Tuesday, June 20, 2006

The B word

Susan in Italy was asking how long you can keep preserved lemons once you open the jar. This set me thinking. I remembered reading somewhere about toxins and the word ‘botulism’ was mentioned. BOTULISM? Something about home bottling and canning. I opened the fridge door with my heart beating the soundtrack from Jaws and peered in. There was the jar of home roasted pimentos I had stored in olive oil; there was the jar of olives I made up the other day, with garlic and herbs and olive oil. Hmmm. Out went the pimentos and I am keeping a close eye on the olives.

A little research reveals some reassurance. Although botulism is a very very nasty toxin that attacks the nervous system and causes paralysis it is also extremely rare. Food is contaminated before preservation, and the bacteria germinate and reproduce in anaerobic conditions, producing toxin, which is then ingested. Foil-wrapped baked potatoes, sautéed onions and fermented fish are culprits, plus, let’s be careful here, garlic in oil. I have occasionally seen that garlic in oil ferments, but I didn’t know about the botulism bit.

Food with a high acidity is generally safe because the bacteria cannot live in an environment with a pH lower than 4.6 – lemons, pears and pickles generally have a pH of 2-4 (pears eh?). So we are fairly safe with the lemons it would seem, plus all that salt.

They (preserved lemons) do throw off a sort of sediment, and the lemon pulp particulates in the lemon juice also sink to the bottom of the jar, leaving clear lemon juice and a sort of lemon mud around the base. It does no harm. You can add more lemons and salt, and you need to top up the jar with lemon juice, but otherwise, if you keep the jar in cool, or chilled conditions, there should be no need to worry. As far as I can see they keep for at least six months or for up to a year, depending on who you trust.

It’s the garlic in the olives that worries me, but I think if I add some vinegar that should change the pH… Ah ha! I know! I will add some chopped preserved lemons to the olives - what a very good idea!


Bonnie said...

We were looking at flavouring oils as a Christmas present for friends and family. While researching, we found that if the flavours (garlic, herbs etc) weren't completely dry then botulism would become present. We made chutney instead as we didn't want to risk poisining our nearest and dearest. I think it tasted better anyway...

Susan in Italy said...

Oh June!! So sorry to spur such alarm! I too have heard about the possibility of botulism growing in anaerobic conditions and that it is indeed extremely rare. I look at it as a risk of eating delicious food, like hunting for mushrooms.

June said...

To be perfectly honest I am just stirring things up a bit! The number of cases of botulism per year in either the US or the UK is vanishingly small; there has not been a case of botulism in the UK for over 20 years. Most cases on both continents are due to faulty meat canning. But I think it is good to re-evaluate these scary things from time to time - blue mould on cheese = good; blue mould on olives = not so good.

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