Resistance of Yeast Flora of Labaneh to Potassium Sorbate and Sodium Benzoate

Abstract

Ten yeast cultures belonging to eight species representing the yeast flora 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°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 ≤105 cfu/g after 14 d at 5°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 <105 cfu/g for 7 d at 5°C in two commercial labaneh samples that had initial yeast counts of 4.8 × 102 and 9.0 × 102 cfu/g; 200 and >400 mg/kg were required when the storage was extended to 14 d. In commercial labaneh with 9.6 × 103 cfu/g, >300 and >400 mg/kg of potassium sorbate and sodium benzoate, respectively, were needed to limit the yeast count to ≤105 cfu/g after 7 and 14 d at 5°C.