Molecular Dynamics of Soy-Protein Isolate Films Plasticized by Water and Glycerol

ABSTRACT: The effects of water and glycerol on the molecular mobility of a soy-protein isolate (SPI)-based film were investigated using ¹H nuclear magnetic resonance (NMR). SPI-films were prepared with different glycerol contents and equilibrated to various levels of water activity (a_w). The distributed transverse relaxation of film samples showed 2 distinct components: a solid-like fraction (T_2s*) and a liquid-like fraction (T_2m*). The peak T_2s* values of films with lower glycerol concentration were more sensitive to variation in a_w. As a_w increased, the change of solid-like to liquid-like fraction was observed in higher glycerol films. As glycerol content increased, a minimum longitudinal relaxation time (T₁) occurred at lower a_w. Our results suggest that NMR techniques can be used to quantify the plasticizing effects on biopolymer films.     

共干燥技术在蛋白质/多糖膜制备中的应用

为了改善蛋白基可食性膜的阻水性和机械性，选择大豆分离蛋白作为基料，多糖藻酸丙二醇酯（PGA）、果胶、卡拉胶、芦荟多糖作为增强剂，甘油作为增塑剂，考察共干燥技术在形成蛋白质／多糖复合型可食性膜中的应用，及对膜阻水性和机械性的影响。研究结果表明，蛋白质和多糖通过共干燥法比多糖直接加入法所形成的膜的机械性、阻水性均有一定程度的改善。而且，在两种多糖的加入方式下，形成的SPI／多糖膜的WVP由低到高都可依次排为：SPI／藻酸丙二醇酯〈SPI／果胶〈SPI／卡拉胶〈SPI／芦荟多糖。     

六种藏药对食用油脂抗氧化作用的初步研究

通过在日常食用的菜籽油、酥油、猪油、花生油、大豆油中添加中藏药藓生马先蒿、斑唇马先蒿、益母草、珠牙蓼、蜜花香薷和白苞筋骨草的乙醇提取物,以VC、VE为对照,利用Na2S2O3-I2滴定法,测定不同时间油脂POV的方法,初步研究了中藏药对常用食用油脂的抗氧化作用。结果发现6种藏药乙醇提取物对所选5种油脂均有一定的抗氧化效果。     

8种食用植物油碳原子当量42和44甘油 三酸酯含量的测定

目的 了解碳原子当量在食用植物油掺伪中的应用价值。方法 采用气相色谱法和高效液相色谱法分别对8种常见食用植物油的碳原子当量42(ECN42)和44(ECN44)甘油三酸酯含量进行了计算和比较。结果 花生油与菜籽油各指标较接近, 大豆油、玉米油和葵花籽油各指标较接近, 而高品质的橄榄油与山茶油各指标较接近。但橄榄油和山茶油的ECN42和ECN44值远低于高亚油酸的大豆油、玉米油等种籽油类, 且差异具有显著性(P<0.05); 而山茶油与橄榄油之间, 只有实际和理论甘油三酸酯含量最大差值(ΔECN42、ΔECN44)有显著性差异(P<0.001)。结论 本文首次对国内市场中常见食用植物油的ECN42和ECN44甘油三酸酯含量进行检测和总结, 此结果为进一步开展食用植物油掺伪鉴别研究奠定了基础。     

氯化钙改性谷朊粉可食性复合膜的研究

本文研究了交联剂氯化钙对小麦谷朊粉复合膜性能的影响，应用综合评分法得出，氯化钙的最佳添加浓度为0．67％，此时综合得分为最高达120．99，在此条件下制得的复合膜，其拉伸强度提高了13．4％，水蒸气透过系数（WVP）降低了7．3％。应用氯化钙交联可以明显提高可食陛膜的强度，改善复合膜的机械幽抱。     

食用菌保健蛋糕的研制

食用菌对人体具有营养和保健作用。主要介绍了食用菌保健蛋糕的加工工艺过程,通过正交实验确定了该产品的最佳配方,并对生产中容易出现的质量问题进行了分析讨论。     

叶丝加料机内部导流装置的研究及应用

传统的叶片加料机无法满足现有的叶丝加料工艺要求,为了提高加料过程的料液有效利用率和加料均匀性,需对叶片加料滚筒设备的内部导流装置进行重新设计,设计的主要内容包括导流板、钉、板带钉,并对板及钉结构做了相关的防粘壁设计。应用效果表明,烟丝在该滚筒内部能够被充分抛起并与料液充分接触,与叶片加料相比,叶丝加料的料液有效利用率提高了5%,加料均匀性提高了3%,同时出料端的烟丝松散无湿团,滚筒内壁无烟丝烟末粘连现象。     

一种食用油掺杂地沟油快速检测系统的设计

食用油在加工过程中一般不会混有金属离子,可通过电导率实现对食用油掺杂地沟油进行检测。在此基础上,设计了一种食用油掺杂地沟油快速检测系统。该系统以ARM为核心,利用数据采集技术,完成了食用油掺杂地沟油检测系统的软硬件设计。系统测试实验证明,该系统能够准确测定食用油的电导率信息,从而获知食用油中是否掺杂地沟油,以及分析食用油中掺杂地沟油含量的信息。该检测系统具有检测速度快、功耗低、价格低廉和便携的优点。     

去除正丙醇提高糖蜜酒精质量

新的食用酒精质量标准将正丙醇作为一项质量指标来考查。正丙醇属中级杂质，与水、乙醇混溶，沸点较接近乙醇，分离难度较大。应从多方面着手，控制正丙醇含量：1．使用产正丙醇少的酵母菌种。2．发酵液的组成要合理。3．防止杂菌感染。4．强化杂醇油提取工作。5．在醛塔的顶部加水。增加精馏塔精馏段塔板数。(丹妮)     

Antimicrobial effectiveness of bioactive packaging materials from edible chitosan and casein polymers: assessment on carrot, cheese, and salami

Antimicrobial packaging is one of the most promising active packaging systems for controlling spoilage and pathogenic microorganisms. In this work, the intrinsic antimicrobial properties of chitosan (CH) were combined with the excellent thermoplastic and film-forming properties of sodium caseinate (SC) to prepare SC/CH film-forming solutions and films. The antimicrobial effectiveness of SC, CH, and SC/CH coatings on the native microfloras of cheese, salami, and carrots was evaluated. In vitro assays through the test tube assay indicated that the most significant antimicrobial effect was achieved by CH and SC/CH solutions on carrot and cheese native microfloras. SC film-forming solutions did not exert antimicrobial activity on any of the native microflora studied. SC, CH, and SC/CH films stored in controlled environments showed that the retention of the antimicrobial action was observed until 5-d storage, at 65% relative humidity in both temperatures (10 °C and 20 °C). In vivo assays were also performed with SC, CH, and SC/CH applied as coatings or wrappers on the 3 food substrates. CH and SC/CH applied at both immersion and wrapper exerted a significant bactericidal action on mesophilic, psychrotrophic, and yeasts and molds counts, showing the 3 microbial populations analyzed a significant reduction (2.0 to 4.5 log CFU/g). An improvement of the bactericidal properties of the CH/SC blend respect to those of the neat CH film is reported. The ionic interaction between both macromolecules enhances its antimicrobial properties. Practical Application: The continuous consumer interest in high quality and food safety, combined with environmental concerns has stimulated the development and study of biodegradable coatings that avoid the use of synthetic materials. Among them, edible coatings, obtained from generally recognized as safe (GRAS) materials, have the potential to reduce weight loss, respiration rate, and improve food appearance and integrity. They can be used in combination with other food preservation techniques in order to extend the effectiveness of the food preservation chain. Moreover, antimicrobial films and coatings have innovated the concept of active packaging and have been developed to reduce, inhibit, or delay the growth of microorganisms on the surface of food in contact with the package. The use of antimicrobials packaging films to control the growth of microorganisms in food can have a significant impact on shelf-life extension and food safety. In addition, antimicrobial films can be prepared by the combination of inherent antimicrobial materials (that is, CH), with good film-forming protein-based ones (that is, SC). Therefore, the objective of this work is to study the performance of 2 biodegradable and edible biopolymers and their combination as natural packages for selected food products.