That's milk which has not undergone pasteurization, the century-old process of using heat to kill potentially harmful bacteria.

生鲜奶是未经巴氏杀菌处理过的牛奶。而巴氏杀菌是一种拥有百年历史利用高温将潜在有害细菌杀灭的工艺。

There was a whole subculture of pasteurization activists back then.

当时存在巴氏杀菌活动家的整个亚文化。

Another version, called ultra-high temperature processing, or ultra pasteurization, blasts the milk with considerably higher temperatures over just a few seconds.

另一种称为超高温处理或超巴氏杀菌的版本在短短几秒钟内用相当高的温度对牛奶进行喷射。

This led to the invention of pasteurization, as you all know from your middle school science classes, but it also led to an understanding that fermentation was a biological process involving living organisms.

这导致了巴氏杀菌法的发明，正如你们在中学科学课上所知道的，但它也让人们得以理解发酵是一个涉及到生命有机体的生物过程。

Raw milk can carry microbes that are the sources of deadly diseases, so in order to kill as many of those microbes as possible, and keep milk fresh longer, we use a technique called pasteurization.

生牛奶可能携带致命疾病的来源微生物，因此为了尽可能多地杀死这些微生物，并使牛奶保鲜时间更长，我们使用了一种称为巴氏杀菌的技术。