乳酸菌发酵蔬菜亚硝酸盐含量测定——盐酸萘乙二胺法预处理条件的研究

在蔬菜腌渍发酵中会产生亚硝酸盐,食品中亚硝酸盐含量测定国家标准是盐酸萘乙二胺法.但其样品预处理条件仅适合肉制品,对于其他样品仅可作为参考.因此,对于蔬菜发酵过程中亚硝酸盐测定样品预处理条件有必要进行筛选和确定.本实验在单因素实验的基础上进行正交实验,结果表明:处理条件pH=9,不加入沉淀剂,水浴温度65℃,水浴时间10min的组合回收率为100.35%,比国家标准方法(肉制品为样本)的预处理条件测得回收率(89.68%)有明显提高.并以三种发酵菜来检别预处理条件,测定结果达到满意的准确度(回收率>98%).     

一测多评法测定6种大豆异黄酮的质量分数

基于高效液相色谱紫外双波长检测方法,建立只用一个对照品同时测定6种大豆异黄酮含量的一测多评方法,以降低食品中大豆异黄酮含量测定的分析成本并提高分析效率。样品经甲醇超声波辅助提取后,采用C_(18)反相色谱柱;柱温25℃;进样量10μL;检测波长262 nm和248 nm;流量1.0 mL/min;以体积分数0.2%甲酸水溶液和甲醇运行洗脱。通过一测多评分析确定6种大豆异黄酮的定量标准曲线、线性范围、相对校正因子、相对保留时间及相对峰面积,并对检测结果的精密度、稳定性、重复性、加样回收率以及系统的耐用性和适应性进行验证,且与外标法实验结果相比对,6种大豆异黄酮在检测范围内均呈现出良好的线性关系(R~2 0.999 9)。     

等电点沉淀法鱼分离蛋白结构与功能变化研究进展

以蛋白质分离提取为出发点,系统回顾了国内外有关分离蛋白特别是鱼分离蛋白的研究现状,阐述基于等电点絮凝沉淀原理的蛋白分离技术在食品蛋白配料中的重要性。集中探讨了分离后蛋白质结构与性质的变化,现有研究均表明分离过程中蛋白质空间结构的变化与分离鱼蛋白产物的食品功能特性具有相关性。因此研究鱼分离蛋白的结构变化规律,对于通过调控以改善鱼蛋白配料的食品功能特性有重要指导意义。     

污染微滤膜的超声波辅助清洗实验研究

超声波清洗技术用于清洗酵母菌溶液和大豆分离蛋白(ISP)溶液污染的聚偏氟乙烯(PVDF)微滤膜。实验中所用的超声波频率为40kHz,超声波的强度为1.43～2.85W/cm2。实验结果表明:对于酵母菌溶液污染的微滤膜超声波辅助水洗是恢复水通量的有效方法;而且超声波强度越高,达到相同FR(水通量恢复率)的清洗时间tc越短;但对于大豆分离蛋白溶液污染的微滤膜单纯用超声波辅助水洗的效果相对较差,而超声波辅助NaOH溶液的化学清洗的效果较好,在浓度为3g/L的NaOH溶液超声波辅助清洗6min即可使其FR值达到91%。     

不同提取方法对蔬菜亚硝酸盐检测结果的影响

为了对蔬菜中的亚硝酸盐检测的前处理方法进行改进,本实验采用国标方法、振荡提取法和超声波提取法,分别提取蔬菜中的亚硝酸盐;采用盐酸萘乙二胺法检测蔬菜中的亚硝酸盐的回收率,并测定不同超声时间对结果的影响.结果显示提取液超声波10 min时提取效果最佳,回收率最高.与国标法相比,超声提取法简便、快捷、检测结果准确度比较高.     

脉冲电场技术提高高温大豆粕蛋白提取率的研究

对采用脉冲电场技术辅助提取高温豆粕中大豆分离蛋白组分的工艺进行了研究。通过响应曲面分析法对调制工艺进行优化,确定最优提取工艺条件为:电场强度29.85kV/cm、流速50.95mL/min,料液比1:10.07,脉冲时间441.5μs,大豆分离蛋白提取率最大值为62.04%,比热处理、微波处理和超声波提取率分别提高了0.74%、13.19%和10.1%。     

超声波辅助提取大豆粗脂肪技术用于大豆粗脂肪酸值测定的可行性研究

国标法检测大豆粗脂肪酸值时,索氏抽提法提取大豆粗脂肪耗时长、操作繁琐。本实验论证了超声波辅助技术替代索氏抽提法提取大豆粗脂肪,可以大大缩短大豆粗脂肪酸值检测时间。通过比对,两种方法测得的酸值的线性相关系数达到0.995 9,且两种方法制取的大豆油脂肪酸组成种类和含量均无显著差异。因此,可以利用超声波辅助提取大豆脂肪快速检测大豆粗脂肪酸值。     

超声波辅助双酶法与碱法提取米糠蛋白功能特性的比较研究

采用超声波辅助双酶法与碱法提取米糠蛋白,分别测定米糠蛋白的功能特性,并对米糠蛋白进行十二烷基硫酸钠-聚丙烯酰胺电泳分析(SDS-PAGE)、氨基酸分析和热变性分析。结果表明:利用超声波辅助双酶法提取的米糠蛋白其功能特性较碱法提取的米糠蛋白有所改善。碱法提取的米糠蛋白分子质量分布大概在65.46、46.77、33.42、23.66、13.09、8.07 ku和2 ku,超声波辅助双酶法提取的米糠蛋白的分子质量分布主要集中在2 ku。从超声波辅助双酶法提取的米糠蛋白和碱法提取的米糠蛋白中均分离出17种氨基酸,两者氨基酸组成一致,主要氨基酸均为谷氨酸、天门冬氨酸和精氨酸,但各氨基酸含量有一定的差别。经差式扫描量热法测得超声波辅助双酶法提取的米糠蛋白热变性温度为75.83℃,碱法提取的米糠蛋白热变性温度为76.75℃。     

大豆分离蛋白中蛋白质含量的快速测定

采用基于经典凯氏定氮法原理设计的KDN-08A半自动定氮仪对大豆分离蛋白中蛋白质含量进行快速测定.结果经t检验,与经典凯氏定氮法测得结果无显著性差异,且回收率在99.53%～100.19%之间.表明该方法测定结果准确可靠、操作简单快速,适用于大豆分离蛋白中蛋白质含量的测定.     

蔬菜中硝酸盐、亚硝酸盐提取与测定的研究

目的:研究蔬菜中硝酸盐、亚硝酸盐对保障人类健康具有重要意义.方法:本实验选择用简便、高效的超声波提取技术提取蔬菜中的硝酸盐和亚硝酸盐,用紫外分光光度法测定其含量.结果:研究表明,利用紫外分光光度法同时测定蔬菜中硝酸盐和亚硝酸盐含量的方法简单、快速、选择性好.结论:硝酸盐测定的相对误差在-2.52％～1.14％之间,亚硝酸盐测定的相对误差在1.98％～4.26％之间,符合定量测定要求.     

婴幼儿谷类辅助食品中亚硝酸盐测定方法的改进

目的改进国标方法测定婴幼儿谷类辅助食品中亚硝酸盐含量。方法使用高峰氏Taka淀粉酶降解样品中的淀粉、蛋白质和脂肪,酶解后的样品经过滤,使用分光光度法测定亚硝酸盐含量。结果与国标方法相比,改进方法不需使用沉淀剂,过滤时间缩短,滤液澄清,方法回收率为92.7%～101.2%,相对标准偏差为0.64%～2.89%。结论经验证,改进后的方法能满足方法学要求,实验效率大大提高,可以满足产品质量控制的要求。     

连续流动分析-盐酸萘乙二胺分光光度法测定酱油中的亚硝酸盐和硝酸盐

建立了一种同时测定酱油中亚硝酸盐和硝酸盐的连续流动分析-盐酸萘乙二胺分光光度法。酱油样品经25 ℃超声15 min预处理,乙酸锌-亚铁氰化钾体系沉淀蛋白质后,自动进样且采用气泡隔断样品,并经透析膜透析,采用双通道同时测量亚硝酸盐和硝酸盐。结果表明,亚硝酸盐在0.025～1.0 mg/L质量浓度范围内线性良好,加标回收率在83.54%～98.56%之间,精密度试验结果相对标准偏差（RSD）＜3%;硝酸盐在0.25～5.0 mg/L质量浓度范围内线性良好,加标回收率在92.95%～102.32%之间,精密度试验结果RSD＜2%。该方法准确、高效、灵敏,可以用于测定酱油中亚硝酸盐和硝酸盐。     

Cold plasma hydrophilization of soy protein isolate and milk protein concentrate enables manufacturing of surfactant-free water suspensions. Part I: Hydrophilization of food powders using cold plasma

In this study, we found that treatment with cold plasma influenced the wetting properties of soy protein isolate and milk protein concentrate powders. Cold plasma treatment significantly decreased the apparent contact angle of the powders, indicating hydrophilization of the powders. Cold radiofrequency low-pressure plasma treatment had a larger effect on powder wettability than corona atmospheric plasma discharge. In addition, cold plasma treatment had a more noticeable effect on the wettability of the hydrophobic milk protein concentrate than on the inherently hydrophilic soy protein isolate. Both the soy protein isolate and milk protein concentrate demonstrated zero hydrophobic recovery over time. Scanning electron microscopy showed that cold air plasma treatment of food powders caused minor surface oxidation, though these changes were not observed using FTIR spectroscopy. We suggest that cold plasma treatment has important implications for the production of stabilizer-free food suspensions.     

Physicochemical and Functional Properties of Winged Bean Flour and Isolate Compared with Soy Isolate

The proximate composition, amino acid profile and functional properties of isolated winged bean proteins were determined and compared with soy protein isolate. Winged bean protein extracted at pH 10 and pH 12 had protein contents of about 90% and 80%, respectively. Alkali extraction of winged bean proteins at pH 10 and pH 12 did not affect the amino acid distribution of the isolated proteins. Oil and water absorption, emulsion, and foaming properties of winged bean isolated compared favorably with soy isolate. Least gelation concentration for winged bean isolate was 18% compared to 14% for soy isolate. Thus, winged bean protein isolate with its high protein content, high lysine and other essential amino acid content and good functionality has a good potential as an ingredient in food products.     

改良比色法检测食品中的亚硝酸盐

近些年,与亚硝酸盐有关的食品安全问题时有发生,传统比色法又有其局限性,因此本实验对传统比色法进行了改良。将对氨基苯硫酚和萘基乙二胺盐分别修饰到金纳米颗粒上,通过与NO₂-的化学反应使金纳米颗粒发生聚集,并且聚集程度与NO₂-的浓度呈正相关,此方法的标准曲线的R2=0.9946,回收率97.00%~100.28%,相对标准偏差(RSD)是0.77%~3.88%,检测限达到了5.12 ng/mL,并比较了三种常见食品的亚硝酸盐含量的变化。通过与传统比色法的对比,此方法操作简单(一步法)、稳定性好、响应快、检测限低,可用于分析食品中微量亚硝酸盐产生过程和水中微量亚硝酸盐的检测,有利于食品工业的发展进步。     

Rice Dreg Protein as an Alternative to Soy Protein Isolate: Comparison of Nutritional Properties

Rice dreg protein could be a valuable source of plant-based proteins, as an alternative to soy proteins in some food products. Here, nutritional properties of rice dreg protein were compared with those of soy protein isolate. The protein content of rice dreg protein was approximately 62.6 g/100 g sample, with large amounts of fat, carbohydrate, and ash. The denaturation temperatures of rice protein isolate from rice dreg protein were 47.4 and 97.2°C, respectively. This indicated that these proteins could be denatured during rice syrup processing to form aggregates, but were relatively more stable than rice endosperm protein and soy protein isolate. The main amino acids in rice dreg protein and rice protein isolate were Glu, Pro, Arg, Asp, and Leu, with Lys as the lowest content. Most of essential amino acids and nutritional parameters of rice protein isolate and rice dreg protein met the suggested nutritional requirements for a child according to FAO/WHO, and were relatively higher than those of soy protein isolate. In addition, rice protein isolate showed better digestibility than soy protein isolate during four hours sequential pepsin and pancreatin digestions. The final digestibility value was 96.66% for rice protein isolate compared to 91.41% for soy protein isolate. Thus rice dreg protein could potentially replace soy proteins as a good source of value-added protein for human nutrition in response to the increasing demand for plant proteins.     

In vitro digestibility of rare sugar (D-allulose) added pectin–soy protein gels

Confectionery gels are known to be high-caloric products due their high sugar content. Changing their formulations by substituting the sugar with alternative natural sweeteners and functionalising them, the addition of proteins has gained attention. Understanding the rate of digestion of these products is also important for selecting the appropriate formulation. In this study, in vitro gastric digestion behaviour of the gels formulated with D-allulose, a low-calorie rare sugar, soy protein isolate (SPI) (1%, 2.5%) and pectin (4%) were examined. Digestion decreased the hardness of the gels (P < 0.05), but, at 2.5% SPI concentration. Moisture content of the samples increased after digestion and presence of SPI induced higher water uptake. At the end of 2 h of digestion, 1% soy protein isolate containing gels had the highest brix values showing that after a certain concentration, soy protein isolate governed the system due to improved soy protein–pectin interaction or due to improved gelation with Maillard reaction. NMR relaxometry experiments further confirmed the changes in the gels with the increase in T₂ values. Power law model was fitted for the dissolution behaviour using the ^oBrix values of the digestion medium. Dissolution of sugar and the contribution of SPI to the gel network were clearly observed in SEM images. Results showed that these gels had the potential to slow down the emptying rate of stomach thus could lead to ‘fullness’ for a longer time.     

马来酸酐酰化改性对大豆分离蛋白功能性质的影响

研究马来酸酐酰化改性对大豆分离蛋白功能性质的影响。结果表明:随着马来酸酐用量的增大,大豆分离蛋白的酰化度增大,等电点降低;随着酰化度的增大,大豆分离蛋白构象松散,色氨酸残基的微环境趋向于暴露于水的状态,亲水性增强;经马来酸酐酰化改性后,大豆分离蛋白的溶解性、发泡性、乳化性及乳化稳定性均显著提升,但泡沫稳定性有所下降。研究表明,马来酸酐酰化改性大豆分离蛋白是一种非常有前景的功能性食品添加剂。     

大豆分离蛋白的功能性和改性研究进展

大豆分离蛋白（soy protein isolate，spi）是大豆蛋白中最为精制的形式，广泛应用于食品工业，在不同的产品中表现出不同的功能性。大豆分离蛋白可以用物理、化学、酶法和生物工程方法进行改性。结果表明，大豆分离蛋白经过改性后能拓宽大豆分离蛋白在食品工业中的应用及达到人们所希望的功能特性。