Our almost 2 years old toddler loves oignons accompagnying pickled gherkins. Unfortunately, trying to pick one by herself, she spilled all the pickle from a brand new (commercial, pasteurized) jar. I guess the lack of pickle will affect the gherkins conservation : how long will they remain edible (kept in the fridge) ? Still a few weeks, or rather a few days ?
The shelf life of pickled gherkins stored dry
food-preservationfood-safetypickling
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I'd never heard of ESL until your question, so I had to look that up. A local company did a lot of work developing UHT milk; I remember samples when they were first starting up production, and they were trying to find flavors additives which would mask the flavor change from the UHT processing. Since then a lot of companies have adopted the processing methods for other products, or just adopted the packaging. So, before I relied on any random box-packed product to be shelf stable, I'd check into how it was produced.
Proper UHT milk doesn't go bad until it's opened. It's sterile, and in a pretty sturdy container. Once opened, bacteria will get back into the container, and the milk will go bad as normal. When the local company started production of UHT milk, they were putting 2 year code dates on packages, and that was just the longest date the government would allow; I've had boxes 3-4 years old, which were fine.
There are three major things that will effect the "natural" shelf life of the compote, in that they could extend it considerably past the normal shelf life of the ingredients individually:
How sweet is it? If it is sufficiently sugary, to the level of a jam or jelly, the sugar in the compote will act as a preservative.
This is because any bacteria or mold that try to colonize the product will be dessicated, as water exits their cells into the sugar medium via osmosis.
The problem here is that sugar is hydrophylic, and will easily attract water from the environment when the jar is opened, or when a wet spoon is put into it. If the surface becomes diluted with water, and thus the sugar is less concentrated, mold can get a foothold. So this kind of product is best stored in the refrigerator once opened.
How acid is it? Very, very acidic foods are less hospitable to most pathogens.
How salty is it? This one doesn't usually apply to compote recipes, but high enough salt levels also make foods inhospitable to most pathogens, again due to the dessication of their cells via osmotic pressure.
The specific recipe you linked to--at least the compote portion itself, excluding the vinegar syrup and the rest of the recipe--appears to have none of the characteristics that lead to a long shelf life. It should be held no longer than its most vulnerable ingredient, which would be the weak sugar syrup, so it is probably good for several days to a week in the refrigerator.
Now, in general, things named compotes tend to be far sweeter, and far more acidic than the recipe you have linked to.
In these cases, as ElindilTheTall points out, a very, very sweet recipe (jelly-like or jam-like sweetness) will last for many weeks in the refrigerator, and a couple of weeks at least at normal room temperature.
Finally, many compotes are amenable to home canning, if they are sufficiently acidic.
Canning has risks, especially for botulism, so you should only use recipes and methods from a very reputable source when doing canning, to ensure that the product is sufficiently acidic to be safe for the canning method used. Follow all of the techniques and prescriptions in the methods, as well, but I won't turn this into an essay on canning, which is not my area of expertise.
For those compotes that are properly canned, you should get an indefinite shelf life prior to opening, as long as the seal on the canning jar remains intact.
Best Answer
You might see some loss of quality within a couple of months, but under refrigeration they will not become close to "unsafe" in that length of time. They're already "pickled", the worst you will face is dried out pickles. You can always add more "pickle" in the form of vinegar, salt, sugar and water (boiled and cooled), but it seems pretty unnecessary - two potato salads and you're done with them.