61C-13

Temperature, incubation time, water activity, pH, vanillin and sodium benzoate effects on Aspergillus flavus probability of growth

A. LÓPEZ-MALO, Departamento de Ingenieria Quimica y Alimentos, Universidad de las Americas - Puebla, Sta. Catarina Martir, Cholula, Puebla, 72820, Mexico, E. Palou, and S. M. Alzamora, Departamento de Industrias. FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, 1428, Argentina.

Fungal growth can be avoided by applying selected factors or combinations. Determining if mold growth or no growth occurs under the combined effect of preservation factors can reveal the effectiveness of factors interactions. Probabilistic modeling could be used as a useful tool to select antimycotic combinations.

The combined effects of incubation temperature (T, 15 or 25°C), incubation time (t, 100, 200, up to 700 h), aw (0.98, 0.96 or 0.94), pH (5, 4 or 3), vanillin (V) or sodium benzoate (NaB) concentration (0, 200, 400 up to 1000 ppm) were evaluated on Aspergillus flavus growth o no growth response.

aw and pH adjusted potato dextrose agar was prepared by triplicate for every combination of factors. Filter sterilized V or NaB solutions were used. Solidified plates were inoculated (2 μL of a 106 spore/mL suspension), incubated and observed up to 700 h. If growth was observed the response was 1, if not was registered as 0. Backward stepwise logistic regression was used to develop a simplified model able to predict mold probability of growth.

From a total of 3888 observations, in 1488 growth was observed from which 1358 cases occurred at 25°C while only 130 at 15°C. The obtained model predicts the probability of growth under a set of conditions and can be used to calculate critical values of aw, pH, T, t, and V or NaB concentration needed to inhibit mold growth for different probabilities. The reduction of pH increased the number of combinations of T, aw and antimicrobial agent concentration with probabilities to inhibit growth higher than 0.95. With a probability of growth of 0.05 and using the logistic model, as an example, the critical pH values decreased as t increased.

The model can be used to compare the effectiveness of selected combinations of factors to inhibit A. flavus growth and identify combinations with enhanced antimycotic effect.

Session 61C, Food Microbiology: General I
2:00 PM - 5:30 PM, 2002-06-17

2002 Annual Meeting and Food Expo - Anaheim, California