Growth of Bacillus cereus in natural and acidified carrot substrates over the temperature range 5–30°C

Minimally processed refrigerated foods have a relevant potential in the food market, although the potential risk posed by sporulated emerging psycrotrophs pathogens has to be evaluated. Bacillus cereus is one of these pathogenic micro-organisms. In this paper, the ability to grow of several strains of B. cereus in nutrient broth and in a carrot-based substrate (broth) was evaluated. All the strains tested grew at 12°C or higher temperatures both in nutrient broth and in carrot substrate. One of the strains was able to grow rapidly even at 5°C. Acidification of the carrot substrate proved to be efficient inhibiting B. cereus. For the two strains tested, growth was not observed at pH below 4·75 acidifiying with citric acid or with lemon juice. When the effect of pH was combined with refrigeration, acidification at pH 5·0 was sufficient to inhibit B. cereus at 12°C or lower temperatures. Therefore, the combination of these two factors could have a great potential to control B. cereus growth in minimally processed foods, such as carrot based products. Additionally, lemon juice can be considered as a more natural alternative to citric acid.     

Kinetics of mould growth in the stored barley ecosystem contaminated with Aspergillus westerdijkiae,Penicillium viridicatum and Fusarium poae at 23–30 °C

BACKGROUND: Owing to the lack of a rapid method for determining fungi on cereals, the best way to enhance the safety and nutritive value of stored grain is to develop prognostic tools based on the relationship between easily measurable online parameters, e.g. water activity (a_w) and temperature (t) of grain, and fungal growth. This study examined the effect of unfavourable temperature (23 and 30 °C) and humidity (0.80–0.94 a_w) storage conditions on mould growth in the stored barley ecosystem with its adverse microbiological state provided by contamination with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae. RESULTS: Among the applied storage parameters, a_w turned out to be the main factor affecting mould development. The longest lag phase and period of fungal activation were observed for grain with 0.80 a_w, which was not threatened with fungal development for at least 30 days. However, in grain with 0.92 and 0.94 a_w, fungal activation occurred within 24–48 h. CONCLUSION: The obtained data and the identification of critical points in mould growth may be used to develop a control system for the postharvest preservation of barley based on a_w and temperature of grain, which are easy to measure in practice. © 2012 Society of Chemical Industry