I know why this happened. My usual brand, Nancy's, had been on sale for a couple of months, but now it was back to the regular price of $5.29 a half gallon. I had been paying a dollar less. So when I saw something nearby on sale, I grabbed it. It was whole milk plain yogurt, and only $4 for 2 quart tubs. Good price.
I use yogurt in my breakfast smoothie every morning. The first day it seemed a little foamy and pasty. The second too. And I didn't like a certain discomfort in gave me after I drank it. So I checked the label. It had as its second ingredient cornstarch!
I had succumbed to the temptation to go with price over quality, not intentionally but carelessly.
And what I got wasn't yogurt. True yogurt doesn't need thickeners, which is what the cornstarch is. As is the tapioca in other brands, or the gelatin.
If the right bacteria are present for the right amount of time, milk will turn into thick yogurt and no other thickener is needed.
Nicely, bacteria also convert sugar into acid, lactose into lactic acid in the case of yogurt. You can read about it here.
So you have helpful bacteria, the kind that coexist inside of us and help us convert food to nutrients, working to ferment milk and convert its difficult-to-digest sugar lactose into lactic acid, which thickens the milk, separating the liquid part from the protein part, whey and curds, through fermentation.
The result is more digestible milk with less sugar.
Along comes the food industry. In the name of something I can't imagine, it 'improves' on the process and instead gives us a milk product so inadequately fermented that it has to add cornstarch and then to make up for lost sugars, adds sweeteners.
Most yogurts come with added sweeteners, but the label PLAIN helps us avoid those. Nothing on the label helps us avoid the adulterants. For that we need to turn the tub over and squint at the list of ingredients. If it has more than milk and bacteria in it, it's not yogurt. Or not all yogurt.
I confess to being overly influenced by price, even though I realize that good food always costs more than bad. (Fresh spinach costs far more per pound than cookies, even if it's not organic spinach.) So in this frugal mindset, I resent paying for cornstarch when I think I'm paying for a milk product.
Corn is in everything. The government subsidizes corn and we have a glut of it. Cows eat corn to make milk (though they shouldn't - it makes them sick). But it's cheaper to skip the cow and just add corn to milk products.
I don't want to pay for yogurt that has been 'extended' by cornstarch. Or thickened by it. I don't like the texture - pasty, foamy - and I don't like the idea of it.
There are only one or two yogurts out there now that are made from whole milk and yogurt-making bacteria and nothing else. Good luck finding them at an affordable price!