米糠蛋白酶解产物功能特性及乳液稳定性研究

目的 研究改善米糠蛋白的溶解性。方法 选用胰蛋白酶对米糠蛋白进行酶法改性,分析其在不同水解度下(1%、3%、7%)酶解产物的功能特性及不同pH、离子强度和温度对米糠蛋白酶解产物乳液的影响。结果 酶解可显著提高米糠蛋白的溶解性,在水解度7%时的溶解性最高;而酶解产物的起泡性、起泡稳定性、乳化性和乳化稳定性呈现先增加后下降的趋势,并在水解度为3%时达到最大值;经酶解后持油性显著增加,而持水性显著降低。米糠蛋白及酶解产物乳液在不同pH下平均粒径和电位呈现相似变化趋势,在等电点附近极不稳定,在pH7-8时乳液趋于稳定;低水解度(1%、3%)的酶解产物乳液对高温和盐离子的抵抗能力高于米糠蛋白。结论 水解度为3%的酶解产物,其功能特性显著提升,制备的乳液在高离子强度和加热条件下较为稳定,该结果为米糠蛋白酶解产物制备食品乳液提供理论依据。     

大豆分离蛋白膜研究

以大豆分离蛋白(SPI)和甘油为成膜基质,研究多聚磷酸钠、羧甲基纤维素钠(CMC–Na)、微波及磷酸化对大豆分离蛋白膜性质影响。结果表明,多聚磷酸钠可显著提高膜的水溶性(ρ0.01)和抗拉伸强度(ρ0.05),显著降低膜的氧气透过性(ρ0.01)和水蒸气透过性(ρ0.05);CMC–Na能显著提高膜抗拉伸强度(ρ0.01)和氧气透过性(ρ0.05),显著降低膜的水溶性、透光率及水蒸气透过性(ρ0.01);微波处理可显著提高膜的抗拉伸强度(ρ0.05),降低膜的水溶性(ρ0.05);磷酸化可显著降低膜的氧气透过性(ρ0.05)、透光率及抗拉伸强度(ρ0.01)。     

米糠蛋白的起泡特性及其泡沫微观形态

考察pH值和NaCl浓度对米糠蛋白起泡特性及泡沫微观形态的影响,并对二者之间的内在关系进行阐述。结果表明,当米糠蛋白溶液中不添加NaCl、pH?4时起泡能力较差,但泡沫稳定性可达最大值（88.3±7.3）%,而当溶液的pH值偏离4时起泡能力增加,在pH10和12条件下起泡能力分别可达（73.3±0）%和（168.9±10.2）%,泡沫稳定性分别为（74.7±2.5）%和（68.5±2.1）%;另外在米糠蛋白溶液pH值为4和7条件下分别添加1%的NaCl后,可显著提高起泡能力至（77.8±3.8）%和（90.0±5.8）%。米糠蛋白泡沫的微观形态随时间变化规律说明,不同pH值条件下起始阶段气泡的直径大小分布与泡沫稳定性相关,而当添加NaCl后米糠蛋白起泡能力和泡沫稳定性的改变则与气泡数量和平均面积二者的综合效应有关。     

稻米蛋白提取工艺及其特性研究

以粳稻米为原料,分析其糙米、白米和米糠的营养成分及蛋白组成特点,研究提取条件对糙米、白米和米糠蛋白提取量的影响,并对这三种蛋白的溶解性及分子量分布特征进行比较。结果表明：糙米、白米中的蛋白均以谷蛋白为主,但糙米中谷蛋白含量比白米低4.78%,而清蛋白含量比白米高55.93%;糙米中清蛋白和球蛋白含量分别比米糠低77.22%、44.59%,但谷蛋白含量比米糠高47.00%。提取时间、温度及液料比对三种原料的蛋白提取量均有不同程度的影响,其中液料比是提取三种蛋白时最显著的影响因素 (p ＜ 0.01);温度对白米蛋白提取影响显著(p ＜ 0.05)、对米糠蛋白极显著(p ＜ 0.01),而对糙米蛋白不显著;时间仅对提取白米蛋白有显著影响(p ＜ 0.05),对其他两种蛋白的提取没有明显作用。采用响应面法对提取条件进行优化,得到三个回归模型,经验证,用该模型可以预测稻米蛋白的提取量。稻米蛋白溶解性与SDS-PAGE 电泳分析表明,糙米蛋白的溶解性及其蛋白分子量分布介于白米蛋白与米糠蛋白之间。     

可溶性丝素蛋白的功能性质

研究了可溶性丝素蛋白的功能性质。结果表明,丝素蛋白具有表面活性,能降低溶液的表面张力;经高速剪切作用后,丝素蛋白的表面疏水性显著增强;随着丝素蛋白质量浓度的增加,丝素蛋白溶液的乳化性、起泡性均增强,当丝素蛋白质量浓度大于5g/L时乳化能力增幅不明显,当丝素蛋白质量浓度为15g/L时,它的起泡能力最高,质量浓度继续增加至20g/L时其起泡能力下降,当丝素蛋白质量浓度高于15g/L时,泡沫稳定性的增幅变缓;丝素蛋白在pH3～10范围内具有较好的乳化性、起泡性,在pH4时最强。     

酸沉除镉制备米糠蛋白乳液稳定性的研究

采用粒径分布、微观结构、Zeta电位和分层系数研究米糠蛋白质量分数和预热处理对盐酸、酒石酸、苹果酸和柠檬酸酸沉除镉制备米糠蛋白乳液稳定性的影响。结果表明:当米糠蛋白质量分数为0.5%时,4种酸酸沉除镉制备米糠蛋白的乳液稳定性无显著性差异(P0.05),并且乳液稳定性均较差;当米糠蛋白质量分数为1.0%和2.0%时,酒石酸、苹果酸、柠檬酸酸沉除镉制备米糠蛋白乳液的粒径较小,显示出较好的乳液稳定性;4种酸酸沉除镉制备的米糠蛋白经过预热处理之后,乳液粒径减小,乳液稳定性提高,并且乳液稳定性无显著性差异(P0.05)。     

米糠蛋白的静高压联合酶法改性工艺优化及其特性研究

采用静高压联合碱性蛋白酶对米糠蛋白进行改性。考察静压力、保压时间对米糠蛋白溶解性的影响,优化静高压改性条件。以米糠蛋白溶解性、乳化性和乳化稳定性为指标,通过单因素试验和正交试验综合评分法优化了酶法改性工艺。结果表明,米糠蛋白最适改性条件为静压力200 MPa、保压时间15 min、碱性蛋白酶添加量1 500 U/g、pH 8、酶解温度50 ℃和酶解时间80 min,在此条件下米糠蛋白溶解性、乳化性、乳化稳定性、起泡性和泡沫稳定性分别增加了57%、88%、182%、185%、43%。     

罗非鱼头蛋白质的提取及性质研究

以罗非鱼头为原料,采用加热浸提、酶法水解、酸/碱溶解-等电点沉淀法提取鱼蛋白,冷冻干燥得到4种鱼蛋白粉,分别记为热提鱼蛋白(HFP)、酶解鱼蛋白(EFP)、酸溶鱼蛋白(AFP)和碱溶鱼蛋白(ALFP),并探讨了4种鱼蛋白的营养特性、溶解性和乳化性。结果表明:ALFP和AFP的蛋白含量分别为89.97%和85.87%,必需氨基酸占总氨基酸的比例达到49.72%和48.63%,而脂肪和灰分含量以及白度值均低于HFP和EFP,且差异显著(P<0.05)。溶解性和乳化性的研究显示,EFP和HFP在pH 2.0～10.0内溶解度均高于93%,但体系的乳化活性和稳定性较差;而AFP和ALFP的溶解度随pH值的变化非常明显,在pH 4.0～6.0内,体系的溶解性和乳化性极差,而在pH值低于4.0或高于6.0时,溶解度大大增强,乳化活性和乳化稳定性随之提高,且乳化活性和稳定性明显高于HFP和EFP。酸/碱溶解-等电点沉淀法可用于制备营养价值高,乳化特性相对较好的鱼分离蛋白。     

米糠多糖的脱蛋白研究

采用Sevag法、三氯乙酸法和酶法对米糠多糖进行脱蛋白研究.结果表明,酶法脱除蛋白的效果最好,Sevag法的多糖损失较小,结合酶法和Serag法脱蛋白可大大提高蛋白脱除率,具体操作条件为:0.0055mg/mL木瓜蛋白酶、pH6.0、60℃水浴,再加入总体积为1/2的氯仿-正丁醇(2:1)溶液进行脱蛋白,重复操作4次,此时蛋白脱除率为71.23%.多糖损失率为17.38%.     

米糠蛋白酶法改性前后的功能特性变化研究

以蛋白质为配料的产品中,蛋白质功能性质往往比营养价值更重要,直接影响到米糠蛋白的应用前景。实验研究了经碱性蛋白酶改性后的米糠蛋白功能特性,并与其改性前进行了比较。测定了改性前后米糠蛋白的溶解性、乳化性及乳化稳定性、起泡性及泡沫稳定性,并确定浓度、温度等因素对上述指标的影响。实验结果表明,改性后米糠蛋白的溶解性、起泡性及乳化性与改性前相比均有较大改善,分别提高了140.46%、117.38%、100.50%。米糠蛋白溶解性在pH4.0～6.0较低,在碱性条件下较高,随温度升高而增大;米糠蛋白乳化性、起泡性在碱性条件下较高,随温度的升高其起泡能力和乳化能力均增强。     

Ultrasonic assisted alkali extraction of protein from defatted rice bran and properties of the protein concentrates

Alkaline extraction for the preparation of protein concentrate from rice bran was compared with a range of ultrasonic treatments. Results revealed that the extraction time decreased, and the reaction rate constant increased, with increasing ultrasonic power. The reaction rate constants were 0.0065, 0.0130, 0.0237 and 0.0924 at 40, 60, 80 and 100 W respectively. The defatted rice bran protein concentrate (DRBPC) using ultrasonication (100 W for 5 min) and conventional methods showed no significant difference in bulk densities ( P  > 0.05) but it had higher yield (%) and was lighter brown using ultrasonication ( P  ≤ 0.05). The SEM showed that the residual rice bran after extracting protein using ultrasonication exhibited more damage than the conventional method. The functional properties of both samples were not significantly different ( P  > 0.05) in terms of foam and emulsifying stability. However, the water and oil absorption, foam capacity and emulsion activity were significantly different ( P  ≤ 0.05). The nitrogen solubility index of both DRBPC samples gave similar profiles with the lowest solubility at pH 4–6.     

糙米酵素流变学特性研究

研究糙米粉在不同温度和浓度条件下剪切速率和表观黏度的变化关系,并确定在各温度和浓度条件下其稠度系数和流变指数,建立流变学方程.试验结果表明,糙米粉的黏度随温度的升高而增大,且发酵后的糙米酵素粉黏度随温度的变化范围大于未发酵;糙米粉的黏度随浓度的增大而增大,且发酵后的糙米粉黏度随浓度的变化范围小于未发酵的.     

Effect of addition of protein concentrates from natural and yeast fermented rice bran on the rheological and technological properties of wheat bread

The effect of substituting wheat flour with 0%, 5%, 10% and 15% protein concentrates from natural and yeast fermented rice bran on the rheological properties of their dough and bread properties was studied. Rheological properties of wheat dough were influenced by addition of rice bran protein concentrates. Overall acceptability score and specific loaf volume of 100% wheat bread were not significantly different from composite bread up to 10% rice bran protein substitution, and therefore, the optimised level of substitution was established. The optimised composite bread contained higher total amino acid content, radical scavenging activity and ferric reducing ability power (43.04–48.87 g/100 g, 182.77–201.65   mmol TEAC/100 g and 613.29–637.81 mmol TE/100 g) than control (33.86 g/100 g, 109.43 mmol TEAC/100 g and 540.13 mmol TE/100 g). Springiness, cohesiveness and resilience values of wheat bread were not significantly different from composite bread. Scanning electron microscopy revealed that composite bread had surfaces with embedded granules like protein deposits with small spores.     

挤压米糠流变特性的试验研究

基于流变学原理。确定了挤压米糠的表观黏度模型，并对模型进行了线性回归建模，以便进行试验拟合。试验研究了挤压米糠的流变特性，结果表明米糠的表观黏度随剪切速率的增加而减小。呈现出假塑性流体的流动行为；米糠的表观黏度随温度的升高和原料水分的增加而减小。用计算机程序试验拟合了米糠黏度的方程。     

Functional properties of protein hydrolysates from Riceberry rice bran

Protein hydrolysate from pigmented Riceberry rice bran has great potential to be used in food products due to its protein content and antioxidative activities. In this study, characteristics, solubility, heat stability and emulsification properties of protein hydrolysates from the bran fraction of two rice cultivars, commercial rice bran (CBH) and Riceberry bran (RBH), were investigated. Both CBH and RBH showed the lowest solubility near their isoelectric point between pH 2 and 3. Solubility of RBH increased with increasing pH as the hydrolysates became more negatively charged; however, solubility of CBH was less dependent on pH. Heating did not significantly affect solubility of both hydrolysates which could be due to reduced aggregation of low‐molecular weight peptides and/or the exposure of charged and polar groups after hydrolysis. Oil‐in‐water emulsions stabilised by RBH were more stable compared to those stabilised by CBH. Maximum stability was achieved with RBH at pH 6 where no creaming was observed after 14 day storage. Higher stability could be due to increased surface protein coverage, more negative charge and higher viscosity of RBH‐stabilised emulsions. In addition, higher carbohydrate content and the presence of flavonoid could also contribute to an increase in stability. These results can be applied in food products using rice bran protein hydrolysate as nutritional ingredients.     

Precipitation of rice bran protein using carrageenan and alginate

Precipitation of rice bran protein, a high-quality nutritional protein, using polysaccharides (alginate and carrageenan) was investigated at various pH, temperature and amount of polysaccharide with the objective of obtaining higher protein recovery and possible wider industrial application. Both alginate and carrageenan were found to be effective in precipitating rice bran protein. At pH 3.5, the maximum amount of protein precipitated were 95% for a carrageenan-to-protein ratio of 2:1, and 93% for an alginate-to-protein ratio of 1:1. However, change of temperature (20-55 °C) did not have a significant effect (p > 0.05) on the amount of protein precipitated. The precipitate formed using alginate and carrageenan had protein content of 42.15 and 26.48 g/100 g of precipitate, respectively. The freeze dried product obtained from the rice bran extract precipitated with polysaccharides was capable of forming foam and emulsion, indicating its possible utilization as a food ingredient.     

Effects of rice bran fiber on heat-induced gel prepared with pork salt-soluble meat proteins in model system

The technological effects of rice bran fiber on pork salt-soluble meat proteins in a model system were investigated. Rice bran fiber at levels of 0% (control), 0.1%, 0.5%, 1%, and 2% was added at the same time as salt-soluble meat protein to maintain similar moisture levels in all samples. Samples with increasing amounts of added rice bran fiber had higher pH, yellowness, sarcoplasmic and total protein solubilities. The moisture content, myofibrillar protein solubility and water holding capacity were the highest in the treatments containing with 1% rice bran fiber. However, the lightness and redness, textural properties decreased with increasing rice bran fiber levels. SDS gel electrophoresis did not reveal any changes in proteins regardless different rice bran fiber levels. The apparent viscosity indicated that improvements in water holding capacity and decreased texture due to added rice bran fiber.     

Structural properties of high-protein,low glycaemic index (GI) rice flour

Low glycaemic index (GI) rice flour was prepared by the enzymatic hydrolysis method. The protein content of treated (high-protein, low GI) rice flour was about 3.5 times higher than untreated rice flour, suggesting its use in infant formula or other protein-fortified food products. The GI of untreated and treated rice flour was found to be 88.0 ± 0.2 and 46.1 ± 0.2, respectively. High-protein, low-GI rice flour was studied for thermal and structural properties, which showed significant (p < 0.05) differences from untreated rice flour. The results of thermal properties showed a decrease in transition temperatures and enthalpy of gelatinization. The ratio of peaks at 1045 cm^?1 and 1015 cm^?1 of treated rice flour was significantly (p<0.05) lower than that of untreated rice flour. This could be ascribed to the loss of crystallinity due to enzymatic degradation. These results further support the decrease in transition temperatures and enthalpy of gelatinization. The results of the rheological studies of high-protein, low-GI rice flour revealed that both untreated and treated rice flour samples exhibited non-Newtonian shear-thinning flow behaviour (n < 1), which is characterized by a decrease in viscosity with an increase in shear rate.     

Purification of soluble rice bran fiber using ultrafiltration technology

Defatted rice bran (DRB), an excellent source of soluble rice bran fiber (SRBF), is a byproduct of rice bran oil extraction from whole rice bran. The common process for purifying SRBF extracted from DRB, dialysis and alcohol precipitation, is a complex process. Ultrafiltration technology was evaluated as an alternative process. Membranes of molecular weight cut-off (MWCO) 1, 5, and 10 kDa were used to purify the SRBF at 100 kPa. The apparent viscosity and °Brix of the SRBF solution increased after ultrafiltration, which demonstrated that the SRBF solution was concentrated during the ultrafiltration process. The apparent viscosity of the retentate collected in the ultrafiltration unit with the 1 kDa MWCO membrane had a higher (P < 0.05) viscosity than those collected in the 5 and 10 kDa MWCO membrane. The SRBF solution purified with 1, 5, and 10 kDa MWCO had similar concentrations of arabinose, galactose, and glucose, while the retentate of SRBF obtained from 10 kDa MWCO membrane had slightly lower xylose concentration than that resulting from 1 kDa MWCO. The 10 kDa MWCO membrane at a pressure of 100 kPa more effectively purified the SRBF solution than did 1 and 5 kDa MWCO membranes at the same pressure.