I have a box of soylent powder that labels expiration date 09/2018. Does it expire immediately as I turned in September, or it is still valid.
The expiration date does not necessarily mark the period of time the product is safe to consume, but merely the amount of time that Soylent is able to guarantee the nutritional content of the product. After one year, the product should almost certainly still be safe to eat but it’s possible that some nutrients in the product might be starting to break down. I would venture to guess that process is gradual rather than occurring all at once. I don’t speak for the company, but personally I would not hesitate to consume Soylent powder that is within a few months past its expiration date.
Dry goods like Soylent powder will go a very long time, maybe indefinitely, before they become dangerous to eat. (If water gets into the bag, that’s another story, but I’m assuming you kept the powder dry and sealed). And as tsapience points out, some nutrients do break down, but slowly; it’s not like on August 31 it was great to eat and on September 1 it’s not. Go ahead and eat it.
When I switched to RTD from Powder I had a bunch of boxes of Powder left over that I very slowly worked through. It all still tasted fine a year or two after the expiration date (vitamin/mineral/nutrient degradation I can’t really speak to but I would guess it would take 5- 10 years for it to be significant).
Don’t let [somewhat] arbitrary dates on a package boss you around! I tell my milk containers when they expire, they don’t tell me!