Isolation, Identification, and Evaluation of Spoilage Potential of Four Bacillus Strains Isolated from Slimy Rice Noodles

This study isolated four strains of Bacillus from slimy fresh rice noodles (FRN) and preliminary identified them as B. cereus, B. amyloliquefaciens, B. altitudinis, and B. subtilis, respectively, using morphological, physiological, and genetic analyses. The spoilage potential of each of these strains was then evaluated in FRN. The results indicated that both B. amyloliquefaciens and B. subtilis can cause FRN to become sticky and smelly, accompanied by an increase of acidity and high amylase activity. B. cereus and B. altitudinis mainly caused odor deterioration of FRN. There were 29, 20, 25, 25, and 27 volatile organic compounds (VOCs) identified from control FRN and FRN samples inoculated with B. cereus, B. amyloliquefaciens, B. altitudinis, and B. subtilis, respectively. The compositions of VOCs in the samples inoculated with B. amyloliquefaciens and B. subtilis were similar; esters, volatile organic acids, and acetoin were the main volatile compounds in the FRN. For B. cereus and B. altitudinis, the main adverse flavor substances were acetic acid and ammonia. This study provides a theoretical basis for quality control in the production, storage, and sale of FRN.