INFLUENCE SACCHAROSE AND ARTIFFICIAL SWEETENERS ON PHYSICOCHEMICAL PROPERTIES OF MALTODEXTRINS SOLUTIONS WITH DIFFERENTIAL VALUE OF DEXTROSE EQUIVALENTS

Izabela Przetaczek-Rożnowska
Department of Analysis and Food Quality Evaluation, Agricultural University, Cracow, Poland

ABSTRACT

The solution of commercial potato maltodextrines (with differential value of Dextrose Equivalent) and one laboratory maltodextrine produced from potato starches with artificial sweeteners were examined for retrogradation at temperature 8°C using a turbidometric analysis. As well all of the samples were investigated by determination on retrogradation flow curves and viscosity curves using a rotational rheometer Rheolab MC1. It was found, that addition artificial sweeteners to maltodextrines solutions as well as degree of starch's depolymerization have an influence on solutions' physicochemical properties. A value of Dextrose Equivalent and a kind of sweeteners changed value of turbididty and rheological parameters.

Key words: maltodextrines, artificial sweeteners, rheological properties, retrogradation.

INTRODUCTION

Maltodextrines as products of starch's hydrolysis are used in food industry. That kind of products are willingly used by producers because they have a few useful properties [20]. Depending on value of dextrose equivalents and a method which was used during starch hydrolyze, maltodextrines have divers physicochemical properties and can be used in differential purpose. They can be utilized for regulation among others hygroscopic properties, viscosity, water binding capacity or plasticity [13,20]. Maltodextrines, especial from potato starch, are used as a stabilitation factor, a filler agent, a factor which control humidity in product and also as a factor which gets better a tastiness, improves drying, combing ingredients and they are helpful as a aromas, fats and pigments carriers [8,19,24].

A quality properties of food and an sensory attractiveness of product depend on a kind and an amount product of starch hydrolyses and on the others ingredients which are attend in product. The main determinant which changing starch and maltodextrines physicochemical properties while making products are sugars [1,4,21]. A few manuscripts show that a kind of starch and sugar and also their concentration determine a changing of products` properties [1,3,5,17]. However, only few papers have been concentrated on maltodextrines-sugars solutions properties.

The present study was designed to investigate the effect of addition artificial sweeteners on some physicochemical properties of maltodextrines solutions.

MATERIALS AND METHODS

The experimental material were maltodextrines (below called as a commercial maltodextrines) obtained from Przedsiębiorstwo Przemysłu Ziemniaczanego NOWAMYL S.A. in Łobez and one maltodextrine which was made in a laboratory from potato starch obtained from Przedsiębiorstwo Przemyslu Spożywczego PEPEES S.A. in Łomża. The commercial maltodextrines had three different dextrose equivalents (DE). One of them (below Cl – commercial maltodextrine which value of DE was the lowest) had DE = 7, another one had DE = 17.18 (below Cm – commercial maltodextrine which value of DE was middle) and the last one had DE = 20.75 (below Ch – commercial maltodextrine which value of DE was the highest). The maltodextrine which was made in a laboratory (below Lm – Laboratory maltodextrine which value of DE was middle) were used as a comparison and its dextrose equivalent amounted to 17.47. The laboratory maltodextrine was a product from hydrolyses which were researched by using BAN 480L enzyme α-Amylase (EC 3.2.1.1) 480 KNU/g (Novozymes–Denmark)

During the research were used saccharose (which sweetness were 1) obtained from Chempur, Piekary Śląskie in Poland, sorbitol which swetneness were 0.55 times less than saccharose (Dakart, Kielce in Poland), acesulfam K which were 200 times sweeter than saccharose (Nutrinova, Germany) and aspartam which were 180 times sweeter than saccharose (Nutra Sweet, Switzerland).

The above indicated maltodextrines were examined for retrogradation at temperature 8°C using a turbidometric analysis [11]. For that investigation maltodextrines solutions 2 % (w/w) were prepared in water and in saccharose solution 10 % (w/w). The other sweeteners were prepared in such a way that their sweetness was comparable with that of the saccharose solution. The samples were blended at room temperature for 5 min by using a mechanical strirrer (385 r.p.m.). Then, the solutions were heated in a water bath at 95±0.5°C for 1 hour with continuous stirring (385 r.p.m). The solutions obtained were refrigerated in water bath at 25°C with continuous stirring. Initial turbidity was determined by absorbance at λ = 640 using spectrphotometer UV/VIS Jasco, type V-530 (Japan). The samples were kept at 8°C by 21 days and the measure were made after 1, 3, 5, 7, 10, 14 and 21 day. Before each measurement the samples were placed for 5 min in a 25±0.5°C water bath.

The reological experiments were performed using a rotational rheomether Rheolab MC1 with coaxial cylinders (for Cm, Ch and Lm – exterior diameter = 48.80 mm and interior diameter = 45.00 mm, for Cl – exterior diameter = 27.12 mm and interior diameter = 25 mm) as a measuring system (Physica Messtechnik GmbH, Germany). The reometer was programmed using US 200 software via a networked PC. To determine flow curves, 50 % (w/w) solutions of maltodextrines in water and in solutions of saccharose or its substitutes were prepared. The concentration of saccharose was 10% and the solutions of other sweeteners were prepared in such a way that their sweetness was comparable with that of the saccharose solution. The solutions were blended at room temperature for 15 min by using a mechanical stirrer (300 r.p.m.). Then, the samples were heated in a water bath at 95±0.5°C for 15 min with continuous stirring (300 r.p.m). The solutions obtained were immediately placed in the measuring element of rheometer and thermostated for 10 min prior to determination. The flow curves were obtained at 50°C±0.5°C at a shear rate increasing from 1 to 300s^-1 during 10 min, a shear constant 300 s^-1 during 2 min and shear decreasing from 300^-1 to 1 during 10 min. The curves were described using [22]
the Herschel-Bulkley model     τ = τ₀ + K · ()ⁿ
and
Newton model     τ = η

where:
τ – shear stress [Pa]
τ₀ – yield stress [Pa]
K – consistency coefficient [Pa·sⁿ]
– shear rate [s^-1]
n – flow index
η – dynamic viscosity coefficient [Pa·s]

To determine curves which show a dependent viscosity on temperature, solutions of the highest and middle dextrose equivalent maltodextrines were prepared in the same way as the samples for determined flow curves, while for maltodextrine which DE=7.00, the concentration were lower and amounted to 25% (w/w). Reduction of concentration was necessary because sensitiveness of the rheometer wasn't enough.

The curves temperature depending were obtained at from 20°C to 60°C, at a shear rate constant 10 s^-1. The curves were described using the Arrhenius model [15]:

η = η_∞ exp (E_a/RT)

where:
η – viscosity [Pa·s]
η_∞ – material constant [Pa·s]
E_a – flow activation energy [kJ/mol]
R – gas constant 8.314 [J/(K·mol)]

A calculation of all of the parameters were made by using US 200 software via a networked PC.

A register of abbreviations which were used in this paper:

RESULTS AND DISCUSSION

The retrogradation properties of various maltodextrines solutions are presented in Fig. 1a-1d. Large differences in initial turbidities of the various maltodextrines were observed. The samples from laboratory maltodextrine having the highest. The differences may be related to the nature of the starches, and a different from method which were used for obtained starches' hydrolysates. However, additive acesulfame K and aspartame to the solutions of laboratory maltodextrine did not contribute to changing a value of turbidity to after 7 day (Fig. 1a) An attendance saccharose and sorbitol in solutions of laboratory maltodextrine induced a reduction turbidity development.

Samples made from all of commercial maltodextrines (without sweeteners) showed lower initial rate of turbidity development than samples of laboratory maltodextrine (Figs. 1a-d). A development of retrogradation is dependent on range of biopolymers' chain [14], therefore source for different initial turbidity amongst commercials and laboratory maltodextrines were a methods which were used for producing a product of starch hydrolyses. Probably, the most important phase which was responsible for different properties between commercials and laboratory maltodextrines was drying.

The analyses showed that turbidity for almost all of solutions fairly slowly developed for 21 days. However, an addition all of sweeteners brought some changing range of turbidity about. Examining this analysis in details, an unusual phenomenon was observed. Even low amongst of sweeteners in solutions has a influence on turbidity. Simultaneously, the experiments indicated that a value of dextrose equivalent was significant for range of turbidity. Solutions of commercial maltodextrine which value of DE was with a presence of saccharose or sorbitol developed turbidity fairly rapidly after firs day (Fig. 1b). Also a solution of the same product of starch hydrolyses without sweeteners showed rapidly developed turbidity after 1 day our analyses. A source of that effect probably was a greater activity of short amylopectin chains and a mirror variety of chains` length. According to Zhang and Jackson [25], short and branch chains can contribute to crystals initiation and their gain.

Our experiments reveal that 2% (w/w) solutions of maltodextrines in water and in solutions of saccharose or its substitutes did not develop rapidly turbidity for the 21 days. However an addition sorbitol or aspartame to solution of commercial maltodextrine with a middle value of DE induced a development turbidity in that solutions (Fig. 1c). In comparison with solutions of maltodextrine with a middle value of DE without saccharose or artificial sweeteners, turbidity of this maltodextrines' solutions with aspartame or sorbitol fairly rapidly developed after 7. to 14. day (Fig. 1c).

In the case of solutions of maltodextrines which had the highest value of dextrose equivalent with addition saccharose, sudden growth of turbidity value was observed after 10 day (Fig. 1d). However, attendance the rest of sweeteners in solutions of maltodextrine which value of DE was the highest did not bring significantly changing about value of turbidity (Fig. 1d).

Fig. 1 a. Actual turbidities of 2% solutions of laboratory maltodextrine without and with sweeteners as a function of days storage at 8°C

Fig. 1 b. Actual turbidities of 2% solutions of commercial maltodextrine (DE = 7.00) without and with sweeteners as a function of days storage at 8°C

Fig. 1 c. Actual turbidities of 2% solutions of commercial maltodextrine (DE = 17.18) without and with sweeteners as a function of days storage at 8°C

Fig. 1 d. Actual turbidities of 2% solutions of commercial maltodextrine (DE = 20.75) without and with sweeteners as a function of days storage at 8°C

The results of rheological experiments were showed as a flow curves (Figs. 2a-d) and as a viscosity curves (Figs. 3a-d). Tables 1-8 show the value of rheological models parameters describing the flow and viscosity curves.

Among all solutions of maltodextrines in water without addition sweeteners, samples of commercial maltodextrine which DE was 7.00 obtained the highest value of shear stress (Fig. 2.b). The rest of solutions of commercial and laboratory maltodextrines demonstrated very similar value of shear stress while the hole range of using shear rate (Figs. 2a,c,d). Saccharose or sorbitol markedly decreased the shear stress of all maltodextrines solutions compared to samples without sweeteners (Figs. 2a-d), which agree with the findings of other authors [2,7,10] who studied saccharose influence on starches solutions. Addition acesulfame K or aspartame to all maltodextrines solutions had not an influence on changing value of shear stress (Figs. 2a-d). Dissimilar behavior could be caused by a different extent of penetration products of hydrolyses starches by various of sweeteners [18] and different concentration of sweeteners in maltodextrines solutions also.

Tables 1-4 show the values of the Herschel-Bulkley and Newton parameters describing the flow curves. High value of determination coefficients (R²) confirm that this model described well the experimental curves.

Fig. 2 a. Viscosity curves 50% (w/w) solutions of laboratory maltodextrine in water and in solutions of sweeteners at 50°C

Fig. 2 b. Viscosity curves 50% (w/w) solutions of commercial maltodextrine (DE = 7.00) in water and in solutions of sweeteners at 50°C

Fig. 2 c. Viscosity curves 50% (w/w) solutions of commercial maltodextrine (DE = 17.18) in water and in solutions of sweeteners at 50°C

Fig. 2 d. Viscosity curves 50% (w/w) solutions of commercial maltodextrine (DE = 20.75) in water and in solutions of sweeteners at 50°C

The samples prepared from laboratory maltodextrine and commercial maltodextrines which value of DE was the lowest and the highest in solution of saccharose exhibited higher values of the yield stress (τ₀) (Tables 1, 2, 4), while an attendance this sweetener in samples obtained from commercial maltodextrine which DE was middle caused increase value of this parameter (Table 3). On the other hand samples prepared from all of maltodextrines excluded commercial maltodextrine with the lowest value of DE with acesulfame K or aspartame revealed lower value of the yield stress (Tables 1-4).

An addition sorbitol to samples did not cause a constant dependence. A samples prepared from commercial maltodextrines which value of DE were the lowest or middle indicated higher value of the yield stress comparison to solutions without sweeteners (Tables 2 and 3), meanwhile the same sweeteners present in solution of commercial maltodextrine with the highest value of DE caused decreased the yield stress (Table 4), while addition sorbitol to solution of laboratory maltodextrine inconsiderable different (Table 1).

Comparison of the value of consistency coefficient (K), which is a measure of fluid viscosity, demonstrated that it was considerably affected by added sweeteners. Most of solutions with sweeteners demonstrated higher value of that parameter than samples prepared without saccharose or its substitutes (Tables 1, 3 and 4). However, only acesulfame K or aspartame added to solutions of commercial maltodextrine which DE was middle pointed out not significantly different (Table 2).

Worthy of notice is a fact that viscosity of maltodextrines solutions was dependent on degree of starch degradations and its value was decreasing for samples which value of DE was higher (Tables 1-4), which is consistent with other studies [6,8] but contrary with Tur's and her team study [23].

Based on the obtained the values of flow index (n), it was found that the solutions of all maltodextrines without sweeteners behaved as Newtonian fluids, which is consistent with other authors studies [6,9,16]. In most cases even addition of sweeteners in solutions did not change value of this parameter compared to samples without saccharose or its substitutes (Tables 1, 3 and 4). Merely solutions prepared from commercial maltodextrine which DE was the lowest with in solution sorbitol behaved as non – Newtonian fluids, were shear thinning (Table 2). Also samples with sorbitol and saccharose markedly increased the viscosity (η) of the Newton model compare to solutions prepared without sweeteners or with acesulfame K or aspartame. Addition acesulfame K or aspartame to maltodextrines solutions did not reveal significantly difference (Tables 1-4).

To determine curves which show a dependent viscosity on temperature were obtained at from 20°C to 60°C, at a shear rate constant 10 s^-1 (Figs. 3a-d). Tables 5-8 show the value of the Arrhenius model parameters describing the viscosity curves.

Almost all of maltodextrines solutions without sweeteners or with saccharose or its substitutions demonstrated high values of determination coefficients (R²) confirm that this model describe well the experimental curves (Tables 1, 3 and 4). Only solutions of commercial maltodextrine which value of DE was the lowest indicated lower value of R² (Table 2).

Based on the obtained viscosity curves (Figs. 3a-d) it was found that solutions of maltodextrines with sweeteners had low initial viscosity. Saccharose and sorbitol markedly increased the initial viscosity examined at temperature 20°C. Meanwhile, acesulfame K and aspartame caused inconsiderable difference (with the exception of solutions prepared from commercial maltodextrine which value of DE was the lowest) compared to solutions without sweeteners.

The highest reduction of viscosity was observed for solutions prepared with sorbitol (Figs. 3a-d). Samples of starch hydrolyses products in solutions of saccharose had lower value of viscosity than solutions prepared with sorbitol, while samples with acesulfame K or aspartame did not caused significant difference (Figs. 3a-d).

Fig. 3 a. Viscosity curves of 50% (w/w) solutions of laboratory maltodextrine in water and in solutions of sweeteners at temperature from 20°C to 60°C

Fig. 3 b. Viscosity curves of 50% (w/w) solutions of commercial maltodextrine (DE = 7.00) in water and in solutions of sweeteners at temperature from 20°C to 60°C

Fig. 3 c. Viscosity curves of 50% (w/w) solutions of commercial maltodextrine (DE = 17.18) in water and in solutions of sweeteners at temperature from 20°C to 60°C

Fig. 3 d. Viscosity curves of 50% (w/w) solutions of commercial maltodextrine (DE = 20.75) in water and in solutions of sweeteners at temperature from 20°C to 60°C

The values of The Arrhenius model parameters were showed in Tables 5-8. The meaning of material constant (η_∞) is still a subject for discussion, but flow activation energy (E_a) measures a susceptibility samples to change temperature. Higher value of flow activation energy means that samples are more sensitive to change temperature. There is a negative correlation between value of flow activation energy and a value of material constant and higher value of E_a result lower value of material constant, which agrees with the findings of other authors [12].

Among all solutions prepared without saccharose or its substitutions, the highest value of flow activation energy obtained samples from laboratory maltodextrine and commercial maltodextrine which DE was the highest (Tables 5 and 8). On the other hand solution of products starch`s hydrolyses which had the lowest degree of depolymerization revealed the lowest value of flow activation energy confirm that viscosity depends linear on degree of depolymerization and decreasing with increasing value of dextrose equivalent [6].

Samples of laboratory maltodextrine in solutions of saccharose or its substitutions obtained insensibly lower value of flow activation energy or insignificant difference (for samples with sorbitol) (Table 5). Addition sweeteners to samples prepared from commercial maltodextrines which DE were the lowest and middle caused increasing value of this parameter (Tables 6 and 7). In cause of commercial maltodextrine which DE was the highest addition sweeteners revealed inconsiderable difference or insensibly decreasing value of flow activation energy (Table 8).

CONCLUSIONS

1. A kind of addition a sweeteners to maltodextrines solutions as well as degree of starch`s depolymerization have an influence on turbidity development.

2. Addition sorbitol to samples prepared from commercial maltodextrine which value of dextrose equivalent was the lowest caused that the solutions behaved as non-Newtonian fluid shear thinning.

3. Samples with saccharose or sorbitol revealed increase shear stress compared to solutions without sweeteners.

4. All of sweeteners contributed to increase value of consistency coefficient regardless of starches depolymerization.

5. Acesulfame K and aspartame did not change viscosity value for samples from all of maltodextrines compared to solutions without saccharose or its substitutions.

6. All of maltodextrines samples in solutions of saccharose or sorbitol had the highest value of viscosity at temperature 20°C.

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Accepted for print: 30.07.2009

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