ... , N-I )
(aw)= W'+I - W,-I aI ' i +I - ! i - 1
(second-o rdc r centred finitc
di fte rences) (6)
For t =t,v
(aw) = W,v - WN _1
aI 'N - t N- I
(first -order backwa rd fin ite
diffe renees) (7)
A lincar and a s igmoid func lioll (Eq . 8) \Ve re used to
ex press lhe relat ionship e ncountered betwee n thc d rying
rate an el lhe l110isture content.
_(a:)=y+ (~l I +e ii
(8)
Ali the modcls presented, with exception of the linear, \Vere
obtained after using the nan-linear regression af the SPSS
software package.
The quality af ali modc1s was evaluated by the conelation
coefficicnt (r), reduced chi-squarc (Z2), mean bias error
(MBE) and root mean square errar (RMSE) (Guiné and
Fernandes 2006), determined by the following equations:
l N , I( ), - - -- V . -V -X - N . exp.1 f1r",i.1 - 11 1=1
(9)
MBE-_If(v-v) - ~ pred.1 cxp.i
N i= 1
(10)
RMSE= (lI) l N
_'\'(V . - V ), N f1 pred./ cxp.i
where Ve'\JJ.I and VI"-L'd,i are the experimental and predicted
values for the observation i; N is the numbcr af
observations; and 11 the number af parameters in the model.
The higher the vaI ue of"r" and the lower the values of/.
MBE and RMSE, the better the model fitted the
experimental results.
RESULTS AND DISCUSSION
Physical Properties of Portuguese 'Longal' Chcstnuts
Table I shows some physical properties Df the 'Longal '
chestnuts used in al1 drying assays. The dimcnsions of
ellipsoiJ axis ar chestnuts (a, b, c) varied within the ranges of 2.62-2.82, 3.10-3.29 anel 1.69-1.9 1 cm, respectively,
corresponding to variatian coeffícients less 1ha11 7.9, 6.4
anel 16.4%. The arithmetic anel geometric mean diameters
of chestnuts varied between 2.47-2.66 anel 2.39-2.58 cm,
respectively, corresponding to variation coefficients less
than 6.3 anel 7.1%, respectively. The low values obtained
for the variation coefficients~ \Vith the exception af
dimension c, that was the most difficult to measure, are
indicative of the existence of homogeneity among the
chestnuts used in ali assays.
ln terms of chestnut sphericity, this parameter varied within
the range of 76.9 to 79.2%, indicating that chestnuts might
be approximated to spheres.
86
When comparing the dia meter (D, results not shown)
detennined by immersion in water (considering chestnuts as
spheres) with D" or Dp" detennined by equations (12) and
( 13), respectively, linear relationships were encountered
between both parameters, namely:
Da = 0.7707 X D + 0.7304 (1=0.922) ( 12)
D, = 0.8139 X D + 0.5451 (1= 0.916) ( 13)
These reslllts indicate that either Dg or Da may be llsed to
estimate the diameter af 'Longal' chestnuts when it is
intended to approach them as spheres.
Drying curves of Portuguesc 'Longal' chestnuts
The experimental points dctcrmined along the drying of
'Longal' ehestnuts at 20, 40, 50, 65, 85 and 100°C are in
Figure 1. ln each graph the prcdicted points obtained in the
fits by lIsing Eq. 4 are also presented, as well JS the model
cqllation and the correlation coefficient.
Figure 1 shows that the fíts to lhe experimental data at 20,
40, 50, 65, 85 and 100°C are good, with eorrelation
coefficients ranging from 0.989 to 0.998. Thc 1..2, MBE and
RMSE values were also low, varying between 3.05x 1 ()"I
aml 9.87xIO·", _6.77xI0·4 and 1.69xI0·2 and 1.59x10·' anel
2.79xI0·',respectively.
Thc drying rate vallles determined by derivation of Eg. 4
are in Figure 2, with correlation coeffícients ranging from
0.863 to 0.969. The quality of lhe model is quite good
taking into account the similarity with the experimental
data, and the 'l, MBE and RMSE values, which were low,
between 5.43xI0·H and 5.28x I 0 .. 1, -2.49xI0·' and 3.71xI0·3,
2.21 x I 0-4 anel 2.07x 1 0.2, respectively.
By observing the dtying rate curves obtaineel, no constant
rate period was observeel (Figure 2). Higher temperatures
corresponded to taster drying processes, which is reflected
on the incrcasing dehydration constants: 0.003 for 20°C,
0.019 for 40c C, 0.029 for 50°C, 0.062 for 65°C, 0.142 for
85°C. aJ1(1 0.189 for 100°C.
ln terms of the relation between drying rate curves anel
moisture contcnt, both linear and sigmoidal (Eg. 8)
functions seem to represent well the experimental data
(Table 2). The cOITelation coeffieients of both models
varied between 0.902-0.956 and 0.927-0.967, respectively.
The i, MBE anel RMSE valucs were low again, varying
between 5.27xl O·H and 3.86x 1 0.4, -2.57xHr' and 1.86x I 0.3
,
l
aml 2.1 7x I0·' and l.77x I O", for the li near model, and
belween 4.09x I 0.6 and 2. 76x I O", -1.30x 1 O·' and 1.50x 1 0.3,
and 1.84x I 0.3 anel 1.50x I O", for sigmoidal model,
respecti ve ly.
Tablc 1: Phys ical properties or'Longal' chestnuts used in the dry ing assays'.
Temperature of a b c t he assay (0C) (cm) (cm) (cm)
20 2.75+0.20 3.20+0.15 1.7 1+0.28 40 2.72+0.20 3.23 +0. 19 1.86+0.27
50 2.62+0. 17 3. 10+0. 16 1.69+0.22 65 2.76+0.20 3.26+0.21 1.9 1 +0.27 H5 2.67+0.21 3. 16+0. 18 1.74+0.24
100 7.82+0. 17 3.29+0. 17 1.88+0.29 + Results me lhe dverages of the detcrmlnatlOll s...:.... Stcl ndard devi3tlon.
1.0
O,S o
1 , o.c, ~.
;: o., ~ ~~ ;: 0.2
:: 0.0
-0.2
"
1.0
I o., o
1 0.6 j ,' ~
OA
~
;: 0-1
:: 0,0
I -0.2 , o
Drying Curve at 20"C
o E ~pt:rimcnt~ l U;IW
• Modcl
---~---~
!
lllU 2I)() 3011 400 suo T imc( hours)
Drying C urves a t SO"C
".'"", ~.I= O.O .. UI+O. 765 *('(·O.Ql~. ' ''''1"'1 , - 0.997
600
r f f ! o E .'r~rimcntal dat;l
. I .... loocl
~ t ~ ~ • ! ! f t , ,
211 60 ' 00 l ::'.tJ
T ime (hollrs)
1.0
O.R
1 o., ,. ~ ;: 0.4 , ; " ;: 0_2
:: 0.0
·0.2 100
1.1)
0'
1 , O.,
,1 ~
" 0.4 ,
i 0.2
:: 0.0
..IJ.2 14ft
I •
O
I • i i
o
D" DK (cm) (cm)
2.55+0. 15 2.46+0. 17 2.60+0.16 2.53 +0. 18 2.47+0. 12 2.3 9+0. 13 2.64+0. 15 2.57+0. 16 2.53 +0.16 2.45+0. 17 2.66+0. 15 2.58+0. 16
Oryi ng C urve at 40"C
t
,o
\V " ,nol. l " U.112+0.620*c-1·0.0 1'" ""'P"I r = IJ .9H9
50 ' 00 15U
T illle (hulIrs)
Dr)' ing Cur'ves at 65UC
\" ••. ,1,1 = 0.024+U.757·,,1·0.1ó1 . , .. ", •• ) r "' U.993
f § •
20 lO 41' T im c- (holl rs)
(P (%)
76.9+6.0 78.5+4.4 77. 1+4. 1 79.2+4.6 77.4+4.0 78.7+4.6
o [ XflCTIIllcnt al dala • Mod c-I
2()()
o E~ pcrilllc nt al dat ;)
• Modcl
• !
'O
250
Drying Curves at 85°C Orying Cnrves at IOO"C 1.0 - --- --- -'-- - - - - - - - - - - ---, 1.0
O.S O
• , 0.6 ! • ,
" ~
OA
• g 0.2
:: (LO
-0.2
O
W """,,1= 0. 11 (o.j.0.687*('1 ·0, I') 'l<mpo)
r = 0.994
f
'O 15 Ti rnc(hou rs)
o Experimental data
• ~l (l dc l
• 'I f
,o 25
1 • O.s -100
~ 0.6
i , , .1
OA
:. 0.2
0 .0
.().2 _
O
' . •
\ " ",,~,.I == U. 03:Õ+O.1I05*el·0.11O • '''''I"') .·= 0.996
• •
" T im"lhuurs)
Figure l: Drying data of ' Longa l' chestnuts at 20, 40,50,65, 85 and 100°C.
87
o [r;pcrimcl1tal data • Mudei
l O 12
0.0025
:.. 0.0020 o ;' • o :. . ~ i 0.00 15
, 0 .00 10 " " ~ 0.0005 .,
0.0000
Drying Rate at ZO"C versus Time
o
•• o
-1I\\'/dl",,,,ld = 0.0018*l,I·I,U.1 ' "o'p")
r - 0.92 1
i.
o Exp~ri !l1c n t;l 1 d:\ln
' MoJcI
o ... °oo~" ••• ,~
o o o o
0.111 5
I • 11.0 ' 0 I • o
IUlOS
0 ,01111 I
-o.uns
Drying Rate at 40"C versus Time
-d\Vlul,,",<ld '" 0.0 I 18*cl·U.U1". '''''I'''' r - O.9 IH
o o
o • • • o o o • o o o
o o o
o EX1,~rimcnt;L l dal:t.
' Modcl
o
o
" III{) :wn 31KI 5l1li 7011 " sn ,ou ,so 2011 250
O.()~S
-=,i:: O.o:w o D
·t ~. 0.01 5
!!: , (1,1110
:t (1 ,005
~ O.IKMI ., ·O.()O~
"
Time(h,,"")
Drying Rate at 50"C versus Time
20
- d\V/dl ~,,"'1 '" O.0222*l~·8.V : ~ , '~'~I""
r = O.9~
• o • o
o
o E~p~nm~ntnl ti nia
, Mod cl
~ • c: o D • ~ e
o o o
<lO CiO !lO Timc lh"urs)
120 140
Drying Rate at 85"C versus Time 0. 12 ----::.......:::-------- - - ------,
:::: O.HI -=: • f, o •
O,O!!
-d\\'/dl,,",d .-l '" o. o~n6* c" '· ' ~:· "" "1"'1
r oo 0.91'19
~ ~ ~.
" ~ '" ~ ~
~ .,
(l ,050
11.0411 o ~ o
(UI)U
(),O ~(I
n.Ol 0
II .OUO
· O.OIU
" 0. 1(,
• ,. ;::: 0. 14 • ,
-=~ o' r 0.12 100 o , o
Timc(huIIN)
Drying Rate at 6SnC versus Time
o
-d\\'ldt .... d,1 '" 0.0-169*,,1 · •.•• 1, "'~I··)
1" - 11 .1) 12
o o
o o
o
o
"' 20 30 ·10 Tim" (hn urs)
o Exp.:ruIlCIII ;11 IIJ ta
• ~'I ()dd
o o
o
,,,
Drying Rate at IUO"C versus Time
o .(I\"/uln,o~.I "" O.l;;Z~~" 'O. ,~" " .. ~) r "" U.1-I63
6"
" O' é o. "
. o
o Experimental dnla
' Modd ~. 0. 10
1," o 1 ·.~ p",nl1lclII:t.1 lI:t.l:l o , (1.114
" ~ 0.02
~ (U)O
-0.02
o
• o • •
o o
lU " 20 25 Timc (lloufli)
~ O.UK , ~ 11.01'1
~ 0.04 ~ "1 0.U2
n.OO II
• o
4
o
o
o
o
6 , Tim" l llours)
Figure 2: Drying rates of 'Longal' chestnllts at 20, 40, 50, 65, 85 and 100' C.
• tI.'l odd
o o
o • lU "
Table 2 : Linear and s igmoidal models for the drying rates in function of moisture contento
Model T("C) 1110l1eJ Pal"U11lel erS Corre/fIliou Coe{ficielll (r)
Linear mo dei 20 A ~ -0.0005; B ~ 0.0032 0.924
(8Wi 40 A - -0.002; B - 0.01 83 O.90X - \& J = A +B x W 50 A - -0.0011: B - 0.0277 0.952
65 A ~ -0.0004; 8 ~ 0.058 0.906 85 A - -0.0 114; 8 - 0.1266 0.956 100 A - 0.0089; B - 0.1447 0.902
Sigmoidal model (Eg. 8) 20 Not adequate --
(8W ) A 40 Not adequate --50 y- -O.OOI ; A - 0.023: 13 - 0.158; C - OA02 0.957 - & = y+ [ C-IV ) 65 Y ~ 0.006; A - 0.03 7; 8 - 0.059; C - 04 00 0.930
I + e H ) 85 y - -32.935 ; A - 33.963 ; 8 7.167; C - -24.724 0.967 100 Y - 0.034; A - 0.086; 8 - 0.059; C - OA27 0.927
88
I·'
Evaluatioll of the effect of drying on chestnuts
dimen sions
Drying at 40, 50. 65, 85 and 100"C did not cause signifi cant
changes in chestnuts dimensions, indieating thar the effect
of shr inkage may be neglected. ln fac t, lhe average
geometric diamcters of the chestnuts \Ve re ident icaJ at tbe
beginning and at the end of a I! assays (Table 3). Even ar high tcmperaturcs no significant reduction on ches tnuts size
was deteeled. Moreover, the fru it wilhout outer shell a fter
dry ing corresponded always to 76.5 - 80 .2% o f lhe frui l
wirh olltcr shell, no differences being detected among
drying expcrimcnts at different temperatures.
Evaluation of the adequac)' of Fick's second law to the
drying process
Assuming that chestnuts may be approximated to sphcres,
and considcring that lhe dry ing rate depeneis solely OIl the
moisture movement by diffusion witl1 in the chestnut, the
process might bc represented by lhe fo llowing Fick's
second law equation fo r non-s leady state:
aW. = D (a ' w+~xaw ) ( 14) aI "P ar' r ar
where D ilI' is lhe apparenl di t'fusivity, r is the radius and t is
time. Assuming uniform initial tlloisture content (Wo) and
that the internal mílSS transfer resiSlance is controlling oveI'
external resistancc, the analyti cal solution of Eq. 14 is the
fo llowing:
w- w ,. ( IS)
w -w o ,
where WL
• is the equili br ium dry-basis moisture contenl.
Considering tl1at only lhe first term is significant and W"
may be estimated by Eq. 4 for t--+", (W,. = y) , taking the
natura l logarithm Df each side of Eq. IS, the fo llowing
linear equat ion will be obtained:
(1 6)
89
Fitti ng lhe da la by Eq. 16, linear corre lations \Vere obtained
(Figure 3), wi th coefficient corre lat ions ranging between
0.947 and 1.000. These resulls indicale Ihat the assumpl ions
assull1cd seem to be adequale.
Estimation of the apparent diffusivitics of ' Longal'
chestnut variety
Taking into accoullt Eq. 16, lhe apparenl diffusivities of
Longal chestnu t may be determined by the following
equation:
s/opex R' Ir '
( 17)
Considering the slope for each temperature (Figure 3) and
the average radi us 01' lhe chestnuts, based e ither on DI! or
Da, lIsed in each assay, lhe apparenl diffusivitics obtained
for ' Longal' cheSlnut are in Table 4.
Table 4: Apparent diffusivi ties of water in 'Longa l'
chestnut.
Temperature D a p
("C) (m'/s) 20 1.25x10·' 40 6.53x I O'" 50 1.08x I O~ '"
65 2.89x I (r'" 85 5.24x I0·'" 100 8.42xI0·' "
W hen comparing thesc va lues with lhe ones repol1ed by
Gui né anel Fernandes (2006) for the same chestllut va ricty
dri ed at 70-90'C (4.45xHr" to 6.87x Hr' m' /8), lhe prescnt
results are one order of magni tude lower. T his might be
related to the \Vo rse quality o f lhe chestnuls uscd in the
assays, as the year 2009 was not adequate for a good qua li ty
of the nuts. So, in the future it woul d be interest ing to study
the ro le of the harvest year on the drying charactc ri stics of
chestnuts. Howevcr, lhe results determincd at 20-401JC
(1.25xIO· 1I to 6.53x IO· 1I Ill~/s) are in accordance to the one
determineel for lhe New Zealand chestnut vari ety "" 10 15" at
30'C (Cletus and Curson 2008), numely 5.l x IO·" m'/s.
Table 3: A verage geometric diameters of chestnuts detennined before and aftel" the drying assays.
Temperature Dg initial Dg final Dg jina] Dg final (without outer
" "
O.DO
-0.50
~ -1.00
~~ , -1.50
S ~
-2.00
o
("C)
40 50 65 85 100
'00
(with outer peel)
20D
2.50+0.22 2.40 +0.13 2.50 +0.19 2.39 + 0.22 2.54 : 0.10
20"C Time(hunrs) 300 400
(with outer peel)
2.45 + 0.19 2.34 + 0.11 2.40 + 0.18 2.32 + 0.23 2.43 : 0.09
500 flUO 700 o 0.00 +-
(without outer peel) peel) I Dg final (with outer peel) ("lo)
I. 93 + 0.22 78 .8 1.79 + 0.14 76.5 1.91 +0.15 79.6 1.86 + 0.2 1 80.2 1.89 + 0.10 77.8
40"C T iml'(hours)
50 100 150 200 250
. + +
- 1.00 I In(IW.W,. ~'(WwlV. l ) = -0,0032 t· 0.022 1 r " () ,,)9]
+ +
++ +.
+ ••••
+
-2.00 j • +
-3.00
-4.00
+
IIl ((W-Wd(W,,-IV,_J) = ·0.0156 I - 0.211 r = O.947
+
+ +
+ +
+
+
-2.50 '---------- ----------------" -5.00 _~ _ __________________ ..J
o 0.00
- I,O()
~ 6 -2.0U ::: g
-J.OO :: !
--"t.DO
-5.DO
o 0.00
-0.50
~~ -1 .00
i -1.50
" [ ·2.00
~ ·2.50
-3.00
-3.50
lO
+
50"C Time (huurs)
(,0 !lO 100 120
In( IV_\V,)/ IW" W, I) =- -U. (21)() 1+ 0.0251 r = O.'lX6
+ +
+ +
+ +
+
85"C Time (hours)
10 15 20
In((W-W,)I(W,, -W,)) = ·0.136 t - 0.0113 r = 1.000
140
+
25
o 0.00 ..
-1.00
~ -2.00
~ ; ·3.00
-4.(J()
65"C T illll'(hours)
10 20 30 40 50 (,0
-~------~--~--,
+ I,, \(W.W,).'(\\',, _W.)I = -O.()(i67 t + O,07ú4
.. r = 0.%2
+ + + +
+
+ +
+
-5.00 ------------------------"
0.00
-0.50
~ t -1.00
~ :::;; -1.50
~ -= -2.00 ~
-2.50
-3.00
o 4
100"C Time (hours)
III
II1{(W-W,}' I\~·.,_W. 1l = -0. 1')1·1 t ·! 0.0191 r · 0,990
+ +
+ +
+ +
" 14
+
Figure 3: In((W-WJ/(W,,-WJJ versus lime for the drying assays at 20, 40, 50,65,85 anel 100°C.
90
l
CONCLUS IONS
Thcre was homogenei ty al11Qng the chcstnuts used in the
dryi ng experiments. An exponc ntial empirical model fittcd
we ll the experimental drying data for severa I temperatures
between 20 0 e and iOO°C. Linear and sigmoid fun ctions
al50 fiU cd well lhe drying experimental rates.
Approximating chestnurs (sphericity being highcr than
77% ) to spheres, the apparcnt diffusivity predicted by
Fick's sccond law was bctwecn 1.25x I 0.11 m2/s. ar 20°C, to 8.42x 10'11> 01' /5, at 100"C
REFE REN CES
Atwnas io, G.; l. Cinquanta; D. Albanese; and M.D. Mattco 2004. "Effects of drying tC01peralurcs 011 physico-chemical propcrt ies af dried and rchydrated chestlllJls {Castanea salivar', Food Chemisuy. 88, 583-590.
Cletus, A.S.; and J.K. Carson 2008. "DI)'illg curves and apparcnl diffusivity of Ncw Zealand chcs tnut variety " tOI5"". .1olll"l/al of Foud Engil1eering. 85, 38 1·386.
Guiné. R.P.F.; aml R.M.C. Fel11undcs 2006. "Analys is 01' lhe drying kinctics 01' chestnuls" . JOl/mal of Food Engilleerillg, 76. 460-467,
Giiner. M. 2007. " Pneumatic convcying characteristics of some agricultural seeds" . JVI/mal af Food Engillcering, 80, 904-9t3 ,
INE 2008, "Estatisticas Agricolas 2007" (ISSN 0079-4 139), Klllçkan. A.; and M. Güncr 2008. "Physical propcrties and
mcchanicul behavior of olivc frllits (Dica cl/ropaca L.) under compress ion loading". Jmmwi of Fooel Eng;nccrillg , 87. 222- 228.
Koyuncu , T.; U. Serdar; anel I. ToslIn 2004. " Oryi ng charactcristics and energy requircment for dehydration of cheSlnuts (Cas/aneo SlU; I'C/ Mill )", )0/(1"1101 t?f Food
Engill(!cring, 62. 165-168. Mohscnin, N.N. 1970. Physical Propcr/ies oI Piam al/d Anill/al
Mafericlis. Gordon i.!nd Brcach Sciencc Publishcrs, Inc .. Nc\V York.
BIOGRAPHY
ELSA RAMALHOSA was bom in Oporto, Pot1ugaL She studied in College of Biotechno logy - Pot1uguese Catho lic Uni versity in Oparto, whcrc in 1995 she obtained hcr B.Se. dcgree in Food Engineering. Afterwards , she took her Ph.D. in Analytica l C hemistry in University af Aveiro, Portuga l. Since 2000, she is professor a f Transporl Phenomena at Instituto Politécnico de Bragança, Portugal.
HUGO LAMAS \Vas bom in Paços de Ferreira, Pot1ugaL l-Io studied at the Secondary School of Paços de Ferreira, where in 2007 he obtained his diploma. C urrcntl y he <lttcnds lhe 2nd Semeste r a f the 3rd yea r Df Faoel Engineering with success at 1nstituto Politécnico de Bragança, Portugal.
91
JOSÉ ALBERTO PEREIRA obtained his B,Sc, degree in Agricultural Engineering fram Universi dade de Trás-osMontes e Alto Douro, his M.Sc. in Qua lity Contrai fmm Faculdade de Farmácia of Uni vers idade do Porto and Ph.D. in Agricultural Sc iences fram Univers idade de Trás·os· Montes e Alto Douro. C urrently he is Professor at the Instituto Politécnico de Bragança, Portuga l. Hi s \Vo rk area compri ses the effec t of agricultural pract ices on qualily am! chemical composition of vcgetablc fooel proclucts. Hc is CD
author of 80 papers in re fereed international j ourna ls, integrate the edi torial board of fÚtlr refereed journals and has participated in several projects anel supervised different Ph.D ., M.Sc. and undcrgraduate students.
ALCINA M. M. BERNARDO MORAIS currently holds an appoi ntment as Coordinato r of Faod Engineering of the College of Biotechnology - Portuguese Cathol ic U niversily (ES B - UCP), She got her B, Sc, degrec in Chemical Engineering from University of Porto, Portugal , in 1985; her M, Sc" in 1986, aml her Ph ,D" in 1990, in FooJ Process ing fmm Ecole Nat ionalc Supérieu re des Industries AgricoJ es et Alimentaires o f Massy - France. ln 1990. she became Assista nl Professor at ESB . ln 1991 , she attc nded a Postharvest Technology course at Univers ity of California 111 Davi s - Californi a, EUA, and she pursucd a postdoctoral programme at Uni versity of Florida 111
Gainesville - Florida, USA, From 1999 to 200 1. she held an appaintment as Associate Sub-director af lhe Extension of the College of Bioteehnology in Caldas da Raínha (EESBC R - UC P), She is cO-lI mhor 01' 38 papers 111
rcfereed internati onal joumals. She is authorl cO·í:lUthor of 16 papers in non-peered in ternational journals, and 12 papers in national journals and technica l publicat ions. She has served as National Del egate for on EC COST Action, as member af corresponding Managing COlTIm ittee, and as Nationa l Coordinator for a EU CYTEO Act ion. She is responsible for the module Fruits and Vegetables af the EraslTIus Mundus Maste r Course 111 Fooel Scicnce. Technology and Nutri tion (SEFOTECR NUT), She hus been involved as a responsible paTineI' a r coordinator of national and inte rnation,,1 R&D projects (total of 5), Furtherl11ore, she supervised 8 externally funded research fe llowships, including 3 successfully cOllcluded Ph.O. theses and 2 M. Sc . theses. She a lso supcrvisec1 2 PostOoctoral programmes. She delivered 6 invited lectuTcs and 62 volunteered presentatio ns in professio nal meet ings \Vorldwide, has served in the a rganizati on or sc iemifíc committces of 5 national ~lI1d international symposia, aml has acted as invited revlewer of several refereed international journals.
Recommended