Effect of kafirin protein coating on sensory quality and shelf-life of 'Packham's Triumph' pears during ripening

BACKGROUND: Pears are exported in large quantities from South Africa, resulting in large revenues. Minimisation of quality losses once the fruit has reached the export destination is as important as following strict export and distribution protocols. Kafirin can form edible films. In this study an edible coating made from 20 g kg^?1 kafirin coating solution was applied as a postharvest treatment to retard quality deterioration of ‘Packham's Triumph’ pears during storage at the typical ripening temperature (20 °C). Changes in physicochemical and sensory quality were monitored over a period of 24 days. RESULTS: The kafirin coating was unable to retard the onset of ripening but decreased the respiration rate and retarded the progression of senescence. However, moisture loss was exacerbated in the kafirin‐coated fruit during ripening at 20 °C, especially towards the end of the shelf‐life. CONCLUSION: The kafirin coating extended the eat‐ripe quality of the pears by 1–2 weeks. However, the appearance of the fruit was unacceptable after 14 days of storage in terms of wrinkled skin. Further work is needed to improve the water barrier properties of the kafirin coating by incorporating a wax or triglyceride into the coating formulation or more simply by applying a kafirin coating to waxed fruit. Copyright © 2011 Society of Chemical Industry     

Some compositional changes in malted sorghum (Sorghum vulgare) grain and its value in broiler chicken diet

Grains of two sorghum (Sorghum vulgare L) varieties were germinated at room temperature for 2, 4 and 6 days. Germination resulted in an increase in protein content due to dry matter loss; this rose with increasing time of germination. The absolute amount of tannin was unchanged until the fourth day of germination but decreased markedly by the sixth day. Fractionation of the grain protein of one variety showed that there was a large increase in the albumin-globulin fraction (rich in lysine) and a decrease in the kafirin and cross-linked kafirin fraction (low in lysine) as a result of germination. Although these changes resulted in a more than 30% increase in lysine content on the fourth and sixth days of germination, a substantial loss in dry matter occurred when germination was continued up to 6 days. When 14-day-old Hubbard chicks were fed a diet containing about 59% malted sorghum supplemented with lysine, they showed better (P < 0.05) weight gain and efficiency of feed conversion than those on malted sorghum without lysine supplementation. However, malting reduced the amount of lysine needed to supplement the diet from 0.25% for unmalted sorghum to 0.18% for malted sorghum.     

响应面优化超声波-微波协同提取高粱醇溶蛋白工艺

以高粱种子为原料,采用超声波-微波协同辅助提取高粱醇溶蛋白。在单因素试验结果的基础上利用响应面法优化高粱醇溶蛋白提取工艺,建立提取工艺回归数学模型。结果表明：最佳提取工艺条件为超声时间26 min、液料比10∶1（mL/g）、微波时间260 s,在该条件下高粱醇溶蛋白的得率为6.79%,与理论得率接近,可为实际生产提供理论依据。     

高粱醇溶蛋白-卡拉胶复合纳米颗粒负载姜黄色素的特性研究

本研究以姜黄色素为芯材,高粱醇溶蛋白为壁材,卡拉胶自组装,采用反溶剂法制备负载姜黄色素的中空和实心复合纳米颗粒,并对其理化性质及体外消化特性进行研究。结果表明,制备中空(C-HNP)和实心纳米颗粒(C-SNP)的最佳芯壁比为1∶10,其粒径约为71 nm和135 nm,电位为-37.7 mV和-38.2 mV,包埋率为89.6%和84.1%,负载率为8.01%和7.49%。透射电镜显示两种纳米粒子呈规则的球形形态,C-HNP具有内部中空结构。红外光谱结果显示复合颗粒中酰胺峰Ⅰ和Ⅱ均发生蓝移,卡拉胶和姜黄色素一些吸收峰发生相应偏移,说明它们与蛋白质分子发生相互作用。体外消化模拟实验显示复合纳米颗粒显著地增加了姜黄色素的体外溶解释放率,C-HNP具有更高的控释能力。结果表明,高粱醇溶蛋白是一种适合疏水性分子包埋与控释的生物原材料。     

Encapsulation and protection of resveratrol in kafirin and milk protein nanoparticles

Food proteins have been widely used as carrier materials for the encapsulation of bioactive ingredients. Combination with hydro-soluble proteins provides better properties to prolamin-based particles. Kafirin obtained from sorghum belongs to cereal prolamin proteins. In this study, kafirin nanoparticles in the absence and presence of beta-lactoglobulin (β-Lg) or casein were prepared for the encapsulation and protection of resveratrol. The particles stabilised by 2% β-Lg or 0.2% casein were the smallest in size. Encapsulation efficiency of resveratrol was between 67% and 76% in kafirin/milk protein particles and the highest in kafirin/casein particles. Encapsulation in kafirin/milk protein particles improved DPPH˙ scavenging capacity of resveratrol but decreased its ABTS˙⁺ scavenging capacity. Stability of resveratrol ranked in order kafirin/casein > kafirin/β-Lg ~ kafirin.     

高粱醇溶蛋白结构与功能活性的研究进展

高粱醇溶蛋白是高粱中的主要贮藏蛋白,可应用于食品加工和医疗保健领域。从高粱醇溶蛋白组成、结构和功能及活性方面进行了阐述,综述了高粱醇溶蛋白在运输生物活性成分、制备包装薄膜、改善高粱蛋白消化率、生产无麸质面团、制备生物活性肽等领域的研究现状,并对其发展前景进行了展望。研究综述为高粱醇溶蛋白在食品领域的开发和应用提供了参考。     

Preparation and characterization of kafirin‐quercetin film for packaging cod during cold storage

This study mainly evaluated the physical properties of kafirin‐quercetin (KQ) edible films and their application on the quality of cod fillets during cold storage. The results showed that the addition of quercetin significantly increased mechanical properties of KQ films, while decreased water vapor permeability, water solubility, and transparency. As quercetin was 0.4% (wt/vol), the film had the highest tensile strength (4.96 ± 1.23 MPa), the lowest water vapor permeability (1.08 ± 0.09 g·mm·m^?2·h·KPa^?1) and water solubility (22.02 ± 0.45%). Moreover, compared with the pure kafirin and polythylene films, KQ films could effectively inhibit the cod meat deterioration by restraining the growth of microorganisms and decreasing TVB‐N and TBARs. The KQ_0.4% film was the best to prolong the shelf life of cod fillets during cold storage. Therefore, KQ edible films could be used as a potential food packaging material to protect and retain the quality of aquatic products.     

高粱醇溶蛋白对浓香型白酒窖泥味的消减机制

窖泥味在浓香型白酒中被视为一种异臭味,添加高粱醇溶蛋白对浓香型白酒中的窖泥味有消减作用,对高粱醇溶蛋白消减窖泥味的作用机制进行了研究。浓香型白酒中的3-甲基吲哚和4-甲基苯酚是使其产生窖泥味的关键气味物质。香气轮廓实验表明,高粱醇溶蛋白的加入可显著降低浓香型白酒中的窖泥味,而对其他风味无显著影响。采用顶空固相微萃取法分析发现,高粱醇溶蛋白可使模拟酒样中的3-甲基吲哚和4-甲基苯酚的挥发度分别降低38.99%和46.39%。且当添加200mg/L高粱醇溶蛋白后,3-甲基吲哚和4-甲基苯酚的气味阈值分别提高到1.50μg/L和0.31μg/L,气味阈值分别为添加高粱醇溶蛋白前的4.59和1.73倍。为进一步解释高粱醇溶蛋白对窖泥味物质消减作用机制,分别在25、45、65℃下进行紫外- 可见分光光度法分析,发现高粱醇溶蛋白与3-甲基吲哚、4-甲基苯酚可自发络合形成复合物,高粱醇溶蛋白与3-甲基吲哚络合物的生成反应为焓变驱动,高粱醇溶蛋白与4-甲基苯酚络合物的生成反应为吉布斯自由能驱动。研究应用分子对接模型实验表明:高粱醇溶蛋白分子表面的疏水口袋通过空间匹配和分子间作用力将3-甲基吲哚和4-甲基苯酚包裹或连接在内,主要的分子间相互作用力为氢键和疏水作用。希望研究结果可为降低浓香型白酒中的异臭味提供解决方案,为食品中异臭味成分的消减研究提供新思路。