Perfectly safe! "Best before" means that there may be some loss of quality (e.g. flavour, texture) but its not dangerous. (As long as the packaging is intact - they even have a best before on tins of beans and soup these days, and we all know they last forever!). What you have to watch is "use by" - on perishables like meat and dairy. They CAN be dangerous, especially for vulnerable groups (very young/old, sick).
Yes, what Mazda said. Many times, the date is just a suggestion, as the government has regulated they put "Best by dates on. Some products, like dried packages, are good for a few months well after the expiration date. Just not as "fresh." In the old days, before "Best by" dates, we had to the tests of taking a sniff and looking inside at the contents, and using out common sense. Still always a good idea.
A good look and sniff is always worth it My DSis was in a rush one morning, gave one of my nephews some Weetabix (which in the way of kids he'd had every day for months, got bored just when she opened a new packet and suddenly demanded again) and was just making herself a coffee when a little voice piped up "Mummy, why is my breakfast moving?" Anything fluffy and/or moving in my house goes in the bin
I think you just run a higher risk of them being moldy past the Best By date. Seals and bags aren't meant to last forever, and over time moisture could seep in and cause mold. I think another issue you would run into, particularly with a cake mix is possible loss of strength of the leavening agents. I work at a grocery store and I usually explain it this way (as this was how it was explained to me) Expiration date or Use by date: exactly as it says, you typically find this on highly perishable items and it tends to be the safest bet to just discontinue use of these items on this date. Best by date: The product will start losing flavor/quality/potency after this date. For this product to be at it's "best", it should be used before this date. It's typically safe for a little while after the date, but you will probably find it will react/taste a little differently than it would when it's fresh. How long you can keep a product past it's best by date depends on the product. Sell by date: I deal the most with these dates. The sell by date is the last day I can sell a product, knowing that it will still be good in the time it should take you to go through it, or the bulk of it. If I have a product with a sell by date of 2-19-11, and I sell it to you, depending what it is, you'll still have time to use it. If I don't sell that product by that date, I have to get rid of it. Again, that window of use is going to depend on the product itself.
As long as the packaging stays intact your cake mix should be OK for a few weeks after your best before, though as said there leavening agent may weaken a little. I'd say its fine ti use, but if you're worried use it sooner rather than later and maybe use it for "cookies from cake mix" where the raising is not so important
I'd definitely use it, but not for company. Here's an article from StillTasty.com, my go-to website for expiration stuff: http://www.stilltasty.com/articles/view/5 http://www.stilltasty.com/fooditems/index/16662
