Keogh B P
Appl Microbiol. 1970 Jun;19(6):928-31. doi: 10.1128/am.19.6.928-931.1970.
A study has been conducted on the effect of freezing and storage in liquid nitrogen on 13 strains of lactic streptococci. Cultures were frozen in droplet form and collected in mesh bags. After rapid thawing, the activity of the frozen cultures was compared with a culture of the same organism of the age usually used in cheese-making. The activities of the test and control cultures were traced simultaneously by continuous recording of the pH changes in inoculated milks. Viable counts were performed before and after freezing in liquid nitrogen and after storage in liquid nitrogen. There was no decrease in viable count or loss in activity of the cultures due to freezing and storage. Frozen cultures of some strains showed a shorter lag period after inoculation of milk than control cultures. Frozen concentrated cheese-starter cultures behaved normally in the manufacture of Cheddar cheese.
一项关于冷冻及在液氮中储存对13株乳酸链球菌影响的研究已经展开。培养物以液滴形式冷冻，并收集在网袋中。快速解冻后，将冷冻培养物的活性与通常用于奶酪制作的同龄相同生物体的培养物进行比较。通过连续记录接种牛奶中的pH变化，同时追踪测试培养物和对照培养物的活性。在液氮冷冻前、冷冻后以及在液氮中储存后进行活菌计数。由于冷冻和储存，培养物的活菌数没有减少，活性也没有损失。一些菌株的冷冻培养物在接种牛奶后的延迟期比对照培养物短。冷冻浓缩奶酪发酵剂培养物在切达干酪制作中表现正常。
