Pickles are perfect. Everyone knows this, of course, except for the fools and tragically undeveloped palates that persist in the population. The versatile pickled cucumber goes well with cocktails, workouts (well, OK sorta, not really), and the most ambitious of cheeseburger recipes. One more thing that makes them perfect: they can last a really, really long time.
Pickles can last for as long as 1-2 years past the expiration date printed on their jars. That's whether you store them in the refrigerator or not, provided they've been properly sealed. That has everything to do with the pickling process that turned them from mostly boring, plain ol' cucumbers that rot within 5 days into pickles (or gherkins if you enjoy them across the pond). That process begins with putting the cucumbers into a solution of salt water (brine) and vinegar, that has been boiled. You stick the cucumbers in a sterile jar, fill it with the solution, and then give it a good airtight seal for at least 48 hours -- or longer if you want tastier pickles. Al Roker -- he of Guinness World Record weather reporting fame -- once explained the biochemical process perfectly on an NBC educational program as a war between good bacteria and bad bacteria, in which the brine is the ideal battlefield for the good bacteria to gain a foothold. Take it away, Al!
"...We want a class of good bacteria, called lactic acid bacteria, to colonize the cucumber and start to preserve it, before the bad bacteria invades and starts to rot it. Both sides use a form of natural chemical warfare, starting with fermentation. In fermentation, bacteria of all kinds, good and bad, eat and digest starches like the natural ones in cucumbers and other plants and convert them into sugars they use as food and fuel to grow and multiply. As soon as a cucumber is put into salty brine, the good microbe army has the edge."
Basically, the brine -- remember, it's got the acidic vinegar -- becomes an idea medium for the good microbes to ferment the pickles without causing them to rot. It also increases the acidity of the overall solution and gives pickles their distinct, sour taste, while simultaneously preserving the pickles for quite a while. Per Mr. Roker:
"...By growing rapidly and producing all that lactic acid, the good bacteria increases the acidity of the brine and what was soaking in it, which decreases the pH to below 4.6, a level acidic enough to pickle our pickle, and keep it preserved for months, even years."
So please, enjoy those pickles well past their "best by" date if you've come across a jar. Food expiration dates are mostly bullshit anyway.