Michelle Berriedale-Johnson investigates

Lactic acid bacteria do not, as such, have anything to do with dairy products; they are bacteria used widely in the food industry to ferment hundreds of foods from yogurt to sauerkraut. The bacteria feed on sugars (they can only grow when some sort of sugars are present) and, as a result of 'carbohydrate fermentation', they produce lactic acid. The lactic acid lowers the carbohydrate content, and therefore the pH level, of the food (makes it more acid) to the point where other micro-organisms are unable to grow – thus dramatically increasing the shelf life of the food. This acidity also changes the texture of the food giving it the more intense and sharper flavours of fermented foods. This process is self limiting as the lactic acid bacteria cannot survive once the food becomes too acidic so, at that point, the process stops.

However, the difficulty for those with cow's milk/lactose (or grain) sensitivities, is, on what substrate was the bacteria grown? What sugars were they fed on? If it was lactose then will enough lactose still be present in the bacteria to affect someone who is seriously sensitive? Quite possibly, yes. Similarly, if it was grown on a grain-based substrate such corn, will someone who is highly sensitive to corn react? Theoretically, the protein which causes the sensitivity should have been metabolised by the bacteria but, it is becoming clear that those who are seriously sensitive can react to individual molecules in a protein, not just to whole proteins, so someone who is seriously corn sensitive could react to bacteria cultured on a corn base.

(For more on the allergenicity of molecules, read this report of a recent Allergy Research Foundation.)

So what should a dairy sensitive person do about lactic acid or lactic bacteria when they see it on label? What they need to know is on what substrate it was cultured. However, it is unlikely that even the manufacturer will know (lactic acid bacteria are just an ingredient which they buy in) although the more allergen aware manufacturers are starting to realise that this kind of information may be important for their hard core customers.

So, as always, a hyper-sensitive person should avoid it – just in case. As of now, lactic acid bacteria is usually cultured on a grain base, but this is not always the case and dairy (eg lactose) could have been used. Hopefully, with greater awareness, will come more information so that allergy sufferers can make that much-to-be-wished-for 'informed choice'.

First published March 2012

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