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Analysis of the Difference in the Quality Acceptance of Various Culture Media for the Detection of Coliform Bacteria in Raw Milk Using Different Standard Strains
LIU Shuai, XU Miaomiao, CHEN Yiwen, ZHANG Jie, WANG Hui, LI Xian, LIU Yumeng, CUI Shenghui, ZHANG Yalun
Journal of Dairy Science and Technology    2023, 46 (4): 22-27.   DOI: 10.7506/rykxyjs1671-5187-20230801-037
Abstract40)   HTML9)    PDF (1632KB)(38)       Save
In order to ensure the quality of raw milk and enrich quality control strains for the acceptance evaluation of culture media for the detection of coliform bacteria in raw milk, three brands of violet red bile agar (VRBA), violet red bile agar with 4-methylumbelliferyl-β-D-glucuronidehydrate (VRBA-MUG), lauryl tryptose broth (LST) and brilliant green lactose bile broth (BGLB) were selected and evaluated for their physical indicators such as appearance, pH and moisture content as well as microbial indicators such as growth rate and selectivity using the methods specified in China’s national standard for quality requirements for culture media and reagents in food microbiological examination (GB 4789.28-2013). Besides, using Citrobacter freundii ATCC 43864 as a reference strain, seven strains of C. freundii were selected for acceptance evaluation of the four media. The results showed that the color of all three brands of dry powdered media was normal. Their moisture content was 5%–6%, and their pH was in line with the national standard. The growth rate of the seven tested strains of C. freundii was greater than 0.7 on the three brands of VRBA and VRBA-MUG, while only CMCC 48098 and CICC 22910 achieved turbidity of 2 on the three brands of LST and BGLB, and produced gas in the catheter; the same results were obtained with ATCC 43864. In summary, the three brands of VRBA, VRBA-MUG, LST and BGLB all comply with GB 4789.28-2013, and CMCC 48098 and CICC 22910 can be recommended as supplements to quality control strains for the acceptance evaluation of the four media.
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Progress in the Determination of Flavor Quality and Residual Microorganisms in Pasteurized Milk
YANG Shanshan, DING Ruixue, LIU Yumeng, SUN Xueting, YUE Xiqing, WU Junrui
Journal of Dairy Science and Technology    2019, 42 (4): 40-45.   DOI: 10.15922/j.cnki.jdst.2019.04.009
Abstract191)   HTML1)    PDF (1572KB)(310)       Save
Pasteurized milk is favored by consumers worldwide because of its mild sterilization conditions, which can not only kill most pathogenic bacteria in raw milk but also maintain the main nutrients and flavor of fresh milk to the maximum extent. However, because low-temperature sterilization cannot completely inactivate all microorganisms in raw milk, some microorganisms remain in the final product and cause spoilage, which restricts the production, sale and consumption of pasteurized milk. The traditional method of detecting dairy quality is simple and rough. Therefore, this paper reviews the recent progress in the determination of the nutritional and microbial quality of pasteurized milk and other dairy products, in order to provide a theoretical basis for improving product quality and optimizing processing conditions.
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