88D-21 |
Solute type effects on Debaryomyces hansenii growth response in selected water activity and pH media |
E. PALOU1, A. Lopez-Malo, M. R. Arce-Garcia, M. T. Jimenez-Munguia, L. Luna-Guevara, J. J. Gomez-Diaz, and L. Beristain. (1) Ingenieria Quimica y Alimentos, Universidad de las Americas-Puebla, Cholula, Puebla, 72820, Mexico
Debaryomyces hansenii is frequently implicated in the spoilage of high acid and/or low water activity foods. D. hansenii growth response must be determined in order to establish product shelf-life of foods where stability relies either on acidity, water activity reduction or their combination with the addition of antimicrobial agents. The effects of water activity (aw, 0.99 - 0.94), pH (5.5 - 3.0), and concentration (100 — 600 ppm) of potassium sorbate (KS) using a central composite experimental design were evaluated on the growth response of D. hansenii. The experimental design was repeated using sucrose or sodium chloride as solutes to adjust aw. Laboratory media (Sabouraud broth) were made for every combination of factors, inoculated with 106 yeast cfu/mL, and incubated at 25ºC. Viable yeast number was determined by surface platting every 24 h up to 120 h onto potato-dextrose agar plates. Logarithmic representations of the survival or growing fraction were statistically analyzed (ANOVA). Yeast growth was observed only in media formulated with sucrose (aw 0.98) at pH higher than 4.0 in the presence of less than 300 ppm of KS. The use of sodium chloride to adjust aw allowed yeast survival when preservation factors were applied at their milder levels. Several combinations of factors conduced to decrease viable yeast numbers, and in several cases, the number of survivors was under the level of detection. Inhibitory combinations of factors for 120 h of incubation included at least 200 ppm of KS, aw lower than 0.98 and pH lower than 4.25. ANOVA demonstrated the significant effect (p<0.05) of each individual factor as well as their interactions; also that solute type significantly affected yeast response. Our results can be used to assess the efficacy of potassium sorbate to control D. hansenii spoilage potential in acidified, salted and/or sugared food products.
Session 88D, Food Microbiology: General
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