I'm doing a science fair project and I need some help. My question is does whole milk or soy milk spoil faster? Does anyone know which one spoils faster or if they spoil at the same rate? Please explain why.

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    If you submit a science fair project without an actual experiment you're going to do very poorly. Why not pour 2 glasses and monitor their progress over a day... or you could do a really good experiment and have a control group that rests in the fridge and put another group that stays on a table and another group that sits on a window sill... – Mr. Mascaro Jan 22 '15 at 21:16
  • Good idea, but my science teacher tells us to research...which is why I am asking...3 questions and then turn them into him so he can decide which questions I can do and which ones I really shouldn't do. So if you have any experience, will you tell me your results and why they were like that? – yinyang1092 Jan 22 '15 at 21:45
  • Look at the expiry dates on the containers. That should give you a good idea. – Mr. Mascaro Jan 22 '15 at 21:48
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    You'll probably want to take into account shelf-stable products versus fresh (refrigerated) types, and also pasteurization (e.g., "UHT") or other processing techniques. All that said, we collectively seem to like (e.g., view, upvote) experiments (examples such as this one or this one or perhpas it's just @jolenealaska... ;-)); if you end up doing an experiment, please do submit a self-answer! – hoc_age Jan 23 '15 at 12:00
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    This actually sounds like a great science fair experiment, particularly if you test various kinds of cow milk (e.g. "raw", skim, whole) and soy milk (e.g. unsweetened vs. sweetened). The challenging part will be establishing a standard for "spoiled" and measuring it. Good luck!!! :) – Erica Jan 23 '15 at 13:07

Not sure about why, but in my experience cow's milk spoils much faster than soy milk.

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They're all good for about a week past the date on the carton, according to this link for milk substitutes and this link for milk. Of course, shelf life for milk depends almost completely on the method of pasteurization.

It's worth noting that "spoiled" milk is almost always related to natural milk bacteria, rather than a food borne pathogen: they out compete almost everything else. We eat various varieties of spoiled milk on a daily basis, and I would be a lot less concerned with milk past its expiration date than any milk substitute.

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    The "natural milk bacteria" part is true for raw or low temperature pasteurized cow milk. ESL milk and UHT milk 1) lose the innoculation with lactic bacteria from the udder, and 2) provide a different milleau which promotes the growth of other bacteria, not the original lactobacilii. The new colonies are not necessarily pathogenic, but can't be assumed to be safe, and also don't taste good. – rumtscho Jan 23 '15 at 17:19
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    Soy milk doesn't last 7 days after the date on the carton, but 7 days after opening. – trlkly Mar 29 '15 at 9:03
  • If it is the kind of soy milk that is pasteurized like UHT milk, so it can be stored in an unopened carton on the shelf. There are brands of soy milk that need refrigeration. And the advice given on the packaging for soy milk and soy yoghurt tends to be pessimistic, I have seen soy milk last 2 weeks opened in the fridge (it won't always!) – rackandboneman Nov 12 '15 at 20:57

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