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

¹ Department of Nutrition and Food Technology, Faculty of Agriculture, University of Jordan, Amman, Jordan
² Department of Food Science and Nutrition, Faculty of Science and Allied Health Professions, Applied Sciences University, Amman, Jordan

The mean psychrotrophic and mesophilic yeast counts were 2.6 x 10⁶ 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 10⁷ 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 7°C. Saccharomyces cerevisiae, which could be grouped in seven biovariants, was in all labaneh samples. Trichosporon brassicae, Cryptococcus cuwatus, and Kluyveromyces marxianus were in 33, 28, and 17% of labaneh samples, respectively. Trichosporon cutaneum, Debaromyces 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 7°C. 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.

Key Words: yeast flora • labaneh spoilage • psychrotrophic yeasts • concentrated yogurt

Submitted on February 9, 1994
Accepted on June 16, 1994