Why do mayo and other things have to be refrigerated once opened when they keep them on regular shelves?!
Answers: in stores or at home before they are opened?
Because once these types of products have been opened, the oxygen in the air makes them spoil-unless you refrigerate them, when the process is slowed. All foods decay with time and refrigerating, freezing, vacuum-packing, tinning, bottling, etc or any other sealing/preservation process merely slows down the decay process, not stop it. Oxidization causes faster decay because the product is essentially back in its natural state - mayo, for example, contains eggs. If you cracked open an egg and left it out for, say, 48-72 hours, it would be spoiled and smell & taste terrible. Also, bacteria can form on opened, incorrectly stored food.
because it is vacuumed seal close once open bacteria can form
Because once the air gets to it they start to rot.
If you have ever since left mayo it's not nice!!
they are sealed to keep bacteria out
Once they are opened they are exposed to the air and the coolness of the fridge keeps them from going off.
Because they are vaccuum sealed and once opened the seal is broken and the protection escapes and therefore refrigeration is neccesary for its longevity.
Once opened they need to be refrigerated because they contain eggs.They can need to be kept cold if they contain any dairy products.Milk,sour cream,cheese or eggs.Just be sure to read ingredients and if they say keep refrigerated,do it.