Antioxidant Properties of Genistein in a Model Edible Oil System

ABSTRACT:  Antioxidant properties of genistein were tested during the low temperature oxidation of linseed oil. Four linseed oil solutions were prepared: linseed oil, linseed oil containing 2 μmol added genistein/g oil, linseed oil containing 4 μmol added genistein/g oil, and linseed oil containing 200 ppm butylated hydroxyanisole (BHA). Dimethyl sulfoxide (DMSO) (1.7%) was added to all solutions to allow for the solubilization of genistein. Antioxidant activities were analyzed using 2 techniques: (i) the oven stability test carried out at 60 °C with periodic determination of peroxide values (PV); and (ii) oxidation on a heated (60 °C) FTIR-ATR crystal with periodic scanning and collection of infrared spectra. Induction points (IP) for each solution were determined. A strong correlation ( r = 0.91) was noted between the 2 analytical methods used. Three significantly ( P < 0.10) different levels of IP were generally observed. The shortest IP (17 h for PV, 36.9 h for FTIR) was found for the linseed oil. Intermediate IP's were obtained for the 2 μmol added genistein/g oil (32.4 h for PV, 43.5 h for FTIR) and 4 μmol added genistein/g oil (33.9 h for PV, 44.2 h for FTIR) samples. The longest IP (39.9 h for PV, 54.2 h for FTIR) was obtained for the 200 ppm BHA containing solution. Although genestein was not as effective as BHT in retarding oxidation, the results clearly demonstrate that it is able to act as an antioxidant in a bulk oil system.     

Lipid Oxidation in Oil‐in‐Water Emulsions: Involvement of the Interfacial Layer

More polyunsaturated fats in processed foods and fewer additives are a huge demand of public health agencies and consumers. Consequently, although foods have an enhanced tendency to oxidize, the usage of antioxidants, especially synthetic antioxidants, is restrained. An alternate solution is to better control the localization of reactants inside the food matrix to limit oxidation. This review establishes the state‐of‐the‐art on lipid oxidation in oil‐in‐water (O/W) emulsions, with an emphasis on the role of the interfacial region, a critical area in the system in that respect. We first provide a summary on the essential basic knowledge regarding (i) the structure of O/W emulsions and interfaces and (ii) the general mechanisms of lipid oxidation. Then, we discuss the factors involved in the development of lipid oxidation in O/W emulsions with a special focus on the role played by the interfacial region. The multiple effects that can be attributed to emulsifiers according to their chemical structure and their location, and the interrelationships between the parameters that define the physicochemistry and structure of emulsions are highlighted. This work sheds new light on the interpretation of reported results that are sometimes ambiguous or contradictory.     

Effects of temperature,pH and light on the stability of aloin A and characterisation of its major degradation products

This study explored the stability and degradation products of aloin A under varying pH, temperature and light conditions usually encountered in processing. The stability of aloin A was significantly affected by temperature and pH. The content of aloin A decreased by more than 90% within 12 h at 50 °C and within 6 h at 70 °C, respectively. A significant decrease in stability was also observed at higher pHs. At pH 8.0, less than 2% of aloin A remained within 12 h. However, aloin A exhibited good stability at acidic pH levels with 94% remaining at pH 2.0 for 14 days. Light exerted no influence on the stability during the experimental period (14 days). Aloe‐emodin, elgonica‐dimers A and B were characterised as major degradation products of aloin A at pH 5.0 or below, and elgonica‐dimers were mainly formed at 4 °C as well. 10‐hydroxyaloins A and B were found under any condition except at pH 2.0 and 3.0, and they were mainly formed under high temperature, neutral‐basic and any light conditions.     

凝胶层析法分离猪股骨降血压肽及其体外稳定性

将猪股骨酶解液超滤分离后,对分子质量小于5 kD的酶解滤液（IC50值为1.362 mg/mL）进行凝胶层析分离,研究洗脱液、流速、上样量3 个因素对猪股骨降血压肽分离纯化效果的影响。结果表明：以去离子水为洗脱液,流速0.6 mL/min,上样量体积分数1%时,能够得到最佳分离效果,其最高活性组分IC50值达到0.401 6 mg/mL。研究凝胶层析分离后抑制率最高的组分的稳定性,发现其有较好的耐热和耐酸碱、耐盐性,在pH 2～6中有良好的溶解性。     

罗非鱼鱼鳞肽钙复合物的稳定性研究

以罗非鱼鱼鳞为原料制备肽-钙复合物,以钙的结合量为指标,研究了体外胃肠道模拟消化、小肠刷状缘膜酶、共存食物成分、pH、热处理等因素对罗非鱼鱼鳞肽钙复合物稳定性的影响。结果表明,罗非鱼鱼鳞肽钙复合物对消化酶、小肠刷状缘膜酶的降解具有较高的耐受性,对NaCl、乳糖具有较好的稳定性（p>0.05）;但对50℃以上的热处理较为敏感,钙结合量显著下降（p<0.05）。鱼鳞肽钙复合物在pH2.0的酸性条件下易于解离,但在弱碱性条件比较稳定,pH9.0时钙结合率可达89.65%。推测肽钙复合物在小肠内主要以结合物的形式存在以阻止钙在碱性条件下的沉淀。      

乳酸乳球菌乳脂亚种冷冻干燥保护剂优化及其贮藏稳定性

采用单因素试验、Plackett-Burman试验设计和Box-Behnken响应面法,筛选和优化乳酸乳球菌乳脂亚种KLDS4.0326真空冷冻干燥保护剂工艺,并分析冻干菌粉在不同温度下的贮藏稳定性。结果表明：脱脂乳粉、海藻糖和甘油含量是影响菌体细胞存活率的关键因素;以菌体细胞存活率为响应值,对3 个因素进行优化分析,保护剂最佳配比为：脱脂乳粉10.77 g/100 mL、海藻糖7.81 g/100 mL、甘油3.31 g/100 mL,此条件下菌体细胞存活率为（87.43±1.62）%,与理论预测值接近。在4 ℃和25 ℃条件下保藏12 个月后,菌体细胞存活率分别为40.63%和8.67%,冻干菌粉在4 ℃条件下具有更高贮藏稳定性。     

水酶法提取番木瓜籽油工艺及其氧化稳定性分析

以番木瓜籽为原料,通过单因素试验和正交试验研究不同酶种类、酶解时间、料液比、酶添加量、酶解温度等因素对番木瓜籽油提取率的影响,确定番木瓜籽油提取的最佳工艺条件,并以番木瓜籽油过氧化值为评价指标,考察温度、光照、抗氧化剂对番木瓜籽油氧化稳定性的影响。结果表明,番木瓜籽油的最佳提取条件为：选用中性蛋白酶,酶添加量2.5%、酶解时间5 h、料液比1∶7、酶解温度45 ℃。在此条件下,番木瓜籽油的提取率为85.73%。温度、光照、氧气均会引起贮藏过程中番木瓜籽油过氧化值的升高。添加抗氧化剂可明显提高番木瓜籽油的氧化稳定性,其中叔丁基对苯二酚的抗氧化效果最好。     

石灰乳化的工艺与设备改良

本文就常见的糖厂石灰乳化间的工艺和设备进行探讨和实践,提出因繁就简、因地制宜地对现有流程设备进行改良挖潜、对现行工艺管理进行加强与改进的一些措施,这是许多糖厂提高石灰乳质量的一个行之有效的办法。