Improvement Of Lactic Acide Bacteria Starter’s Producing Conditions And The Influence To The Cheese Making

Lactic acid bacteria (LAB, Lactic acid bacteria)is a kind of Gram-positive,catalase-negative bacilli or cocci. They can transform the carbohydrates (mainly glucose)to above50%lactic acid. The lactic acid bacteria fermented products are called lacticacid fermented food. After the fermentation, the content of vitamins, amino acids,minerals and other nutrients in the original food have increased, so the nutritional valueof food is greatly improved.Lactic acid bacteria plays an important role in the fermentation process of makingcheese: reducing the pH of milk, improving the flavor of cheese and giving cheese agood texture, etc. Therefore, the activity of lactic acid bacteria is directly related tocheese quality. In this thesis, we studied Streptococcus thermophilus used in Vieux Panécheese and viscous lactic acid bacteria used in Brique cheese. The research is to find outthe irregularity sources in the expanding culture. The results show that it is veryimportant to inoculate according to the volume of culture medium. Furthermore, wemust regulate carefully the tank’s temperature to make sure the culture temperature isinvariable. The acidification irregularity in Vieux Pané cheese making is mainly fromthe milk’s quality rather than the acidification activity of Streptococcus thermophilus.Taking the existing viscous LAB as a reference, we selected between twosubstitutes of viscous LAB S1and S2by the simulation of expanding culture in the lab,by the experiments of expanding culture in the tank, and by the acidificationexperiments on the reference culture medium Nilac. The results show that theacidification activity of S2is more closed to the reference than S1. So S2is a bettersubstitute viscous LAB.