Ning Shu nodded: "Cows aren't afraid at all. Their stomachs are very willful. If one is wasted, there are still three more!"
Jiang Yao thought for a moment: "So that's why milk needs to be pasteurized before drinking it."
Qian Qian looked at Jiang Yao's chest: "Not all milk needs to be pasteurized, right?"
"That's right!"
Lu Zhe nodded: "Additionally, pasteurization kills all bacteria indiscriminately, not just the harmful ones but also the beneficial ones. And fresh cow's milk won't ferment without any bacteria present, it will just go bad directly, so you still need to add lactic acid bacteria separately."
Shen Bing nodded and said, "It would be great if we had some yogurt, even just a tiny bit. With the current temperature, the bacterial colony could propagate rapidly. But we have absolutely none, so we need to think of other methods."
Ning Shu cupped her chin thoughtfully: "So we can only use stuff from our mouths or intestines?"
Jiang Yao said helplessly: "It feels kind of uncomfortable."
Shen Bing said: "Think positively. The world's first lactic acid bacterial spores were isolated from animal feces."
Jiang Yao turned pale with fright: "So you mean all the lactic acid products we eat are from..."
Ning Shu and Qian Qian shrieked.
Shen Bing shook his head: "Most lactic acid bacteria we eat nowadays are industrially extracted from cleaner sources, such as napa cabbage which is rich in lactic acid bacteria. But I also know that female students from a certain industrial university successfully extracted lactic acid bacteria from their stockings and made yogurt with it."
Qian Qian blushed and said: "Then...do you still need my socks?"
Lu Zhe shook his head: "With our current conditions, we simply cannot isolate lactic acid bacteria. And different media may introduce other types of bacteria, like E.coli, Staphylococcus, Bifidobacterium etc., some good and some bad.
Different people also have different gut flora compositions, some people's extracts are suitable for making yogurt while others' are not!"
"Then what should we do?"
"Do it in batches!" Lu Zhe took out some tin cans: "Luckily we have a lot of milk. Now Sea Swallow produces over ten jin (5kg) of milk per day. By the way, apart from drinking, there's a lot left over. What have you guys been doing with it?"
Jiang Yao blushed: "Washing our faces and feet..."
Lu Zhe nodded: "Guys, we're surviving on a deserted island, and you're using milk to wash your feet?"
"We can't drink it all, so what else can we do?"
Lu Zhe thought for a while. Without a way to preserve the excess milk, other than pouring it away, using it to wash up is still more valuable.
Washing faces and feet, nourishing the skin, is indeed better than just throwing it out.
"How come you don't wash me too?"
"You're a guy, why would you wash with milk too?"
"No, you guys got the conversation off track again." Lu Zhe used his paratrooper knife to slice a tin can cleanly down the middle, making the bottom into a small aluminum cup.
"Since we still have a lot of milk, we can make 20-something small aluminum cups like this. After sterilizing the milk, pour it into the small cups, then inoculate with different bacterial sources. See which cup of milk ferments into the best yogurt. Then we can culture that lactic acid bacteria strain for yogurt making. We can even make milk tofu in the future."
Ning Shu frowned: "I understand everything else, but what do you mean by inoculating with different bacterial sources?"
Lu Zhe explained: "First, number these improvised aluminum cups. Cup one use Class Leader's saliva, cup two use Class Leader's intestinal extract, cup three use Jiang Yao's saliva, cup four use Jiang Yao's intestinal extract, and so on...
Because everyone has a different constitution, the bacterial flora composition also differs between body parts and between people. This is also one reason for differences in body odor. Therefore, the quality of the resulting yogurt will also differ.
And for bacterial inoculation, it's not limited to just the above two sources. Sweaty areas like armpits and between the toes may also contain lactic acid bacteria colonies that can be used for inoculation."