Yeast Flora of Labaneh Produced by In-Bag Straining of Cow Milk Set Yogurt

The mean psychrotrophic and mesophilic yeast counts were 2.6 x lo6 and 4.4 x 106/g, respectively, in labaneh samples from 18 dairy plants directly after packaging. Labaneh was produced traditionally by straining set yogurt in cloth bags, directly after packaging. At the end of the shelf-life (14 d at 7"C), these mean counts increased to 1.1 x lo7 and 1.4 x 107/g. The percentages of samples showing yeast count >106/g were 50 for psychrotrophic and 56 for mesophilic yeasts after packaging and increased to 78 and 83 after 14 d at 7C. Saccharomyces cerevisiae, which could be grouped in seven biovariants, was in all labaneh samples. Trichosporon brassi- cae, Cryptococcus cuwatus, and Kluyveromyces marxianus were in 33, 28, and 17% of labaneh samples, respectively. Trichosporon cutaneum, De- baromyces hansenii, Pichia farinosa, Geotrichum candidum, and Candida blankii were in 6% of the samples. All labaneh samples showed the characteristic signs of yeast spoilage after 14 d at 7C. All yeast species and their biovariants were able to grow at 7'C; thus, psychrotrophic yeasts are the main cause of spoilage of traditionally produced packaged labaneh kept under refrigeration.