[Inhibition of Bacillus coagulans growth in laboratory media and in fruit purees]

The growth of two strains of B. coagulans was inhibited in laboratory media at pH < or = 4.5, and at water activity (aw) levels of 0.96 for B. coagulans NRS 609 and 0.95 for B. coagulans ATCC 803. The growth of both strains was also inhibited in apple and strawberry purees (pH = 3.5) stored at 37 degrees C for over two months. B. coagulans was able to grow in banana puree (pH approximately equal to 5.0) but acidification of the puree at pH = 3.5 was enough to prevent growth. The addition of up to 3,000 ppm vainillin ("natural" preservative) or 1,000 ppm potassium sorbate (traditional preservative) at pH higher than the inhibitory level previously determined could not prevent growth of B. coagulans in laboratory or in fruits, but 100 ppm lysozyme retarded growth in laboratory media at different pH levels (from 4.5 to 6.7) and in banana puree. As lysozyme showed to be effective at pH < or = 6.7, it might be used to prevent growth of B. coagulans at an eventual increment of pH during storage.