PCR法检测原料乳中金黄色葡萄球菌肠毒素A基因型

通过建立PCR方法来检测原料乳中金黄色葡萄球菌肠毒素A基因型,优化其退火温度并验证了其敏感性、特异性.结果表明此方法在退火温度为58.7℃时扩增效果较为理想;灵敏度为1.357 pg/μL;以大肠杆菌、枯草芽孢杆菌、嗜热链球菌、志贺氏菌、沙门氏菌的基因组DNA为模板作为特异性检测对照组并分别进行PCR扩增反应,结果为阴性.同时对采集的乳样进行检测,乳房炎乳样中检测出了金葡菌肠毒素A基因,正常乳中没有检测出金葡菌,初步判断乳房炎是由金葡菌引起的.     

生鲜牛乳中硫氰酸钠的风险评估研究

采用离子色谱法对上海地区的500批次生鲜牛乳中硫氰酸钠含量进行检测。结果表明：生鲜牛乳中硫氰酸钠含量总体情况符合Pearson5分布（皮尔逊V型分布）,90％的数据分布在0．2—3．71mg／kg之间,最小、最大、平均含量分别为0．2、9．66和1．5mg／kg。基于乳制品中硫氰酸钠的每日摄入量和点评估方法得到硫氰酸钠的膳食暴露量为2．0μg／kg标准人每日,结合相关的硫氰酸钠的风险评估研究,表明本研究中上海地区生鲜牛乳中的硫氰酸钠的含量属于正常的生理浓度,对人体正常膳食无健康影响。     

电导率法检测原料乳掺假的方法研究

研究了使用电导率法检测原料乳中掺假的方法,根据乳中掺入电解质时电导率有显著增大、掺乳非电解质时电导率有显著减小的特性,使用电导率仪测定待检乳样的电导率,根据一定温度下电导率值与该温度下正常乳样的电导率对比,有显著差异的判定为乳样中有掺假物。此法具有成本低廉,操作方便快捷,检验时间短等特点,为快速定性检测方法,可以在线应用,适用于乳品企业进行原料乳掺假的快速检测。     

酸性蛋白酶在生料酿酒中的应用研究

酸性蛋白酶适宜pH为2.0～6.0,适宜作用温度为30～55℃,它能有效水解原料中的蛋白质,提高醪液中氨基酸氮的含量,促进酵母生长繁殖,同时破坏原料颗粒间质细胞壁结构,有利于糖化酶的作用。在生料酒曲中添加2％～3％的酸性蛋白酶,以大米、玉米、高粱等淀粉质原料为主的生料酿酒生产中,能提高原料出酒率1.84％～2.68％,缩短发酵时间1～2d,提高设备利用率20％,降低生料酒中杂醇油的含量,改善酒质。     

碱性蛋白酶助浸水的研究

本研究将碱性蛋白酶应用于生产黄牛软鞋面革的浸水工序，并将其与常规工艺进行了对比。通过对坯革进行物理机械性能检测和感观评定，确定利用碱性蛋白酶作为生产黄牛软鞋面革的浸水助剂，不仅可以缩短浸水时间还可以减少黄牛皮颈部皱纹，提高得革率，使坯革粒面细致，革身丰满、柔软。     

原料牛奶中微生物的污染问题与检测分析

原料牛奶在整个生产环节中,如牛乳房微生物、挤奶环节、储存过程等都有可能发生微生物污染事件,在初始阶段乳烃素的作用下存在一段抑菌周期,经过抑菌期后原料牛奶就会出现变质现象.原料牛奶是整个乳制品供应链中的最上游,其质量安全直接影响下游的终端乳制品,是整个乳品行业能保持健康发展的基石.近年来,原料牛奶的质量安全问题已成为社会...     

Hydrolysis of Milk Protein by a Bacillus licheniformis Protease Specific for Acidic Amino Acid Residues

A serine protease, which preferentially cleaves peptide bonds at the carboxylic site of Glu and Asp was evaluated with milk proteins as substrate. The enzyme hydrolyzed casein almost 10 times more efficiently than whey protein. In the casein assay, whey protein did not inhibit the protease, but the enzyme activity in a chromogenic assay was severely inhibited by one whey protein, β-lactoglobulin. Capillary electrophoresis of β-lactoglobulin hydrolysate revealed a peptide profile corresponding to the numbers of susceptible bonds, The enzyme may provide advantages in preparation of functional protein fractions and in cheese ripening.     

人工合成椰奶的研制及其稳定性研究

本文主要对人工合成椰奶的配方及产品的稳定性进行了研究,通过正交试验得到了合成椰奶主要配方的最佳比例:椰子油30%,酪蛋白酸钠4.5%,麦芽糊精12%;乳化剂选择了单甘脂和蔗糖酯以2:1比例复配的复合乳化剂,添加量为1.5%;稳定剂为O.03%的CMC;杀菌方式是75℃20 min.可得到椰香浓郁、口感细腻、均匀稳定的产...     

Vitamin D Stability in Milk

A method was developed to determine vitamin D₃ in milk. It includes saponification, solid phase extraction and HPLC. Recovery of added vitamin D₃ was 93%. Vitamin D₃ concentrations in commercial milks were variable. Stability studies showed that on exposure to light, there was a slight loss of vitamin D₃ from fortified milk. Air exposure did not affect stability in milk. Upon standing there was some stratification of the vitamin in milk containers with slightly more vitamin D₃ in the top layer of milk than at the bottom.     

Rapid Detection of Pseudomonas in Seafoods Using Protease Indicator

The effects of Pseudomonas and the proteases it synthesizes in seafoods rendering them unfit for consumption are not fully recognized. A sandwich enzyme-linked immunosorbent assay (ELISA) was developed wherein protease produced by Pseudomonas isolated from shrimp was used as antigen, and anti-protease IgG conjugated with alkaline phosphatase was the second antibody. Purified protease and seafood samples, naturally contaminated or artificially inoculated with Pseudomonas, were positive by ELISA. The conventional culture method took 3 days to complete, but ELISA detected Pseudomonas with in 24h. The rapidity, simplicity and efficacy of this test make it useful for implementation of HACCP systems.     

应用紫外分光光度法评估原料奶中芽孢杆菌芽孢数

从原料奶中分离富集出芽孢,应用紫外分光光度法对芽孢中的2,6-吡啶二羧酸进行检测,在385 nm至265 nm之间进行紫外扫描,求得一阶导数光谱,根据283 nm至276 nm的最小值与最大值之差求得2,6-吡啶二羧酸的含量,通过与芽孢的平板计数相比较,该方法与平板计数法呈明确的线性关系,可以对原料奶中的芽孢水平进行评估。     

我国生乳质量安全问题原因的剖析及对策

通过对我国目前生乳行业的调查研究,得出影响我国生乳质量安全问题的原因为管理和科技两方面因素.通过论述得出解决这两方面问题的对策关键在于采取正确的管理措施,提高生产中的科技水平,加强饲料,饲养,卫生,兽药的规范生产.     

用米浆水培养酱油酿造用曲霉菌的研究

文章考察了用米浆水替代制曲配料用水来制备酱油生产用米曲霉、黑曲霉及红曲霉的制曲效果。以麸皮、豆粕为原料,以1∶0.8的比例添加不同pH值的米浆水配料,选用AS 3.042米曲霉、AS 3.350黑曲霉、AS 3.972红曲霉为菌种,在33℃条件下恒温制曲。结果表明:对于米曲霉和黑曲霉,用浸米时间为24～72h的米浆水配料,均可以获得与对照组相当的成曲的蛋白酶活、糖化酶活和孢子数;而对于红曲霉,米浆水对提高成曲的酶活力、孢子数无显著贡献。     

Contribution of Enterobacteriaceae to Sensory Characteristics in Soft Cheeses Made from Raw Milk

Microbiological and sensory methods were used to analyze 22 soft cheeses, of which 19 were made from raw milk, one was made from both raw and pasteurized milk and two were made from pasteurized milk. Moderate correlations (r-value 0.5–0.6 and p-value <0.01–0.05) were found between the levels of Enterobacteriaceae 37°C and the intensity of the sensory characteristics “bitter”, “metallic”, “pungent”, “manure” and “ammonia”. The present study indicates that it is possible to predict high levels of Enterobacteriaceae in soft cheeses made from raw milk using only the human senses (odor and taste).     

加压CO2对污染乳中金黄色葡萄球菌杀菌效果的研究

通过加压二氧化碳对人工污染金黄色葡萄球菌的乳进行处理,对时间,温度,压力三个单因素试验对金黄色葡萄球菌的杀菌情况进行研究。结果显示单因素试验中,伴随着因素水平的增加,杀菌率随之提高。然后选取三个因素中最适宜的条件进行正交试验,并通过方差分析得出压力因素对金黄色葡萄球菌杀菌效果最显著、温度次之,时间不显著。在7.5 MPa,45℃,60 min时,杀菌效果最好达到98%以上。     

原料乳中多种致病菌的快速过滤富集及多重PCR检测

针对目前原料乳中致病菌的检测方法繁琐费时耗力的缺点,建立一种能同时检测原料乳中多种致病菌的快速检测方法,采用多重PCR快速灵敏检测技术与一种不需要预增菌就可以直接从原料乳中快速过滤富集菌体的技术相结合来同时检测原料乳中主要致病菌——沙门氏菌、大肠杆菌O157:H7、金黄色葡萄球菌、单增李斯特氏菌和蜡样芽孢杆菌。整个过程只需7～8h即可完成,且检测灵敏度可达102cfu/mL。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。     

掺水量对原料乳的理化指标的影响

本论文通过对牛乳不同掺水比例导致的牛乳理化指标变化的研究,为乳制品企业的原料收购及质量保证提供了科学依据。     

Changes in the Microflora of Valdeteja Raw Goat's Milk Cheese throughout Manufacturing and Ripening

Changes in the microbiological flora of Valdeteja, a ripened home-made raw goat's milk cheese produced in northwest Spain, were studied during the manufacture and ripening processes using the spiral plating method. High counts of all microbial groups were observed in milk (7.66, 7.57, 6.13, 6.91, 2.47, 5.18, 3.27 and 3.85 log₁₀ cfu/g for aerobic mesophilic bacteria, lactococci, lactobacilli, leuconostocs, enterococci, Enterobacteriaceae,Micrococcaceae and moulds and yeasts, respectively). Counts increased between 0.76 and 1.96 log units from milk to curd. Lactic acid bacteria (lactococci, lactobacilli and leuconostocs) were the dominant microorganisms throughout ripening. Lactococci dominated over the lactobacilli up to day 27 of ripening. Leuconostocs were stable from day 2 of ripening. The final levels of typical enterococci were 3.62 log₁₀ cfu/g. Aerobic mesophilic bacteria, Enterobacteriaceae andMicrococcaceae reached their maximum in curd and decreased significantly throughout ripening. The decrease ofEnterobacteriaceae was very marked, although they did not completely disappear at the end of the ripening process (2.74 log₁₀ cfu/g). Moulds and yeasts counts increased significantly during ripening, giving final levels of 6.09 log₁₀ cfu/g. A strong correlation (P<0.001) was found between pH and lactobacilli (R=−0.87), leuconostocs (R=−0.82) and moulds and yeasts (R=−0.74) and between a_w and various microbial groups (e.g. EnterobacteriaceaeR=0.83).     

高密度CO_2在牛奶杀菌中的应用研究

新鲜牛奶由于其营养丰富很容易腐败变质,所以杀菌是牛奶加工过程中的重要环节。高密度CO2技术作为一种新型的非热力杀菌技术,不仅能够避免传统的热力杀菌所带来的不良热效应,还能保存食品原有的风味和营养,已经受到越来越多的关注。该文对高密度CO2在牛奶杀菌中的应用研究进行了阐述,为牛奶杀菌工艺开辟了新思路。     

应用流式细胞技术快速定量检测UHT奶产品中的微生物

采用基于单个活细胞的新型荧光标记技术,精确区分UHT奶样品中的活菌细胞与死细胞以及其他大颗粒物质,并应用流式细胞技术(flow cytometry,FCM)对UHT奶产品进行微生物快速定量检测。通过与传统的平板计数检测方法进行比对,结果表明,FCM方法的检测范围为101~107CFU/mL,远远高于平板计数法。2种方法的计数结果相关性分析表明,在一定菌液浓度范围内,FCM方法的定量结果与平板计数法线性相关良好,且对不同类型菌种都能精确标记定量,是更为快速、准确的检测方法。