Modelling of the inactivation kinetics of the trypsin inhibitors in soy flour

The inactivation kinetics of trypsin inhibitors (TIs) in soy flour was measured over a large range of temperatures (80–134°C) and moisture contents (0.08–0.52 g (g ds)⁻¹). The inactivation of TIs showed a two‐phase inactivation behaviour. The influence of moisture content on the inactivation rate of TIs was large at moisture contents <0.30 g (g ds)⁻¹. Six different inactivation kinetics models were used to describe the decrease of the trypsin inhibitor activity at constant moisture content. The models were compared statistically using a corrected Akaike information criterion. The most parsimonious models at moisture contents ≤0.30 g (g ds)⁻¹ were the model with two first‐order reactions each for a different TI group, and the model with an irreversible inactivation of a native TI to a partially active intermediate TI, followed by a denaturation step. The nth order reaction model was favoured at moisture contents ≥0.40 g (g ds)⁻¹. The kinetics parameters of the model with two firstorder reactions were modelled as a function of moisture content. The overall inactivation model described well the experimental inactivation data of TIs. © 1999 Society of Chemical Industry     

Physicochemical and functional properties of Caryota urens flour as compared to wheat flour

Starch digestibility, thermal, pasting and gelling properties of Caryota urens (CU) flour were investigated using wheat flour as reference. Amylose content of CU and wheat flour was 32.1% and 28.3%, respectively. CU flour had very low content of protein and lipid but had a high content of total starch (98.2%) and resistant starch (RS) [42.5%]. Gelatinisation temperature (78.5 °C) of CU flour was higher than wheat flour. Pasting behaviour of CU flour was similar to that of high swelling tuber and root and waxy starches. CU flour retrograded to a greater extent than wheat flour. Very specific gelling behaviour was noticed for CU flour where it produced significantly harder gel with high paste clarity, fracture ability, adhesiveness, gumminess and chewiness. Expected glycaemic index (eGI) of CU and wheat flour was 92.4 and 100.4, respectively. CU flour had high eGI despite high content of resistant starch.     

热烘改性对大豆分离蛋白功能性的影响

研究了利用热处理对大豆分离蛋白(SPI)进行改性。热烘改性对SPI的吸水性、吸油性、发泡性和泡沫稳定性无显著性影响,常温粘度、高温粘度、耐热性、凝胶性和保水性分别比对照提高了118%、135%、108%、81%和83%。比较适宜的热烘改性条件为10min/85℃。     

Antioxidant activities and functional properties of soy protein isolate hydrolysates obtained using microbial proteases

Soy protein isolate (SPI) hydrolysates were prepared using microbial proteases to produce peptides with antioxidant activity. The process parameters (substrate and enzyme concentrations), hydrolysis time, functional properties and the effects of ultrafiltration were further investigated. The results showed that the soy protein isolate exhibited a 7.0‐fold increase in antioxidant activity after hydrolysis. The hydrolysis parameters, defined by the experimental design, were a substrate concentration of 90 mg mL^?1 and the addition of 70.0 U of protease per mL of reaction. The maximum antioxidant activities were observed between 120 and 180 min of hydrolysis, where the degree of hydrolysis was approximately 20.0%. The hydrolysis increased solubility of the soy protein isolate; however, the hydrolysates exhibited a tendency to decrease in the interfacial activities and the heat stability. The SPI hydrolysates fractions obtained by ultrafiltration showed that the enzymatic hydrolysis resulted in samples with homogenous size and strong antioxidant activity.     

Decreased fat accumulation in 3T3‐L1 pre‐adipocytes treated with extracts of heat‐processed soy flour and breads

The potential anti‐adipogenic effects of gluten‐free soy breads made from germinated soybean (GS), steamed soybean (SS) or roasted soybean (RS) were evaluated in an in vitro adipocyte cell model. GS and RS increased the total phenolic (TP) and total flavonoid (TF) contents of flours compared with the raw soybean (NS) flour. RS and GS had the highest TP (1.04 GAE mg g^?1) and TF (0.92 CAE mg g^?1) contents. Baking increased the TP content of breads, 0.09–0.26 GAE mg g^?1, compared with the flours. Fermentation during breadmaking increased the DPPH scavenging activities compared with the flours. The ABTS scavenging exhibited similar patterns to those of DPPH. Lipid accumulation in 3T3‐L1 cells shows that the alcoholic extracts (100 μg mL^?1) of SS flour and bread decreased adipocyte differentiation by 1.6‐ and 2.1‐fold, respectively, compared with control. SS bread extract substantially downregulated the adipogenesis‐related genes such as acetyl‐CoA carboxylase and glycerol‐3‐phosphate dehydrogenase.     

Physicochemical,antioxidant properties and in vitro digestibility of wheat–purple rice flour mixtures

The physicochemical characteristics, antioxidant properties and in vitro digestibility of high‐antioxidant content flours made from different combinations of Thai purple rice flour and refined wheat flour from 25%, 50% to 75% (w/w) were investigated and these were compared with whole flour from purple rice and refined wheat flour. The increase in substitution levels of purple rice flour affected all the functional properties of flours, at the same time the levels of dietary fibre, protein digestibility and antioxidant compositions were also changed. The purple rice flour exerted a particularly strong effect on starch digestibility as the purple rice increased to 50% in the mixture. Moreover, purple rice flour showed lower amounts of rapidly digested starch (RDS), whereas slowly digested starch (SDS) of whole flour from purple rice and 75% substitution purple rice flour was found to be the highest for all samples. The in vitro starch digestibility of all samples also showed a positive correlation between dietary fibre and antioxidant compounds. Overall, the addition of purple rice flour improved the final nutritional properties, notably a lower predicted glycaemic index, and a higher antioxidant potential, which are two important nutritional properties for human health.     

Thermo‐rheological and functional properties of gamma‐irradiated wholewheat flour

The effects of different doses (0, 0.5, 1, 2.5, 5 and 10 kGy) of gamma irradiation on the thermal, rheological and functional properties of the wholewheat flour were evaluated. Water and oil absorption capacity of the flour increased from 85.92% to 91.44% and 1.10 to 1.91 g g^?1 of flour, respectively, with increase in irradiation dose. The dough development time decreased with dose from 4.0 to 3.0 min. The transition temperatures (T_o, T_p and T_c) decreased as the dose increased; enthalpy of gelatinisation (?H) decreased from 5.18 to 4.27 J g^?1 with dose. The flow behaviour showed a shear‐thinning behaviour, and the hysteresis area decreased with dose. The structural recovery decreased with dose. FTIR did not show formation of any new chemical groups.     

磷酸化改性对南极磷虾蛋白功能特性的影响

目的以磷酸化南极磷虾蛋白为原料,蛋白功能特性为评价指标研究磷酸化改性对南极磷虾蛋白功能特性的影响。方法功能特性的评价方法采用国际通用方法。结果磷酸化改性能够明显改善南极磷虾蛋白的溶解性、吸油性、乳化性、起泡性及泡沫稳定性,但其确切的改性机制仍需开展深入研究。结论磷酸化改性能够改善南极磷虾蛋白的功能特性,拓展了南极磷虾蛋白的应用领域和范围。     

物理改性在蛋清蛋白功能特性改善中的应用

文章对近年蛋清蛋白物理改性研究成果进行了综述,阐述了物理改性方式对蛋清蛋白功能提升的作用,分析了各种改性方式在提升蛋清蛋白不同功能特性中的特点.     

Enzymatic and extrusion pretreatments of defatted rice bran to improve functional properties of protein concentrates

This study evaluated effects of enzymatic, extrusion and combined pretreatments on functional and thermal properties of protein concentrates from defatted rice bran to improve their applicability to food formulations. After the pretreatments, protein concentrates were recovered by alkaline solubilisation and isoelectric point precipitation. Water absorption capacity, oil absorption capacity, emulsifying and foaming properties, and thermal stability were determined in protein concentrates. Yields of each pretreatment were above 62% protein. Enzymatic hydrolysis increased all functional properties studied, mainly for emulsifying activity index (an increase of 71.1%) and foaming capacity (an increase of 60.3%). The extrusion affected positively the oil absorption capacity, emulsifying activity index and foaming capacity. The combined process was able to raise the functional properties. The principal component analysis confirmed that 95.5% improvement in functional properties of concentrates had a strong positive correlation with the pretreatments. However, the pretreatments affected thermal stability and the enthalpy of denaturation negatively.     

Effect of green plantain flour addition to gluten‐free bread on functional bread properties and resistant starch content

Green plantain flour (GPF) was used as a functional ingredient to produce gluten‐free (GF) bread based on a flour blend of rice flour and GF wheat starch (50:50) to improve their functional properties and to increase their resistant starch (RS) content. In pretrials, an addition of up to 30% GPF provided acceptable bread quality with maximum RS content. Based on these trials, two 2³ factorial screening experimental designs were applied, where water content, baking temperature and baking time of GF bread containing 30% GPF addition were optimised. The best baking conditions to achieve satisfying GF bread quality – higher loaf volume, softer crumb firmness and regular porosity structure at the highest RS content could be defined to a maximum addition of water at 160%, baking temperature of 180 °C and baking time of 90 min. The incorporation of GPF showed good potential to improve the quality of GF bread.     

Improvement of functional properties of acid-precipitated soy protein by the attachment of dextran through Maillard reaction

The functional acid-precipitated soy protein (SAPP)–dextran conjugate was prepared by dry-heated storage at 60 °C under 79% relative humidity (RH) for 5 days through Maillard reaction between the ε-amino of lysine in soy proteins and the reducing-end carbonyl residue in the dextran. The covalent attachment of dextran to SAPP was confirmed by SDS-polyacrylamide gel electrophoresis and gel filtration chromatography. Functional properties of soy protein depend on the structural and aggregation characteristics of their major components (storage globulins 7S and 11S). The conjugate seemed to be predominantly formed by 7S, and the acidic subunits of 11S in soy protein. The emulsifying properties of the SAPP–dextran conjugate were about four times higher than those of SAPP. The solubility of the protein was not enhanced as a result of preheating, but rather it was not decreased when the conjugated protein was heated at 90 °C for 20 min due to the presence of the polysaccharide. The excellent emulsifying properties of SAPP–dextran conjugate were maintained even at pH 3.0 and were further improved at pH 10.0. The object of Maillard reaction is to guarantee the suitable reaction degree, and the resulting soluble conjugate can have excellent emulsifying properties.     

Gluten‐free pasta: effect of green plantain flour addition and influence of starch modification on the functional properties and resistant starch content

Green plantain flour (GPF) is rich in indigestible carbohydrates, especially in resistant starch (RS). The objective of this study was to improve the functional pasta properties and RS content by producing gluten‐free (GF) pasta based on rice flour with different amounts of GPF addition (15–60% of total flour blend). Egg albumen (3.5–6.0% of total flour) and dough moisture (36–40%, dough humidity%), at constant emulsifier (0.5% of total flour) addition, were optimised in the first trials. The results showed that an addition up to 30% GPF with higher amount of egg albumen (6%) at dough moisture of 38% provided pasta with acceptable cooking quality and high RS content. Some qualities and/or RS content of GF pasta samples was further improved by adding 30% pregelatinised flours from the native GPF or drum‐dried green banana flour (DDGBF) in combination with applying varied steps of cooking and/or cooling, which were applied after pasta extrusion prior to drying them. The study suggests that GPF, in its native form, but particularly when pregelatinised, is a promising ingredient to be used for the production of GF pasta.     

Physicochemical and functional properties of full‐fat and defatted Moringa oleifera kernel flour

Full‐fat and defatted Moringa oleifera kernel flours were analysed for their functional properties. The effect of pH and NaCl concentrations on the functional properties of the flours was investigated following standard procedures. The protein content of full‐fat and defatted flour was 36.18 and 62.76 g/100 g, respectively. The concentrations of other proximate constituents of the defatted flour were higher than those of the full‐fat flour. Nitrogen solubility was lowest at pH of 4.0 and 9.0, respectively, with maximum solubility occurring at pH of 6.0. Defatting increased the water absorption and fat absorption capacities of Moringa oleifera kernel flour. The foaming capacity and foam stability of the defatted flour were 86.0% and 82.0 mL, whereas that of full‐fat flour were 20.6% and 18.5 mL respectively. The defatted flour showed better emulsification (97.2 mL g^?1) than full‐fat flour (66.0 mL g^?1). The least gelation concentration of the defatted and full‐fat flours was 14% and 16% (w/v) respectively. Moringa oleifera kernel flour can be a valuable source of vegetable protein in fortified food products formulation.     

酶解—磷酸化协同改性对卵白蛋白特性与结构的影响

为考察酶解和磷酸化协同改性对卵白蛋白特性和结构的影响,针对酶解和磷酸化协同改性的卵白蛋白的功能特性变化进行分析,并通过FT-IR、DSC和SEM对协同改性的卵白蛋白结构变化进行分析。结果表明,协同改性后的卵白蛋白的溶解度、凝胶强度、乳化性较酶解后的和未改性的卵白蛋白都有较大的提高,但起泡性和泡沫稳定性有所降低;结构上,卵白蛋白因酶解导致其肽链发生断裂,使得更多的氨基酸残基暴露出来,α-螺旋和β-折叠均有所增加;协同改性的卵白蛋白热变性温度较酶解的和未改性的卵白蛋白分别升高了7.13,10.19℃;此外,由于磷酸基团的嵌入,使蛋白的结构发生了变化,分子结构由球状体变成了层叠的片状结构。     

还原糖对牡蛎蛋白肽糖基化反应产物功能特性与抗氧化性的影响

以葡萄糖(Glc)、乳糖(Lac)、半乳糖(Gal)为糖基供体,对牡蛎蛋白多肽(OP)进行干法糖基化改性,比较分析糖基化产物(OP-GMPs)的功能特性(溶解性、热稳定性和乳化性)及抗氧化性(还原能力,DPPH·、·OH的清除能力)。结果表明,与双糖(Lac)相比,单糖(Glc、Gal)对OP的功能特性和抗氧化性改善效果较好;其中,质量比Gal:OP=2:1时,OP-GMPs的溶解性最大且对DPPH·的清除能力最强,为3:1时,其乳化性最强,为4:1时,其对·OH的清除能力最强;Glc:OP=3:1和4:1时,OP-GMPs的热稳定性和还原能力最强。因此,糖基化改性可有效改善OP的功能特性与抗氧化活性,为其在功能食品及调味品中的应用提供参考。