Effect of temperature and soluble solid on Bacillus subtilis and Bacillus licheniformis spore inactivation and quality degradation of pineapple juice

Bacillus subtilis and Bacillus licheniformis spores can survive processing temperatures used in the thermal processes of high-acid foods. Therefore, this study investigated the thermal inactivation of B. subtilis and B. licheniformis spores in pineapple juice at different temperatures (85-100 degrees C) and soluble solids (SS, 11-30 degrees Brix). The quality of juices and microbial loads after the thermal treatments during storage at 4 degrees C for 35 days was then checked. A linear decrease in D-value was observed with increasing temperature of treatment. Furthermore, the D-values determined in pineapple juice were: D-90 degrees C=13.2 +/- 0.5 mins, D-95 degrees C = 6.8 +/- 0.9 mins and D-100 degrees C = 2.1 +/- 1.7 mins for B. subtilis spores, and D-85 degrees C = 16.6 +/- 0.4 mins, D-90 degrees C = 7.6 +/- 0.5 mins and D-95 degrees C = 3.6 +/- 1.5 min, for B. licheniformis. Generally, the susceptibility of the bacteria to soluble solid change was affected by the interaction between temperature, SS and strain. In addition, pasteurization processes of >= 95 degrees C for >= 33.8 mins was needed to ensure a recommended 5-log reduction of B. subtilis spores and limit vitamin C degradation of pineapple juice within three-week of storage at 4 degrees C.

Automated summary

This study investigated the thermal inactivation of B. subtilis and B. licheniformis spores in pineapple juice at different temperatures and soluble solids, and found that the susceptibility of the bacteria to soluble solid change was affected by the interaction between temperature, SS and strain. Pasteurization processes of >= 95 degrees C for >= 33.8 mins were needed to ensure a recommended 5-log reduction of B. subtilis spores and limit vitamin C degradation of pineapple juice within three weeks of storage at 4 degrees C.