Short communication: Microbiological quality of raw cow milk and its association with herd management practices in Northern China

Contamination of raw milk with bacterial pathogens is potentially hazardous to human health. The aim of this study was to evaluate the total bacteria count (TBC) and presence of pathogens in raw milk in Northern China along with the associated herd management practices. A total of 160 raw milk samples were collected from 80 dairy herds in Northern China. All raw milk samples were analyzed for TBC and pathogens by culturing. The results showed that the number of raw milk samples with TBC <2 × 10⁶ cfu/mL and <1 × 10⁵ cfu/mL was 146 (91.25%) and 70 (43.75%), respectively. A total of 84 (52.50%) raw milk samples were Staphylococcus aureus positive, 72 (45.00%) were Escherichia coli positive, 2 (1.25%) were Salmonella positive, 2 (1.25%) were Listeria monocytogenes positive, and 3 (1.88%) were Campylobacter positive. The prevalence of S. aureus was influenced by season, herd size, milking frequency, disinfection frequency, and use of a Dairy Herd Improvement program. The TBC was influenced by season and milk frequency. The correlation between TBC and prevalence of S. aureus or E. coli is significant. The effect size statistical analysis showed that season and herd (but not Dairy Herd Improvement, herd size, milking frequency, disinfection frequency, and area) were the most important factors affecting TBC in raw milk. In conclusion, the presence of bacteria in raw milk was associated with season and herd management practices, and further comprehensive study will be powerful for effectively characterizing various factors affecting milk microbial quality in bulk tanks in China.     

Biotin exposure–based immunomagnetic separation coupled with sodium dodecyl sulfate,propidium monoazide,and multiplex real-time PCR for rapid detection of viable Salmonella Typhimurium,Staphylococcus aureus,and Listeria monocytogenes in milk

In this study, we established a rapid and sensitive method for the detection of viable Salmonella Typhimurium, Staphylococcus aureus, and Listeria monocytogenes in milk using biotin-exposure-based immunomagnetic separation (IMS) combined with sodium dodecyl sulfate (SDS), propidium monoazide (PMA), and multiplex real-time PCR (mRT-PCR). We used IMS to lessen the assay time for isolation of target bacteria. We then optimized the coupling conditions and immunomagnetic capture process. The immunoreaction and incubation times for 5 μg of mAb coupled with 500 μg of streptavidin-functionalized magnetic beads using a streptavidin-biotin system were 90 and 30 min, respectively. Treatment with SDS-PMA before mRT-PCR amplification eliminated false-positive outcomes from dead bacteria and identified viable target bacteria with good sensitivity and specificity. The limit of detection of IMS combined with the SDS-PMA-mRT-PCR assay for the detection of viable Salmonella Typhimurium, Staph. aureus, and L. monocytogenes in spiked milk matrix samples was 10 cfu/mL and remained significant even in the appearance of 10⁶ cfu/mL of nontarget bacteria. The entire detection process was able to identify viable bacteria within 9 h. The combination of biotin-exposure-mediated IMS and SDS-PMA-mRT-PCR has potential value for the rapid and sensitive detection of foodborne pathogens.     

几种常见微生物降胆固醇机制探讨

高胆固醇血症是引起动脉粥样硬化等严重疾病的潜在危险因素,对于降胆固醇方法的研究也成为了医学和食品界的研究热点。用微生物降胆固醇的方法具有成本低、效率高等优点,本文主要介绍乳酸菌、酵母菌、红曲霉等几种常见具有降胆固醇能力的微生物及其降胆固醇作用机制。     

现代发酵工程技术在南方臭豆腐卤水的工业化应用

南方臭豆腐是家喻户晓的传统美食,具有闻起来臭吃起来香的特点,但由于技术上的缺陷和不成熟,致使臭豆腐的工业化生产受阻,商业化程度较低。南方臭豆腐的品质主要取决于卤水的品质,因此生产的关键是卤水发酵。目前卤水发酵存在以下问题:生产条件粗放,无操作性较强的生产工艺;发酵的机制不清楚,自然发酵,无代谢调控;卤水发酵的原料配比随意性强,没有科学配比,不利于质量稳定;卤水浸泡豆腐的过程控制简单;油炸条件粗放,没有连续性,没有对油炸程度进行研究,批次之间差异大。针对卤水生产过程粗放、不标准、不规范的问题,怎样利用现代发酵工程技术解决这类产品链的问题,提升技术含量,本文从菌种培养工业化、代谢调控装备现代化、代谢过程控制智能化三方面进行了综述探讨,为南方臭豆腐新型工业化生产提供了借鉴。     

Changes in cuticle compositions and crystal structure of ‘Bingtang’ sweet orange fruits (Citrus sinensis) during storage

Changes in composition and structure of orange cuticle during storage at 4°C or 25°C for 40 days were investigated. The total epicuticular wax content of fruits increased during storage at 4°C for 30 days and then decreased as storage time prolonged to 40 days, while it increased continuously at 25°C for 40 days. The total intracuticular wax content of fruits increased to 9.70 μg cm^?2 stored at 4°C for 10 days and then decreased to 6.74 μg cm^?2 for 40 days. The total intracuticular wax content of fruits was decreased to 5.17 μg cm^?2 stored at 25°C for 10 days and then increased to 10.06 μg cm^?2 for 30 days. Fatty acids were the most abundant component of the epicuticular wax and terpenoids were restricted to the intracuticular wax. Terpenoids were restricted to the intracuticular wax, and their amounts in the fruit stored at 4°C increased continuously during the first 20 days of storage at 4°C and then decreased as storage time increased up to 40 days. Although significant changes were found in the contents of the cutin monomer, their proportions did not change significantly during storage at 4°C or 25°C. Size of wax platelets crystals wax increased during storage of fruits at 4°C up to 30 days; however, the crystals were degraded and decreased as storage prolonged to 40 days. Furthermore, the shape of the fruit cuticle surface wax crystals changed from flattened platelets to small granulelike after storage at 25°C for 20–40 days. The obtained results provide detailed information about the changes in orange cuticle occur during storage at varying temperatures, which may help in preserving the quality of citrus fruits during storage.     

甘薯糖蛋白提纯及生理活性研究进展

甘薯糖蛋白是近年来在甘薯中发现的一种新的生物活性物质,具有重要的营养功能和潜在的医疗保健作用,它是一种宝贵的植物蛋白资源。主要综述了国内外甘薯糖蛋白的提取纯化方法、生理活性方面的研究新进展．以期对甘薯糖蛋白进一步的开发利用提供帮助。     

冰温技术在果蔬贮藏中的应用研究进展

本文介绍了冰温贮藏技术的起源、机理及发展历程。简述了冰温贮藏对果蔬品质的影响;综述了该技术在果蔬保鲜上的应用现状和最新进展。并对果蔬冰温保鲜技术的研究方向和发展前景做了展望。     

一种嫩栗香型茶醋研制

为了提高黔南茶园夏、秋茶茶树鲜叶的利用率,以夏季都匀毛尖茶为原料,利用固态发酵的方法,旨在研发一款嫩栗香型都匀毛尖茶醋。结果表明:在32℃、85%恒温光照培养箱中,以6g茶叶发酵12d得到的茶醋品质最佳,色泽黄绿色,口感醇和,酸甜爽口,醋味中带有糯米香和嫩栗香,其中糖度为17.47%,酒精度为8.1%,pH为3.47,酸度为213.33Mv,ΔE值达到27.36;铜、锌、铁等理化指标及菌落总数、大肠菌数、霉菌和酵母等微生物限量均符合食品安全国家标准。     

高速逆流色谱分离纯化荷叶黄酮槲皮素

以含量为4.4%的荷叶黄酮粗粉为原料,在优化高效液相色谱分析荷叶黄酮槲皮素条件的基础上,通过对不同溶剂体系的优选及操作参数的优化,建立了高速逆流色谱分离纯化荷叶黄酮槲皮素的技术方法。结果表明,采用流动相甲醇和0.4%磷酸、梯度(0min90%甲醇→10min60%甲醇→20min40%甲醇→40min20%甲醇)洗脱、检测波长360nm、流速1.0mL/min、柱温30℃、进样量20μL的技术参数可作为高效液相色谱分析荷叶黄酮槲皮素的方法;采用氯仿:甲醇:水(体积比8:10:5)为溶剂系统(上相为固定相,下相为流动相)、流速2mL/min、转速850r/min、进样量150mg的高速逆流色谱操作技术参数,可分离制备荷叶黄酮槲皮素单体,其纯度大于99%。     

影响魔芋葡甘聚糖吸附香兰素的因素研究

为探讨魔芋葡甘聚糖吸附香兰素的基本特征,以魔芋葡甘聚糖溶液浓度、pH值、温度和时间为试验因素,进行单因素试验,对结果进行方差分析。结果表明,随着魔芋葡甘聚糖浓度增大,香兰素吸附量呈增大趋势;随pH值升高,吸附量增加;温度越高,吸附量越低;随时间的延长,吸附量逐渐减少;魔芋葡甘聚糖吸附香兰素的工艺条件为：合适的魔芋葡甘聚糖与香兰素配比,魔芋葡甘聚糖溶液pH=9．0-11．0,常温下吸附,吸附时间10min。