乳糖酶水解生产低乳糖牛乳工艺的优化

研究低乳糖牛乳的生产条件.通过单因素分析和正交试验对牛乳的水解条件进行优化.结果表明,在加酶量2 500 U/L、水解温度40℃、水解2h时牛乳中乳糖水解效果最佳,水解率达到74.5％.     

干热变性大米淀粉对鸡肉丸品质的影响

以干热变性大米淀粉替代卡拉胶,研究其对鸡肉丸品质特性的影响.结果表明,在鸡肉丸中添加一定比例的干热变性大米淀粉,可有效提高鸡肉丸的硬度和咀嚼性.与卡拉胶相比,添加干热变性大米淀粉的鸡肉丸的弹性、黏聚性及回复性更好,并能维持鸡肉丸在贮藏过程中的各质构特性的稳定性.同时,添加干热变性淀粉能够明显改善鸡肉丸的解冻汁液流失和蒸煮损失.感官评定结果表明,添加干热变性大米淀粉在一定程度上提高了其总体感官水平,且当添加量为1.2％时能够代替0.6％卡拉胶作为鸡肉丸的品质改良剂,获得品质更加优良的鸡肉丸产品.     

嗅觉可视化技术对虾储藏期内新鲜度变化的研究

新鲜度是虾类产品品质和加工适性的一个重要指标。研究利用自制的4×4可视化传感器阵列提取储藏在4℃下1～7 d的南美白对虾的挥发性气味信息。将提取的传感器阵列与虾顶空挥发性气体反应前后的颜色变化值作为特征值,对其进行主成分分析。构建以前7个主成分作为输入变量的虾新鲜度等级的BP神经网络判别模型。对训练集样本,模型的判别正确率达100%,对预测集样本,模型的识别正确率达91.30%。研究结果表明:利用嗅觉可视化技术来检测虾的新鲜度是可行的。     

响应面优化酶解核桃蛋白制备抗氧化肽的工艺

为优化碱性蛋白酶酶解核桃蛋白制备抗氧化活性肽的工艺条件,考察酶解条件对酶解产物的抗氧化活性的影响。以羟基自由基的清除率、超氧阴离子自由基的清除率、还原能力为考察指标,使用响应面分析法,研究温度、pH值、底物浓度和酶添加量对制备抗氧化活性肽工艺的影响。经过优化得出最优酶解条件为:温度51℃、pH值8.13、底物浓度3.16%、酶添加量3.30%,在此最优条件下核桃多肽对羟基自由基的清除率为55.93%、对超氧阴离子自由基的清除率为47.85%、还原能力为55.34%。在10mg/mL的浓度下,核桃多肽的还原能力是VC的55.3%,对羟基自由基和超氧阴离子自由基的清除率分别是VC的93.8%和52.2%。     

电导率法快速鉴别地沟油的方法研究

通过试验研究了采用电导法鉴别地沟油的方法,探讨了影响电导率测定的各因素。结果表明:正己烷加入量为25 mL,去离子水加入量为20 mL,25℃水浴恒温搅拌30 min,分离油、水相,测定水相电导率为最佳测定条件。不同油脂电导率测定对照试验表明,地沟油的电导率远远大于合格食用油,电导率可作为快速鉴别地沟油的一种方法。而折光率测定结果表明,不同油脂折光率数值相差不大。     

超高压处理对干红葡萄酒中11种酚酸的影响

经超高压处理的干红葡萄酒在存贮一年后,采用高效液相色谱法测定其中11种酚酸物质的含量.结果表明,随着处理压力和处理时间的改变,此11种酚酸含量发生显著的变化;超高压处理的酒样与未经超高压处理的酒样相比,一年后的变化比刚处理后的变化更显著.     

复凝聚法制备山核桃油微胶囊的研究

以改性乳清分离蛋白聚阳离子及阿拉伯树胶聚阴离子为壁材,采用复凝聚法在山核桃油表面形成包覆结构,利用转谷氨酰胺酶进行固定化,冷冻干燥脱水获得微胶囊成品.根据微胶囊包油率,对制备条件和固化条件进行评价.结果表明,最佳制备条件为:山核桃油添加量为0.6mL,改性乳清分离蛋白添加量20mL,阿拉伯树胶添加量为6％,pH4.5,搅拌速度为300r/min.最佳固化条件为:固化pH6.0,固化时间为10h,固化温度为10℃,转谷氨酰胺酶添加量为25U/g阿拉伯树胶.最终包油率可达84.15％.在贮藏过程中,微胶囊化后的核桃油可有效的抑制山核桃油过氧化值升高.     

Ethyl carbamate formation regulated by ornithine transcarbamylase and urea metabolism in the processing of Chinese yellow rice wine

Ethyl carbamate (EC) is a potential carcinogenic compound present in most of the fermented foods. In this work, EC was inhibited through different strategies during vinification of Chinese yellow rice wine. EC can be inhibited by the use of ornithine in contrast to the control at peak point. However, the utilisation of urease resulted in little inhibitive effect on EC. The comparative data of intracellular ornithine transcarbamylase (OTCase) and arginine deiminase (ADI) among four experiments showed that EC was positively regulated by intracellular OTCase, but ADI was not determined. Extracellular urea and citrulline content was significantly increased by adding ornithine (P < 0.05), whereas ethanol played a minor role in EC formation. The correlation analysis between EC and OTCase or urea revealed a linear association (correlation coefficients above 0.8). These findings suggested that OTCase may be a required factor regulating EC formation during the brewing of Chinese yellow rice wine.     

Preparation and characterization of pullulan–chitosan and pullulan–carboxymethyl chitosan blended films

The characteristics of pullulan–chitosan and pullulan–carboxymethyl chitosan (CMCH) blended films were investigated. The viscosity of the film-forming solutions, mechanical properties, barrier properties (water and oxygen), water solubility, and color are reported. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurements were used to study the interactions and compatibility between the polysaccharides. The addition of the chitosan or CMCH to pullulan effectively modified the mechanical and oxygen barrier property of the film. The improvements in the film properties have been related to strong interactions between chitosan/CMCH and pullulan polymers, which were observed with FTIR spectroscopy. The ratio of pullulan and chitosan to achieve films with optimum mechanical properties, oxygen and water barrier properties was identified to be 1:1. Increased concentrations of chitosan lead to the formation of inter-molecular hydrogen bonds rather than the intra-molecular hydrogen bonds which were suggested from XRD measurements.     

Impact of surfactants on the lipase digestibility of gum arabic-stabilized O/W emulsions

The bioavailability of lipids from an emulsion can be controlled and regulated by the property of the stabilizing interfacial layer. Here we evaluate how low-molecular weight surfactants including hexadecyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and Tween 80 (T80) influence the interfacial behavior of lipase and bile extract on the surface of lipid droplets stabilized with gum arabic (GA). The lipolysis behavior was influenced by surfactant type and concentration. The results showed that anionic SDS could completely displace GA from droplet surface. Cationic CTAB might either adsorb onto existing GA layers or displace GA, whereas non-ionic T80 could co-adsorb with GA on the interface. When the concentration of surfactants was much higher than the critical micelle concentration (CMC), all the surfactants would form a dense adsorption layer on the droplet interface to prevent lipase from the direct contact with lipids. A considerable amount of surfactant in the aqueous phase may also compete with the bile salt and lipase, thus leading to suppressed digestion of lipids. Ionic surfactants would denature the lipase resulting in reduced enzyme activity, and T80 micelles may interact with the lipase, hindering their adsorption onto the droplet interface as well. These results were confirmed both by the digestion model and interfacial techniques. The results provided guidance for the development of emulsion-based delivery systems for functional lipid foods.