正交设计法优化大豆分离蛋白膜工艺参数

该文以大豆分离蛋白(SPI)为主要原料,添加甘油制成可食性膜,研究成膜介质和成膜方法对膜性能影响;并比较酸性和碱性条件下可食性膜性能,选择出最佳成膜工艺参数。酸性条件下为:蛋白质与甘油比例为2:1、pH为3、温度80℃、底物浓度8%;碱性条件下为:蛋白质与甘油比例为3:1、pH为10、温度90℃、底物浓度10%。     

明胶-壳聚糖可食性复合包装膜性能影响因素

主要研究明胶含量、明胶浓度,甘油含量对明胶―壳聚糖可食性复合膜性能影响。通过对复合膜厚度、抗拉强度、断裂伸长率及透光率检测表明,明胶在成膜液中含量、浓度及甘油含量均对复合膜性能具有显著影响。     

普鲁兰、甘油共混对结冷胶食用膜性能的影响

研究了普鲁兰、甘油共混对结冷胶食用性膜的机械性能、水蒸汽透过率、阻氧性和吸水率的影响。结果表明,普鲁兰的添加,提高了结冷胶食用膜的延展性、水蒸汽透过率和阻氧性,但降低了结冷胶食用膜的抗拉强度和吸水率;甘油增加了膜的延展性和水蒸汽透过率,但降低了膜的阻氧性。     

甘油含量对大豆蛋白膜功能性质的影响

大豆蛋白膜是一种可降解、可食用和可再生的新型包装材料,但是其机械性能尚不能满足日常使用的需求。研究甘油含量对可食性大豆蛋白膜功能性质的影响,结果显示随着甘油含量的增加,大豆蛋白膜抗张强度下降,而断裂延伸率、水蒸气透过率和氧气透过率升高。当甘油添加量为大豆蛋白的30%时,大豆蛋白膜具有较好的机械性能。因此,甘油含量是影响大豆蛋白膜机械性能的主要因素之一。     

基于分子交联的蛋白膜性能改良技术的研究进展

蛋白膜由于具有无毒害、可降解、绿色环保、可延长食品保质期、提供营养等优点,在可食膜研究领域具有重要地位。如何改善其相对较弱的机械强度以及某些不足的阻隔性能,是研究者长期以来一直关注并将持续关注的问题。本文首先阐述了蛋白膜的成膜机制、性能指标,接着重点对基于分子交联的蛋白膜性能改良技术,包括物理交联、化学交联、酶法交联以及物理能交联等进行综述,最后对蛋白膜交联的意义和发展趋势进行了展望。     

甘油与甲基纤维素对高直链玉米淀粉- 壳聚糖复合膜性能的影响

以高直链玉米淀粉(HACS)和壳聚糖(CS)为基本材料,甘油为增塑剂,甲基纤维素(MC)为增强剂制备可食性复合膜,研究高直链玉米淀粉与壳聚糖的质量比,甘油的添加量以及甲基纤维素的添加量对复合膜物理性能的影响,包括抗拉强度(TS)、断裂伸长率(E)、水蒸气透过系数(WVP)和色度。结果表明,壳聚糖添加量的增大与甘油添加量的增加都使高直链玉米淀粉- 壳聚糖复合膜的抗拉强度降低,断裂伸长率和WVP 显著增大,膜颜色变黄;甲基纤维素的添加改善了复合膜的机械性能和WVP,随着甲基纤维素添加量的增加,复合膜的抗拉强度和断裂伸长率都随之增大,WVP 逐渐降低,且对膜的颜色没有显著影响。     

Growth of Staphylococcus aureus as Related to 17O NMR Water Mobility and Water Activity

¹⁷O NMR data were determined for three solute-BHI (Brain Heart Infusion) mixtures. For each solute, NaCl, raffinose and glycerol, NMR data (linewidths and signal intensity) were determined as well as water activity (a_w), moisture contents, and effects on growth of Staphylococcus aureus in media of various moisture contents. Liquid (highly mobile) water content in all media tested was determined by NMR. This mobile water was important and had a stronger correlation with S. aureus growth rate than did a_w or moisture content, although solute effects limited empirical prediction. NMR linewidth also correlated with lag phase.     

可食性魔芋葡甘聚糖成膜特性研究

以魔芋胶 (KG)为基材 ,研究KG的浓度、增塑剂的种类与浓度和干燥温度等因素对膜的抗张强度 (TS)、耐破度 (BS)、伸长率 (E)以及水蒸气透过系数 (WVP)的影响。结果表明 ,随KG浓度的增大 ,各指标均有所升高 ,但浓度太高 (>10 g/L) ,制膜困难 ,且表观性状不够理想。综合考虑 ,浓度以 8g/L为宜 ;随增塑剂浓度的增加 ,膜的TS下降 ,E增大 ,阻湿性能明显降低 ;3种增塑剂中 ,甘油的增塑效果最明显 ,聚乙二醇 4 0 0次之 ,乙二醇最差 ;随干燥温度的提高 ,膜的TS有所增加 ,E和WVP有所降低 ,但温度太高 ,膜显微黄色 ,脆性增大 ,一般 60℃较为理想     

Mobility of Water in a Starch-Based Fat Replacer by 170 NMR Spectroscopy

The effects of concentration, type and level of ingredients, heat and freeze/thaw treatments on the water mobility of starch-based fat re-placers were investigated. Water mobility in the starch-based fat re-placer samples containing gums, proteins or emulsifiers was similar to that of samples without additional ingredients. Water mobility was not affected by heat treatment, but was increased by freeze/thaw treatments. Water mobility in the solute containing samples was lower than in samples without additional ingredients and changed only slightly after heat and freeze/thaw treatments.     

NMR技术研究木聚糖酶对馒头老化特性的影响

在储藏过程中,为了提高馒头质量,降低老化速度,采用TA-XT Plus物性仪测定馒头样品硬度及NMR技术测定其水分分布变化,研究木聚糖酶对馒头样品老化速度的影响。结果表明:馒头储藏0³6h内,馒头的表皮硬度及芯部硬度均缓慢增加,相对于空白馒头样品,添加XYL馒头样品硬度较弱;达到36h时,硬度显著增加,特别是添加L-XYL的馒头样品。馒头储藏期间,质子信号A及A1持续下降。在0³6h内,所有添加木聚糖酶的馒头样品质子信号下降速度较慢;36¹20h内,添加S-XYL的馒头样品质子信号下降缓慢,但添加L-XYL的馒头样品质子信号下降速度快。由此可知,相对于空白样品,在0³6h内,添加XYL的所有馒头样品老化速度较慢,保鲜度较好。在36¹20h内,添加S-XYL的老化速度较慢,而添加L-XYL的老化速度较快。      

核磁共振研究膳食纤维面包制作过程的水分迁移行为

利用核磁共振测定三种不同配方面包在制作过程(和面、发酵、醒发和焙烤)中质子的自旋-自旋弛豫时间(T2),面团中流动性不同的水分,表现出不同的弛豫时间。实验表明,在面包制作过程中,其束缚相和自由相的迁移行为不同,此外140MPa处理的膳食纤维具有强持水性,添加至面包中可改善其储藏性。     

玉米醇溶蛋白成膜工艺条件的探讨

对玉米醇溶蛋白的成膜条件进行了研究,结果表明,玉米醇溶蛋白在８０％乙醇中溶解效果良好,在４０℃恒温条件下可以在光滑的不锈钢板上形成具有的一定强度的可食性薄膜。     

Water Mobility in Glassy and Rubbery Solids as Determined by Oxygen-17 Nuclear Magnetic Resonance: Impact on Chemical Stability

Although chemical reactivity in solid food systems has been studied as a function of water activity and glass transition, the possible effects of water mobility on chemical reactions have not been investigated. The effect of the glass transition on water mobility at constant temperature and water content was determined. The relationship between the experimentally determined water mobility in polyvinylpyrrolidone (PVP) systems and chemical reactivity data from the same PVP systems was evaluated. Water mobility, as determined via ¹⁷O-NMR, was not affected by the glass transition; PVP systems at constant water activities and water contents, but different physical states (glassy and rubbery), had the same water mobility. An evaluation of four chemical reactions showed no relation between water mobility and kinetic data. The effect of water on chemical reactions is multidimensional and cannot be reduced to a single physicochemical parameter.     

An absorption model for the thickness effect in hydrophilic films

The permeability parameters for moisture transmission through hydrophilic films are well known to be thickness dependent, this effect appearing in permeability studies based on diffusion models. In our model we assume that, besides diffusion, some of the water vapour of the diffusion flux is removed by the hydrophilic components of the films. This water is immobilized and becomes hydration water of the hydrophilic molecules. This paper describes a diffusion–adsorption model, with thickness‐independent parameters, which explains this phenomenon.     

Polarity Homogeneity and Structure Affect Water Vapor Permeability of Model Edible Films

A continuous gravimetric measurement method was perfected to determine with accuracy the water vapor permeability of edible films. Two substances, methylcellulose and paraffin wax, with different physicochemical properties, were used as films. Factors affecting permeability included the polarity of film components, the homogeneity or dispersion of material in the film and the structure which depends on the distribution of paraffin wax in the composite films. The thickness and the Water Vapor Transmission Rate (WVTR) measurement methods resulted in different values for permeability. WVTR increased with hydrophilicity and heterogeneity. Modeling trials con-cerning water vapor transport indicated the major influence that structure had on permeability. Waxlaminated fiIms had a very high barrier efficiency, comparable with that of synthetic films.