Experimental Analysis and Computer Simulation of Starch-Water Interactions during Phase Transition

The phase transition of a waxy corn starch, Amioca, with a limited amount of water available, upon heating, was investigated by using experimentation and computer simulation. A model based upon the stoichiometric ratio of water to anhydro-glucose unit was developed to simulate conversion of starch (gelatinization and/or melting) with different water contents. Simulation results showed a minimum ratio of 14 water molecules to one anhydrous glucose unit was required for complete gelatinization. A phase diagram based on this was constructed to relate water contents to gelatinization and melting of starch.     

Rheological and Stability Transitions in Meat Batters Containing Soy Protein Concentrate and Vital Wheat Gluten

Physical/rheological properties of meat batters during heat-processing were studied. Vital wheat gluten (VWG) and soy protein concentrate (SPC) were incorporated into meat batters which were heated to 40, 50, 60 and 70°C and held for 0, 30 and 60 min. Amounts of fat and aqueous fluid released during heating were determined. A two-cycle compression test and shear modulus determination were used to evaluate rheological changes. VWG and SPC did not have any significant effect on either stability or textural changes. There was a significant interaction between temperature and time for stability and textural characteristics. Significant changes in rheological and stability properties of meat batters occurred in the 50–70°C region. Shear modulus showed a major increase at 54–57°C.     

聚葡萄糖在我国的研究和应用进展

聚葡萄糖属于水溶性的膳食纤维,是一种低热量、无糖、低血糖指数、稳定、具有极高耐受性的特殊碳水化合物,具有益生元的特点,可广泛应用于各种食品中,尤其是低能量、高纤维等的功能性食品中.因其有着特殊的生理保健功能,使其在食品领域有着较大的发展潜力.     

Frozen State Transitions in Freeze-Concentrated Lactose-Protein-Cornstarch Systems

Differential scanning calorimetry study of frozen state transitions of mixtures of lactose, proteins, cornstarch, and water revealed that maximum freeze-concentration was achieved by annealing at temperatures T′_m-1. The onsets of glass transition of maximally freeze-concentrated solids, T′_g, were lower and onsets of ice melting, T′_m, were higher for mixtures of proteins and polysaccharide than those of lactose. The established state diagrams showed solids concentrations C′_g, of the maximally freeze-concentrated systems of, 82, 78, 78, 78, and 75% for lactose, lactose/albumin, lactose/gelatin, lactose/cornstarch, and lactose/cornstarch/gelatin solutions, respectively. The state diagrams established with experimental and predicted T_g values are useful in characterization of thermal phenomena and physical state of the systems at various water contents and in the freeze-concentrated state.     

Sensory Studies of High Potency Multiple Sweetener Systems for Shortbread Cookies with and without Polydextrose

Time-intensity (TI) sweetness and bitterness curves determined for six potent sweetener combinations with and without polydextrose were compared to sucrose in shortbread cookies. Hardness, fracturability and cohesiveness of shortbreads were determined. Sweetener combinations of aspartame/cyclamate, aspartame/cyclamate/saccharin, acesulfame K/saccharin, aspartame/saccharin/acesulfame K, acesulfame K/aspartame and aspartame/saccharin gave sweetener TI profiles similar to that of sucrose. Bitterness TI profiles were similar for all potent sweetener combinations but higher than for sucrose. Polydextrose increased hardness and fracturability and decreased cohesiveness of cookies compared to those made with high potency sweeteners without polydextrose. Textural characteristics of polydextrose cookies approached those of sucrose shortbreads.     

Phase Transitions of Amorphous Sucrose and Frozen Sucrose Solutions

Amorphous sucrose showed typical thermal transitions of amorphous materials. The temperatures of those transitions, glass transition, crystallization and melting, decreased with increasing moisture content. The glass transition temperature of dry amorphous sucrose at 57°C was decreased to -46°C as the sucrose was plasticized with excess water. That value remained constant due to maximal freeze-concentration with 72-73% sucrose in the unfrozen matrix which showed ice melting at -34°C. Concentrated solutions may become supercooled resulting in partial freeze-concentration with resultant lowering of glass transition temperature.     

A Thermodynamic Study of the Starch-Water Surface Interaction

The heats of immersion, in water, of corn starch U. S. P. and a directly compressible corn starch were determined as a function of moisture content. This study, in conjunction with an equilibrium vapor phase adsorption study, allowed the thermodynamic parameters characterizing the two systems to be calculated. In both cases, hysteresis was observed in the heat of immersion data. Plots of the differential enthalpies provided evidence that both starches swell in water at room temperature. Average adsorbate-solid hydrogen bond energies were calculated for the two starch-water systems ( - 8.57 Kcal/mole, corn starch U. S. P. -water; - 7.80 Kcal/mole, Starch 1500-water).     

Phase Transitions of Amylose-Lipid Complexes in Starches: A Calorimetric Study

When heated with an excess of water, maize and wheat starches show irreversible endothermic gelatinization in the temperature range 65–75 °C. In addition, a second reversible endothermic transition near 100 °C is observed for these starches, but not for potato starch or waxy maize starch. This transition can be reduced or eliminated by extraction of the starches with methanol. The X-ray powder diffraction pattern of the material in starch which undergoes the 100 °C transition is the same as that of a helical amylose-lipid complex. The amylose-palmitic acid complex shows similar endothermic transitions near 100 °C, as does a complex formed between starch and lysolecithin. Accordingly, these transitions are disordering transitions of amylose-lipid complexes. These complexes can be formed in an exothermic reaction when starch is gelatinized in the presence of lipid.     

Multiple Phase Transitions of Starches and Nägeli Amylodextrins

At temperatures above that required for gelatinization, an order-disorder transition is observed for wheat, maize, waxy maize and potato starches. This transition is the melting of the crystallites in the granules. A second, higher temperature, transition occurs in wheat and maize starches. This also appears to be a melting transition. Potato starch Nägeli amylodextrins show increased thermal stability of the crystalline regions with increasing hydrolysis of the amorphous regions. Extensive hydrolysis lessens the destabilizing effect of the amorphous regions on the crystallites sufficiently that the gelatinization transition occurs to only a small extent, the crystalline regions melting, instead, at temperatures above the gelatinization temperature.     

Pasting of Wheat Flour Extrudates Containing Conventional Baking Ingredients

Pasting properties of extrudates affect product quality and can be controlled by addition of ingredients. We determined the effects of 6 conventional baking ingredients (sucrose, nonfat dry milk (NFDM), dry egg, shortcning, glyceryl monostearate (GMS), and sodium bicarbonate) on pasting properties of wheat flour in extrusions using the Rapid Visco-Analyser (RVA). Pasting parameters determined included: initial peak, onset, and peak times; peak and breakdown viscosities and differences between them; ascending and descending slopes and the angle between their lines. Sucrose, shortening, and GMS affected pasting properties significantly. GMS had the greatest effects on peak times and viscosity values.     

Thermal Transitions of Admixed Starch/Fish Protein Systems During Heating

The thermal transitions of starch-fish protein mixtures were investigated by a thermal scanning rigidity monitor technique and differential scanning calorimetry. Three transitions due to protein denaturation and one transition due to starch gelatinization were identified by both techniques during thermal processing of these mixtures. The gelatinization of starch caused an increase in rigidity of the system to a degree dependent upon the starch type. Thermal transitions of starch and fish protein seemed to proceed independently in mixture systems. However, the presence of salt and sucrose, necessitated by the inclusion of fish protein, caused starch gelatinization to shift to higher temperatures.     

聚葡萄糖在冰淇淋中的代脂作用

主要探讨了聚葡萄糖在冰淇淋生产中的代脂应用，得出聚葡萄糖作为一种水溶性膳食纤维及优质填充剂，可取代部分蔗糖和脂肪，用于低热量，低糖和低脂食品中。     

低热量葡聚糖制备中酶的作用

低热量葡聚糖是水溶性食物纤维的一种．由于其中含有难消化成分，因而热量低。本文对低热量葡聚糖制备中各种酶的作用进行了较系统的探讨。     

新型食品配料——聚葡萄糖制备工艺的研究

聚葡萄糖是一种用途广泛的食品添加剂,生产工艺通常采用传统的三步法,该方法存在生产程序复杂,产品纯度和色泽不稳定等缺点,本文介绍作者对合成工艺研究的新成果——一步制备法,利用搅动的反应体系,将聚合、中和及脱色、干燥在一个反应器中进行,不仅大大简化了生产程序,而且产品纯度、色泽及主要质量指标均优于三步法。     

不同相变对亚稳态奥氏体不锈钢耐腐蚀性的影响

针对奥氏体不锈钢在冷加工和热处理过程中发生相变,并容易被腐蚀的情况,通过实验验证了奥氏体不锈钢在冷加工过程和热处理过程中的相变方式,以及不同组织对其耐腐蚀性的影响。通过冷加工变形试样制备、高温回火、金相分析、扫描电子显微镜下观察和能谱分析,分别对马氏体和σ相相变的机理进行验证。通过金相腐蚀试验,分别对2种相存在条件下材料的耐腐蚀性能进行比较。结果表明冷加工变形下产生的马氏体,会在一定程度上降低材料的耐腐蚀性能,而高温回火产生的σ相对材料耐腐蚀性的影响更为明显。     

纤维素酶酶系对草浆改性的研究

在草浆酶改性过程中,以纤维素酶为主的酶系对草浆滤水性能的改善是必需的,而木聚糖酶对草浆滤水性能的改善起到了辅助作用。纤维素酶酶系中含有相对较低的木聚糖酶活和较高的FPA活力时,浆的滤水性能改善更加明显。在酶改性处理剂量范围内,酶改性处理对纸浆强度性能影响不大。     

聚葡萄糖作为水溶性膳食纤维的发展及法规现状

本文介绍了聚葡萄糖产品的历史及随应用需要而发展的产品品种,简要介绍了膳食纤维的定义,与粗纤维的分别以及分类.并根据定义以及分类将聚葡萄糖作为水溶性膳食纤维进行归类.聚葡萄糖在众多国家被认可为膳食纤维及食品添加剂或食品,本文介绍了聚葡萄糖作为膳食纤维被认可的国家以及相关规定,聚葡萄糖作为食品添加剂在各国的规定,聚葡萄糖作为膳食纤维的检测方法发展历史,同时介绍了聚葡萄糖在国内的法规现状及进展.聚葡萄糖不仅是一种水溶性膳食纤维,同时还是一种良好的Oligo益生元,本文介绍了Oligo(欧力多)低聚糖项目的情况以及功能性低聚糖通用技术规则,行业标准的相关定义,详细介绍聚葡萄糖符合各项定义的特性及作为膳食纤维及Oligo益生元的生理功效.     

Effects of Drying Conditions on Water Sorption and Phase Transitions of Freeze-Dried Horseradish Roots

The water sorption isotherms for freeze-dried horseradish roots (Armoracia rusticana) were determined using the interval sorption technique, and the thermal behavior of dried and rehumidified products was analyzed using differential scanning calorimetry. The hygroscopicity of the dried material increased when the surface temperature during freeze-drying was increased from 20°C to 60°C. Both sorption and thermal data showed that drying at high surface temperatures affected the physical structure of the material, resulting in increased water adsorption, decreased glass transition temperature, and increased unfreezeable water content. Water sorption isotherms and thermal data can be used to determine the proper drying and storage conditions for horseradish roots.     

Enzymatic Degradation of Polydextrose® and of a High-Molecular Polydextrose Fraction

The enzymatic degradation of the alternative carbohydrate, Polydextrose® (PD) and of a high-molecular fraction of PD (PD-D) obtained by dialysis was studied. The reaction products were measured by thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC). Taking into account the experimentally determined extraneous activity of enzymes, a digestibility of 22.5% was measured under in vitro conditions. This digestibility was brought about primarily by glucoamylase activity. The results also served to demonstrate contemporary concepts of the structure of PD which, instead of an arbitrary one, proposes a defined arrangement of α-glucosidic 1,4 and 1,6 bonds within structurally different segments of the PD molecule. It has been documented by in vivo studies that the digestibility of PD in the small intestine is obviously based on the interaction of a number of substrates and enzymes and can be influenced by the composition of the diet.     

Thermal Transitions in Gelatinized Wheat Starch at Different Moisture Contents by Dynamic Mechanical Analysis

Gelatinized starch was analyzed by DMA and the resulting overlapped tan 5 curve was characterized. At high moisture contents (>30% w/w), transitions around ice melting region of tan 5 peak (>50°C wide) showed skewness at the low temperature side. After deconvolution, a symmetrical, sharp, main peak was correlated with the ice melting endotherm but the cause of the lower temperature asymmetrical peak was not identified. At <30% moisture, two deconvoluted Gaussian peaks indicated at least two separate, broadly distributed domains (slightly frequency dependent). Transitions (other than ice melting), if caused by glassy rubbery transitions, were small in tan 5 and broad (50–100°C wide).