This is a quality issue rather than a safety issue first ie once opened all sorts of yeasts and moulds start to grow and this impairs the flavour. Safety wise you could use it up to 11 days but you wouldn't want to.
As someone who's spent years deciding on use by dates for safety reasons they are not put there willy nilly but are very carefully thought out i.e. the dates are stretched to the very lsat date possible the product will taste good.
" the dates are stretched to the very lsat date possible the product will taste good. "
lol - in that case I think some people choosing the dates (not you - as if I read your post properly you used to do this as a job) need to extend them a bit, as DH's chocolate eclairs say "eat within 2 days" - yet still taste just as good 4 days later.
I have always believed that the "best before" and "use by" dates are actually 'earlier' than the actual 'events' of being past it's best etc etc, imagine if all the food we had "suddenly" didn't taste as good on the very last day......I'd be seroiusly questioning the quality of the food!
smells ok - just tomato and spices - so will use it. thanks ladies (sweetkitty - sounds like an interesting job! It would put me off food though think about the mulding process - could be good for my diet lol)
The dates are firstly assessed on the taste and quality of the product on the proposed shelf life then they are assessed on the safety aspect. The safety always comes first. So say for instance the safety was 11 days but after 8 days it was tasting and smelling a bit off then the shelf life would be set at 8 days, at no time is safety compromised to allow a longer shelf life. For companies the more shelf life they can have on a product the better as it prevents waste.
Any new product will have a shelf life trial which looks at the taste and quality as well as what is growing in the product, it should taste as good on day it was made as it does on the last day of life.
These trials are conducted first at 5deg then at 8deg to represent a standard fridge and are subject to a bit of temperature abuse (to mimic taking them home in teh car etc) so it's worst case.
As for my job yes sometimes it was interesting but like everything else it was mostly routine and boring.
QofQ even if you were a value shopper if you bought someone that was rancid and it had say a week of it's shelf life left you would probably take it back and ask for a refund or never buy it again. Makes no difference whether it's value or the best there is, I think.