荸荠淀粉糊粘度特性研究

测定了荸荠淀粉糊的Brabender 黏度曲线,利用NDJ-8S数字显示黏度计研究了淀粉乳浓度、pH值、增稠剂、糖、盐等因素对荸荠淀粉糊黏度的影响以及荸荠淀粉糊的流变性。实验结果表明,荸荠淀粉糊化温度低,峰值黏度大,冷稳定性优良,不易发生老化,但热稳定性差。荸荠淀粉糊的黏度随淀粉浓度增加而呈幂次方上升;酸使糊黏度下降,碱使糊黏度上升;黄原胶与魔芋胶均使淀粉糊的黏度增加;葡萄糖和蔗糖对糊黏度的影响呈现先上升后下降的趋势;NaCl与CaCl2均能降低淀粉糊的黏度。荸荠淀粉糊属于非牛顿假塑性流体。     

Flow properties of corn starch–milk–sugar system prepared at 368.15 K

The rheological properties of corn starch–milk–sugar (CMS) paste were investigated using a concentric cylinder viscometer. Three types of sugars, namely, glucose, fructose and sucrose were used to prepare the paste. The paste was prepared at three different starch concentrations, 2, 4 and 6 wt.%, while the sugar concentrations of the three types were varied up to 16 wt.%. Milk with three different fat contents was used in preparation of the CMS paste. At constant starch and sugar concentrations and using skim milk, glucose was found to have the largest effect on the apparent viscosity of the CMS past. On the other hand, the fructose has the lowest effect on the CMS paste viscosity. It was also demonstrated that the pastes prepared with full cream milk have higher viscosity than the ones prepared using skim milk. The rheological CMS paste properties were modelled using Herschel–Bulkley model. The model was adequate and accurate.     

Influence of pH and hydrocolloids addition on yam (Dioscorea alata) starch pastes stability

Yam tubers (Dioscorea alata) are a non-traditional starch source that could be used as food ingredient. The stability of yam starch pastes (6/100 g suspension) submitted to different pH conditions during gelatinization and the effect of hydrocolloids addition (guar and xanthan gums) on starch syneresis under refrigeration were analyzed. Changes in pH (3, 5, 6) or the addition of gums (0.1–0.5/100 g suspension) did not affect the starch gelatinization temperature nor the gelatinization enthalpy as determined by differential scanning calorimetry. Rheological behavior was characterized by amylograph profiles and oscillatory rheometry. Amylograms showed that yam starch pastes maintained a high viscosity under heat treatment and mechanical stirring in neutral to slightly acidic conditions. Brabender viscosity increased when gums were added; the effect of guar gum on viscosity was more marked than that of xanthan gum. During refrigerated storage exudate production was observed of pastes without gums. Xanthan gum, at a concentration of 0.5/100 g suspension, showed higher effectiveness than guar gum to reduce exudate production during refrigerated storage. The addition of hydrocolloids could allow yam starch to be used in foods requiring low temperatures.     

盐及非盐物质对常用低浓度食品胶溶液粘度影响的研究

对饮料生产中常用的食品胶－黄原胶、海藻酸钠、瓜尔胶和琼脂在低浓度水相体系中外加盐（阴、阳离子）、乙醇、蔗糖及柠檬酸对溶液粘度的影响作了探讨性研究,结果表明四种胶溶液（０．１０％黄原胶、０．３０％海藻酸钠、０．２５％瓜尔胶、０．１０％琼脂）中、瓜尔胶溶液对盐的耐受性最好,即大多数阴阳离子都不会对其粘度产生影响,而常用金属盐阳离子及Ｃｌ＾－、ＳＯ３＾２－对黄原胶溶液粘度的影响与阴阳离子对海藻酸钠和琼脂     

食品胶协同干热处理对马铃薯淀粉理化特性的影响

为了改善马铃薯淀粉加工特性,选用瓜尔胶、羧甲基纤维素钠和黄原胶3种食品胶分别与马铃薯淀粉复配后进行干热处理,研究食品胶协同干热处理对马铃薯淀粉糊化、老化和流变特性的影响。研究发现,中3种食品胶协同干热处理均能够降低糊化温度与糊化焓,并且均能增强淀粉体系稳定性,使其呈现出弹性流体性质,不仅如此还均能提高淀粉糊热稳定性以及耐剪切能力,此外均能增强淀粉凝胶的冻融稳定性。结果表明,3种食品胶协同干热处理均能起到改善马铃薯淀粉加工特性的作用,对其改善程度对比分析发现,黄原胶协同干热处理改善马铃薯淀粉特性效果最好。     

The viscosity of dilute solutions of guar gum and locust bean gum with and without added sugars

The apparent viscosities of dilute solutions of guar and locust bean gums have been measured. The intrinsic viscosity [n] of guar gum solution is greater than that of locust bean gum solution, but the interaction coefficient k of guar gum solutions is less than that of locust bean gum. Addition of glucose, sucrose, or glucose syrup increases the apparent viscosity of the gum solution. The intrinsic viscosity of the gum solution is decreased but the interaction coefficient is increased.     

Steady-shear flow of semidilute guar gum solutions with sucrose, glucose and sodium chloride at different temperatures

Steady-shear flow curves of aqueous solutions of guar gum at 0.22% at different temperatures (5-65 °C), guar gum (0.22%) with sugars (sucrose or glucose) at different sugar/water ratio (0.10, 0.20 and 0.40) at 5 °C, guar-sugar (at 0.40 sugar/water ratio) at different temperatures (5-65 °C) and guar gum and guar-sucrose (0.40 sucrose/water ratio) with NaCl (1%) at 5 °C, were determined using a controlled-stress rheometer over a wide range of shear rate (1-1000 s⁻¹). Apparent viscosity increased with decreasing temperature and increasing sugar content independent of sugar type. Synergic effect on apparent viscosity due to sugar addition was found and was correlated with sugar content. Salt addition decreased slightly the apparent viscosity and increased the shear-thinning behaviour of the guar gum solution. Steady-shear flow curves were satisfactorily described by the Cross model. Semi-empirical correlations of Cross model parameters with sugar content and temperature were obtained.     

New Directions for Starch and Glucose Research

Enzymes have become a prime commercial tool for modification of starch and glucose. Today we see enzymes used to convert starch to glucose and again to convert glucose to a mixture of glucose and fructose, invert sugar in the terminology of cane and beet sugar manufacturers. We will expect to see greater use of enzymes to modify starch granules to produce a new way of dextrinization of starch. Enzymes may also be used to modify starch molecules to increase the degree of branching producing new properties among which can be those giving solutions of low viscosity, but high solids contents. Starch or glucose derivatives can also be sources of sugar for derivatizing protein to produce glycoproteins a potential new class of water soluble gums or food additives. Low caloric sweetners are possibly by more extensive modification of glucose similar to thio-glucose or sugar sweetner attached to nondigestible polysaccharides such as cellulose. Isomerization of glucose to fructose can provide crystalline fructose which may find wider use in special diet foods. Appropriate derivatization of starch could produce polymers compatible with pure synthetic plastics in which they could act to modify and improve plastic properties.     

Influence of selected hydrocolloids on triticale starch rheological properties

The aim of the study was to define the influence of selected nonstarch polysaccharides (guar gum, xanthan gum and arabic gum) on several rheological properties of triticale starch pastes/gels, at constant polysaccharide concentration (6.5 g/100 g). These included pasting characteristics, flow curves at 50 °C and mechanical spectra at 25 °C. It was found that the presence of a gum in a system modified the rheological properties of triticale starch gels/pastes, depending on the type and concentration of the gums. In the case of guar and xanthan gums, higher pasting viscosity was observed and the shear stress was increased compared with native starch. The presence of guar gum reduced the degree of thixotropy hysteresis, negative values for this being found for systems with xanthan in spite of their shear‐thinning behaviour. Systems containing arabic gum displayed lower values of pasting and flow viscosity. The type and concentration of gums added to the polysaccharide influenced the viscoelastic properties of the gels.     

THE EFFECT OF CARBOHYDRATE ADJUNCTS ON BREWER'S WORT FERMENTATION BY SACCHAROMYCES UVARUM (CARLSBERGENSIS)*

The use of carbohydrate adjuncts such as sucrose, fructose and glucose in brewer's wort significantly modifies the initial wort sugar spectrum and also the pattern of sugar uptake during fermentation by a strain of Saccharomyces uvarum (carlsbergensis). Under these conditions, the concentration of glucose and fructose in the wort was observed to increase when compared to worts in which corn starch was employed as an adjunct and glucose was taken up at a faster rate than fructose. The increase in glucose concentration in the wort also resulted in severe repression of maltose and maltotriose utilization with significant levels of these sugars remaining in the beer produced.     

EFFECTS OF HYDROCOLLOIDS AND ASPARTAME ON SENSORY VISCOSITY AND SWEETNESS OF LOW CALORIE PEACH NECTARS

Effects were studied of interactions between each of three hydrocolloids-xanthan gum, guar gum and methylcellulose- and aspartame on sweetness intensity and sensory viscosity of low-calorie peach nectars (60% fruit purée with no sucrose added). The flows of the nectars were characterized as near Newtonian without hydrocolloids, as Bingham plastic at lower hydrocolloids concentrations and as pseudoplastic at higher concentrations (Ostwald flow for guar and methylcellulose, and Herschel-Bulkley for xanthan). Hydrocolloids concentrations were selected to cover viscosity range of commercial whole nectars: 0.10 and 0.20% xanthan or guar, and 0.15 and 0.30% methylcellulose. Aspartame concentrations tested were derived from the calculation of equisweet concentration as referred to a control nectar sample with sucrose (14°Brix) and of the upper and lower limen value: 0.216, 0.360 (equisweet), 0.502, and 0.644 g/L. Addition of either guar or methylcellulose did not alter the perceived sweetness in aspartame-sweetened peach nectars. Xanthan addition, even at 0.10%, significantly lowered sweetness of samples sweetened with the highest aspartame concentration (0.644 g/L). Addition of aspartame did not modify the perceived viscosity in samples thickened with either xanthan or guar gums. At all methylcellulose concentrations tested, samples with the lowest aspartame concentration (0.216 g/L) were perceived as less viscous.     

The Relationship Between Wheat Flour and Starch Pasting Properties and Starch Hydrolysis: Effect of Non‐starch Polysaccharides in a Starch Gel System

Non‐starch polysaccharides (NSPs) and celite (used as inert filler) were incorporated into wheat flour and wheat starch paste preparations at levels of 1, 2.5, and 5% in both addition and replacement modes. Pasting properties of gums were compared using a Rapid Visco Analyser. Use of guar gum and locust bean gum elevated the peak and final viscosities of the resulting pastes (when used in either addition or replacement modes), whereas arabic gum significantly reduced the peak and final viscosity properties of the pastes. Samples which comprised wheat starch yielded higher peak and final viscosity characteristics compared to wheat flour containing samples, however higher breakdown and setback values were observed for samples using wheat flour as a base compared to wheat starch. The firmness of the gels (as determined using a texture analyser) increased with the use of wheat starch compared to wheat flour. Little significant difference was observed between NSP used and mode of application (replacement or addition). In vitro starch degradation was conducted on the wheat flour gels. Guar gum and locust bean gum reduced the amount of starch degradation in these gels, whereas arabic gum and celite increased the amount of starch hydrolysis (or were similar to the control). The rate of starch hydrolysis appears to be related to the viscosity altering behaviour of the NSPs in a starch‐rich system. The results indicate that selection of NSPs is important as gum arabic has the potential to increase starch hydrolysis compared to the control.     

EFFECT OF SUGARS ON THE THERMAL AND RETROGRADATION PROPERTIES OF OAT STARCHES

The thermal and retrogradation properties of oat starches from two cultivars (NO 753-2 and AC Stewart) were characterized in the presence of glucose, fructose and sucrose at a concentration of 36% w/v. In both oat starches, amylose leaching (AML) and swelling factor (SF) decreased in the presence of sugars (sucrose > glucose > fructose). These decreases were more pronounced in AC Stewart starch. The decrease in AML showed that sugars interact with amylose chains within the amorphous regions of the starch granule. The gelatinization transition temperature and the enthalpy of gelatinization increased in the presence of sugars (sucrose > glucose > fructose). The above increase was also more pronounced in AC Stewart starch. The decrease in SF and the increase in gelatinization parameters indicated that these changes were influenced by the interplay of factors such as starch-sugar interaction, changes in water structure in the presence of sugars, and the antiplastizing properties of sugars relative to water. The retrogradation enthalpy and the X-ray diffraction intensities of NO 753-2 and AC Stewart starch gels (stored at 4C) increased in the presence of sugars (glucose > fructose > sucrose). These changes were more pronounced in NO 753-2 starch. The results showed that interaction (during storage) between leached amylopectin and sugar molecules was the main causative factor influencing oat starch retrogradation.     

Effect of Sweeteners and Stabilizers on selected Sensory Attributes and Shelf Life of Ice Cream

Guar and locust bean gums were combined with sucrose, 36 DE corn syrup and/or 42 high fructose corn syrup (HFCS) in a minimum fat (10%) ice cream formulation. A total of 27 combinations were evaluated for sweetness, iciness, chewiness and vanilla intensity. Replacing 50% of the sucrose with 42 HFCS did not significantly affect sweetness or vanilla intensity. Chewiness was enhanced when high corn syrup levels were combined with a high guar to locust bean gum ratio. Storage study data showed that ice creams containing high levels of HFCS became objectionably icy earlier than ice creams containing low levels or no HFCS. With a high guar to locust bean gum ratio ice creams became both detectably and objectionably icy sooner than if a low ratio of these gums was used.     

Preparation of resistant starch from starch–guar gum extrudates and their properties

Mixtures of starch, guar gum and citric acid were extruded at a temperature of 150 °C and screw speed of 180 rpm. Properties of the extrudates such as bulk density, expansion ratio, apparent viscosity and resistant starch content were measured with different concentrations of guar gum. Extrusion with citric acid influenced the physical properties and resistant starch content of the extrudate. Expansion ratios were lower for samples extruded with citric acid, and decreased as starch–gum concentration increased. The apparent viscosity of the extrudate increased with increasing guar gum concentration; however, citric acid at 2.0% concentration was found to lower the viscosity of the extrudate. Resistant starch content increased from 6.23% for extruded starch only to 14.21% for starch–gum extrudate, and further enhanced to 16.19% with the addition of 2.0% citric acid to the starch–gum extrudate. Resistant starch increased with increase of gum concentration and decreased with increase of starch–gum concentration from 7.5% to 12.5%.     

Evaluation of the time-dependent stability of starch-hydrocolloid binary gels involving NMR relaxation time measurements

A novel, non-destructive method of evaluation of the time-dependent stability of starch gels and binary starch-non-starchy hydrocolloid gels is presented. The low-field NMR technique applied provided the following results. On storage at room temperature, binary potato starch gels with xanthan gum are more stable in time than gels with guar gum and κ-carrageenan. Xanthan and guar gums as well as κ-carrageenan are dispensable as stabilizers of stored potato starch gel and building the cassava gel structure lasted over 96 h. In the binary system with cassava starch, guar gum performed best regardless storage temperature. At room temperature, admixture of hydrocolloids to plain cornstarch gels resulted in remove of water molecules from the gel network. Stabilization of cornstarch gels with hydrocolloids was, practically, dispensable and even non-beneficial regardless storage temperature. None among tested hydrocolloids stabilized the oat starch gel. On cold storage, κ-carrageenan performed best.     

Rapid Visco-Analyzer (RVA) Pasting Profiles of Wheat,Corn, Waxy Corn,Tapioca and Amaranth Starches (A. hypochondriacus and A cruentus) in the Presence of Konjac Flour,Gellan, Guar,Xanthan and Locust Bean Gums

The Rapid Visco-Analyzer (RVA) 20min test was used to study the effects of different levels of konjac flour, guar, gellan, xanthan and locust bean gums on starch cooking properties. Wheat, corn, waxy corn, tapioca and A. hypochondriacus and A. cruentus starches were affected to different degrees by different levels of the gums. Peak viscosity increased at the higher gum concentrations, especially with locust bean gum at the 0.4 g level. The increase in viscosity was more pronounced with wheat and corn starches than with waxy corn and tapioca starches which consist mostly of highly branched amylopectin thus preventing close physical association between molecules. Amaranth starches showed much lower viscosity with all the gums than the other starches. Peak viscosity, time to reach the peak and maximum setback viscosity were affected by the gums. The increase in viscosity of starch/hydrocolloid systems is due to the release of amy-lose and low molecular weight amylopectin which promotes the formation of polymer complexes and significantly adds to the viscosity of the system.     

慈菇淀粉糊特性研究

对慈菇淀粉糊与马蹄、绿豆、马铃薯、豌豆、玉米和木薯淀粉糊凝沉性和冻融稳定性进行比较,研究不同条件对慈菇淀粉糊黏度和透明度的影响。结果表明：慈菇淀粉糊凝沉速率较低,介于马蹄与木薯淀粉之间;冻融稳定性与木薯淀粉相似;在微酸和微碱条件下,慈菇淀粉糊的透明度下降,在强酸和强碱条件下,透明度上升;在低pH值时,淀粉糊黏度下降,pH＞7时,淀粉糊黏度上升;蔗糖和葡萄糖能增大淀粉糊的黏度,也能提高其透明度,而NaCl与CaCl2对其淀粉糊黏度和透明度的作用则相反;随剪切时间延长,其表观黏度减小,这表明慈菇淀粉糊属于典型的非牛顿假塑性流体。     

Viscosity of guar gum and xanthan/guar gum mixture solutions

The viscosity of diluted guar gum solutions and the viscosity of xanthan and guar gum mixture solutions have been studied. Guar gum solutions showed pseudoplastic behaviour. Apparent viscosity increased with gum concentration and decreased with the temperature at which viscosity was measured. A maximum in the plot of viscosity versus increasing dissolution temperature was observed at 60 °C. This behaviour was related to differences in molecular structure of the polymers solved at different temperatures. Mixtures of xanthan and guar gum showed a higher combined viscosity than that occurring in each separate gum. This synergistic interaction was affected by the gum ratio in the mixture and dissolution temperature of both gums. The effect of polysaccharide concentration (1.0, 1.5 and 2.0 kg m⁻³), xanthan/guar gum ratio (1/5, 4/2, 3/3, 4/2 and 5/1) and dissolution temperature (25, 40, 60 and 80 °C for both gums) on the viscosity of solutions of mixtures were studied. The highest viscosities were observed when 2.0 kg m⁻³ gum concentration was used together with a ratio of xanthan/guar gum of 3/3 (w/w) and dissolution temperature of 40 and 80 °C for xanthan and guar gum, respectively. © 2000 Society of Chemical Industry     

Comparison of the effects of gums on dynamic rheological properties of acetylated sweet potato starch

Dynamic rheological properties of acetylated sweet potato starch (ASPS) pastes mixed with 3 commercial gums (guar gum, locust bean gum, and xanthan gum) were investigated at different gum concentrations. The dynamic moduli of the ASPS-gum mixtures were higher than those of the control, and they increased with an increase in gum concentration. In particular, the G′ value of xanthan and G″ value of guar gum at a 0.6% gum concentration were much higher as compared to those of other mixtures. Tan δ values of ASPS-xanthan mixtures were much lower than those of other samples, indicating that the elastic properties in the ASPS-gum mixture systems were strongly affected by the additions of xanthan. These results suggest that the presence of gums in ASPS modifies the viscoelastic properties, and that these modifications are dependent on the gum type and gum concentration.