Retrogradacja skrobi i maltodekstryn (ang.).pdf

ACTA Acta Sci. Pol., Technol. Aliment. 9(1) 2010, 71-81

ISSN 1644-0730 (print) ISSN 1889-9594 (online)

RETROGRADATION OF STARCHES

AND MALTODEXTRINS OF ORIGIN VARIOUS

Joanna Sobolewska-Zielińska, Teresa Fortuna

University of Agriculture in Krakow

Background. The retrogradation which occurs during the processes food storage is an es-

sential problem in food industry. In this study, the ability to retrogradate of native starches

and maltodextrins of different botanical origin was analysed.

Material and methods. The materials were starches of various botanical origin, including

commercial samples: potato, tapioca, wheat, corn, waxy corn starches, and laboratory iso-

lated samples: triticale and rice starches. The above starches were used as material for

laboratory production of maltodextrins of medium dextrose equivalents (DE in the range

from 8.27 to 12.75). Starches were analysed for amylose content, while the ratio of non-

branched/long-chain-branched to short-chain-branched fractions of maltodextrins was

calculated from gel permeation chromatography data. The susceptibility to retrogradation

of 2% starch pastes and 2% maltodextrin solutions was evaluated according to turbidimet-

ric method of Jacobson.

Results. The greatest starch in turbidance of starch gels was observed within initial of the

test. days. Initial retrogradation degree of cereal starches was higher than that of tuber and

root starches. The waxy corn starch was the least prone to retrogradate. The increase

in turbidance of maltodextrin solutions were minimal. Waxy corn maltodextrin was not

susceptible to retrogradation. Among other samples, the lowest susceptibility to retrogra-

dation after 14 days was found for rice maltodextrin, while the highest for wheat and triti-

cale maltodextrin.

Conclusions. On the basis of this study, the retrogradation dependence on the kind of

starches and the maltodextrins was established and the author stated that all the maltodex-

trins have a much less ability to retrogradation than the native starches.

Key words: starches of various origin, maltodextrin, retrogradation

Corresponding author – Adres do korespondencji: Dr Joanna Sobolewska-Zielińska, Department

of Food Analysis and Quality Assessment of University of Agriculture in Krakow, Balicka 122,

30-149 Cracow, Poland, e-mail: rrsobole@cyf-kr.edu.pl

J. Sobolewska-Zielińska, T. Fortuna

INTRODUCTION

Retrogradation plays an important role in forming consumers’ utility of food prod-

ucts. It is usually described as recrystallization during storage after starch pasting. The

change in crystalline structure after pasting involves the formation of ordered double-

helical structure from amorphous glucans [Kulik and Haverkamp 1997].

Retrogradation is induced by low temperature, high amylose content and the pres-

ence of polar substances, such as salts [Nebesny 1991]. On the other hand, the surfac-

tants hinder retrogradation. Overall starch susceptibility to retrogradation is also con-

trolled by its molecular weight, concentration, temperature, and presence of non-starch

components (salts, saccharides, lipids, acids, hydrocolloids, surfactants) [Durán et al.

2001, Jacobson et al. 1997, Sandhu and Singh 2007, Smits et al. 2003]. In consequence

of retrogradation the intermolecular distances between starch molecules diminish. This

leads to the removal of water from gel, and in consequence dehydration of the material.

The phenomenon could be observed as occurrence of water on gel surface, known

as synaeresis [Karim et al. 2000, Napierała 1998].

During storage of starch gel, especially at low temperature, insoluble starch – espe-

cially amylose – precipitates [Karim et al. 2000, Napierała 1998]. Retrogradation occurs

not only in amylose fraction but also amylopectin from gelatinized granules. Associa-

tion of linear amylose molecules takes place quickly at the first stage of retrogradation,

while slow increase in starch gel rigidity is attributed to amylopectin crystallization

[Zobel 1988]. This process is also faster at low temperature. Significant acceleration

may be obtained by repeated cycles of freezing and thawing of starch gel [Colwell et al.

1969, Fortuna and Juszczak 1998, Jankowski 1990]. It was found that cereal starches

are more prone to retrogradation than potato, and in the cases of bimodal distribution

small granules are less susceptible to this process than large granules and non-fraction-

ated starch [Fortuna and Juszczak 1998].

The aim of the study was to evaluate the susceptibility to retrogradation of starches

of various botanical origin and the corresponding maltodextrins produced on laboratory

scale. Before the actual evaluation basic characteristics of the studied material were

examined.

MATERIAL AND METHODS

The material consisted of starches of various botanical origin, consisting of com-

mercial samples:

– potato starch “Superior” (Przedsiębiorstwo Przemysłu Ziemniaczanego S.A. in

Niechlów)

– wheat starch (Przedsiębiorstwo Przemysłu Ziemniaczanego S.A. in Niechlów)

– corn starch (National Starch & Chemical)

– waxy corn starch (National Starch & Chemical)

– tapioca starch (National Starch & Chemical)

and laboratory isolated samples:

– triticale starch (variety Pronto s-elita, cultivated at Danko-Horyń)

– rice starch from rice flour originated from Thailand.

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Retrogradation of starches and maltodextrins of origin various

The starches were used to produce maltodextrins on laboratory scale, by enyzmatic

hydrolysis with commercial preparation BAN 240 L produced by Novozymes (Den-

mark). The suspension at 25°C was treated with 0.025 cm 3 of enzymatic preparation

BAN 240L and heated in 40 minutes to reach 84°C. The temperature was controlled all

the time, and the mixing rate was 550 rpm. By modifying reaction time (under optimal

conditions – 84°C) depending on susceptibility of starch to enzymatic hydrolysis, the

maltodextrins with medium dextrose equivalents were obtained (DE in the range from

8.27 to 12.75). The value of dextrose equivalent was evaluated by Schoorla-Regen-

bogen method [PN-78/A-74701 1978].

Initial starches were analysed for amylose content according to Morrison and

Laignelet [1983]. In the maltodextrins the ratio of non-branched/long-chain-branched to

short-chain-branched fraction was calculated from gel permeation chromatography data.

GPC analysis was performed by using four columns with following sizes and gels

[Sephacryl/Pharmacia]:

– diameter 16 mm, length 35 cm, filled with S-200

– diameter 16 mm, length 88 cm, filled with S-200

– diameter 16 mm, length 88 cm, filled with S-500

– diameter 16 mm, length 88 cm, filled with S-1000.

For calculation of molecular weight, pullulan standards P-10, 50, 200, 800 (Shodex

Standard, Macherey-Nagel) were applied, which were corresponding to molecular

weights: 12.200, 48.000, 186.000 and 853.000 Da. The standards at quantity 5 mg were

dissolved in 2.5 cm 3 distilled water and put on the columns [Praznik et al. 1983, 1987].

GPC analysis was performed at ambient temperature by using 0.003 M sodium carbon-

ate as an eluent (flow rate 16.5 cm 3 /h). The eluate was divided in fraction collector in

130 fraction with volume 5 cm 3 each. Fraction analysis included:

– determination of total carbohydrates by anthrone method, measuring the absorb-

ance at λ = 540 nm [Morris 1948] by using Specord M 42 (Carl Zeiss, Germany)

spectrophotometer

– determination of iodine-starch complex, at wavelengths λ = 525 nm and 640 nm

[Praznik et al. 1983]

– determination of apparent amylose in each of the fractions. Blue value was used

as an indicator of amylose content (BV), which is defined as the absorbance of io-

dine diluted in 100 cm 3 of water by 10 mg of starch (d.m.). It is calculated as fol-

lows:

BV = A·10 mg/d.m.

where:

A – absorbance at λ = 640 nm,

d.m. – dry mass in 100 cm 3 of measuring solution [mg].

Total carbohydrate content was used as dry mass for each of the analysed fractions

[Morris 1948], and the formula was adjusted to the volume 5 cm 3 .

By means of turbidimetric method, according to Jacobson et al. [1997], the suscepti-

bility to retrogradation of 2% starch pastes and 2% maltodextrin solutions was evalu-

ated. The studies were performed at 8°C.

Acta Scientiarum Polonorum, Technologia Alimentaria 9(1) 2010

J. Sobolewska-Zielińska, T. Fortuna

RESULTS AND DISCUSSION

Table 1 contains the results of amylose content. It was measured because of many

reports which demonstrate that the retrogradation susceptibility depends on the amylose

level [Fredriksson et al. 1998, Hoover 2001]. The highest content of linear glucans was

observed in potato starch, while the lowest in waxy corn. The level of amylose reported

here for potato starch is slightly higher than in the studies of Fortuna and Juszczak

[1998], and even more as compared to results of Swinkels [1985]. The content of amy-

lose in triticale starch is slightly lower than in the reports of Gambuś et al. [1992] and

Fortuna and Juszczak [2000]. It could be caused by the varietal differences between

analysed samples. Gambuś et al. [1992] examined starch from triticale variety Ugo,

Fortuna and Juszczak [2000] – variety Bolero, and the presented results refer to the

variety Pronto s-elita. Amylose content in tapioca starch is higher than reported by

Swinkels [1985] and Fortuna and Juszczak [2000]. In case of corn starch slightly lower

values are given by Fortuna and Juszczak [2000], while Swinkels [1985] and Rahman

et al. [2000] report higher amylose levels. Examined rice starch is less abundant in amy-

lose than samples from the studies of Jane et al. [1996] and Schierbaum et al. [1991],

and its values are only a half of those reported by Fortuna and Juszczak [2000] and

Rahman et al. [2000]. In case of wheat starch the data correspond well to those observed

by Fortuna and Juszczak [2000]. The level of amylose in waxy corn starch is also in the

limits reported by these authors. According to Jane et al. [1996] such starch contain

amyloze at levels from 0 to 2%.

Table 1. Amyloses content of native starches

Kind of starch

Amylose content, g/100 g d.m.

Potato

29.6

Tapioca

21.5

Wheat

20.0

Triticale

21.8

Corn

19.8

Waxy corn

1.0

Rice

7.2

It is worth of noting that various methods were used to measure amylose content

in starch. The reported data are based on the method of Morrison and Laignelet [1983],

which allow to measure so called apparent amylose. During the measurement some

interference of lipids present in the sample could be found [Knuston 1999].

After examination of native samples, the maltodextrins were obtained on laboratory

scale, and DE corresponding to those hydrolysates were given in Table 2.

In order to obtain maltodextrins with medium DE, in the range between 8.27

to 12.75 the time and dosage of the enzymes were adjusted (Table 2). In the case of potato

starch, which is least prone to the action of α-amylase, the time was extended. The resis-

tance of this starch to the action of enzymes is reported by many authors [Fuwa et al.

1977, Sawicka-Żukowska et al. 1999]. The shortest times of enzymatic action were

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Retrogradation of starches and maltodextrins of origin various

Table 2. Selected physico-chemical properties of maltodextrins

Kind of maltodextrin DE value

Time of hydrolyse

min

Amount of fraction nb/lcb

Amount of fraction scb

Potato

8.73

15*

1.1a

98.9a

Tapioca

11.64

1.6a

98.4a

Wheat

12.75

1.0a

99a

Triticale

9.13

3.4

96.6

Corn

8.27

5.1

94.9

Waxy corn

8.84

0.2

99.8

Rice

9.06

1.2a

98.8a

*Double dosis of enzymatic preparation was applied.

Values in the table marked with the same letters do not differ statistically at the level of significance

α = 0.05.

applied in the case of wheat maltodextrin. According to Wjibenga [1991] wheat starch

is hydrolysed fastest, among various starchy materials. This view is also supported

by other sources [Fortuna et al. 2001, Gallant et al. 1972, Rojas et al. 2001, Sawicka-

-Żukowska et al. 1999].

Maltodextrins are starch hydrolysates, so the determination of amylose would be

in this case misleading. However, in case of hydrolysates the iodine affinity could still

be applied in order to classify non-branched/long-chain-branched glucans, that have

higher absorbance at λ = 640 nm or bigger ratio A 640 /A 525 and short-chain-branched

fraction with higher absorbance at λ = 525 nm and lower ratio A 640 /A 525 [Huber and

Praznik 1984]. In Table 2 the results of GPC data are give, and the amounts of nb/lcb

and scb fractions are reported. The lowest content of nb/lcb, and the highest scb glucans

was found for maltodextrin derived from waxy corn starch. Figure 1 demonstrates the

molecular weight distribution of the maltodextrins with the numbers of collected frac-

tions. Chromatography data clearly indicate, that in analysed samples there are no glu-

cans with molecular weights in the range between 10 7 -10 8 . Oligosaccharides are appar-

ent only at approximately 60 analysed fraction. In the case of waxy corn maltodextrin

the small shift towards higher average molecular weights could be observed.

Figures 2 and 3 represent the retrogradation ability of 2% starch pastes stored for 21

and 2% maltodextrin solutions stored for 14 days. Turbidimetric analysis of retrograda-

tion allows to obtain the qualitative description of this process. The effect of storage was

represented on graphs as turbidance changes. Turbidimetric assessment of retrograda-

tion [Jacobson et al. 1997] allows to distinguish between starches and maltodextrins.

Initial turbidity measurement, as in the work of Jacobson et al. [1997], allowed to divide

the native starches into three groups (Fig. 2). First included potato and tapioca starches,

which displayed low turbidity, the second waxy corn starch, and the third wheat, triti-

cale, corn and rice starches. Similar results were obtained by Craig et al. [1989]. Initial

retrogradation degree of cereal starches was then higher than tuber and root starches.

Such a dependence was already mentioned by Błaszczyk et al. [2001]. The highest

change in turbidity was observed in two first days for majority of starches, with the excep-

tion of tapioca starch, where it increased mainly between 3rd and 7th day. According

Acta Scientiarum Polonorum, Technologia Alimentaria 9(1) 2010

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