ce

And Lifubli

GlycoalkaloidsTechnological factors

to dduc

ureucti. Th

compounds was found in dice blanched potato at the lowest temperature (65 C) and pre-dried at 120 C.

blue-retail tare quiriginat

eshed potatoes are a good source of phenolic compounds, which

Grigor, Zhang, Quantick, & Shahidi, 2001).The introduction of new varieties of potatoes for consumption

or food processing requires the checking of not only substancesof pro-nutritional functioning on the human body, but shouldexamine the content of toxic compounds, such as glycoalkaloids.Potatoes contain two glycoalkaloids, a-chaconine (ca. 60%) and

100 g on average in mature tubers (Friedman & McDonald,Machado, Toledoka, & Anioof total g

he surface1.5 mm thick), and within the eyes and damaged areas (W& Munzert, 1994; Friedman, 2006; Friedman & McDonaldOstry et al., 2010). There are also great differences in TGA contentbetween individual tubers of the same variety of potato (Friedman,2006; Friedman & McDonald, 1997; Leri et al., 2011; Leszczynski,2000).

Potato dehydration involves the use of a number of processesincluding cleaning, peeling, slicing and washing in water, and ther-mal processes such as blanching, steaming, pre-drying or dehydra-tion. All the stages affect the content of pro- and anti-nutritional

Corresponding author. Tel.: +48 71 3205239; fax: +48 71 3205221.E-mail addresses: elzbieta.rytel@wnoz.up.wroc.pl, elzbieta.rytel@up.wroc.pl (E.

Food Chemistry 141 (2013) 24952500

Contents lists available at

he

lseRytel).play an important role in foods, especially for their sensory attri-butes. Phenols give a specic acrid and bitter taste, and are respon-sible for colour and appearance, and may result in sedimentationand turbidity, particularly in juices, wine or soft drinks (Alasalvar,

1997; Knuthsen, Jensen, Schmidt, & Larsen, 2009;& Garcia, 2007; Peksa, Goubowska, Rytel, Lisins2002; Speijers, 1998). The greatest concentrationkaloids (TGA) is in the skin and just beneath t0308-8146/$ - see front matter 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.foodchem.2013.04.131owski,lycoal-(up tonsch

, 1997;2008), while in Europe the varieties are an attractive novelty andan interesting alternative to the traditional white or cream-coloured potato esh. With the ever-increasing consumption of po-tato products, such as French fries, chips and dehydrated potatoes,the introduction of new products with coloured esh should inter-est consumers looking for original snacks. In addition, the colour-

Friedman, 2006; Friedman et al., 1991; Haase, 2010; Leri, Innocen-ti, Andrenalli, Vecchio, & Mulinacci, 2011) with a lethal dose of 35 mg kg1 body weight, which is similar to strychnine and arsenic(Haase, 2010; JECFA, 1992). Potatoes, with a traditional yellow orcream-coloured esh, specically Solanum tuberosum, usually con-tain small amounts of glycoalkaloids, ranging from 310 mg to

1Dehydrated potatoes

1. Introduction

Over the last few years, red- andlated products have appeared in thecountries and the U.S. market. Theytries of southern Africa, where they oThe blanching process much inuenced on the decrease in glycoalkaloids content than pre-dryingprocess.

2013 Elsevier Ltd. All rights reserved.

eshed potatoes and re-rade in some Europeante popular in the coun-e from (Mulinacci et al.,

a-solanine (ca. 40%) (Blankemeyer, Stringer, Rayburn, Bantle, &Friedman, 1992; Friedman & McDonald, 1997; Friedman, Rayburn,& Bantle, 1991; Haase, 2010), which are important natural toxiccomponents of potato tubers (Friedman & Dao, 1992; Friedman &McDonalds, 1997; Ostry, Ruprich, & Skarkova, 2010). Glycoalka-loids are potent poisons (Blankemeyer et al., 1992; Donald, 2008;Keywords:Red- and blue-eshed potato,

blanching process (29%). Potato dice blanched at the highest temperature (85 C) and pre-dried at 120 Cwas characterised by the lowest quantity of glycoalkaloids content, whereas the highest content of theseThe inuence of dehydrated potatoes procontent in coloured-eshed potato

El _zbieta Rytel a,, Agnieszka Tajner-Czopek a, MagdaaDepartment of Food Storage and Technology, Wrocaw University of Environmental anbDepartment of Plant Production, Czech University of Life Sciences in Prague, Czech Rep

a r t i c l e i n f o

Article history:Received 18 October 2012Received in revised form 11 March 2013Accepted 30 April 2013Available online 24 May 2013

a b s t r a c t

The aim of this study wasused in the laboratory proeshed potato varieties.Studied potatoes of colo

5.47 mg 100 g1. The prodcontent in potato products

Food C

journal homepage: www.essing on the glycoalkaloids

ioowska a, Karel Hamouz b

e Science, Chemonskiego 37/41, 51-630 Wrocaw, Polandc

etermine the effect of different temperatures of blanching and pre-dryingtion of dried potato dice on the content of glycoalkaloids in red and blue

d eshed varieties were characterised by a low glycoalkaloids content aton of dehydrated potato dice inuenced on the decrease in glycoalkaloidse majority of these compounds were removed during the peeling (70%) and

SciVerse ScienceDirect

mistry

vier .com/locate / foodchem

compounds, and in production practice it is most desirable to pre-serve the maximum amount of nutrients and minimise the concen-trations of anti-nutritional compounds or toxins. The quality of thenal product depends not only on a properly performed manufac-turing process, but also on the use of appropriate materials withinteresting appearance. The inuence on the quality of the readyproduct is not only dependent on the production process, but alsothe appropriately selected of raw material with interesting proper-ties of consumption.

Knowledge instead of learning about the factors that contributeto the loss of toxic compounds is a signicant issue, especially inthe introduction of new varieties in production. Accordingly, theaim of this study was to determine the effect of different temper-atures of blanching and pre-drying used in the laboratory produc-tion of dried potato dice on the content of glycoalkaloids in red-and blue-eshed potato varieties.

2. Material and methods

2.1. Raw material

The material used for the study included four varieties of pota-

were determined in the samples.

A high-pressure liquid chromatography HPLC (pro Star) wasused (Varian, Walnut Creek, CA, USA). The HLPC was equipped witha UV detector 310 type, Microsorb NH2 analytical column(25 46 cm LD) (Rainin Instrument, Woburn, MA, USA), and a soft-ware rm Varian Chromatography System for monitoring thechromatograph.

2.3.2. Conditions of glycoalkaloids separationA mixture of tetrahydrofuran (Merck, Germany), acetonitrile

and water 50:20:30 + KH2PO4 (1.02 g) per 1 l was used as an elu-ent. The process was carried out at a temperature of 35 C, witha speed of ow of 2 cm3 min1 and pressure of 11.2 MPa, applyinga light wavelength of 208 nm.

2.3.3. Sample preparation for chromatographic analysisThe dried material (1 g) was homogenised with 4 cm3 of water

and 30 cm3 of methanol (Labscan, Ireland) for 2 min, followed byltration. The ltrate was brought to a nal volume of 50 cm3 withmethanol. A 5 cm3 aliquot of extract was cleaned up on the SPE col-umn (Bond Elut C18; 500 mg; 6.0 cm3, Varian, USA). Glycoalkaloidswere rinsed with methanol and evaporated to dryness in a vacuumat a temperature of 50 C. The resultant residue was dissolved in1 cm3 of THF:ACN:H2O 50:20:30. Before application into the col-umn, the sample was cleaned using 0.45 lm lters. The volume ofthe injection was 10 ll.

Standard solutions (1 mg cm3) were prepared by dissolving3

Dehydrated dice

2496 E. Rytel et al. / Food Chemistrytoes: Rote Emma and Rosemarie with red-esh, and Blaue St. Gallerand Blaue Annelise with blue esh from the experimental plotsbelonging to testing station of The Central Institute for Supervisingand Testing in Agriculture at Prerov nad Labem (The Czech Repub-lic). The research was conducted during the growing seasons in2010 and 2011. The samples of potato tubers were harvested afterreaching full maturity. The potatoes were collected four timeswithin 2 years of research (in 2010 and 2011).

We used the potatoes to prepare dehydrated potato dice. In or-der to determine the effect of blanching and pre-drying tempera-ture on the glycoalkaloid content in potatoes, we applied twotechnological variants that are presented in Figs. 1 and 2.

2.2. Potato sample preparation for analysis

The following samples: unpeeled potatoes, peel, potato afterpeeling, potato after cutting and washing, potato after blanchingand pre-drying, were frozen and freeze-dried using a lyophilizer

Unpeeled potato

Potato after peeling

Potato after blanching

Potatoes after cutting and washing

(10x10x10mm)

Peel

Pre-drying potato (120 C/ 1 h)

Dehydrated dice 50 C/12 h

(moisture 10-11%)

65 C/5min 75 C/5min 85 C/5min Fig. 1. The scheme of the dehydrated dice processing, blanching at differenttemperatures.2.3. The concentrations of a-solanine and a-chaconine

2.3.1. Apparatus(rm Edwards). These prepared samples and potato dice were thendried and ground using an electric grinder (rm Retsch). After-wards, the content of glycoalkaloids (a-chaconine and a-solanine)

50 C/12 h (moisture 10-11%)

Fig. 2. The scheme of the dehydrated dice processing, pre-drying at differenttemperatures.Pre-drying potato

120 C/1 h 140 C/1 h 160 C/1 h Unpeeled potato peel

Potato after peeling

Potato after cutting and washing (10x10x10mm)

Potato after blanching 75 C/5min

141 (2013) 2495250010 mg of a-solanine and a-chaconine (Sigma) in 10 cm of metha-nol. Standard solution was dissolved to obtain samples containingfrom 1 to 50 lg cm3 of both a-solanine and a-chaconine. On the

column 10 lL of solution was injected (Peksa et al., 2002; Saito,Sanford, & Webb, 1990).

2.4. Analytical methods

The quantities of a-solanine and a-chaconine were determinedusing the method of Saito et al. (1990) and Peksa et al. (2002). Allthe analyses were carried out twice.

2.5. Statistical analysis

about 20% lower compared to the blue-eshed varieties. The TGAcontent in potatoes should not exceed 20 mg 100 g1 (Ginzberg,Tokuhisa, & Veilleux, 2009; JECFA, 1992; Knuthsen et al., 2009;Machado et al., 2007) since higher amounts of these compoundsare detrimental to human health. In our study, only the peel ofBlaue Annelise had TGA above safe levels. In addition, the peelhad a higher proportion of the less harmful glycoalkaloid a-sola-nine compared to potato tubers. Glycoalkaloids are commonlyfound mainly in and directly below the potato peel (Friedman &McDonald, 1997; Peksa, Goubowska, Anioowski, Lisinska & Rytel,2006; Rytel, Goubowska, Lisinska, Peksa, & Anioowski, 2005), and

E. Rytel et al. / Food Chemistry 141 (2013) 24952500 2497The results obtained in the experiment were subjected to statis-tical calculations using Statistica 10.0 software. A multi-way anal-ysis of variance and Duncans test (P 6 0.05) was applied for thedetermination of the signicance of differences between means.All experiments were performed in four replications from twoyears of investigation and the present results show the mean ofall data combined.

3. Results and discussion

The examined potato varieties differed in the content of glycoal-kaloids (a-chaconine and a-solanine) (Tables 1 and 2). Higheramounts of glycoalkaloids were found in blue-eshed varieties(5.68 mg 100 g1) fresh weight (f.w.) compared to red-eshed vari-eties which contained an average 5.26 mg 100g1 f.w. The exam-ined potatoes contained less than 10 mg 100g1 f.w. TGA, i.e.below the permitted limit for potatoes for direct consumption orfurther processing, and therefore can be recommended for thesepurposes. However, it must noted that they still require constantcontrol of anti-nutritional compounds, due to their signicant var-iability under the inuence of external conditions, e.g. duringgrowth, transport and storage (Rytel, Peksa, Tajner-Czopek, Kita,& Lisinska, 2011). Next are the important factors affecting the suit-ability of potatoes for direct consumption or food processing is thea-solanine/a-chaconine ratio in the tuber, due to the higher toxic-ity of a-chaconine (Donald, 2008). In general, potatoes containabout 2 times more a-chaconine than a-solanine.

In our study, the a-solanine to a-chaconine ratio was from 1:1.8(Blaue St. Galler) to 1:2.1 (Rote Emma) (Table 1). According to Taj-ner-Czopek, Rytel, Kita, Peksa & Hamouz (2012) in blue-eshedpotatoes the ratio was 1:1.8 (Blue Congo) and in the red-eshedpotatoes was 1:2.2 (Rosalinde). Similarly, our results showed alower a-solanine to a-chaconine ratio in red-eshed varieties. Inpotato varieties with conventional yellow or cream-coloured esh,the ratio varies over a wide range from 1:1.2 to 1:2.4 and even upto 1:3.7 (Friedman, 2006; Friedman & Levin, 2009, chap. 6; Peksaet al., 2002; Rytel, 2012; Tajner-Czopek, Jarych-Szyszka, & Lisinska,2008), which primarily depends on the variety.

We also examined potato peel, which contained from15.33 mg 100 g1 TGA f.w. to 24.45 mg 100 g1 TGA (Table 1), withthe amount of TGA in potato peel of red-eshed varieties, to be

Table 1Total glycoalkaloids content (mg100 g1) in potatoes and peel.

Analysed compounds Red-esh potatoes

Rote Emma Rosemarie

Peel a-chaconine 10.12a 0.11 12.20c 0.19a-solanine 5.21a 0.09 7.17d 0.07TGA 15.33a 0.10 19.37d 0.08

Unpeeled potatoes a-chaconine 3.74bc 0.06 3.41a 0.04a-solanine 1.74b 0.03 1.63a 0.03TGA 5.48c 0.07 5.04a 0.06SD standard deviation; n = 8, (Duncan test, p < 0.05).a,b,c,d,e,f Row indicate signicant differences.therefore potato peelings are treated as a waste product in the foodindustry. However, potato peel also contain phenolic compoundswith high antioxidant activity and good antibacterial properties,in higher amounts than in potato esh (Desotillo, Hadley, & Holm,1994; Mder, Harshadrai, & Kroh, 2009; Onyeneho & Hettiarach-chy, 1993). According to some authors (Desotillo et al., 1994;Mder et al., 2009) potato peel and their extracts can be used asa good source of pro-health compounds (polyphenols), but priorto their use they should be examined with regard to the concentra-tion of toxic glycoalkaloids.

The production of dehydrated potato dice and treated at differ-ent temperatures of blanching and pre-drying signicantly inu-enced TGA (a-chaconine and a-solanine). The largest amounts ofTGA were removed during peeling (Table 2), on average by 70% such high losses can be explained by the thickness of peeling. Itmust by noted that in our experiment, the potatoes were peeledmanually, whereas mechanical peeling used in industrial produc-tion of chips or steam peeling used in French fries and dehydratedproducts result in a signicantly lower decrease in TGA. Accordingto Rytel et al. (2005) steam peeling applied to French fries produc-tion resulted in a 40% decrease in TGA, but Mder et al. (2009)found that steam peeling used in the production of potato granulesremoved as much as 77% TGA. Peksa et al. (2006) reported thatmechanical peeling of potatoes for chips decreased TGA contentby only 25%, compared to 60% removal by manual peeling in anexperiment by Tajner-Czopek et al. (2008).

The next step was cutting tubers and washing with water. Aftercutting, TGA content decreased by an average of 9% compared tothe respective content of potatoes after peeling (Table 2). Manyauthors (Donald, 2008; Peksa et al., 2006; Rytel, 2012) indicate thatglycoalkaloids poorly dissolve in water, so cutting and rinsing incold water cannot signicantly affect the content of glycoalkaloids.

Blanching had a signicant impact on the reduction of the con-tent of glycoalkaloids (Table 3, Fig. 3). On average, TGA decreasedby 26% in red-eshed varieties and by 31% in blue-eshed varieties(Fig. 3) compared to the respective potato concentrations after cut-ting. Blanching process signicantly inuenced on the loss of gly-coalkaloids. The higher the temperature of blanching was used,the greater the TGA changes were. Dice blanched potatoes at65 C contained on average 13% less TGA (red-eshed potato)and 21% (blue-eshed) compared to those of potatoes after the

Blue-esh potatoes

Mean Blaue Annelise Blaue St. Galler Mean

11.16b 0.18 15.66e 0.09 11.96c 0.10 13.81d 0.086.19c 0.02 8.79f 0.02 6.09b 0.03 7.44e 0.04

17.35b 0.05 24.45f 0.11 18.05c 0.06 21.25e 0.103.58b 0.10 3.65b 0.05 3.85c 0.05 3.75bc 0.041.69ab 0.04 1.76b 0.04 2.09d 0.03 1.93c 0.035.26b 0.05 5.41c 0.04 5.94d 0.06 5.68e 0.07

an

an

.41c

.02b

.52a

istryTable 2Total glycoalkaloids content (mg 100 g1 d.m.) in unpeeled potato, potato after peeled

Technological factors Red ash potatoes

Rote Emma Rosemarie Me

Unpeeled potatoes 25.32b 0.28 23.49c 0.13 24Peeld potatoes 6.55a 0.05 5.48b 0.06 6Potatoes after cutting 6.04a 0.08 4.99a 0.05 5

SD standard deviation; n = 8, (Duncan test, p < 0.05).a,b,cColumns indicate signicant differences.

2498 E. Rytel et al. / Food Chemcutting stage. Raising the temperature by 10 C resulted in a fur-ther signicant TGA loss, by an average of 26% (compared to pota-toes after cutting). In the blanched red-eshed Rosemarie potatoes,TGA decreased by 37% compared to samples after cutting. Thehighest TGA decrease was observed after blanching at the highesttemperature (85 C), on average by 42% in relation to those of po-tato after cutting.

The aim of the study was mainly the improvement the colour ofready products, and temperature and time of this process de-pended on the quality of raw material (reducing sugars content)and degree of granulation. Temperature and time of hot water orsteam treatment on the raw material should be kept to a mini-mum, due to unnecessary loss of pro-healthy compounds, like Cvitamin. The potato dice is generally blanched at 75 C because this

Table 3TGA content (mg 100 g1 d.m.) in cut potato blanching in different temperature and pre-d

Technological factors Red-esh pot

Rote Emma

Blanching 65 C/5 min 5.52e 0.0675 C/5 min 5.08d 0.0285 C/5 min 3.99b 0.08

Pre-drying 120 C/1 h After blanching in 65 C 5.47e 0.03After blanching in 75 C 4.93c 0.08After blanching in 85 C 3.30a 0.02

SD standard deviation; n = 8, (Duncan test, p < 0.05).a,b,c,d,e,f: Columns indicate signicant differences.

4.43

2.67

4.09

3.743.5

0

1

2

3

4

5

6

7

dehself-der

TGA

(mg

100g

-1)

temp. of blanching in 65C/pre-drying intemp. of blanching in 85C/pre-dryin in temp. of blanching in 75C/pre-drying itemp. of blanching in 75C/ pre-drying itemp. of blanching in 75C/pre-dryin in

E

A

DC

B

LSD=0.13

Fig. 3. TGA content (mg 100 g1) in dehydrated dice potato. (AE) Indicate signicansignicant differences between blue-eshed potatoes (Duncan test, p < 0.05).d cutting.

Blue esh potatoes

Blaue Annelise Blaue St. Galler Mean

0.12 21.39c 0.12 29.94c 0.09 25.67c 0.10 0.07 7.17b 0.03 8.28b 0.02 7.73b 0.08 0.09 6.19a 0.08 7.55a 0.05 6.87a 0.03

141 (2013) 24952500is enough temperature to deactivate enzymes taking part in dark-ening process of potato pulp and improve the colour of ready prod-uct. Whereas treatment time is selected depending on the degreeof granulation the raw material and its destiny.

Usually blanching is performed at 75 C and the duration is se-lected depending on the neness of the material and its intendeduse. Blanching of 10 10 mm dice at 85 C did not adversely affectthe quality of the raw material. After 5 min blanching, the dicesmaintained their shape and were not disintegrating.

Maintaining the proper shape and texture of raw material afterblanching depends on the chemical composition of material used.Examined varieties were characterised by proper content of drymatter and starch, recommended for dried products production,on average 2025% and 1519%, respectively.

rying.

ato Blue-esh potato

Rosemarie Blaue Annelise Blaue St. Galler

4.19d 0.06 5.37e 0.04 5.40f 0.033.14bc 0.06 4.91d 0.09 5.04d 0.082.77b 0.02 3.66b 0.04 3.73b 0.063.40c 0.05 4.82d 0.07 5.19e 0.043.14bc 0.07 4.42c 0.09 4.73c 0.072.54a 0.06 3.24a 0.06 3.31a 0.05

4

5.05

3.12

5.72

4.15

dehself-eulb

120C120Cn 120Cn 140C160C

c

a

d

b b

LSD=0.23

t differences between red-eshed potatoes (Duncan test, p < 0.05). (ad) Indicate

419423.

and

osem

.14c

.82b

.35a

istryThe difference in TGA between the samples blanched at 65 and75 C was approximately 10%, and between 75 and 85 C was 16%(Table 3). Red-eshed potato varieties showed greater changes inthe content of a-chaconine and a-solanine, irrespective of theblanching temperature.

The next step was the pre-drying of blanched dice at differenttemperatures (Fig. 1). The process of pre-drying for 1 h at 120 Csignicantly affected the loss of tested compounds (Table 3,Fig. 3). At this stage, TGA in potatoes decreased by 12% in red-eshed varieties and by 11% in blue-eshed varieties (Table 3).Fig. 2 presents the inuence of the various temperatures of pre-drying of dice blanched at 75 C for 5 min, we observed a signi-cant TGA decrease in the samples (Table 4). The biggest TGA lossesoccurred at the highest temperature (160 C), with TGA decreaseby 7% in red-eshed varieties and by 14% in blue-eshed varieties.Raising the temperature of pre-drying from 120 to 140 C, did notresult in any signicant changes in TGA in blue-ash varieties andabout 6% decrease in red-eshed varieties. Signicant TGA lossesoccurred only at 160 C, on average by 17%, in red-eshed varietiesand the major changes were blue-eshed varieties (Table 4).

Fig. 3 presents TGA content in the dice obtained after blanchingand pre-drying at different temperatures. The biggest TGA lossesoccurred in dice blanched at 85 C and pre-dried for 1 h at120 C, regardless of the potato variety, with larger changes inthe red-eshed varieties. Dice blanched at the standard tempera-ture of 75 C and pre-dried at higher temperatures 140 and160 C, had on average less glycoalkaloids than those of diceblanched at 65 and 75 C and pre-dried at the lowest temperatureof 120 C. The use of higher temperatures than those used mostcommonly, i.e. 75 C in blanching and 120 C in pre-drying resultedin higher TGA decreases. High changes in TGA content in blanchingat 85 C can be caused not only by higher temperatures, but by thewater, which probably leached some of the glycoalkaloids.

According to Friedman (2006), glycoalkaloids do not dissolveeasily in water and therefore boiling or blanching do result in aconsiderable decrease (Friedman, 2006; Mulinacci et al., 2008).Many authors (Donald, 2008; Friedman, 2006; Peksa et al., 2006)report signicant TGA decrease after peeling and frying. Chip pro-duction results in a 7277% TGA decrease in potatoes and thus theproduction of French fries contributes to a 8090% TGA loss. Mderet al. (2009) showed that only the peeling and blanching processes

Table 4TGA content (mg 100 g1 d.m.) in potato after blanching in 75 C/5 min

Pre-drying temperature Red-esh potato

Rote Emma R

120 C 4.93c 0.08 3140 C 4.86bc 0.04 2160 C 4.78a 0.07 2

SD standard deviation; n = 8, (Duncan test, p < 0.05).a,b,c: Columns indicate signicant differences.

E. Rytel et al. / Food Chemused in industrial production of granules signicantly reduce theamount of TGA in potatoes, while drying had no effect on theTGA content. In the current study, we found similar relationships.A long process of nal drying (1214 h) in low temperature (50 C)did not inuence on the degradation TGA content. According toFriedman (2006), the temperature range needed to signicantlydecrease TGA is 170180 C, and additionally the degradation isaccelerated by frying particulate material (French fries or chips)in hot oil. Frying results in glycoalkaloids transfer to the oil, whileon the other hand, the use of oil that is highly saturated with thesecompounds results in the diffusion of TGA to the fried potato slices(Friedman, 2006). Drying of the particulate material is not associ-ated with leaching, and therefore dehydrated potatoes may containhigher amounts of TGA than fried products. In our research, nalFriedman, M., & Levin, C. E. (2009). Analysis and biological activities of potatoglycoalkaloids, calystegine alkaloids, phenolic compounds, and anthocyanins. InJ. Singh & L. Kaur (Eds.), Advances in potato chemistry and technologydehydrated products contained, on average, about 16% of the initialTGA content in the material.

4. Conclusions

Studied potatoes of red and blue eshed varieties were charac-terised by a low glycoalkaloids content and proportion between a-solanine and a-chaconine that ranged from 1.0:1.8 to 1.0:2.1. Theproduction of dehydrated potato dice at different temperaturesof blanching and pre-drying signicantly inuenced TGA (a-chac-onine and a-solanine). The highest amounts of TGA were removedduring peeling and blanching by about 70% and 29% respectively.The highest TGA losses occurred in dice blanched at 85 C andpre-dried for 1 h at 120 C, regardless of the potato variety, withlarger changes in the red-eshed varieties. Dice blanched at 75 Cand pre-dried at high temperatures: 140 and 160 C, had a less gly-coalkaloids content, than dice blanched at 65 and 75 C and pre-dried at a lower temperature of 120 C. The use of higher temper-atures than those used most commonly, i.e. 75 C in blanching and120 C in pre-drying resulted in higher TGA decreases.

References

Alasalvar, S. A., Grigor, J. M., Zhang, D., Quantick, P. C., & Shahidi, F. (2001).Comparison of volatiles, phenolics, sugars, antioxidants and sensory quality ofdifferent carrot varieties. Journal of Agricultural and Food Chemistry, 49,14101416.

Blankemeyer, J. T., Stringer, B. K., Rayburn, J. R., Bantle, J. A., & Friedman, M. (1992).Effect of potato glycoalkaloids, a-chaconine and a-solanine on membranepotential of frog embryos. Journal of Agricultural and Food Chemistry, 40,20222025.

Desotillo, D. R., Hadley, M., & Holm, E. T. (1994). Potato peel waste stability andantioxidant activity of freeze-dried extract. Journal of Food Science, 59,10311033.

Donald, G. (2008). Potatoes, tomatoes, and solanine toxicity (Solanum tuberosum L.,Solanum lycopersicum L.). In D. G. Barcelux (Ed.), Medical toxicology of naturalsubstances: Foods, fungi, medicinal herbs, toxic plants, and venomous animal(pp. 7783). Heboken, NJ: John Wiley & Sons.

Friedman, M. (2006). Potato glycoalkaloids and metabolites: Roles in the plant andin the diet. Journal of Agricultural and Food Chemistry, 54(23), 86558681.

Friedman, M., & Dao, L. (1992). Distribution of glycoalkaloids in potato plants andcommercial potato products. Journal of Agricultural and Food Chemistry, 40,

pre-drying 1 h in different temperature.

Blue-esh potato

arie Blaue Annelise Blaue St. Galler

0.07 4.42a 0.09 4.73c 0.07 0.03 4.80b 0.07 3.72b 0.07 0.05 4.68b 0.08 3.34a 0.03

141 (2013) 24952500 2499(pp. 127161). USA: Elsevier-Academic Press.Friedman, M., & McDonald, G. M. (1997). Potato glycoalkaloids: Chemistry, analysis,

safety and plant physiology. Critical Reviews in Plant Sciences, 16(1), 55132.Friedman, M., Rayburn, J. R., & Bantle, J. A. (1991). Developmental toxicology of

potato alkaloids in the frog embryo tetragenesis assay-Xenopus (FETAX). Foodand Chemical Toxicology, 29(8), 537547.

Ginzberg, I., Tokuhisa, J. G., & Veilleux, R. E. (2009). Potato steroidal glycoalkaloids:Biosynthesis and genetic manipulation. Potato Research, 52, 115.

Haase, N. U. (2010). Glycoalkaloid concentration in potato tubers related to storageand consumer offer. Potato Research, 53(4), 297307.

JECFA. (1992). Evaluation of certain food additivies and naturally occurring toxicants.Thirty-ninth report of the Joint FAO/WHO Expert Committee on Food Additives.WHO Technical Report Series, no. 828. (pp. 3133). Geneva: WHO.

Knuthsen, P., Jensen, U., Schmidt, B., & Larsen, K. I. (2009). Glycoalkaloids inpotatoes: Content of glycoalkaloids in potatoes for consumption. Journal of FoodComposition and Analysis, 22, 577581.

Leri, F., Innocenti, M., Andrenalli, L., Vecchio, V., & Mulinacci, N. (2011). Rapid HPLC/DAD/MS method to determine phenolic acids, glycoalkaloids and anthocyanins

in pigmented potatoes (Solanum tuberosum L.) and correlations with variety andgeographical origin. Food Chemistry, 125, 750759.

Leszczynski, W. (2000). The quality of table potato. _Zywnosc, Nauka, Technologia,Jakosc, 4(25), 527. 7, (in Polish).

Machado, R. M. D., Toledo, M. C. F., & Garcia, L. C. (2007). Effect of light andtemperature on the formation of glycoalkaloids in potato tubers. Food Control,18, 503508.

Mder, J., Harshadrai, R., & Kroh, L. W. (2009). Composition of phenolic compoundsand glycoalklaoids a-solanine and a-chaconine during commercial potatoprocessing. Journal of Agricultural and Food Chemistry, 57, 62926297.

Mulinacci, N., Ieri, F., Giaccherini, C., Innocenti, M., Andrenelli, L., Canova, J., et al.(2008). Effect of cooking on the anthocyanins, phenolic acids, glycoalkaloids,and resistant starch content in two pigmented cultivars of Solanum tuberosum L.Journal of Agricultural and Food Chemistry, 56, 1183011837.

Onyeneho, S. N., & Hettiarachchy, N. S. (1993). Antioxidant activity, fatty-acids andphenolic-acids compositions of potato peels. Journal of the Science of Food andAgriculture, 62, 345350.

Ostry, V., Ruprich, J., & Skarkova, J. (2010). Glycoalkaloids in potato tubers: Theeffect of peeling and cooking in salted water. Acta Alimentaria, 39(2), 130135.

Peksa, A., Goubowska, G., Anioowski, K., Lisinska, G., & Rytel, E. (2006). Changes ofglycoalkoaloids and nitrate contents in potatoes during chips processing. FoodChemistry, 97, 151156.

Peksa, A., Goubowska, G., Rytel, E., Lisinska, G., & Anioowski, K. (2002). Inuence ofharvest date on glycoalkaloid contents of three potato varieties. Food Chemistry,78, 313317.

Rytel, E. (2012). Changes in glycoalkaloid and nitrate content in potato duringdehydrated dice processing. Food Control, 25, 349354.

Rytel, E., Peksa, A., Tajner-Czopek, A., Kita, A., & Lisinska, G. (2011). Anti-nutritionalcompounds in potatoes, depending on the type of raw material and conditionsof processing potatoes into food products. In N. Yee, W. Bussel (Eds.), Potato V.Food (Special Issue 1, pp. 1522).

Rytel, E., Goubowska, G., Lisinska, G., Peksa, A., & Anioowski, K. (2005). Changes inglycoalkaloid and nitrate contents in potatoes during French fries processing.Journal of the Science of Food and Agriculture, 85, 879882.

Saito, S. L., Sanford, L. L., & Webb, R. E. (1990). High-performance liquidchromatographic determination of glycoalkaloids in potato products. Journalof Chromatography, 508, 141147.

Speijers, G. J. A. (1998) Air Nettox Project Semina Rep 7. In Risk assessment of potato-glycoalkaloids (pp. 4347). Sborg: Danish Veterinary and Food Administration.

Tajner-Czopek, A., Jarych-Szyszka, M., & Lisinska, G. (2008). Changes inglycoalkaloids content of potatoes destined for consumption. Food Chemistry,106, 706711.

Tajner-Czopek, A., Rytel, E., Kita, A., Peksa, A., & Hamouz, K. (2012). The inuence ofthermal process of coloured potatoes on the content of glycoalkaloids in thepotato products. Food Chemistry, 133, 11171122.

Wunsch, A., & Munzert, M. (1994). Effect of storage and cultivar on the distributionof glycoalklaoids in potato tuber. Potato Research, 37, 310 (in German).

2500 E. Rytel et al. / Food Chemistry 141 (2013) 24952500

The influence of dehydrated potatoes processing on the glycoalkaloids content in coloured-fleshed potato1 Introduction2 Material and methods2.1 Raw material2.2 Potato sample preparation for analysis2.3 The concentrations of -solanine and -chaco2.3.1 Apparatus2.3.2 Conditions of glycoalkaloids separation2.3.3 Sample preparation for chromatographic analysis

2.4 Analytical methods2.5 Statistical analysis

3 Results and discussion4 ConclusionsReferences