Effect of heating cast kafirin films on their functional properties

Edible films can be produced from kafirin but the diverse food product requirements necessitate modification of the films. To modify their functional properties, kafirin films were cast, with and without plasticizer, from glacial acetic acid (GAA) and aqueous ethanol (AE), then heated using microwave energy. A power of 80 W for 2 min caused an approximately two‐ and fourfold increase in the tensile strength of non‐plasticized and plasticized films, respectively. Film glass transition temperature increased by about 15%. Film biodegradability was slowed. However, only the digestibility of the non‐plasticized films cast from AE heated for the longest time (4 min) was decreased, by about 25%; while that of the other films was not affected. GAA cast films had higher digestibility than AE cast ones, possibly as a result of acid‐mediated deamidation of kafirin. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis indicated heat‐induced kafirin oligomers. Scanning electron microscopy of heated plasticized films showed more wrinkled structures compared to non‐heated films, whereas the non‐plasticized films appeared more brittle with heating. The results indicate that heat‐induced intermolecular disulfide cross‐linking was involved in modifying the properties of kafirin films. Copyright © 2006 Society of Chemical Industry     

高粱醇溶蛋白消化性研究

该文介绍高粱醇溶蛋白的提取方法,特性和消化性测定方法,并简单分析高粱醇溶蛋白发展前景。     

Sorghum Proteins: The Concentration,Isolation, Modification,and Food Applications of Kafirins

Abstract: Celiac disease is a serious condition affecting millions of individuals. Those afflicted with this illness are resigned to a lifelong avoidance of products containing the storage prolamin proteins found in cereal grains wheat, rye, and barley. Since many food products are based on these cereals, especially wheat, celiac patients have very limited food choices, and those that are available to them are generally poor in quality, often nutritionally deficient, and expensive. Furthermore, this condition also indirectly affects their families and friends with whom they share meals. Thus, a burgeoning need exists to develop nutritious, palatable, and affordable foods, especially staples like bread and pasta, for these individuals and their families and friends who are accustomed to wheat based products. Grain sorghum and its proteins are safe for celiac patients and individuals with varying levels of gluten intolerances. However, the main sorghum proteins, kafirins, are resistant to digestion. They are also difficult to extract and modify in an industrial-scale process and with food-compatible chemicals, thus limiting their use in foods. This review describes studies on kafirin extraction and methods for modifying sorghum proteins for improved nutrition and functionality, as well as food applications. Armed with this knowledge, scientists and technologists will be in a better position to identify opportunities that will further enhance the nutritional and functional value of sorghum proteins.     

反溶剂法制备姜黄素-高粱醇溶蛋白复合颗粒及其特性分析

以姜黄素为芯材,高粱醇溶蛋白为壁材,采用反溶剂法制备包埋姜黄素的高粱醇溶蛋白复合颗粒（简称复合颗粒）,并对其理化性质及稳定性进行研究。结果表明：姜黄素与高粱醇溶蛋白制备复合颗粒的最佳芯壁比（质量比）为1∶10,产品平均粒径为13.17?μm,电位为19.38?mV,得率为87.51%,包封率为62.61%,负载率为6.51%。相比于高粱醇溶蛋白颗粒,扫描电子显微镜显示：复合颗粒呈球形,但表面有多孔结构;红外光谱结果显示：复合颗粒位于1?534、1?655?cm－1等处的波峰均发生红移,α-螺旋含量减少,β-折叠含量增加。24?h紫外光照射后,高粱醇溶蛋白包埋的姜黄素光稳定性提高33%。复合颗粒的粒径和多分散性系数在30?d室内环境贮藏过程中均无明显变化,但在环境pH?5～6,颗粒易聚集。结果表明：高粱醇溶蛋白的包埋作用有益于提高姜黄素的稳定性,可为姜黄素和高粱醇溶蛋白的高值化利用提供理论依据。     

Sorghum kafirin interaction with various phenolic compounds

The ability of various phenolic compounds to bind and precipitate kafirin, the prolamin protein of sorghum, was investigated with regard to effects on its nutritional and functional uses. The protein–phenolic compound interaction was quantified by haze formation and colorimetric determination of total polyphenol bound. Ferulic acid, catechin and extracted phenolics (flavonoids) from condensed tannin‐free sorghum did not complex kafirin. Only tannic acid and sorghum‐condensed tannins had the ability to complex kafirin. The sorghum‐condensed tannins interacted more strongly than tannic acid. The haze of sorghum‐condensed tannins–kafirin was permanent, indicating a strong interaction. The fact that sorghum‐condensed tannins can bind irreversibly to kafirin indicates that this may play a role in decreasing protein digestibility in high‐tannin sorghum and can cause haze formation in lager beer made from high‐tannin sorghum. However, in condensed tannin‐free sorghum, phenolic compounds may not appear to play a major role in decreasing protein digestibility, as these endogenous phenolics may not bind with kafirin. Copyright © 2003 Society of Chemical Industry