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Many condiments such as katchup, mayonnaise and mustard (where I live at least) seem to love rounding all of their expiry dates to "60 days after opened".

Thing is, I never see any difference after the date, at least with mustard. It's easy to consume katchup or mayo under a couple of months, but I only like mustard for very few things, so I have some black mustard from ~3-4 months that tastes just as good.

What is weird to me is that they round the expiry dates. Are they just lazy and think "nah, nobody takes more than two months and it should last that long"?

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By the way I would expect katchup to last much less than mustard, but it's rare getting it to last one month anyway :) –  Camilo Martin Feb 7 '12 at 1:43
    
You seem to be using "rounded" to mean "too soon". You're actually asking why the dates are shorter than the dates you think are safe, right? –  Jefromi Feb 7 '12 at 4:05
    
Also, surely this is a duplicate. Maybe we can just add a tiny bit to the answer on the generic food safety question and point it there? –  Jefromi Feb 7 '12 at 4:26
    
@Jefromi Yes, I mean they're "floored". Of course they're supposed to be good until the expiry date... I don't think this is duplicate because I'd also like to know if there's a correlation, some reason why they're all the same date ("60 days") for a lot of condiments, even salad sauces and other things that remind of junk food. My question is more about if there's a reason why all these condiments seem to have (at least where I live) the same expiry date. –  Camilo Martin Feb 7 '12 at 19:44
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Ketchup and mustard expire due to quality not safety, at least when stored in the fridge. They're quite acidic. 60 days in the pantry for ketchup, I'd definitely call expired ketchup—due to taste. StillTasty gives 6 months in the fridge, which sounds reasonable. I'll add ketchup and mustard to the big question when I next work on it (hopefully I'll have some time tonight) –  derobert Feb 7 '12 at 20:04
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5 Answers

up vote 4 down vote accepted

Food quality isn't binary; it doesn't go from perfectly good to perfectly bad in an instant. Even if it did, the time it would take depends on the storage temperature. And for non-liquid foods, it's possible that only a part went bad (how well does it mix?).

So, you don't get a precise date, but a rough interval at which time the decay starts to set in. As a result, the manufacturer will just pick a rounded date from that interval.

Example: the engineers might calculate that under reasonable circumstances, the product may start to noticably deteriorate after 52-75 days, and become dangerous after 81-112 days. They manufacturer could then say that the expiry date would be 60 days.

(The other answers explain why you'd use the first interval, but not why they're actually intervals.)

:edit:

The likely reason why they're all the same 60 days is probably also engineering. How much preservative do they use? As noted in the comments, the primary preservatives are the acids, but you need quite some sugar to compensate. It seems 60 days is a commonly accepted balance.

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Even if you answered later than the others, your answer really seems to be the most sensible reason for them to do that. I would guess food starts to taste and look strange much before it's bad (or maybe not), so they prefer to round it on some date where the product still looks and feels good, but it's actually edible some time after. I'd guess the aproximation is very rough even. –  Camilo Martin Feb 7 '12 at 19:56
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I'm not sure what the consumer liability laws are like in Brazil, but I expect that they 'good until' dates well short of their 'actual' lifespan to protect the manufacturers from lawsuits for people who don't read the labels anyway and get sick on 3 year old mayo...

A second reason they set short shelf life for such things is to encourage you to buy it more often, thus more money for the manufacturer.

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Both guesses make a lot of sense, especially the second one. For example, I condensed milk after 2-4 days, store the (non-heated recipe) result for a week, and it tastes perfect, yet the expiry date is 3 days. I guess the expiry dates assume reckless storage conditions or something too. –  Camilo Martin Feb 7 '12 at 19:47
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Expiration dates for safety are not about "usually okay". Sure, if you keep mustard in good conditions, it'll probably last longer than that most of the time. But things are labeled with expiration dates that are designed to guarantee that everyone will be safe. Yes, that means that most of the time they're overly conservative. But the alternative is to let people get sick, or even die. It's a big world; if even one in a million bottles goes bad after 60 days, that's a big deal.

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That makes sense, I guess some people may leave condiments outside of the fridge for extended periods of time, and they take that into account. –  Camilo Martin Feb 7 '12 at 19:52
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If by "round" you mean 60 days as opposed to say 58 for some things, and 63 for others, it has to do with the perceived accuracy of numbers. If you read "keeps for 53 days after opening" you might feel it has gone bad after 54 days. But with 60, it's a round number, you realize that there's essentially no different betweeen 59 day old ketchup and 61 day old ketchup. When you find a 90-day-old bottle at the back of the cupboard, maybe you decide you'll toss it because it's so far past 60 days. If you're wondering why so many products have exactly the same shelf life, I think the manufacturers tweak the formula - who would buy a jar of mustard that went bad in just few days? It needs to last about as long as it takes people to use up the jar or bottle.

Me, I keep my ketchup in the cupboard (in Canada, the large bottles say refrigerate after opening and the small ones don't) and keep it for months and months - maybe even a year. No worries. But my chef-daughter announces that a product (eg a carton of milk) "goes bad" on it's expiry date, and refuses to consume anything on or after its date.

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+1 because of the percieved accuracy concept, but indeed, I meant why they all have that same date. Some things however say they only last for three days after opened, notably condensed milk (at least where I live). I've eaten condensed milk way older and couldn't even spot the difference. Also, regarding condiments, I've come to the conclusion that ketchup for example is made from excessive amounts of salt, sugar, vinegar, MSG, and other strong things, plus rotten tomatoes, so any difference will be hard to notice. It will last longer than the lightbulb on the fridge. –  Camilo Martin May 13 '12 at 12:53
    
There are many things we all eat that are designed to keep a long time - they come from a time before "opening" was even an option. You made something and then you ate it until it was gone. Jam, cheese, pickles, and many many sauces - soy sauce, ketchup, worcestershire sauce, chutney, salsa etc etc are strongly flavoured with salt and sugar (both of which are preservatives) and have always kept a long time and added a hit of flavour to what we're eating. That's not a bad thing, that something keeps a while. –  Kate Gregory May 13 '12 at 13:01
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The manufacturer has to test that the expiration date is valid and each tested point has some cost associated with it. Lets say they test with 100 containers at 60 days, testing an additional 100 containers at 61 days has significant incremental cost but very little incremental value.

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