GROWTH OF BACILLUS SUBTILIS AND BACILLUS LICHENIFORMIS IN TOMATO JUICE AT SELECTED OXYGEN PARTIAL PRESSURES (ASEPTIC, PACKAGING)
Abstract
To assess the potential hazard of metabiosis occurring between Clostridium botulinum and Bacillus species in aseptically packaged tomato juice, conditions responsible for growth and pH elevation of selected strains of B. subtilis and B. licheniformis were studied. The effect of tomato juice pH and initial inoculum level on growth was evaluated. High initial inoculum levels were required for B. licheniformis to grow and raise the pH of tomato juice at pH 4.4 aerobically. The inoculum level was not a determinant for B. subtilis. Both species could not grow in tomato juice with a pH less than 4.3. No growth occurred anaerobically in tomato juice, tomato juice with added thiamine, or tomato juice with added nitrate. The thermal resistance of spores of selected Bacillus species was determined. The bacteria were found to survive the process given aseptically packaged tomato juice. Test packs of tomato juice sealed with saran, mylar, oriented polypropylene or low density polyethylene were inoculated and incubated for 60 and 100 days. Growth and pH elevation occurred with all polymers for B. subtilis but the amount of growth was dependent upon the oxygen permeability of the polymer. B. licheniformis required greater oxygen partial pressures for growth.
Degree
Ph.D.
Subject Area
Food science
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