Survival, Growth, and Toxin Production of Bacillus cereus During Cooking and Storage of Fresh Rice Noodles

• Published in: Journal of food protection 2024-03, Vol.87 (3), p.100239-100239, Article 100239
• Main Authors: Mohammadi, Barakatullah, Pérez Reyes, Marco Esteban, Smith, Stephanie A.
• Format: Article
• Language: English
• Subjects: Bacillus cereus; Enterotoxins; Fresh Rice Noodles; Spore-forming Bacteria; Steam Cooking
• ISSN: 0362-028X; 1944-9097
• DOI: 10.1016/j.jfp.2024.100239

•Steam cooking is ineffective against B. cereus spores in fresh rice noodles.•Fresh rice noodles may be a risk if stored at 22°C or higher for more than 4 h.•B. cereus produces enterotoxin in 24 h at 22°C storage and 12 h at 32°C.•Refrigeration (4°C) prevents B. cereus growth and toxin production.•pH of fresh rice noodles decreases at 22 and 32°C storage temperatures. Retail stores maintain fresh rice noodles (FRNs) at room temperature because refrigeration negatively impacts FRNs’ texture. The room temperature and high water activity of FRNs help spore-forming Bacillus cereus to grow and produce toxins. In this study, the effect of steam cooking on survival and different storage temperatures on the growth and enterotoxins production of B. cereus in FRNs were investigated. White rice flour was used to make FRNs. Three treatments of FRNs were used in this study; uninoculated, inoculated (with 4.0 log CFU/ml of B. cereus spores), and autoclaved as a negative control. A slurry of rice flour, cornstarch, and water was steam cooked for 4 min at 90°C and incubated for 168 h at 4°C, and for 72 h at 22 and 32°C. Incubated FRNs were tested for pH, B. cereus growth, and enterotoxins production. Steam cooking reduced the total number of B. cereus spores by 0.7 ± 0.3 log CFU/g. Surviving B. cereus spores in inoculated and uninoculated FRNs germinated over 72 h of storage. No B. cereus was detected in negative controls. An interaction was observed across storage temperatures and time (p