I made an observation. I didn't have milk for a long time, but after opening the milk an not using it up in time it went bad, stale and had to be thrown away. But I remember, when I was a kid, that milk was different, it didn't go bad, but went sour and could still be eaten. I had the same experience with soy milk recently. It didn't turn bad but sour. If it's sour you can eat it, if it's bad/stale you have to throw it away. It depents on which kind of germ gets into soy milk.
Expery dates: I think the industry likes expery dates as they make people throw away things prematurely.
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