Development of an electrochemical method to detect total viable count, Listeria monocytogenes, and somatic cell count in milk

• Main Authors: Hung-Yu Hsu, 許宏伃
• Other Authors: Chuan-Liang Hsu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/99080434769321791335

碩士 === 東海大學 === 食品科學系 === 100 === Total viable count, Listeria monocytogenes and somatic cell count are recognized by the nations as generally acknowledged indexes of raw milk quality, and they are also the important reasons of affecting prices of dairy products, amounts of raw milk content, relish and expiration date. Therefore, it is significant to produce raw milk of low total viable count, L. monocytogenes and somatic cell count for dairy farmers, dairy factories and customers. This research aims at developing an easy, low-cost and rapid quantitative determination electrochemical detecting method applied to the detection of total viable count, L. monocytogenes and somatic cell count. Total viable count and L. monocytogenes are detected through the change of the current that caused due to the electrochemical active materials metabolized by microorganism. The quantitative determination of somatic cell count is current signal which is produced by detecting lactate dehydronase catalyzing lactate to diagnose whether the cow is infected with mastitis by calculating the amounts of somatic cell count. The research has shown that the appropriate conditions of detecting total viable count are 35℃, 1 V, range of cell density between 102-108 CFU/mL (R2 = 0.966), and 1-10 hours of detection time; It’s easier and faster to conduct than Plate Counts that is 48±4 hr. Besides, appropriate conditions of the detection of L. monocytogenes are 37℃, 1 V, and under pH 9.4. Using electrochemical system with fraser broth and high pH values to detect L. monocytogenes; conditions of somatic cell count are 42℃, 0.5 V, pH 9.0, range of cell density between 350 to 780 thousand cells/mL (R2 = 0.907) and 60 seconds DT. It can be estimated the amounts of somatic cell count by detecting current signal of oxidation reduction reaction by LDH and substrate. It’s cheaper and faster than Somatic cell counter. Keywords : total viable count, Listeria monocytogenes, somatic cell count, lactate dehydronase, mastitis