Rangergord
Songster
I did not see this comment when I made my initial reply. On the farm where I grew up the milk was raw and unpasteurized and so it clabbered. Clabbered milk is different from pasteurized sour milk. As Saysfaa mentions clabber contains the bacteria from the cow and Pasturized milk has killed many of those off. Two other factors in this are temperature and time. Temperature selects which bacteria survive and reproduce. Yoghurt is a thermophylic culture needing around 105 degrees Fahrenheit to reproduce, once it cools to below this the culture dies and lactose stops being broken down. Yogurts vary also in the time they are cultured. A mild yoghurt can be cultured in two or three hours. A sour yoghurt containing less lactose may take 4 to 5 hours to culture.I don't know how to quote both of your posts.
Your grandmas is right. Pasteurized milk won't clabber because the enzymes and lactic acid bacteria are killed off along with the harmful microbes. In raw milk, the enzymes and lactic acid bacteria kill the harmful microbes and mold. Theoretically, you could add some back but I don't this that is realistic for people who don't have a cow.
Yogurt and buttermilk are also cultured/fermented which is what processes the lactose so I think so. I'm not sure today's version is as beneficial as what people fed during the great depression because today's versions are made by adding a few strains of lactic acid bacteria back into the milk. Not all the beneficial things are added back in.
Yogurt varies a lot in how much lactose it contains, so maybe not all of it is. And, of course, use plain yogurt.
Modern buttermilk is not milk left over after making butter. It is ordinary pasturized milk that is inoculated with a mesothermic lactic acid bacteria that only reproduces at room temperature. Above and below room temperature it stops culturing. It usually needs 18 to 24 hours to work before buttermilk is thick. Buttermilk, sour cream, cream cheese and cottage or farmers cheese all use a buttermilk culture.
Different cultures produce different textures and flavours in the milk. Clabbered milk has a better texture and flavour than soured pasturized milk. Still the longer clabbered milk is cultured at room temperature, the more off flavours can be detected. Off meaning bad tending toward rotten. For this reason modern cultures have been selected for flavor that is buttery, cheesy or other desirable characteristics. In the old days it was left to chance. Some locales had better bacteria than others. Cheddars natural culture came from a particular area and only in modern times spread around the world.
Maybe clabbered milk is really good for you but the smell of it never enticed me to want to eat it in more modern times!