巴氏牛奶中蜡样芽孢杆菌的风险评估

为了了解巴氏牛奶中蜡样芽孢杆菌的风险状况，调查研究了北京地区乳品企业巴氏牛奶的运输和销售的总体情况以及北京地区居民牛奶消费的相关情况，结合预测微生物学的方法建立了巴氏牛奶中蜡样芽孢杆菌在流通领域的暴露评估模型。从整个评估过程来看，流通领域的温度和时间是影响巴氏奶安全性的主要因素。     

原料乳中蜡样芽孢杆菌的快速检测

目前原料乳中蜡样芽孢杆菌的检测方法繁琐费时耗力,针对此缺点建立一种操作简便快速检测方法,采用过滤富集菌体后PCR技术来检测原料乳中蜡样芽孢杆菌.整个过程只需6 h左右即可完成.检测灵敏度高达101 mL-1.这种方法是对传统检测方法的有效改进,并且达到了原料乳检测快速、准确、灵敏的要求.     

Growth of enterotoxigenic Bacillus cereus on salmon (Oncorhynchus nerka)

We previously demonstrated the widespread presence of enterotoxigenic Bacillus cereus in marine foods. In view of the widespread consumption of raw fish, we sought to determine the ability of this organism to grow on the surface of wild Alaskan salmon at abusive temperatures (12, 16, and 20°C), using an isolate able to produce elevated levels of hemolysin BL enterotoxin and nonhemolytic enterotoxin. An incubation temperature of 37°C for colony formation was found to be selective for B. cereus grown on salmon held for up to 24 h at each temperature. A fivefold increase in log CFU per gram was observed after 26 and 22 h at 16 and 20°C, respectively, while a >4-log CFU/g increase occurred on salmon held at 12°C for 48 h. Generation times of 169.7, 53.5, and 45.6 min were observed at 12, 16, and 20°C. Nonhemolytic enterotoxin was detected when levels of B. cereus were in excess of 10(8) CFU/g. Nisin, at concentrations of 1 and 15 m g/g of salmon, reduced levels of B. cereus 2.5- and 25-fold, respectively. Our results indicate that fresh salmon can serve as an excellent substrate for enterotoxigenic B. cereus and that this organism can reach levels associated with foodborne illness following moderate temperature abuse.     

Prevalence of potentially pathogenic Bacillus cereus in food commodities in The Netherlands

Randomly selected food commodities, categorized in product groups, were investigated for the presence and number of Bacillus cereus bacteria. If positive, and when possible, five separate colonies were isolated and investigated for the presence of four virulence factors: presence of genes encoding three enterotoxins (hemolysin BL [HBL], nonhemolytic enterotoxin [NHE], and cytotoxin K) and the ability to produce cereulide. In addition, the presence of psychrotrophic and mesophilic signatures was determined. The genes for NHE are found in more than 97% of the isolates, those for HBL in approximately 66% of the isolates, and the gene for cytotoxin K in nearly 50% of the isolates. Significant associations between product groups and (combinations of) virulence factors were the relatively low percentage of isolates from the "flavorings" group containing genes encoding NHE and the higher-than-average occurrence of both the genes encoding HBL and NHE in the "pastry" group. Cereulide was produced by 8.2% of the isolates but only in combination with the presence of genes for one or more other virulence factors. Most isolates (89.9%) were mesophilic; minorities of the isolates were psychrotrophic (4.4%) or of intermediate signature (5.7%). In the product group "milk and milk products," the incidence of strains with psychrotrophic or intermediate signatures is significantly higher than in the other product groups. In the product groups "flavorings," "milk and milk products," "vegetable(s) and vegetable products," "pastry," and "ready-to-eat foods," a relatively high number of samples contain high numbers of B. cereus bacteria. Within the product group "ready-to-eat foods," the products containing rice and pasta show a relatively high incidence of high numbers of B. cereus bacteria.     

Toxigenic Bacillus cereus var. fluorescens in human milk

Human milk with high bacterial load of B. cereus var. fluorescens is reported. The organism was identified by morphological, cultural, and biochemical characteristics. Lecithinase and haemolysin were produced in rabbit and bovine blood. The toxigenic nature of the organism was confirmed by production of necrosis on rabbit skin and fluid accumulation in rabbit ileal loop. An antibiotic resistogram also has been included.     

模拟母乳及婴儿配方奶粉的研究

介绍了人乳中的主要功能因子及其对婴儿的生长发育所具有的生理意义。比较、分析了现阶段婴儿配方奶粉与人乳成分中存在的差别及不足，并针对婴儿的生长特点及现阶段生产技术，对婴儿配方奶粉的生产及发展进行了叙述。     

奶粉中低聚果糖质量浓度的测定

为检测奶粉中低聚果糖的质量浓度,建立起奶粉中低聚果糖的正相高效液相色谱法.样品经质量浓度为100g/L硫酸铜和40g/L氢氧化钠去除蛋白,氨基色谱柱分离,示差折光检测器,柱温30℃,流速1 mL/min,流动相为乙腈:水=70∶30(体积比),标准曲线法定量.蔗果三糖、蔗果四糖、蔗果五糖在质量浓度范围内线性关系良好,添加回收率分别是99.1％,99.7％,95.3％,方法的精密度的相对标准偏差为0.3％,1.1％和0.3％,检出限为2,2,4mg/kg.该方法快速灵敏,简便准确,适用于奶粉中低聚果糖质量浓度的检测.     

HPLC法测定婴幼儿配方奶粉中维生素C

建立婴幼儿配方奶粉中Vc的高效液相色谱测定法.方法采用C18(5μm,4.6mm×250mmi.d)反相色谱柱,流速1.0 mL/min;柱温30℃;流动相:v(甲醇):v(6.8 g/L KH2PO4水溶液,用盐酸调pH2.3)=1:99;进样量5 μL;检测波长215 nm.方法的检出限50μg/g,线性范围20～200 μ/mL,加标回收率80.4～86.2%,相对标准偏差为2.90%.该法具有样品预处理简单、灵敏度高、分析时间短等优点,可用于婴幼儿配方奶粉中Vc的直接测定.     

Inhibition of Bacillus cereus in milk fermented with kefir grains

The effects of kefir-fermented milk were tested against a toxigenic strain of Bacillus cereus. The incubation of milk with B. cereus spores plus 5% kefir grains prevented spore germination and growth of vegetative forms. In contrast, when 1% kefir grains was used, no effects were observed. The presence of metabolically active kefir grains diminished titers of nonhemolytic enterotoxin A, as assessed by enzyme-linked immunosorbent assay. During fermentation, kefir microorganisms produce extracellular metabolites such as organic acids, which could play a role in the inhibition of spore germination and growth of B. cereus, although the effect of other factors cannot be ruled out. Results of the present study show that kefir-fermented milk is able to antagonize key mechanisms involved in the growth of B. cereus as well as interfere with the biological activity of this microorganism.     

婴幼儿配方奶粉中叶黄素的添加

介绍了一种可直接添加到婴幼儿配方奶粉中合适的叶黄素粉剂,考察了其理化性质、干粉稳定性,并探讨了奶粉中叶黄素的应用稳定性.结果表明:此叶黄素干粉具有良好的流散性、稳定性、水分散性.与奶粉混合均匀,适于添加到各种婴幼儿配方奶粉中.     

Minimizing the level of Bacillus cereus spores in farm tank milk

In a year-long survey on 24 Dutch farms, Bacillus cereus spore concentrations were measured in farm tank milk (FTM), feces, bedding material, mixed grass and corn silage, and soil from the pasture. The aim of this study was to determine, in practice, factors affecting the concentration of B. cereus spores in FTM throughout the year. In addition, the results of the survey were used in combination with a previously published modeling study to determine requirements for a strategy to control B. cereus spore concentrations in FTM below the MSL of 3 log₁₀ spores/L. The B. cereus spore concentration in FTM was 1.2 ± 0.05 log₁₀ spores/L and in none of samples was the concentration above the MSL. The spore concentration in soil (4.9 ± 0.04 log₁₀ spores/g) was more than 100-fold higher than the concentration in feces (2.2 ± 0.05 log₁₀ spores/g), bedding material (2.8 ± 0.07 log₁₀ spores/g), and mixed silage (2.4 ± 0.07 log₁₀ spores/g). The spore concentration in FTM increased between July and September compared with the rest of the year (0.5 ± 0.02 log₁₀ spores/L difference). In this period, comparable increases of the concentrations in feces (0.4 ± 0.03 log₁₀ spores/g), bedding material (0.5 ± 0.05 log₁₀ spores/g), and mixed silage (0.4 ± 0.05 log₁₀ spores/g) were found. The increased B. cereus spore concentration in FTM was not related to the grazing of cows. Significant correlations were found between the spore concentrations in FTM and feces (r = 0.51) and in feces and mixed silage (r = 0.43) when the cows grazed. The increased concentrations during summer could be explained by an increased growth of B. cereus due to the higher temperatures. We concluded that year-round B. cereus spores were predominantly transmitted from feeds, via feces, to FTM. Farmers should take measures that minimize the transmission of spores via this route by ensuring low initial contamination levels in the feeds (<3 log₁₀ spores/g) and by preventing growth of B. cereus in the farm environment. In addition, because of the extremely high B. cereus spore concentrations in soil, the contamination of teats with soil needs to be prevented.     

Contamination of pasteurized milk by Bacillus cereus in the filling machine

The contamination of pasteurized milk by Bacillus cereus during the filling process was studied in two dairy plants. Samples of pasteurized milk were taken at four different sites along the production line. The samples were stored at 7 degrees C for 7 d, or at 10 degrees C for 5 d, before plate counting and random selection of B. cereus isolates. Isolates of B. cereus were typed by the polymerase chain reaction (PCR)-based method randomly amplified polymorphic DNA (RAPD). Samples taken at three different sites between the pasteurizer and the filling machine were all holding similar low concentrations of B. cereus, while an increase of the B. cereus count was seen in the consumer packages. More B. cereus of different RAPD types was growing in the consumer packages than in samples taken just before the filling machine. Several RAPD types found in the consumer packages were not detected in the samples taken just before the filling machine.     

婴幼儿奶粉中含氮物质的研究进展

目的:论述婴幼儿奶粉中含氮物质的重要性,并对母乳和牛乳之间的成分差异和各种成分的功效作讨论;结果:以牛乳为基础的婴幼儿奶粉中应该改变各种蛋白质的配比,添加功能性蛋白质和肽类,调整婴幼儿奶粉中各种必需氨基酸的含量;结论:接近母乳水平的婴幼儿配方奶粉更符合婴幼儿健康成长的需要.     

Contamination of infant powdered milk in use with enterotoxigenic Staphylococcus aureus

One-hundred and ten of the 114 samples of infant milk formulae collected from nursing mothers contained viable staphylococci, with the highest mean count of 1·0 × 10² cfu g⁻¹, from samples collected the day the tin was opened. The highest mean total aerobic plate count was 2·6 × 10³ cfu g⁻¹. Titratable acidity and pH of the reconstituted milk ranged from 0·06 to 0·8 and 6·40 to 6·52 respectively. 52·0% of the 123 isolates were S. aureus, 49·6% produced β-hemolysin and 17·1% produced α-hemolysin. Enterotoxin A was produced by 6·5%, B by 1·6%, C by 2·4%, D by 1·6% and E by 0·8% of the isolates. The total staphylococcal and aerobic plate counts were not affected by either the period elapsed from the opening of tin to sampling or the brand of milk.     

SPE-HPLC法检测婴幼儿配方乳粉中生物素的质量分数

建立了灵敏有效的测定婴幼儿配方乳扮中生物素质量分数的方法,用盐酸在超声波务件下除去蛋白质提取出生物素后,使用HyperSep C18固相萃取柱进行纯化、浓缩.采用荧光检测器,柱前PDAM衍生剂衍生.色谱柱为BDS HYPERSIL C18(250x4.6 mm i.d.5μm),柱温为50℃,检测波长:Ex为340 nm,Em为395nm.流动相流速1 mL/min.标准曲线相关系数为0.9996;回收率为83.0%～101.5%之间;7次样品测定SD为0.45,RSD为2.35%.     

AA和DHA在婴儿配方奶粉中的应用研究

阐述了配方奶粉中强化AA和DHA对非母乳喂养婴儿营养的重要性,介绍了AA和DHA在婴儿配方奶粉中的应用,评价了AA和DHA添加到婴儿配方奶粉中的稳定性和安全性。     

婴幼儿配方奶粉中脂肪过氧化值测定方法

阐述了婴幼儿配方奶粉中脂肪过氧化值的测定方法,比较了有机溶剂浸泡过夜法、氨水水解法和有机溶剂直接萃取法对过氧化值的影响;比较了不同提取溶剂对过氧化值的影响。结果表明:直接萃取法实验结果较好,采用乙醚做提取剂,优化的条件为乙醇使用量为100 mL,乙醚的使用量为120 mL,通过计算,该方法的重复性限为0.56 mmol/kg,样品质量分数重复性限在3.89~10.4 3 mmol/kg范围内均适用。     

Inhibition of Bacillus cereus by strains of Lactobacillus and Lactococcus in milk

The growth and death or survival of Bacillus cereus in sterile skimmed milk fermented with 18 different lactic acid bacteria (LAB) were investigated. B. cereus alone in milk reached about 10(7)-10(8) colony-forming units (cfu)/ml. When B. cereus was cultivated together with different Lactobacillus or Lactococcus cultures at 30 or 37 degrees C, the B. cereus counts after 72 h of fermentation ranged between < 10 cfu/ml and about 10(6) cfu/ml. The inhibition patterns for the different Lactobacillus and Lactococcus cultures varied. All the Lactococcus cultures (with one exception) reduced pH to 5.3 or lower in 7 h. After 24 h, B. cereus was not detected in any of the fast Lactococcus-fermented milk samples. After 48 h, B. cereus was not detected for 4 of the 12 Lactobacillus cultures. These cultures reduced pH to below 5.0 in 24 h. The other Lactobacillus cultures also inhibited B. cereus, but the counts of B. cereus were still 10(4)-10(6) cfu/ml after 72 h. They also reduced pH at a slower rate. Survival of B. cereus was to a variable extent linked with formation of endospores. Proteinase K did not affect the antimicrobial activity observed. Acid production with decreasing pH, particularly the initial rate of pH decrease, appears to be most important for control of B. cereus with LAB.     

婴幼儿配方奶粉中添加可选择性成分的调查分析

婴幼儿配方奶粉中添加有必需成分和可选择性成分等,针对这些添加成分的名称和来源,国家都有相关标准规定。该项调查对象是广州市售的来自国内外不同产地的58种婴幼儿配方奶粉外包装信息,分析其配料表中标注的可选择性成分(包括部分营养强化剂、菌种和食品添加剂),并与国家规定相比较。结果发现大部分产品都添加有牛磺酸、二十二碳六烯酸、花生四烯酸、低聚半乳糖、低聚果糖和核苷酸,而菌种、L-氨基酸等较少被添加。多数的添加成分符合我国相关规定,但也有少数标注不规范的情况。该研究还有助于消费者和相关专业人士深入了解婴幼儿配方奶粉的配料表。