Effect of Peptide Size on Antioxidant Properties of African Yam Bean Seed (Sphenostylis stenocarpa) Protein Hydrolysate Fractions

Enzymatic hydrolysate of African yam bean seed protein isolate was prepared by treatment with alcalase. The hydrolysate was further fractionated into peptide sizes of <1, 1-3, 3-5 and 5-10 kDa using membrane ultrafiltration. The protein hydrolysate (APH) and its membrane ultrafiltration fractions were assayed for in vitro antioxidant activities. The <1 kDa peptides exhibited significantly better (p < 0.05) ferric reducing power, diphenyl-1-picryhydradzyl (DPPH) and hydroxyl radical scavenging activities when compared to peptide fractions of higher molecular weights. The high activity of <1 kDa peptides in these antioxidant assay systems may be related to the high levels of total hydrophobic and aromatic amino acids. In comparison to glutathione (GSH), the APH and its membrane fractions had significantly higher (p < 0.05) ability to chelate metal ions. In contrast, GSH had significantly greater (p < 0.05) ferric reducing power and free radical scavenging activities than APH and its membrane fractions. The APH and its membrane fractions effectively inhibited lipid peroxidation, results that were concentration dependent. The activity of APH and its membrane fractions against linoleic acid oxidation was higher when compared to that of GSH but lower than that of butylated hydroxyl toluene (BHT). The results show potential use of APH and its membrane fractions as antioxidants in the management of oxidative stress-related metabolic disorders and in the prevention of lipid oxidation in food products.     

黄芩根提取物的制备及其在烟草香气中的作用研究

以黄芩苷为目标制备了黄芩提取物,分析其有效成分并研究了烟用效果.采用裂解气相色谱-质谱联用(PyGC-MS)法,模拟卷烟典型燃烧环境,研究了黄芩苷在不同气氛中的裂解产物,探讨其在卷烟中的致香机理.结果表明,所制备的黄芩提取物含有22.11％的黄芩苷,在卷烟中的作用为增加香气、柔和烟气、改善余味.裂解试验发现,黄芩苷在不同温度和不同环境中发生裂解,生成烃类、酮类、醛类、呋喃类及其衍生物等致香成分,含量最高的为糠醛和苯乙酮.不同温度和不同气氛条件下裂解,产物及含量均有差别.以上结果表明,黄芩提取物可作为潜在的烟用香料.     

全二维气相色谱-飞行时间质谱在香精分析中的应用进展

全二维气相色谱是一种新型的功能强大的分离分析技术.介绍了全二维气相色谱-飞行时间质谱在香精香料研究领域的研究进展,该技术在香精香料的成分分析方面具有广阔的应用前景.     

动物蛋白水解复合酶的研究

以酶解牛骨蛋白为对象,研究动物蛋白水解复合酶的配制并考察其适应性.实验结果表明,由中性蛋白酶、胰蛋白酶、风味酶等3种酶按酶活性1∶3∶2组合配制而成的复合酶,其酶解动物蛋白效果高于单一酶.     

干凝胶法制备惯性约束聚变靶用高渗透性空心玻璃微球

为制备惯性约束聚变靶用高渗透性空心玻璃球（hollow glass microspheres,HGM）,研究了初始玻璃配方、发泡剂种类、炉内载气组分和压力、精炼温度对干凝胶粒子的炉内成球过程和最终HGM的产率、质量和渗透性能的影响。结果表明：初始玻璃配方中的绝大部分碱金属氧化物在精炼过程中都从液态玻璃挥发进入载气,最终...     

β-环糊精包合玫瑰精油制备微胶囊香精的工艺研究

考察了β-环糊精与玫瑰精油的比例、包合过程中的搅拌时间及包合温度等对留香效果的影响,将包合好的香精应用于洗衣粉中,模拟实际洗涤过程进行了留香实验;采用固相微萃取的方式测定不同时间时香精在顶空空间的浓度,并与原始的玫瑰精油进行了对比。实验表明,用包合好的微胶囊香精可以明显改善香精的留香效果;制备最为有效且经济的微胶囊的工艺为:β-环糊精与玫瑰精油的比例为6∶1,包合时间2 h,包合温度40℃。     

原位聚合法制备香精微胶囊的工艺优化研究

以低甲醚化蜜胺树脂为壁材,香精为芯材,采用原位聚合法制备了一系列香精微胶囊．通过对所制备的香精微胶囊进行显微观察、粒度分析、包裹率测试和稳定性考察,研究了工艺条件的影响,并对香精微胶囊的多层造壁效果进行了分析．结果表明,在搅拌速度为600r／min,壁材预聚体滴加时间为30min,50min缓慢升温至75℃保温固化的条件下所得到的香精微胶囊包覆效果良好,产品乳液稳定;双层壁材香精微胶囊的粒径分布最窄,而三层壁材的香精微胶囊具有最高的热稳定性,包裹率可达92．26％．     

冷库稻壳热绝缘层热湿状态研究

本文对冷库稻壳热绝缘层的热湿特性进行了分析。提出用空气层解决冷库工程中热绝缘材料受潮的方法,通过工程实践和热工测试分析,证实了在冷库阁楼稻壳层表面形成自防潮壁垒理论;0℃附近的干燥带的存在。使得对冷库热绝缘层的热湿迁移现象的物理本质有了新的认识,对冷库热绝缘层保持干燥的设计方法起重要的指导作用。     

豆制品中碱性橙Ⅱ、酸性橙Ⅱ和碱性嫩黄O的测定

建立了高效液相色谱紫外检测器测定豆制品中碱性橙Ⅱ、酸性橙Ⅱ和碱性嫩黄O的方法。样品用乙腈-水(7+3)溶液提取,经高效液相色谱仪紫外检测器测定。结果表明:碱性橙Ⅱ、酸性橙Ⅱ和碱性嫩黄O在0.1～20μg/mL范围内呈良好线性关系,相关系数均为0.9999,3个水平(5.0、10.0、15.0mg/kg)加标回收率为88.8%～93.0%,相对标准偏差为0.67%～1.66%(n=6),检出限分别为碱性橙Ⅱ:0.02 mg/kg、酸性橙Ⅱ:0.05 mg/kg和碱性嫩黄O:0.05 mg/kg。此方法具有简单、快速、准确等优点,适用于豆制品中碱性橙Ⅱ、酸性橙Ⅱ和碱性嫩黄O的同时测定。     

Influence of Flavor on Goat Feeding Preferences

Goat feeding preferences for straw pellets flavored with ryegrass (Lolium perenne, cv. Belida) or white clover (Trifolium repens, cv. Huia) aromatic extracts, obtained by means of a cold aromatic extraction method, were assessed with cafeteria trials. Prior to the trials, odor differences between the two plant species, the two aromatic extracts, and the straw pellets sprayed with the two aromatic extracts were verified using sensory analysis performed by 30 human panelists. Since odor differences observed among fresh samples were still detectable in aromatic extracts and moistened pellets, the extraction method was considered effective in reproducing plant odors. Straw pellets sprayed with either distilled water (W) or ryegrass (R) or clover (C) aromatic extracts were used to assess flavor preferences of 12 female Rossa Mediterranea goats. Sprayed pellet preference was evaluated in two sessions conducted in two consecutive weeks. Each session consisted of three two-choice presentations performed on three consecutive days. In both sessions, food intake, proportion of food intake, time spent feeding, and proportion of time spent feeding were significantly affected by pellet type (0.05 > P > 0.001). In particular, straw pellets sprayed with ryegrass extract were highly selected compared to those sprayed with clover (0.01 > P > 0.001) or water (0.01 > P > 0.001). In addition, in the second session, the clover extract was preferred to distilled water (0.05 > P > 0.01). The results of this study gave two main indications: first, goat selectivity for ryegrass against clover was consistent even when straw pellets sprayed with odors of these plants were offered, and secondly, the addition of aromatic extracts to straw pellets increased the preference for pellets.