孕育处理对大断面球铁件力学性能和石墨形态的影响

基于金相组织、力学性能、拉伸断口特征、石墨结晶核心及变异石墨形态分析,研究了孕育处理对大断面QT600－3球铁件力学性能和石墨形态的影响。结果表明,电炉熔炼工艺生产大断面球铁件时,采用随流瞬时孕育,孕育衰退作用减慢,抗拉强度和伸长率提高;YFY－1A作瞬时孕育剂,石墨形态良好,石墨球大小稳定;SPI作瞬时孕育剂,导致石墨形态发生变异。     

Dry inoculation methods for nonfat milk powder

Carriers with inoculated microorganisms are often used to validate low-moisture food safety interventions. In this study, we evaluated dry inoculation methods using silicon dioxide (SiO₂) and a small portion of nonfat milk powder (NFMP) as dry carriers for NFMP. Silicon dioxide was characterized by vapor sorption analysis. One milliliter of inoculum of a 5-strain Salmonella cocktail (serovars Agona, Reading, Tennessee, Montevideo, and Mbandaka) or Enterococcus faecium NRRL B-2354 was inoculated onto 1 g of SiO₂ or 10 g of NFMP as carriers. Both inoculated carriers were air-dried for 72 h [22°C, relative humidity (RH) ～30%], equilibrated to water activity (a_w) 0.25 ± 0.02 (24 h at 22°C, RH 25%), and mixed with preconditioned NFMP (a_w = 0.25 ± 0.02) to reach an inoculation level of 8.2 ± 0.2 log cfu/g. Inoculated NFMP was stored at 22°C, RH 25%, and its bacterial populations were monitored for 30 d. Both sets in equilibrated NFMP were subjected to isothermal treatments in closed aluminum cells at 85, 90, and 95°C. Silicon dioxide maintained moisture content (0.29 ± 0.03%, dry basis) at different water activities. The NFMP inoculated with both carriers exhibited stable bacterial populations over 30 d at 22°C. Strains in NFMP inoculated with SiO₂ showed equal or higher D-values but equal z-values compared with those inoculated with a small portion of NFMP. Enterococcus faecium exhibited comparable thermal resistance to Salmonella under all tested conditions. This study supports E. faecium as a Salmonella surrogate in thermal processing of NFMP and the use of SiO₂ to inoculate NFMP.     

铸态高韧性球墨铸铁的生产

通过对球墨铸铁金相组织控制、化学成分选择及球化、孕育处理工艺的分析,详细介绍了铸态高韧性球墨铸铁QT450-10的生产控制要点。     

发酵环境变化对酵母生长和成品啤酒的影响

啤酒发酵是一个复杂的生物和物质转化过程,在整个酿造过程中,从原料粉碎到开始发酵直至发酵结束降温冷贮,环境变量因素很多,会影响啤酒酵母生长,从而影响成品啤酒中的挥发性风味物质和啤酒品质。该文重点总结介绍麦汁浓度、接种率、发酵温度、压力变量对发酵过程的影响,旨在为解决啤酒酿造过程可能出现的问题提供一些思路,从而提高啤酒质量。     

自然发酵与人工接种发酵湖南芥菜的挥发性风味组分和品质分析

采用固相微萃取结合气相色谱-质谱联用法对自然发酵和接种不同发酵剂发酵湖南芥菜样品的挥发性风味组分进行研究,并同时比较其亚硝酸盐含量、pH值和感官品质。结果表明,控温人工接种发酵和控温自然发酵芥菜其主要挥发性风味成分较相似,相对含量最高的成分为酯类,均在40.02%以上,而大池室温完全自然发酵芥菜的挥发性风味成分相差较大,相对含量最高的成分为醇类,仅为5.51%。4?组芥菜共分离鉴定出64?种（11?类）挥发性风味成分,其中接种植物乳杆菌与戊糖片球菌组合的发酵芥菜鉴定出挥发性风味组分21?种（9?类）,酯类物质7?种;接种植物乳杆菌、戊糖片球菌和肠系膜明串珠菌组合的发酵芥菜鉴定出挥发性风味组分24?种（10?类）,酯类物质8?种;控温自然发酵芥菜共鉴定出挥发性风味成分20?种（9?类）,酯类物质5?种;大池室温完全自然发酵芥菜共鉴定出挥发性风味成分32?种（10?类）,醇类物质7?种,酯类物质6?种。人工接种发酵芥菜的亚硝酸盐含量和pH值都比自然发酵低,人工接种发酵和控温自然发酵芥菜感官评分相近,其评分都高于大池室温完全自然发酵芥菜。因此,接种人工发酵剂对保障发酵芥菜的商品性和安全性具有促进作用,值得进一步研究和推广。     

不同接种方式对食品中热损伤大肠菌群检测的比较研究

目的比较不同接种方式对食品中热损伤大肠菌群检测的影响。方法采用平板计数法、最大或然数法(most probable number,MPN)、表面涂布法、3M Petrifilm~(TM)大肠菌群测试片法、TSA+VRBG计数法等不同的接种方式对热处理食品中受损大肠菌群的检测进行了比较研究。结果平板计数法的结果均为10 CFU/g,MPN法的结果在150~460 MPN/g之间。表面涂布法、3M Petrifilm~(TM)大肠菌群测试片法、TSA+VRBG计数法的结果对数均值和标准差分别为(2.26±0.032)、(2.31±0.026)、(1.82±0.068)。统计分析发现,表面涂布法、3M Petrifilm~(TM)大肠菌群测试片法的检测结果均高于TSA+VRBG计数法,且具有极显著性意义(P0.01),而3M Petrifilm~(TM)大肠菌群测试片法的检测结果又显著高于表面涂布法(P0.05)。结论 MPN法、表面涂布法、3M Petrifilm~(TM)大肠菌群测试片法、TSA+VRBG计数法均适用于热损伤大肠菌群的检测,其中表面涂布法,特别是3M Petrifilm~(TM)大肠菌群测试片法操作简便,且复苏热损伤大肠菌群的效果好。     

黄金行业特征废水中BOD测定影响因素的分析

黄金行业特征废水通常含重金属、氰化物及硫氰酸盐,且具有强碱性,研究好氧自养型微生物、无机盐、溶解氧含量、接种液背景BOD值及废水性质等5个因素对BOD测定结果的影响。研究结果表明,黄金行业特征废水BOD测定需添加丙烯基硫脲抑制硝化细菌,加入微生物生命活动所需的无机盐,保证水样中溶解氧含量饱和或接近饱和,接种液背景BOD值低,选择耐氰耐重金属的微生物进行接种或根据废水性质对接种液中微生物进行驯化后接种,满足以上条件才能保证BOD测定结果准确。     

降低高浓啤酒发酵中高级醇含量的研究

为降低高浓啤酒发酵中高级醇的生成量,研究18°Bx麦汁啤酒酿造过程中的加糖浆方式、酵母接种量和麦汁中α-氨基氮含量对啤酒高级醇生成量的影响。结果表明：18°Bx麦汁发酵高级醇生成量显著高于12°Bx麦汁;分两次加入制备18°Bx麦汁所需的糖浆量、控制18°Bx麦汁的酵母细胞接种量为3×107个/mL以及麦汁中α-氨基氮含量为230mg/L麦汁时,均有利于降低18°Bx高浓啤酒发酵过程中高级醇的生成量。     

风电球墨铸铁轮毂的研制

文章分析产品结构特性,选用了科学合理的铸造工艺、化学成分设计,控制球化处理和孕育处理,生产出各项性能符合风电标准要求的球墨铸铁轮毂,取得了较明显的技术经济效果。     

Influence of chunky graphite on mechanical and fatigue properties of heavy-section cast iron

This research work aimed to find out the influences of the different amounts of chunky graphite on mechanical and fatigue properties of GJS 800 ductile cast iron. Chunky graphite has been a problem of heavy section thick-walled ductile cast iron components. Chunky graphite is branched and interconnected as a network within eutectic cells and has been observed to form in thermal centres of heavy ductile cast iron sections during solidification. This research work proved that chunky graphite in the microstructure decreases the ultimate tensile strength, the elongation to fracture and fatigue life significantly, but does not influence on the yield stress of ductile cast iron GJS 800 substantially. Low nodular count and nodularity rate also decrease the fatigue life of ductile cast iron, and the difference of fatigue life of specimens containing chunky graphite or having low nodular count and nodularity rate is not large. Influence of the amount of chunky graphite on fatigue life increases until 20% chunky graphite content, and above that the fatigue life does not decrease substantially.