Dear Xanthe: 'What are the white patches that have appeared on my pickled peppers?'

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Dear Xanthe: 'White patches on peppers have put me in a pickle'
This week, a keen fermenter is troubled by some pesky white spots

Dear Xanthe 

I have prepared two jars of pickled red peppers and noticed white areas developing on the peppers, even though they are submerged in brine, after three days at room temperature. I am interested to know what this is, if it is OK to eat, or if it is a sign that the peppers have spoiled and I need to try harder!

Dear Anon 

While I’m a keen home fermenter, this is a question for a real expert. I turned to microbiologist Dr Caroline Gilmartin, founder of everygoodthing.co.uk, for a proper explanation:

“White sediments in pepper ferments have two usual causes: either kahm yeast, or a natural sediment that forms from spent microbes and insoluble end products of metabolism.

“Kahm is not a particular species of yeast, but a phenomenon arising from a number of different species that might be present in a ferment, usually visible as a white pellicle on the surface. These grow where the interface of air and liquid meet, mostly being aerobic/microaerophilic (requiring some oxygen to survive). Kahm yeast is not often considered to be dangerous, and people usually scrape it off – unless it’s in large quantities, when it can make a ferment taste cheesy or like old socks.

“Kahm grows more readily when temperatures are higher than room temperature, or when the salt concentration isn’t high enough. People often use a 2 per cent brine solution, but there’s a reason why that isn’t often enough – if you have many peppers and not much brine, for example.

Left: our reader's pesky peppers; right, making use of the peppers once preserved 

“A better rule of thumb is to add 2 per cent salt for the total weight of peppers and water in the jar, thus having 2 per cent brine for everything in the jar. It is possible that kahm has grown in little air pockets caused by the peppers being squeezed against the sides of the jar, but it doesn’t seem to be present on the top, which one might expect.

“From the photograph you sent, I can’t see if your peppers are protected on the top – it’s good practice to put a barrier in place (a food-safe plastic disc, a cabbage leaf or a ziplock bag filled with brine) to stop them coming into contact with the air and keep them submerged, which can prevent kahm or mould from growing.

“At the bottom of the jar, you might find a layer of white sediment. I suspect this is normal sediment being prevented from falling to the bottom of the jar by the proximity of peppers to the sides.

“Any fermented food maker has to make the final call – so I can’t tell you to eat it, but unless it’s slimy or smells unpleasant, I’d certainly be tempted to carry on!”