MICROBIOLOGY OF CHILI BO, A POPULAR MALAYSIAN FOOD INGREDIENT

The predominant microbial flora of a specific Malaysian food ingredien t, chili bo (containing 9% ground dried chilies, 0.6% acetic acid, and 5 to 10% cornstarch, wt/vol) stored for up to 25 days at 28 degrees C without added benzoic acid (product A) and with 7,000 ppm of added be nzoic acid (product B) was examined. Aerobic plate counts for both pro ducts were initially 6.2 to 6.5 log CFU/g increasing to 8.5 log CFU/g for product A after 4 days. Aerobic plate counts for product B did not increase during storage. Lactic acid bacteria (LAB) counts increased in product A from 4.8 log CFU/g to 8.3 log CFU/g and in product B from 2.1 log CFU/g to 7.6 log CFU/g after 17 days. Growth of yeast occurre d in product A. Both products exhibited spoilage after 1 to 2 days of storage at 28 degrees C indicated as accumulation of gas bubbles. In a ddition surface growth of molds (product A) or whitish discoloration ( product B) was observed later in storage. For product A the predominan t isolates were LAB, Bacillus pumilus, Bacillus subtilis, Staphylococc us spp., and yeasts. B. pumillus and B. subtilis predominated initiall y whereas the other types of microorganisms predominated after 25 days of storage. B. pumilus and B. subtilis were also predominant in produ ct B, but after 25 days of storage a homofermentative LAB was found in higher numbers (7.6 log CFU/g). Isolates of heterofermentative LAB bu t not homofermentative LAB or B. pumilus or B. subtilis were able to p roduce gas during growth in chili bo sterilized by autoclaving at 121 degrees C for 15 min. Growth of heterofermentative LAB, B. pumilus, an d B. subtilis was inhibited by acidifying agents, a nisin-containing s upernatant, or incubation at low temperatures.