Undesirable Enzymatic Browning in Crustaceans: Causative Effects and Its Inhibition by Phenolic Compounds

Undesirable enzymatic browning mediated by polyphenol oxidase (E.C. 1.14.18.1) on the surface of seafood from crustaceans have been a great concern to food processors, causing quality losses of seafood products. Seafoods especially from crustaceans are worldwide consumed due to their delicacy and nutritional value. However, black spot formation (melanosis) is the major problem occurring in crustaceans during postmortem handling and refrigerated storage induce deleterious changes in organoleptic properties and, therefore, decreases commercial value. Polyphenoloxidase (PPO), the copper-containing metalloprotein involved in oxidation of phenol to quinone is the major biochemical reaction of melanosis formation. This enzymatic mechanism causes unappealing blackening in postharvest crustaceans. To alleviate the melanosis formation in crustaceans, use of phenolic compounds from plant extract can serve as antimelanotics and appears to be a good alternative to the conventional sulfites which are associated with health-related disorders. In this review, we focuses on the unique features about the structure, distribution, and properties of PPO as well as mechanism of melanosis formation and provide a comprehensive deeper insight on the factors affecting melanosis formation and its inhibition by various antimelanotics including newly discovered plant phenolic compounds.     

烟叶质量评价和叶组配方专家系统的开发

为合理利用烟叶资源,采用信息采集分析处理与感官评吸相结合的方法,在烟叶和烟气化学成分与卷烟品质的相关性分析基础上,建立了包括烟叶质量评价、叶组配方设计、数据管理、计划维护、月库存查询和滚动测算6个功能模块的叶组配方专家系统。应用结果表明,该系统能有效控制卷烟质量及生产成本。     

竹叶特种氨基酸的存在及其生物学意义

在竹叶及其提取物中检出了相当含量的一种羟化赖氨酸—δ－ＯＨ－Ｌｙｓ，主要以游离单体和小肽的形式存在。从桂竹和金毛竹叶样分别测得其含量占干叶氨基酸总量的１．３３％和１．４０％，约相当于其中Ｌｙｓ含量的１／４．醇－水提取的过程有富集δ－ＯＨ－Ｌｙｓ的作用，其在提取物中的含量远远高于Ｌｙｓ．这一特殊的非蛋白氨基酸以相当含量存在于竹叶中，可能有着特殊的生物学意义。     

Analysis of malts by capillary electrophoresis

A range of malts, as well as their high‐ and low‐molecular‐mass fractions, has been examined by capillary electrophoresis in phosphate buffer, pH 2.5, and in carbonate buffer, pH 9.5, and the results have been compared with those for roasted barley and for caramels. The malts fall into two categories: (i) the lightly roasted malts, where the high‐molecular‐mass coloured fraction is negatively charged at pH 9.5 and positively charged at pH 2.5; and (ii) the highly roasted malts (and the roasted barley), where the high‐molecular‐mass fraction migrates close to the electro‐osmotic flow at both pH 9.5 and 2.5, implying that it carries little or no charge. The former category shows migration patterns similar to Class III caramels, whereas the latter migrates differently from Class I, III and IV caramels as well as from the former. Capillary electrophoresis therefore has considerable potential for differentiating between malts and between malts and caramels and roasted barley. © 2002 Society of Chemical Industry     

COMPARISON OF THE MALT CHARACTERISTICS OF TRADITIONAL AND IMPROVED VARIETIES OF SORGHUM VULGARE FROM GHANA

The malt characteristics of six agronomically improved varieties of sorghum in Ghana were compared to traditionally grown local varieties. The diastatic activities of the traditional varieties were found to be better than the improved breeds. The Improved breed, Kadaga, produced extract yields comparable to the traditional varieties. Free amino nitrogen content of Nagawhite worts were also comparable to those of the traditional varieties. The malt characteristics of all the varieties tested varied remarkably, but none of the improved breeds was found to be better than the traditional varieties in terms of their potential in brewing.     

FACTORS CONTROLLING THE FERMENTABLE EXTRACT IN DISTILLERS MALT

The relationships between the alcohol yield obtainable from different malts and some readily measurable parameters have been investigated. Gel filtration studies clearly show that melanoidin-type condensation products, which were previously suggested as a cause of low fermentability, are not produced in significant amounts in highly modified malts. These studies also show important details relating to the hydrolysis of dextrins in distillers' worts and washes. Measurement of the limit dextrinase activity of a range of distillers' malts has indicated that this enzyme is not a limiting factor in determining wort fermentability and its concentration does not correlate with the overall spirit yield. There may be a relationship between the whole amylase complex, as expressed by the diastatic power and wort fermentability. From a study of the reducing sugar contents of worts, it was confirmed that the major factor controlling fermentable extract in malt is the relative amounts of starch-derived sugars in the wort. It now appears possible to determine the fermentability of distilling wort by the standard extract and the reducing power of the wort obtained by the standard I.O.B. extraction.     

MALTING QUALITY OF SRI LANKAN VARIETIES OF SORGHUM

The malting quality of Sri Lankan sorghum was studied using seventeen varieties. These varieties represented four colour categories (brown, yellow, pink and white) of sorghum found in Sri Lanka. The main criteria used for the assessment of malting quality in this study were the malting loss, diastatic power, liquefying power and the quantity of extract. Malting losses of these varieties were somewhat higher than those encountered in malting barley. However, they appeared to depend partly on the malting conditions. The diastatic powers and liquefying powers observed in this study were inferior to those observed with barley malt. However, with some varieties they appeared to be adequate for the purpose of mashing, as indicated by the high extract values obtained, which were comparable with those of some barley malts. Extract values of the four colour categories varied considerably and the best values were observed with the yellow and pink varieties and some varieties of white. Brown varieties in spite of their comparatively high diastatic powers and liquefying powers gave very little or no extract on mashing.     

黄秋葵果胶提取工艺的初步研究

本文以成熟的黄秋葵为原料,研究了Al2(SO4)3沉淀法提取果胶的工艺条件。实验采用正交设计,利用方差分析对萃取温度、萃取时间和萃取的pH值对果胶得率的影响进行了探讨,得出最佳提取条件为:pH4、萃取温度为60℃、萃取时间为90min;在此条件下,黄秋葵的果胶提取率可达25.96%,实验表明,黄秋葵是一种果胶含量高的植物资源。     

烟叶原料配打技术研究

以烟叶化学成分为分析指标,通过聚类分析分别对不同品种、不同产地和各烟叶等级之间配打技术进行了研究。结果表明,用化学成分指标进行聚类分析的结果与烟叶感官评吸结果相一致,此为烟叶配打工作提供了一种较好的方法。     

桑叶南瓜复合饮料的研制及其降血糖效果的研究

对桑叶南瓜复合饮料的生产工艺和保健效果进行了研究．结果表明。当桑叶汁和南瓜汁的体积比为1：4．糖酸比为木粮醇8％、蛋白糖0．01％、柠檬酸0．012％。稳定剂为黄元胶0．1％和CMC-Na0．1％。杀菌条件为121℃，15-20min时．产品具有显著的降血糖效果．