I would very much be in favor of grocery stores sharing responsibility (and regulatory penalties) for selling tainted food! It's kind of mind boggling that this is controversial. "Buyer beware" is not an acceptable basis for society to function.

This is unfortunately exactly how society operates in China. It is basically on the buyer to confirm that they're getting something acceptable. Once they've paid, it is what it is.

I can't think of a case where a supermarket, upon becoming aware of a problem with a food product, didn't immediately pull it from the shelves, post a notice to customers, and offer a full refund to anyone who had purchased it.