sn

a b

sitylaw Uzech

Coloured potatoesSnacks

of fthernthoererop

higher total polyphenol and anthocyanin content. Snacks produced with coloured our had 23 timeshigher antioxidant activities, 40% higher contents of polyphenols, attractive colour and better expansion

hin thregardics. Pel

conditions to obtain a half-product of approximately 1112%mois-ture equally dispersed throughout the pellets volume. To obtainready-to-eat products a thermal process, such as frying or baking,is necessary. During that process, the pellets expand, increasingtheir volume 38 times and the typical porous, light structureand crispy texture of the nal product is created (Lusas &Rooney, 2001).

can also pg to food q

for instance by the preventing fat deterioration in fried proPotatoes are known as one of the richest sources of antio

compounds in the human diet. The main antioxidants are ponols, ascorbic acid, a-tocopherol and b-carotene. In addition, theantioxidant activity of patatin, a tuber storage protein, has beeninvestigated (Hillebrand, Naumann, Kitzinski, Kohler, &Winterhalter, 2009; Lachman, Hamouz, Orsk, Pivec, & Dvorak,2008). Polyphenols are the largest group of plant componentsand can be divided into phenolic acids, avonoids, stilbenes andlignans (Manach, Scalbert, Morand, Remesy, & Jimenez, 2004). In

Corresponding author.E-mail address: agnieszka.nems@wnoz.up.wroc.pl (A. Nems).

Food Chemistry 172 (2015) 175182

Contents lists availab

he

lseextrusion technology. Pellets of approximately 2030% moisturecontent are subjected to a drying process under mild temperature

(Pompella et al., 2014). However, antioxidantsimportant role in food technology by contributinhttp://dx.doi.org/10.1016/j.foodchem.2014.09.0330308-8146/ 2014 Elsevier Ltd. All rights reserved.lay anuality,ducts.xidantlyphe-small, have large expansion, a porous structure and a crispy tex-ture; however, these properties can differ depending upon theraw material used. The specic physical and sensory features ofthese popular snacks are the effect of starch transformation duringprocessing. In the manufacturing of pellet snacks, a raw materialcontaining starch, such as potato starch, akes, granules or grits,are mixed with water, salt and optionally with other dough com-ponents, such as vegetable, cereal or legume our, semolina orgrits, and pellets are formed, usually with the use of low shear

dants within the organism or can be abolished during rst-passmetabolism in the intestine and liver. Among antioxidants ascorbicacid and a-tocopherol preserve their properties in the organismbut another phytochemicals, like polyphenols lose this functionas a result of the attachment of a functional group at exactly thosepositions of the molecule that are responsible for its antioxidantactivity. This is one of the reason why the referring total antioxi-dant capacity (TAC) of food, measured by different in vitro assays,to its importance for human health is to be discouragedAntioxidant activityPolyphenolsAnthocyanins

1. Introduction

Pellet snacks are well-known witproducts for having huge versatilityused and some sensory characteristcompared to control samples. The lowest losses of anthocyanins during snack processing were in snackswith our from the purple-eshed Blue Congo and red-eshed Herbie 26.

2014 Elsevier Ltd. All rights reserved.

e world market of fooding taste, raw materialslet snacks are typically

There is suggested by different authors (Brown, 2005; Lachman,Hamouz, Orsk, & Pivec, 2000; Yen & Chen, 1995) that antioxidantsnaturally presented in food have health-promoting and antiagingeffects in the human body. However, depending on the type of bio-active compounds they can be well absorbed and act as antioxi-Keywords:Salad Blue and Herbie 26 potatoes; however, the our prepared from the Blue Congo exhibited a muchAnthocyanin and antioxidant activity of

Agnieszka Nems a,, Anna Peksa a, Alicja Z. KucharskWioletta Dro _zd _z a, Karel Hamouz c

aDepartment of Food Storage and Technology, Faculty of Food Science, Wroclaw UniverbDepartment of Fruit, Vegetable and Cereals Technology, Faculty of Food Science, WroccDepartment of Plant Production, Faculty of Agrobiology, Food and Natural Resources, C

a r t i c l e i n f o

Article history:Received 2 July 2014Received in revised form 5 September 2014Accepted 6 September 2014Available online 16 September 2014

a b s t r a c t

Coloured-eshed potatoesproduction. The effects ofpellet manufacturing on ahalf- and ready products wimental our and snack p

Food C

journal homepage: www.eacks with coloured potato

, Anna Sok-etowska b, Agnieszka Kita a,

of Environmental and Life Sciences, Polandniversity of Environmental and Life Sciences, PolandUniversity of Life Sciences Prague, Czech Republic

our varieties were used as raw material for coloured our and fried snackmal processes traditionally used in dried potato processing and in snackcyanin proles, total polyphenols and antioxidant properties of obtainedstudied. There was a signicant inuence of potato variety on the exper-

erties. Flours with the highest antioxidant activities were obtained from

le at ScienceDirect

mistry

vier .com/locate / foodchem

lina, salt and oil purchased from the trade were used as additives.

mist2.2. Preparation of coloured potato our

Eight randomly selected tubers of each potato variety werewashed with tap water, strained with the use of paper towels,mechanically peeled and cut into slices of approximately 10 mmthick. Two simultaneous samples of tubers were prepared. Approx-imately 500 g samples of slices were blanched in a 1 L solution of0.5% NaHSO3 at 80 C for 15 min, strained in a sieve and paper,cooled at room temperature and frozen at 20 C. The sampleswere then freeze-dried at 30 C. Dried slices were ground in a knifegrinder, sieved through a sieve of 1 mm mesh size, packed in plas-tic boxes and stored under refrigeration until further investigation.Additionally, slices of raw tubers not blanched were freeze-dried toobtain samples of raw material for analysis.

2.3. Preparation of dough for pellet extrusion

Fifty percent of trade potato grits in a pellet recipe werereplaced by coloured our from four coloured-eshed potato vari-eties. For the control sample of snacks, 335 g of starch and 130 g ofpotato grits were mixed with corn semolina, salt and rape seed oilto obtain 500 g of dough mixture. The moisture content of thedough for extrusion was established at 4045% by adding a suit-potatoes, the major antioxidants are phenolic acids, such as chlor-ogenic acid that comprises approximately 80% of the total phenolicacids (Brown, 2005), caffeic acid, cinnamic acid, p-coumaric acid,ferulic acid and sinapic acid (Friedman, 1997), and other com-pounds, such as ascorbic acid, carotenoids, tocopherols, lipoic acidand selenium (Lachman et al., 2009). As stated by Brown (2005),coloured potatoes contain twice as much phenolic acid as yel-low-eshed potatoes. However, these potatoes contain largeamounts of avonoids, particularly catechin, epicatechin andanthocyanidins.

In recent years, there has been an increasing interest in potatovarieties with coloured esh (Manach et al., 2004; Nicoli, Anese,& Parpinel, 1999; Perla, Holm, & Jayanty, 2012; Peksa et al.,2011; Tajner-Czopek, Rytel, Kita, Peksa, & Hamouz, 2012), mainlybecause of the high anthocyanin content of the raw material. Theauthors emphasise the importance of anthocyanin stability duringfood processing and discuss changes in the overall antioxidantactivity due to thermal processing of potato tissue and preserva-tion procedures.

The aim of the present experiment was to study how thermalprocesses necessary for potato our and nal snack processingaffect particular anthocyanins, total phenolic content and antioxi-dant properties of the extruded material and ready snacks enrichedwith coloured potato our.

2. Materials and methods

2.1. Raw material

Dried potato products, such as starch obtained from Pepees SApotato factory in om _za and trade grits produced by a potato fac-tory in Lublin, Poland, were used as the main components of pelletsnacks in the experiment. Samples of coloured potato our wereobtained from four varieties of red and purple eshed potatoessupplied by the Czech University of Life Sciences, Prague. Red-eshed Herbie 26 and the following three purple-eshed potatovarieties were used: Val, Blue Congo and Salad Blue. Corn semo-

176 A. Nems et al. / Food Cheable quantity of water. The moistened mixture was pressed by asieve and placed in sealed polyethylene bags under refrigerationfor 12 h to equilibrate the moisture in the dough.2.4. Pellet extrusion

Material for pellets was extruded in a single-screw extruder(Brabender DN 20, Germany). The following extrusion parameterswere kept constant: die size (0.5 mm 80 mm), speed of doughsupplier (38 rpm), screw speed (120 rpm), screw loading (2.8 A)and barrel temperature distribution (60 C/70 C/80 C). Strandsthat had previously been subjected to extrusion but were notexpanded were cut into pellets of ca. 27 27 mm and dried atroom temperature for 12 h to ca. 1213% moisture content andsealed in polyethylene bags to equilibrate moisture until frying.

2.5. Preparation of fried snacks

Snacks were obtained from pellets following 48 h of storage atroom temperature. The samples were fried in hot (180 C) rapeseedoil for 1520 s (3 s after expanded product appears on the oil sur-face). The product to oil ratio was kept at 1:20 w/v.

2.6. Analysis

2.6.1. Proximate chemical analysisThe dry weight of the dough, the dough components and snacks

were determined by drying at 102 C until constant weight wasachieved (AOAC, 2000). In the raw material and snacks, the totalphenolics, anthocyanin content and anti-oxidant activity, asdi(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH), 2,20-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and the ferricreducing ability of plasma (FRAP), were also determined.

2.6.2. Extraction of polyphenolsThe freeze-dried potato samples and the defatted samples of

snacks were extracted by 70% aqueous acetone (0.1% acetic acid)in a graduated tube. The mixture was homogenised using a vortexfor 30 s and allowed to stand for 2 h at room temperature. The ace-tonewater solution was partitioned with chloroform to removethe lipophilic compounds. Next, the acetonewater fraction wascollected and placed on a Bchi rotary evaporator until all residualacetone was evaporated. The remaining aqueous extract wasbrought to a known volume with distilled water and stored at20 C until analysis. The samples were ltered with 0.2 lm ltersbefore HPLC-MS analysis.

2.6.3. Determination of total polyphenolsThe total polyphenolic content of the extracts was determined

using the FolinCiocalteu colorimetric method, as described byGao, Bjork, Trajkovski, and Uggla (2000). Potato extract (0.1 ml)and FolinCiocalteu reagent (0.2 ml) were pipetted into cuvettes.After 3 min, 1 ml of a 20% aqueous solution of sodium carbonate(Na2CO3) and 2 ml of distilled water were added. The absorbanceat 765 nm was measured after 1 h, and the results were expressedas mg of gallic acid equivalents per 1 g of dry matter (DM). Data arereported as the mean value for four measurements.

2.6.4. HPLC analysis of anthocyaninsAnthocyanins were determined using a Dionex (USA) HPLC

system equipped with a model Ultimate 3000 diode array detector,a LPG-3400A quaternary pump, a EWPS-3000SI auto sampler and aTCC-3000SD thermo stated column compartment, controlled byChromeleon v.6.8 software. A reverse phase Atlantic T3(250 mm 4.6 i.d., 5 lm) column (Waters, Ireland) and an AtlantisT3 (20 4.6 i.d, 5 lm) guard column (Waters, Ireland) were used.The following solvents constituted the mobile phase: A. 4.5% for-

ry 172 (2015) 175182mic acid and B. acetonitrile. The following elution conditions wereapplied: 01 min, 5% B isocratic; 16 min, linear gradient from510% B; 626 min, linear gradient 1020% B; 2633 min, linear

gradient from 20100% B; and then the initial conditions. The owrate was 1 mL/min, and the injection volume was 40 lL. The col-umn was operated at 30 C. Anthocyanins were monitored at520 nm.

2.6.5. LCMS/MS analysis of anthocyaninsCompound identication was performed on an Acquity ultra-

performance liquid chromatography (UPLC) system coupled witha quadrupole-time of ight (Q-TOF) MS instrument (UPLC/SynaptQ-TOF MS, Waters Corp., Milford, MA, USA) with an electrosprayionisation source (ESI). Separation was achieved on an Acquity

2.7. Statistical analysis

Statistical analyses of all data were performed using a one-wayanalysis of variance (ANOVA). Duncans range test was used todetermine the differences among samples with a probability levelof 0.05. Statistical analyses and standard deviations were deter-mined using Statistica v. 9.0 software (StatSoft Inc., Tulsa, OK, USA).

3. Results and discussion

DM]

3 8 07

A. Nems et al. / Food Chemistry 172 (2015) 175182 177TM BEH C18 column (100 mm 2.1 mm i.d., 1.7 lm; Waters).The detection wavelength was set at 520 nm. The mobile phasewas a mixture of 4.5% formic acid (A) and acetonitrile (B). The gra-dient programwas as follows: initial conditions 99% (A), 12 min 75% (A), 12.5 min 100% (B), 13.5 min 99% (A). The ow rate was0.45 mL/min, and the injection volume was 5 lL. The column wasoperated at 30 C.

Major operating parameters for the Q-TOF MS were set as fol-lows: capillary voltage, 2.0 kV; cone voltage, 45 V; cone gas ow,11 L/h; collision energy, 50 eV; source temperature, 100 C; desolv-ation temperature, 250 C; collision gas, argon; desolvation gas,nitrogen; ow rate, 600 L/h; data acquisition range, m/z 1001000 Da; ionisation mode, positive. The data were collected byMass-Lynx TM V 4.1. software.

2.6.6. Determination of antioxidant activityThe antioxidant activity of aqueous extracts was determined

using the Trolox equivalent antioxidant capacity (TEAC) with ABTSand DPPH radicals and the FRAP method. The TEAC assay withABTS radicals was carried out according to Re et al. (1999), andthe TEAC assay with DPPH radicals was carried out according toa procedure described by Yen and Chen (1995). The antioxidantactivity measured using FRAP was performed according to amethod by Benzie and Strain (1996). TEAC results are expressedas lmol of Trolox equivalents per 1 g of dry matter (DM). Dataare reported as the mean of four measurements.

2.6.7. Physical properties of snacksThe texture of the obtained snacks was determined by using an

Instron type 5544 texture-measuring device with Merlin software.The minimal force (N) necessary to break up a snack was measuredusing a share blade at a displacement rate of 250 rpm. The expan-sion ratio of the snacks was calculated as a quotient of snack size topellet size. The colour of snacks (Hunter lab scale) was measuredusing a Minolta CM-5 chromameter against a white reference stan-dard. Hue angle and chroma colour space parameters were calcu-lated from a and b values.

Hue angle = Arctan (b/a).Chroma = ((a^2) + (b^2))^0.5 (Wrolstad, Durst, & Lee, 2005).

Table 1Total polyphenols content [mg * g1 DM] and antioxidant activity [lmol Trolox * g1

Potato Variety Total polyphenols Antioxidant activity

DPPH

P PF P PF

Salad Blue 3.34 0.14 1.81 0.09 7.81 0.46 22.5Blue Congo 4.27 0.14 1.36 0.11 15.68 0.52 14.2Val 3.01 0.14 1.19 0.12 10.29 0.65 7.09Herbie 26 2.47 0.12 1.57 0.14 4.38 0.40 20.6LSD 0.21 0.18 0.80 1.87P Potatoes.PF Potato our.3.1. The effect of processing coloured potatoes for our onanthocyanins, total polyphenol content and antioxidant activity

Blanching coloured-esh potatoes during our processingresulted in a decrease in anthocyanins, total polyphenols and anti-oxidant capacity of the obtained our in an amount dependent onthe potato variety.

3.1.1. AnthocyaninsThe main anthocyanins found in the purple-eshed varieties of

potatoes studied were petunidin and malvidin. In the red-eshedpotatoes, pelargonidin derivatives were the most abundant antho-cyanin (Table 2). In the tubers Blue Congo and Val, the presence ofanthocyanins such as petunidin-3-rutinoside-5-glucoside, petuni-din-3-feruloylrutinoside-5-glucoside and malvidin-3-feruloyruti-noside-5-glucoside were detected. Additionally, differences in thecontent of petunidin-3-caffeoylrutinoside-5-glucoside, petunidin-2-p-coumaroylrutinoside-5-glucoside and malvidin-3-p-cou-maroylrutinoside-5-glucoside were found between the samplesof raw potatoes examined, and higher levels of those anthocyaninswere found in the Blue Congo variety of potato. In tubers of theSalad Blue variety, the same derivatives were detected; however,in distinctly lower quantities than in the Blue Congo or Val pota-toes, a decrease that was particularly notable for petunidin-2-p-coumaroylrutinoside-5-glucoside. The red-eshed Herbie 26 pota-toes had the highest level of pelargonidin-3-p-coumaroylrutino-side-5-glucoside and also contained notable quantities ofpelargonidin-3-rutinoside-5-glucoside, pelargonidin-3-feruloylru-tinoside-5-glucoside and pelargonidin-3-caffeoylrutinoside-5-glucoside.

The current results are in agreement with reports of otherauthors (Rodriguez Saona, Giusti, & Wrolstad, 1998) who provedthat the dominant anthocyanins in potatoes with red-colouredesh were acylated glucosides of pelargonidin, such as pelargoni-din glycosides-3-O-p-coumaroylrutinoside-5-O-glucoside. Lewis.C.E. (1996) identied 5-glucoside-3-rahmnosyl glucoside deriva-tives of all common anthocyanidins acylated by p-coumaric orferulic acids in red-eshed potatoes. Alcade-Eon, Saavedra, dePascual-Teresa, & Rivas Gonzalo, 2004 showed that acylated gluco-sides of anthocyanins are present in potatoes with coloured esh,of which the aglycons were pelargonidin, malvidin, petunidin,

of dried potatoes of four varieties and obtained our.

ABTS FRAP

P PF P PF

0.70 5.81 0.34 36.10 2.32 5.57 0.34 29.45 1.891.26 9.01 0.39 24.62 1.58 13.31 0.54 17.78 1.93.97 6.97 0.55 14.95 9.50 7.16 0.41 27.39 2.321.69 6.27 0.34 35.07 3.23 1.74 0.06 26.83 2.87

0.64 8.04 0.59 3.53

peonidin and delphinidin acylated by hydrocynamic acid found inthe skin and esh. Burnmeister et al. (2011) and Hillebrand et al.(2009) proved that potatoes with coloured esh contained two

Results suggest that anthocyanins in the Salad Blue potatoeswere better stabilised than in the other tuber varieties. Notable

The highest content of those compounds was found in tubers of the

Table 2Mass spectrometric properties of anthocyanins found in studied coloured eshed potatoes of 4 varieties.

Nr of pik [M]+ (m/z) MS/MS (m/z) Compound

1 787,229 317,066/479,117/625,177 Petunidin-3-rutinoside-5-glucoside2 801,245 331,081/493,144/639,195 Malwidin-3-rutinosside-5glucoside3 949,265 317,067/479,114/787,205 Petunidin-3-caffeylrutinoside-5-glucoside4 933,266 317,066/479,119/771,214 Petunidin-2-p-coumarylrutinoside-5-glucoside5 963,275 317,067/479,120/801,224 Petunidin-3-feruloylrutinoside-5-glucoside6 947,282 331,082/493,137/785,229 Malwidin-3-p-coumarylrutinoside-5-glucoside7 977,296 331,083/493,195/815,241 Malwidin-3-feruloyrutinoside-5-glucoside8 741,224 271,061/433,113/579.171 Pelargonidin-3-rutinoside-5-glucoside9 579,172 271,061/433,113 Pelargonidin-3-rutoside

10 903,258 271,061/433,112/741,203 Pelargonidin-3-caffeoylrutinoside-5-glucoside11 887,261 271,061/443,113/725,208 Pelargonidin-3-pcoumaorylrutinoside-5-glucoside12 917,271 271,061/443,112/755,218 Pelargonidin-3-feruloylrutinoside-5-glucoside

178 A. Nems et al. / Food Chemistry 172 (2015) 175182main and several lateral pigments identied by HPLC-ESI-MS andHPLC-DAD methods as petunidin-3-p-coumaroylrutinoside-5-glu-coside and peonidin-p-coumaroylrutinoside-5-glucoside. Fossenand Andersen (2000) determined the prole of anthocyanins inpurple-eshed potatoes and found feruloyl-glyco and rhamno-pyr-anosides of malvidin and petunidin. The same authors (Fossen,Ovstedal, Slimestad, & Andersen, 2003) stated that anthocyaninsin purple-eshed potatoes were acylated with caffeic acid. Otherauthors (Lachman et al., 2012) have indicated that individual culti-vars of potatoes differ signicantly in their relative proportions ofanthocyanidins and anthocyanins, showing a dominance of one ormore acylated glucosides of pelargonidin, cyanidin, peonidin,delphinidin, petunidin and malvidin.

The content of total anthocyanins in raw material ranged from38.7 mg/100 g DM (Salad Blue) to 96.7 mg/100 g DM (Herbie 26)(Table 3). The process of our manufacturing and potato varietyaffected the anthocyanins content. The anthocyanin content ofthe our from purple-esh potatoes of the Blue Congo and Valvarieties decreased compared to raw material, from 72.2% to68.8%; and in particular, the dominant anthocyanin, petunidin-2-p-coumaroylrutinoside-glucoside, was lost. Nonetheless, thetotal anthocyanin content and the basic pigment, petunidin-3-caf-feylrutinoside-5-glucoside, did not change signicantly in theproduct from Salad Blue potatoes (also purple-eshed) but otheranthocyanins present in the our from this variety showed slightvariations.

Table 31Pigments [mg cyanidin-3-glucoside * 100 g DM] in coloured eshed potatoes and obtain

Nr of pik Potato variety

Salad Blue Blue Congo

P PF P PF

1 1.77 0.084 2.58 0.345 2.33 0.475 1.74 0.4982 0.263 0.172 Traces 0.116 0.051 Traces3 1.71 0.604 2.12 0.760 4.02 0.611 1.34 0.0974 28.34 9.30 30.92 9.72 75.97 12.38 20.85 3.545 2.07 0.385 2.09 0.417 3.52 0.155 0.98 0.0956 3.97 1.125 1.97 0.270 7.03 1.389 1.04 0.0807 0.617 0.104 0.137 0.083 0.72 0.052 0.035 0.008 n.d. n.d. n.d. n.d.9 n.d. n.d. n.d. n.d.

10 n.d. n.d. n.d. n.d.11 n.d. n.d. n.d. n.d.12 n.d. n.d. n.d. n.d.

Sum 38.73 39.81 93.70 25.98

P Potatoes.PF Potato our.Blue Congo variety and the lowest content in Herbie 26 potatoes.Experimental our manufactured from purple and red-eshedpotatoes of the four varieties studied contained from 36% (Herbie26) to 68% (Blue Congo) less total polyphenols compared to theraw material, and the highest loses were found in the our fromthe purple-eshed Blue Congo and Val varieties.

Polyphenolics are soluble in water but susceptible to thermalprocesses. This may be the reason for the distinct loses of thosenatural compounds during blanching, which is the typical processin the industry for potato grit production. They are lost by washingout of the potato and undergoing thermal degradation. Perla et al.losses of anthocyanins (approximately 58%) were observed in theour of Herbie 26, a red-eshed potato, because of raw materialprocessing (mainly the blanching stage), mainly affected bychanges in the content of pelargonidin-3-p-coumaorylrutinoside-5-glucoside (a 62.9% loss). From the results, it can be observed thatthe highest losses of anthocyanins were in the our prepared fromtubers of the Blue Congo variety and the lowest in the our fromred-eshed potatoes of the Herbie 26 variety. Lachman et al.(2012) stated that the total anthocyanin contents and their proleswere strongly associated with potato cultivars of red, purple orblue-coloured esh.

3.1.2. Total polyphenolsOf the coloured-esh tuber varieties studied, the samples con-

tained from 2.47 to 4.27 mg GA/g DM of total polyphenols (Table 1).ed ours.

Val Herbie 26

P PF P PF

1.96 0.048 1.13 0.401 n.d. n.d.0.353 0.107 Traces n.d. n.d.2.73 1.542 1.09 0.255 n.d. n.d.

6 57.77 28.75 18.38 4.55 n.d. n.d.3.64 1.343 0.89 0.141 n.d. n.d.3.75 1.713 1.00 0.412 n.d. n.d.

3 0.521 0.139 0.024 0.006 n.d. n.d.n.d. n.d. 1.76 0.217 3.01 0.622n.d. n.d. 0.439 0.164 0.894 0.156n.d. n.d. 1.78 0.778 2.31 0.515n.d. n.d. 86.70 33.62 32.20 6.970n.d. n.d. 5.99 1.830 2.21 0.455

72.06 22.50 96.66 40.63

our manufactured as a supplement of trade grits in snack pelletsin the conditions related to proceeded in potato industry, was

M]

ty

Sna

0.220.600.680.590.460.16

mistexpressed as ABTS and DPPH and by a method utilising the reduc-tion properties of ferric ions (FRAP). As shown in Table 1, the anti-oxidant and antiradical activity of the potatoes depended on thevariety. The highest activity was observed in tubers of the BlueCongo potato variety and signicantly lower activity, expressedas FRAP and DPPH, in the red-eshed potatoes of Herbie 26. Simi-larly, other authors (Lachman et al., 2008; Lachman et al., 2009)proved that the antioxidant activity of coloured-esh potatoesdepends on the variety and on the place of their cultivation and(2012) studied the effect of different methods of thermal treatmenton potatoes with differing esh colour and found that cooking inwater affected total polyphenols, resulting in losses from 33% to62% depending on potato variety and the content of these com-pounds in the raw material. Friedman (1997) stated that lossesof polyphenols during cooking are mainly connected to losses ofphenolic acids, and Blessington (2005) showed that cooking inwater caused higher losses of total polyphenols compared to micr-owaving, baking or frying.

3.1.3. Antioxidant activityDifferences in the proles of anthocyanins contained in raw

material and in the our could contribute to the differences in anti-oxidant activity. It has been suggested by some authors (Hamouz,Lachman, Vokl, & Pivec, 1999; Lachman et al., 2000) that the anti-oxidant activity of potatoes depends on the composition and on thecontent of particular anthocyanins and also on phenolic acids,mainly chlorogenic acid and its isomers. The antioxidant activityof anthocyanins is mainly determined by the number of freehydroxyl groups in their structure. This may be the reason whypetunidin has a higher antioxidant activity when compared to mal-vidin, peonidin or pelargonidin derivatives.

The antioxidant activity of the studied raw material and the

Table 4Total polyphenols content [mg * g1 DM] and antioxidant activity [lmol Trolox * g1 Dvarieties.

Potato Variety Total polyphenols Antioxidant activi

Douhg Snacks DPPH

Douhg

Control 0.276 0.046 0.157 0.012 0.61 012Salad Blue 0.344 0.030 0.261 0.014 0.26 0.05Blue Congo 0.436 0.018 0.290 0.078 1.12 0.19Val 0.370 0.049 0.244 0.019 0.83 0.34Herbie 26 0.321 0.025 0.240 0.069 0.27 0.05LSD 0.054 0.073 0.28

Control Products without presence of coloured potato our.

A. Nems et al. / Food Cheweather conditions during the growing of the potato plant.Experimental potato our obtained from coloured-eshed

tubers that had previously been blanching in a solution of SO2had higher antioxidant activity than the raw material. The pres-ence of SO2, which is reductive, caused an increase in the reductivepower (FRAP) of the experimental our and the activity was con-rmed by the ABTS and DPPH tests. The highest increase of FRAPantioxidant activity was observed in our from Herbie 26 potatoes(15 times as much as raw material) and the lowest in our fromBlue Congo potatoes (13 times higher). Experimental our manu-factured from tubers of the purple-eshed Salad Blue variety andthe red-eshed Herbie 26 had much higher antioxidant activitythan the raw material and also had higher or similar activity com-pared to the our prepared from the remaining 2 potato varieties.

According to Brown (2005) and Brown, Culley, Yang, Durst, andWrolstad (2005), the antioxidant activity of potatoes with colouredesh is affected mainly by polyphenols in tubers and in particularanthocyanins. Quantity differences and the proles of anthocya-nins can signicantly affect the antioxidant activity of manufac-tured ready products from this type of raw material. Nayak,Berrios, Powers, Tang, and Ji (2011) showed that steam blanchingpotatoes with purple esh preserved the colour of the product afterdrying.

3.2. The effect of pellet snack processing on anthocyanins, totalpolyphenol content and antioxidant activity of ready-to-eat products

3.2.1. Anthocyanins in snacksThere was a signicant decrease in the anthocyanin contents in

snacks compared to the dough, which is later fried to make thesnacks (Table 5). The lowest losses were observed in products sup-plemented with the our from purple-eshed tubers of the BlueCongo variety (37.5%). In the remaining snack samples, muchhigher losses were observed, ranging from 60% (Herbie 26) to70% in snacks with our from Val potatoes. Kita, Bakowska-Barczak, Hamouz, Kuakowska, and Lisinska (2013) fried chipsfrom tubers of the same potato varieties and reported lower con-tents of anthocyanins in the chips, from 22% to 81%, compared tothe raw material. In addition, they showed that the lowest lossesof anthocyanins were observed when Herbie 26 potatoes had beenused for crisps processing, and the highest losses were found withthe use of Blue Congo as a raw material. Lachman et al. (2012) sta-ted that thermal processes, when related to particular potato vari-eties, showed a preservation of, or even a slight increase in, theanthocyanin content and that this was dependent on the type ofprocess used: baking, microwaving, steaming or boiling.

In potatoes with purple esh, the most thermal stabile anthocy-anin was petunidin-3-rutinoside-5-glucoside. Losses of this pig-ment in snacks containing our from purple-eshed potatoesranged from 30% (Blue Congo) to 61% (Val). The most stabileanthocyanin in red-eshed potatoes was pelargonidin-3-rutino-side-5-glucoside. The lowest losses of this pigment (33%) were

of dough and snacks enriched with coloured potato our obtained from potatoes of 4

ABTS FRAP

cks Douhg Snacks Douhg Snacks

0.03 1.08 0.16 0.67 0.07 0.75 0.19 0.48 0.06 0.06 0.57 0.04 1.16 0.07 0.26 0.05 0.80 0.07 0.18 2.18 0.76 1.34 0.28 1.63 0.63 0.96 0.26 0.04 1.85 0.67 1.16 0.24 1.25 0.56 0.89 0.09 0.13 0.52 0.11 1.17 0.07 0.26 0.04 0.73 0.20

0.81 0.26 0.59 0.24

ry 172 (2015) 175182 179found in snacks supplemented with our from Herbie 26 potatoes.The resistance of 3-rutinoside-5-glucoside of petunidin and pelarg-onidin could be an effect of phenolic acid separation from relatedacylated anthocyanins, which most likely increased the concentra-tion of 3-rutinoside-5-glucosides.

The basic factors that decrease the anthocyanin content in foodproducts are the conditions of the thermal processes and extrusion,particularly when conducted at high temperatures and pressures(Camire, Chaovanalikit, Dougherty, & Briggs, 2002). According tothese authors, extrusion cooking at a temperature of 130 Cdegraded 7490% of the anthocyanins in the unheated dough pre-pared from corn meal and fruit concentrates or powders, such asgrape, blueberry, cranberry, concord grape and raspberry.

3.2.2. Total polyphenols in snacksDough destined for pellet extrusion and subsequently snack fry-

ing, enriched with coloured-potato our, had higher contents of

colo

.069

.101

.198

.108

.062

.0058 n.d. n.d. n.d. n.d.9 n.d. n.d. n.d. n.d.

4.405 1.387 6.301 2.533

misttotal polyphenols than dough containing only industry madepotato grits. The highest quantity of polyphenols was found indough prepared with our from tubers of the purple-eshed BlueCongo potato variety.

Dough processing, with low shear extrusion, drying at roomtemperature and frying in oil at 180 C for 20 s, caused a stateddecrease in polyphenol content. Snacks manufactured with theaddition of coloured our had similar contents of total polyphe-nols, from 0.240 (Herbie 26) to 0.290 mg GA/g DM (Blue Congo)and higher values than snacks made with trade potato grits (con-trol sample), which contained 0.157 mg GA/g DM totalpolyphenols.

As shown in Table 4, the highest losses of polyphenolic com-pounds were observed in snacks produced without the experimen-tal our (43% loss compared to the dough before extrusion). Thetotal losses of polyphenols in snacks enriched with our from col-oured-eshed potatoes, as a result of dough extrusion and frying,ranged from 25% (Salad Blue and Herbie 26) to 34% (Val). Themost polyphenols were found in the products supplemented withour from Blue Congo potatoes. These results suggest that thepolyphenols present in tubers of coloured-eshed varieties are bet-ter stabilised during thermal processes than polyphenolic com-pounds in potatoes of traditional coloured esh. Thesedifferences also depended on potato variety and on the polypheno-lic prole.

Brown, Durst, Wrolstad, and De Jong (2008) stated that the

10 n.d. n.d. n.d. n.d.11 n.d. n.d. n.d. n.d.12 n.d. n.d. n.d. n.d.

Sum 5.375 1.858 4.469 2.853Table 5Pigments [mg cyanidin-3-glucoside * 100 g1 DM] in dough and snacks enriched with

Nr of pik Potato variety

Salad Blue Blue Congo

Dough Snacks Dough Snacks

1 0.420 0.028 0.182 0.066 0.272 0.026 0.191 02 Traces Traces Traces Traces3 0.316 0.053 0.119 0.014 0.254 0.015 0.162 04 4.084 0.661 1.387 0.195 3.597 0.171 2.229 15 0.229 0.022 0.063 0.005 0.118 0.018 0.156 06 0.299 0.040 0.096 0.014 0.207 0.007 0.106 07 0.027 0.005 0.011 0.002 0.021 0.004 0.009 0

180 A. Nems et al. / Food Chepolyphenols in tubers of red and purple-coloured esh are betterpreserved in ready-to-eat products after processing by variousmethods, including frying, compared to potatoes of traditionalwhite, crme or yellow esh that mainly contain the polyphenolchlorogenic acid.

3.2.3. Antioxidant activity of snacksThe production conditions of pellet snacks signicantly contrib-

uted to changes in the antioxidant activity of the nal product,compared to the dough (Table 4). The direction of those changesdepended on the potato variety used for our production.

From the data in Table 4, it appears that the antioxidant activi-ties of snacks obtained with our from the Blue Congo and Valpotatoes and products that were not supplemented with colouredour were signicantly lower compared to the antioxidant activityof the dough. In contrast, a 50% increase in antioxidant capacity wasobserved in snacks after the addition of our from Salad Blue andHerbie 26 potatoes. These differences could be due to a higher deg-radation of total polyphenols in snacks supplemented with BlueCongo and Val potato our (approximately 35% of total phenolics)than in snacks supplemented with our from Salad Blue and Herbie26 potatoes (approximately 25% of total phenolics) (Table 4).

The increase in antioxidant activity could also result from thepresence of Maillard reaction products, most likely created duringextrusion and frying of dough that contains suitable quantities ofnecessary substrates, such as reducing sugars and amino acids.Thermal processes can contribute to the creation of brown-coloured complex polymeric compounds known as melanoidinpigments, which can show antioxidant capacity, such as hydroxy-methyl furfural. Similarly, other authors (Nicoli et al., 1999) havenoted an increase in antioxidant activity as a result of vegetableand fruit processing and explained this increase as the effect ofMaillard reactions and fermentation processes or protein hydroly-sis. According to Blessington (2005), thermal processes, such asfrying and microwaving, can increase the antioxidant activity ofpotatoes. In addition, Dewanto, Wu, and Liu (2002) stated thatheating process increased the antioxidant activity of vegetableproducts. They found increases of 44% in the phytochemical con-tent, such as ferulic acid and total phenolics, present in sweet cornsubjected to 115 C for 25 min. Other authors (Turkmen, Sari, &Velioglu, 2005) have suggested that the changes in total antioxi-dant activity depend on the type of vegetable but not on the typeof cooking process. Generally, thermal stages of food processingare suggested to be one of most important factors affecting thedestruction or changes in the phytochemicals naturally presentin raw material and therefore change the antioxidant capacity ofured potato our obtained from potatoes of 4 varieties.

Val Herbie 26

Dough Snacks Dough Snacks

0.256 0.080 0.098 0.036 n.d. n.d.Traces Traces n.d. n.d.0.228 0.021 0.072 0.017 n.d. n.d.3.573 0.234 1.112 0.262 n.d. n.d.0.110 0.005 0.051 0.014 n.d. n.d.0.219 0.005 0.054 0.006 n.d. n.d.0.019 0.000 n.d. n.d. n.d.n.d. n.d. 0.520 0.056 0.347 0.118n.d. n.d. 0.178 0.019 0.065 0.0347n.d. n.d. 0.343 0.043 0.141 0.064n.d. n.d. 4.880 0.536 1.811 0.912n.d. n.d. 0.3801 0.047 0.189 0.068

ry 172 (2015) 175182the processed food (Nayak et al., 2011; Nicoli et al., 1999).

3.3. The effect on physical properties of pellet snack enrichment withcoloured potato our

3.3.1. ColourAs can be observed from the data presented in Table 6, snacks

supplemented with the our from coloured esh potatoes hadnovel visual characteristics not found in traditional snacks. Theydisplayed an interesting colour that was affected by the anthocya-nins present in the purple and red-eshed potatoes that were usedas the raw material.

These compounds did not undergo total destruction duringsnack processing, and this could have affected the resulting colour.All of the snacks that were obtained using coloured our had lowerlightness (L in the range 64.2366.90) than control samples. Theaddition of our from red-eshed Herbie 26 potatoes resulted ina pink colour (Hue = 29.55) that was attractive to the consumer.The saturation of the colour (Chroma) of snacks supplementedwith our from the red-eshed potato variety was more distinct(C = 15.55) than the colour of snacks produced with the our from

colou

mistthe purple-eshed potatoes (C coordinate values between 4.34 and4.90). Snacks made using a traditional recipe, without the additionof coloured our, had a more intense crme-yellow colour(C = 20.01, Hue = 83.17). All of the snacks that were supplementedwith the our from potatoes with purple esh (independent of thepotato variety) were a grey colour with a light blue shade (valuesof Hue coordinate closed to 0).

Processing can change the anthocyanin content and the colourin fruits and vegetables. The overall colour changes could be dueto a number of factors such as pigment degradation, pigmentpolymerisation, reactions with other components of the formula-tion, non-enzymatic browning, oxidation of tannins, and otherreactions completely unrelated to the added coloured our(Wrolstad et al., 2005).

Phenolics, such as phenolic acids and anthocyanins, can be des-tructed by physical factors during food processing or enzyme activ-ity in vegetables and fruits stored in different conditions (Kader,Irmouli, Nicolas, & Metche, 2002; Rossi et al., 2003). The conditionsof food processing can cause a discoloration of polyphenols presentin raw material into yellowish or brownish pigments (Clifford,2000) found in the colour of ready-made products.

3.3.2. Texture and expansion indexIncorporation of the experimental our into the pellet snack

recipe did not signicantly change their texture. Similar to the con-trol sample, snacks supplemented with coloured-eshed potatoour had a hardness of 30 N (Table 6). These results are similarto the data presented by Peksa, Kita, & Zieba, 2004, who measuredthe texture of potato snacks supplemented with dietary bre andPeksa, Miedzianka, Kita, Tajner-Czopek, and Rytel (2010) whodetermined the texture of snacks with added potato proteins.The texture of expanded snacks is dependent on the content of gel-atinised starch, its chemical composition and is correlated with theexpansion index of the nal product (Lusas & Rooney, 2001).

Experimental our used as a component of pellet snacks

Table 6Physical properties of snacks enriched with potato our obtained from potatoes of 4

Feature Control Potato variety

Salad Blue

Colour (Hunter Lab) L 80.56 0.84 65.24 1.13C 20.01 0.46 4.76 0.39H 83.17 0.35 4.62 0.25

Expansion index 3.83 0.41 5.59 0.49

Texture [N] 29.04 9.49 31.09 17.36

Control Snacks without the presence of coloured potato our.

A. Nems et al. / Food Cheimproved their expansion ratio, independent of the tuber esh col-our and potato variety. Snacks supplemented with coloured ourwere noticeably more expanded than control snacks. The expan-sion index of snacks with experimental our ranged from 4.86 to5.59 and was approximately 40% higher compared to traditionalsnacks (on average 3.83). The greatest expansions were observedfrom the addition of our from Salad Blue, Herbie 26 and Valpotato varieties.

The texture of pellet snacks and their expansion indexes aredirectly dependant on the degree of starch gelatinisation, whichis the main component of potato snacks. Only products that havealmost all of the starch in the gelatinised form expand properly(Lusas & Rooney, 2001). The carbohydrate composition andchanges of these compounds in potatoes of coloured esh are notwell recognised but can have an important inuence on the crea-tion of physical features and sensory properties of expandedsnacks manufactured with their addition.4. Conclusions

The antioxidant activity of ours from coloured-eshed pota-toes and the pellet snacks produced with the coloured our servingas one of the dried components varied depending on the potatovariety. Blanching in a solution of SO2 during potato our produc-tion was the most important factor affecting the antioxidant andantiradical activity of coloured our and increased the antioxidantactivity from 2 to 15 times, dependant on the potato variety andmethod of determination. However, this increase was not foundin the ours obtained from the Blue Congo and Val varieties ofpurple-eshed potatoes. Flour with the highest antioxidant activitywas prepared from Salad Blue and Herbie 26 potato varieties, andVal potatoes had the lowest activity. Blue Congo potatoes hadmuch greater total polyphenols and anthocyanins compared topurple-eshed Salad Blue and red-eshed Herbie 26 potatoes. Inpurple-coloured our, petunidin-2-p-coumarylrutinoside-5-gluco-side dominated; and in red-coloured our, pelargonidin-3-p-coumaorylrutinoside-5-glucoside dominated. Thermal processapplied in experimental our production caused a 3868%decrease in polyphenols and a 5872% decrease in anthocyaninsand was particularly high in products prepared from tubers ofthe purple-eshed Blue Congo and Val varieties. The compoundsin the dry matter of purple-eshed Salad Blue and, to a lowerdegree, present in red-eshed Herbie 26 affected the higher stabil-ity of the anthocyanins present in tubers during the blanchingprocess. The least stabile anthocyanins were found in the purple-eshed potatoes, malwidin-3-p-coumarylrutinoside-5-glucosideand petunidin-2-p-coumarylrutinoside-5-glucoside, and the moststable were petunidin-3-rutinoside-5-glucoside. In Herbie 26 our,pelargonidin-3-rutinoside-5-glucoside, pelargonidin-3-caffeoylru-tinoside-5-glucoside and pelargonidin-3-rutinoside anthocyaninswere present in lower quantities but were better stabilised duringthermal processes than the same anthocyanins in the other pota-toes varieties examined.

red eshed varieties.

LSD

Blue Congo Val Herbie 26

64.23 0.21 64.56 0.19 66.90 1.12 0.724.98 0.15 4.90 0.15 15.55 0.29 0.29

347.47 0.82 357.55 10.02 29.55 0.66 98.06

4.86 0.12 5.40 0.46 5.50 0.56 0.52

35.69 15.49 29.52a 10.43 35.94 19.47 7.57

ry 172 (2015) 175182 181Snacks produced with coloured potato our had 23 timeshigher antioxidant activity, particularly when measured by DPPH,compared to control samples with commercial potato grits as theour component and contained on average 40% more of polyphe-nols. The processes of low shear extrusion and frying utilised forsnack production affected a decrease in the antioxidant activity ofproducts with our from the Blue Congo and Val varieties but anincrease in activity in snacks with our from the Salad Blue andHerbie 26 varieties. The anthocyanin content in snacks dependson the variety of potato used for coloured our production. Thehighest content of these compounds and the lowest losses duringsnack processing were in snacks with our from the purple-eshedBlue Congo and the red-eshed Herbie 26 potatoes. The utilisationof experimental, coloured potato ours favourably affected the col-our and expansion index of the obtained snacks and did not chan-ged their texture. In particular, the red-coloured our from Herbie26 potatoes resulted in an attractive snack colour.

Acknowledgements

The authors would like to acknowledge the Wrocaw Universityof Environmental and Life Sciences for nancial support of the doc-toral Grant NO _Z/85/2013/SC.

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Anthocyanin and antioxidant activity of snacks with coloured potato1 Introduction2 Materials and methods2.1 Raw material2.2 Preparation of coloured potato flour2.3 Preparation of dough for pellet extrusion2.4 Pellet extrusion2.5 Preparation of fried snacks2.6 Analysis2.6.1 Proximate chemical analysis2.6.2 Extraction of polyphenols2.6.3 Determination of total polyphenols2.6.4 HPLC analysis of anthocyanins2.6.5 LCMS/MS analysis of anthocyanins2.6.6 Determination of antioxidant activity2.6.7 Physical properties of snacks

2.7 Statistical analysis

3 Results and discussion3.1 The effect of processing coloured potatoes for flour on anthocyanins, total polyphenol content and antioxidant activity3.1.1 Anthocyanins3.1.2 Total polyphenols3.1.3 Antioxidant activity

3.2 The effect of pellet snack processing on anthocyanins, total polyphenol content and antioxidant activity of ready-to-eat products3.2.1 Anthocyanins in snacks3.2.2 Total polyphenols in snacks3.2.3 Antioxidant activity of snacks

3.3 The effect on physical properties of pellet snack enrichment with coloured potato flour3.3.1 Colour3.3.2 Texture and expansion index

4 ConclusionsAcknowledgementsReferences