Analysis of spore-forming bacterial contaminants in herbs and spices and evaluation of their heat resistance

Abstract

The antimicrobial activities of certain spices and herbs are well-documented. Herbs and spices are often exposed to bacterial contamination, spore-forming bacteria in particular. The spores introduced during the production process result in a contamination that causes food alteration during storage. The aim of this study was to isolate spore-forming bacteria from commercially available spices and herbs, such as ginger, cinnamon, black pepper, curcumin, saffron, and clove. The API 50 CHB/E medium was used to identify different genera of spore-forming bacteria isolated from samples. We found that these belonged to the genus Bacillus, such as Bacillus cereus, which was isolated from cinnamon, and Bacillus subtilis, and isolated from curcumin and black pepper. The third species belonged to the genus Brevibacillus, Brevibacillus laterosporus, which was isolated from ginger. The D-values (decimal reduction) of each bacterium were determined at 80, 85, 90, 95, and 100 °C. The Z-value was determined for each bacterium. The whole-cell protein profiles of the identified bacteria were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Since spore-forming bacterial contamination of herbs and spices can occur during their harvest, exsiccation, or through cross-contamination during packaging, we propose different methods for spore elimination.

Keywords:
spices; spore-forming bacteria; D-values; Z-values; SDS-page