|MadSci Network: Microbiology|
It is great that you are doing a project on Lactobacillus, this bacterium has some interesting characteristics which make it very useful in food microbiology. An important characteristic of Lactobacillus is that these bacteria produce large amounts of lactic acid as a by-product during growth. The production of lactic acid reduces the pH in the surrounding environment, or in other terms the surrounding environment becomes more acidic. What does Lactobacillus and lactic acid have to do with pickles? Good question. Pickling is a method used to preserve vegetables from spoilage from bacterial/fungal growth. How do you prevent spoilage? To prevent spoilage the environment the vegetable is stored in must be unsuitable for bacterial/fungal growth. Making the environment acidic is an effective way to make the environment unsuitable for growth of MOST bacteria/fungus (included spoilage organisms). Therefore if Lactobacillus is present during the pickling process its growth will make the cucumbers/pickles more acidic and help prevent the growth of spoilage bacteria/fungus. Why is salt used in pickling? The salt is used to select against the growth of most bacteria/fungus except for Lactobacillus, since Lactobacillus can grow in higher salt concentrations. Therefore the presence of salt ensures that you are allowing the “good” bacteria to grow during pickling and selecting against the growth of the spoilage bacteria.
Another method of pickling which does not involve bacteria but operates on the same principle is to use vinegar during pickling. The vinegar is acidic and will make the solution containing the cucumbers acidic and therefore prevent the growth of spoilage bacteria.
On the internet I could not find any sites that offered a direct connection to Lactobacillus and pickles however if you use a common search engine like Google or Altavista with search words like “food microbiology”, “food microbes” or “Lactobacillus” you are sure to find some useful related information. Happy hunting.
Try the links in the MadSci Library for more information on Microbiology.