The effect of pH,salts and sugars on the rheological properties of cress seed (Lepidium sativum) gum

Effect of shear rate (15–600 s^?1), gum concentration (1–2%), pH (3–9), sucrose (10–40%), lactose (5–15%), NaCl (100–300 mm ) and CaCl₂ (5–50 mm ) was evaluated on apparent viscosity (η_a), flow behaviour index (n), consistency coefficient (K) and yield stress (τ₀) indices of cress seed gum (CSG) solutions. Different rheological models were used to fit the experimental data, although the Herschel–Bulkley model was found the best model. An increase in gum concentration led to an increase in τ₀, η_a, and k and a decrease in n values. The addition of salts lowered the k value; however, the n value showed slight significant change. The presence of sugar resulted in the enhancement of n, k, τ₀ and η_ap values. The existence of yield stress and pseudoplastic behaviour of CSG, its stability against salts, wide range of pH and synergic effect of sugar make it a good thickener and stabiliser in food formulations.     

Protein–polysaccharide interactions at fluid interfaces

Protein–polysaccharide interactions find many applications in food engineering and new food formulations. This review article describes recent research on the effect of protein–polysaccharide interactions on the properties of air–water and oil–water interfaces, as affected by their behaviour in the bulk phase. The interfacial behaviour of protein–polysaccharide mixtures exhibiting associative (i.e., net attractive) interactions as well as their performance in food emulsions and foams has been the subject of several reviews in the last decade. Much less attention has been paid to the interfacial behaviour of protein–polysaccharide mixtures exhibiting unfavourable interactions. Thus we are concerned here with the interfacial behaviour of both kinds of mixtures.     

Enhanced stability of crude protease from kiwifruit (Actinidia deliciosa) by adding hydrocolloid for organic processed food uses

Crude protease originating from kiwifruit (Actinidia deliciosa) was extracted for organic processed food uses. The protease included in the kiwifruit can be utilized for organic uses instead of current commercial enzymes from microbial origin, which are not suitable for organic processed food. Crude protease extracted by physical treatment rather than any biochemical purification methods was appropriate for the organic processed food uses. However, crude protease extract has been found to be unstable for processing and storage usage, which has to be modified to be stable by appropriate methods suitable for organic processed food uses. The proteolytic activity of the protease extracted from kiwifruit was measured using casein as a substrate. The decreased inactivation rate constant of crude protease treated with guar gum and locust bean gum within the temperature range of 30–50°C implied the enhanced stability of crude enzymes by treatment with hydrocolloid. The half-times of crude proteases treated with guar gum and locust bean gum were higher than the half-time of native crude protease at 40°C (optimum temperature of the native crude protease), with values of 55.45 min for the guar gum-treated sample, 50.23 min for the locust bean gum-treated sample and 23.26 min for the native sample, demonstrating the quantitative evidence of the enzyme stability. The relatively stable maintenance of the proteolytic activity has helped to realize hydrocolloid-treated enzyme to be used for hydrolytic function in organic processed food applications.     

几种亲水胶体对淀粉理化性质的改善作用及相关机理研究进展

本文主要综述了亲水胶体中的瓜尔胶、黄原胶和魔芋胶对淀粉形态特征、糊化性质、流变特性、热特性、质构特性、膨胀度和冻融稳定性的影响,进一步探讨了上述三种亲水胶体对淀粉理化性质影响的相关机理,为其在各种淀粉基食品中的应用提供理论据。     

Effect of salts on the rheology of hydrocolloids from mulberry (Morus alba L.) leaves in concentrated domain

Rheological properties of 2–8% mulberry leaf hydrocolloids extracted by hot water (Hw) or sodium bicarbonate (Alk or Alk-v) were evaluated. Steady shear rheological results of mulberry leaf hydrocolloids indicated the structural behavior with a Newtonian viscosity at low shear rate and shear-thinning behavior over intermediate to high shear rate regime. As simulated by Carreau model, the characteristic time constant of mulberry leaf hydrocolloids increased, but the power-law behavior index decreased with increasing concentration. Results from the dynamic rheological experiments revealed that the behavior of 2% mulberry leaf hydrocolloid solutions were characteristic concentrated polymer solution. However, as the concentration was raised up to 4–8%, a gel-like behavior may occur depending on the extraction methods, possibly owing to the formation of aggregates at high polymer concentration. Furthermore, rheological properties of Alk and Alk-v were generally higher than those of Hw. Though mulberry leaf hydrocolloids were ionic polymers, the rheological properties in concentrated domain were not influenced pronouncedly by the addition of 0–200 mM of NaCl, KCl or MgCl₂. In contrast, under sufficiently high CaCl₂ concentration (68 mM or 200 mM for alkaline extracted and water extracted mulberry leaf hydrocolloids, respectively), formation of a three-dimensional gel network was observed, possibly due to the cross-linking of Ca²⁺ with carboxyl groups of mulberry leaf hydrocolloids in addition to charge screening effects.     

Isolation and viscometric characterization of hydrocolloids from mulberry (Morus alba L.) leaves

Hydrocolloid in mulberry leaves was extracted with water or sodium bicarbonate, and characterized rheologically in a highly dilute to a semi-dilute regime. Mulberry leaf hydrocolloid was composed of mainly carbohydrate with high levels of uronic acid. The hydrodynamic behavior of mulberry leaf hydrocolloid in deionized water demonstrated a typical polyelectrolyte behavior in the dilute domain, as indicated by a nonlinear Huggins' plot. Intrinsic viscosity value for alkaline-extracted (Alk) and water-extracted (Hw) hydrocolloid was around 7.25 dL/g and 3.61 dL/g, respectively. The specific viscosity versus concentration plot for both Alk and Hw exhibited a power-law dependence on concentration, with an onset of molecular entanglement occurring at a concentration of around 0.6 g/dL and 1.8 g/dL, respectively. Coil-overlap parameter for Alk and Hw was in the range of 4.35–6.61. The relative chain stiffness parameter (B) for Alk and Hw was in the range of 0.004–0.013, indicating a stiff backbone.     

基于果蔬原料的食品3D打印技术及其应用

作为新兴数字化生产技术,3D打印技术已在许多领域中被广泛应用。其在食品领域中的应用可满足人们对食品定制化、个性化营养和数字化营养的需求,能进一步简化食品供应链体系,拓宽食材来源。水果和蔬菜富含多种营养素,是人类饮食的重要组成部分。相对于面团、巧克力、肉糜等食材,水果和蔬菜具有含水量高、难成形、易褐变的特点,因此很难实现直接3D打印。为了更好地了解水果和蔬菜在食品3D打印领域的应用情况,本文从食品3D打印的原料特性要求、果蔬原料特性以及3D打印果蔬材料的加工技术等方面进行了综述,并对其发展趋势作出展望。     

亲水胶体对苦荞冻糕的抗老化作用

以感官评价和硬度为指标,研究单一亲水胶体(黄原胶、瓜尔胶、海藻酸钠、羟丙基甲基纤维素、卡拉胶)对苦荞冻糕抗老化作用的影响,筛选出抗老化效果良好的3种亲水胶体,在此基础上以硬度为指标,采用响应面分析法确定苦荞冻糕最佳复配亲水胶体抗老化剂。结果表明,最优抗老化剂配方为0.13%黄原胶、0.17%海藻酸钠、0.24%卡拉胶(以浆液总重计),经实验验证,在-4℃条件下添加了复配亲水胶体的苦荞冻糕贮藏时间可延长至原来的2倍(14 d)。     

不同亲水胶体对再制奶油奶酪品质的影响

通过研究刺槐豆胶、卡拉胶、海藻酸钠、瓜尔豆胶和黄原胶5种不同亲水胶体对以切达奶酪为原料,直接酸化法得到的再制奶油奶酪品质的影响,来选择较佳的亲水胶体方案。实验结果表明,亲水胶体对样品各方面的性质影响显著,对持水性和持油性的影响尤为明显。本体系适用不凝胶的亲水胶体。黄原胶和刺槐豆胶是最佳的选择,并建议2种胶体单独使用。