天然植物提取物对萝卜干腐败菌抑菌研究

实验用肉桂、五倍子、陈皮、桂皮、丁香、艾叶、补骨脂、桑白皮、甘草、连翘、大蒜、姜、茶叶水提取液对萝卜干的4种常见腐败微生物(克柔念珠菌,枯草芽孢杆菌,蜡样芽孢杆菌,金黄色葡萄球菌)进行了抑菌试验。并且研究了最有效的添加剂的最低抑菌浓度以及pH有效作用范围。结果表明,茶叶水提取液的抑菌效果最好,其次是五倍子。茶叶水提取液对枯草芽孢杆菌、蜡样芽孢杆菌、克柔念珠菌和金黄色葡萄球菌的最低抑菌浓度分别为:5%、10%、5%和5%。且在pH值3～7范围内抑菌能力稳定。     

清香型小曲白酒中微生物组成及功能微生物的分析

将PCR-DGGE技术和传统微生物培养方法相结合,分析清香型小曲白酒的微生物群落结构及功能微生物。小曲和酒醅中优势微生物种属基本一致。不同季节酒醅中微生物组成无明显变化,但微生物生长和消亡规律存在差异。小曲酒中细菌的种类较多,主要以乳酸菌和芽孢杆菌属为主,但对小曲白酒风味特征影响很小。酵母类主要包括Saccharomycopsis fibuligera、Pichia anomala、Issatchenkia orientalis和Saccharomyces cerevisiae。S.cerevisiae的作用是酒精发酵产生乙醇,Sp.fibuligera、P.anomala和I.orientalis是产酯酵母,增加酒体酯香味。霉菌种类相对较少,Rhizopus oryzae是主要糖化菌。     

清香型大曲淀粉水解酶系解析

对清香型大曲中可能存在的淀粉代谢相关酶类及各自催化作用进行全面分析,并从Brenda数据库中搜索酿酒相关的淀粉水解酶,了解不同来源淀粉水解酶类的酶学特征,并从基因组角度分析酿酒微生物合成的淀粉代谢酶类,对酿酒微生物有更深入的认识,为选育理想的酿酒微生物提供理论依据。     

Biodegradation Study on the Starch-LDPE Film by Soil Micro-organism

Abstract

Degradation of low density polyethylene (LDPE) film containing starch as the biodegradable additive has been studied by isolating a soil microbe identified as Pseudomonous species. The degradation of the film was monitored by mechanical property and the surface starch concentration by UV-spectrophotometry at different intervals of time. The degradation depends on the accessibility of starch i.e., the carbon source in the starch-LDPE film. By adding external carbon source like, monosaccharide and disaccharide sugars some changes in the rate of biodegradation was observed. The ultimate fall in tensile strength was higher for the film when exposed to a nutrient medium without any external carbon source. Mostly the added sugar helps in the growth of micro-organisms. Among the various external carbon sources, maltose was found to be the best. In case of maltose the loss of tensile strength was 50% in 58 days, but the film without additional sugar showed a fall in tensile strength of 48% in the same period.     

Bacterial Growth and Volatile Compounds in Yoghurt-Type Products from Soymilk Containing Bifidobacterium ssp

The growth of bacteria normally used to produce yoghurt was compared in soymilk and cow milk. Whether or not Bifidobacterium ssp. was present, fermented soymilks [soyoghurt (S), soyoghurt + bifi-dobacteria (SB)] were less acidic than fermented cow milks [yoghurt (Y), yoghurt + bifidobacteria (YB)]. When bifidobacteria were present (in SB), streptococci were more numerous than lactobacilli. Bifidobacteria in YB stimulated maximal growth of both yoghurt bacteria. In comparison to nonfermented milks, acetaldehyde and diacetyl increased in all cultures. Ethanol increased only in S/SB and acetone was detected only in Y/YB. Quantities of volatile products in Y/'YB were slightly lower than those in Y/S. In all cultures, n-hexanal was almost totally absent.     

Degradation characteristics of isolated and in situ cell wall lucerne pectic polysaccharides by mixed ruminal microbes

Two pectic polysaccharide fractions were isolated form lucerne (Medicago sativa L) leaves and used in fermentation experiments with mixed ruminal microbes. Both fractions were similar in chemical composition, containing galacturonic acid (52-58 mol%) and the neutral sugars arabinose (14-18 mol%), galactose (6-8 mol%) and rhamnose (8-12 mol%). Fermentation of both fractions was rapid and complete with a half-life of approximately 4 h. Production of total volatile fatty acids matched the degradation profile reaching a maximum level shortly after the rate of degradation began to decrease. The fermentation characteristics of citrus pectin and polygalacturonic acid were similar to those of the lucerne pectic fractions but galacturonic acid was much slower in its rate of degradation while soluble arabinogalactan from larchwood was virtually undegraded. Leaves of early bud stage lucerne and lower nodes and internodes of stems from full bloom lucerne were also fermented by mixed ruminal microbes. Pectic polysaccharides were rapidly and extensively degraded from both tissues. Initial rates were faster for leaves than for stems and the extent of pectic degradation was greater in leaves (8% residual) than in stems (17% residual). Selection of forage lines with increased pectic polysaccharides would provide greater amounts of rapidly available energy that could result in more efficient utilisation of the rapidly degraded protein in lucerne.     

Microbial and Oxidative Changes in Low-Fat Ground Beef During Simulated Retail Distribution

A low-fat ground beef product containing water, carrageenan, encapsulated salt and hydrolyzed vegetable protein (carrageenan-based) was compared to a low-fat, all-beef control during simulated commercial manufacturing and retail distribution. Few differences were found in oxidative stability and microbial growth of the two. No differences (P>0.05) were found in aerobic plate counts, populations of psychrotrophs or mold and yeast populations for the two products. Hunter color ‘a’ values (redness) and overall color scores for surface color were higher (P<0.05) for the carrageenan-based product than the all-beef product. Retail display of low-fat products in aerobic packaging resulted in greater (P<0.05) product discoloration than anaerobic retail display.     

Sodium Lactate Affects Pathogens in Cooked Beef

Cooked, quartered beef top rounds containing either 1, 2, 3 or 4% sodium lactate were aseptically sampled and slice sections were inoculated with Listeria monocytogenes (ATCC 43256), Staphylococcus aureus (ATCC 27154), Salmonella typhimurium (ATCC 13311), Clostridium perfringens (ATCC 12924), or Escherichia coli O157:H7 (ATCC 43895). Inoculated slices were stored at 10°C for 0. 7. 14. 21 or 28 days.‘Three and 4% sodium lactate generally displayed lim-ited proliferation of S. typhimurium, L. monocytogenes and E. coli O157:H7 when compared with control roasts (0% sodium lactate) and roasts containing 2% sodium lactate.     

天然物质对切割蔬菜中常见微生物的抑制作用研究

研究了正离子水和姜黄、虎杖、艾叶、丁香提取物对切割蔬菜中常见微生物(大肠杆菌、荧光假单胞菌、啤酒酵母)的抑制作用,结果表明:正离子水对大肠杆菌、荧光假单胞菌、啤酒酵母无抑制作用,抑制率均为0;姜黄、虎杖、艾叶、丁香提取物对3种微生物均有一定的抑制作用。适宜温度培养7d后,姜黄、虎杖、艾叶、丁香提取物对大肠杆菌的抑制率从大到小依次为:姜黄(51.7%),艾叶(37.2%),虎杖(36.5%),丁香(30.4%);对荧光假单胞菌的抑制率从大到小依次为:丁香(100%),姜黄(55.8%),艾叶(55.8%),虎杖(46.7%);对啤酒酵母的抑制率从大到小依次为:丁香(100%),姜黄(35.3%),艾叶(35.3%),虎杖(33%)。