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I have noticed that when I open a jar of olives (we eat a lot) sometimes some mould starts to grow on the surface of the top layer of olives floating at the top of the brine and there is mould on the brine. This only happens on the few rare occasions that we open a jar then don't touch it for a few weeks.

I have a biology degree and some knowledge of microbiology; we only use clean forks or spoons to remove the olives and I'm sure it's not oil congealing at the top.

I recently bought a large catering tin of olives because we eat a lot of them; so it will work out cheaper this way if I can decant them into jars. But I'm worried that in the process of decanting into the jars, airborne microbes will enter and spoil the olives. I am assuming there is something I can add to them but I'm not sure. I don't think I want to heat them as they are already prepared and ready to consume.

I've never done any preserving or anything but someone told me campden tablets can be added to stop the mould growth. Is this right? If so how much should I add?

Luciano
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VeronicaBee
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3 Answers3

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Decanting to sterilized jars, in very clean conditions, maybe with gloves, would probably do the trick in and of itself. I doubt you would introduce mold spores if you worked quickly and cleanly. However, if you wanted an additive, sodium benzoate or potassium sorbate are both used in the food industry to prevent fungal and yeast growth. .025% to .1% by weight seems to be the recommendation I find on the web. It is quite possible that the olives you have purchased already have these additions.

moscafj
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One possibility, which might be irrelevant depending on what you do now, is to store the aliquoted jars in your fridge. The cold should slow growth of most mould species fairly well.

A further option is to remove the brine and freeze the olives in bags, defrosting as needed. The salt in the brine and oil in the olives should prevent them freezing completely and going to mush on thawing.

bob1
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I would just add a thin layer of olive oil on top to prevent air contact with the olives. Some salt could also help.

MuchiProds
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