Resistance of yeast flora of labaneh to potassium sorbate and sodium benzoate

Ten yeast cultures belonging to eight species representing the yeast nora of labaneh were tested for their resistance to potassium sorbate and sodium benzoate. Changes in counts were monitored after 7, 14, and 21 d at 5 degrees C in yeast-free labaneh containing different concentrations of potassium sorbate or sodium benzoate. More than 400 mg/kg of sodium benzoate were needed to limit the counts of Saccharomyces cerevisiae (biovariants 1, 2, and 7) Cryptococcus curvatus, Pichia farinosa, Candida blankii, Debaryomyces hansenii, and Trichosporon brassicae to less than or equal to 10(5) cfu/g after 14 d at 5 degrees C; 150 and 300 mg/kg were-needed for Geotrichum candidum and Trichosporon cutaneum, respectively. When potassium sorbate was used, >400 mg/kg were needed for P. farinosa and D. hansenii; 350 mg/kg were needed for S. cerevisiae biovar 1, Cr. curvatus, and C. blankii; 250 and 200 mg/kg were needed for S. cerevisiae biovariants 2 and 7, respectively; and <100 mg/kg were needed for T. brassicae, T. cutaneum, and G. candidum. Less than 150 and <250 mg/kg of potassium sorbate and sodium benzoate, respectively, were needed to limit yeast counts to <10(5) cfu/g for 7 d at 5 degrees C in two commercial labaneh samples that had initial yeast counts of 4.8 x 10(2) and 9.0 x 10(2) cfu/g; 200 and >400 mg/kg were required when the storage was extended to 14 d. In commercial labaneh with 9.6 x 10(3) cfu/g, >300 and >400 mg/kg of potassium sorbate and sodium benzoate, respectively, were needed to limit the yeast count to less than or equal to 10(5) cfu/g after 7 and 14 d at 5 degrees C.