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Bacillus causes thinning of soups From August 2010 newsletter

Bacillus causes thinning of soups

Recent research at Campden BRI will help us in our troubleshooting services to clients who have problems with thinning of soup. Thinning is believed to result from starch breakdown, caused by heat resistant amylases from Bacillus species that are not inactivated by the heat process, and/or by the growth of Bacillus species that have survived the heating process and subsequently go on to produce amylase enzymes. However, in many of the problem samples we have received, it has been difficult to identify the cause with any certainty.

Three soups with different pH values (cream of tomato, potato and leek, and cream of chicken) were incubated with spores of B. subtilis, B. licheniformis, and B. megaterium, or B. licheniformis alpha–amylase at 3 different concentrations.

The 3 bacilli were able to grow to a high level in the potato and leek and cream of chicken soups within 48h, causing thinning quite rapidly. Addition of alpha–amylase had a similar effect. In the more acidic tomato soup, only B. licheniformis grew and growth was relatively small and slow. No thinning was observed in this soup following incubation with Bacillus, and only the highest enzyme level had a thinning effect.

These findings will help us target further research into the problem, and will complement our Bacillus identification and process validation services, as well our amylase expertise.

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