Every time when I’m craving yogurt, the first illusion my brain produces is the richness of each bite, the concrete yet smooth texture. I believe I’m not the only one who enjoy the thickness of yogurt more than anything. As a matter of fact, when we want some yogurt, we always say “eat” instead of “drink”. I wonder what turns a gallon of liquid milk to cups of “eatable” yogurt?
At the end of my last post How Milk Becomes Yogurt, caseins all come together and become curd. Now, let’s dive into this specific wonderful process.
Milk consists of protein, fat and lactose. Lactose can blend well with water; fat exists as small particles surrounded by protein molecules. Apart from that, there are also many proteins swimming in the water all by themselves.
Every protein carries more or less some hydrophobic grouping, they hate water molecules more than anything and always try to get together. but they never succeed, because protein molecules also carry —-
Electrons! That’s right, Electrons have two different types of electric charge: positive charge and negative charge. Because two alike electric charges repel each other, hydrophobic grouping can never bring proteins together. Thus, milk remains liquid.
However, when lactic acid lowers the PH value of the milk, electrons lose their electric charges. Hydrophobic groupings finally can get together and combine to a huge “net” with proteins, fat, sugar, water all gathering inside.
And so yogurt becomes thick!