Black-carrot drink şalgam as a habitat for spoilage yeasts

Şalgam is a traditional drink produced via the lactic-acid fermentation of vegetables (black carrot and turnip), sourdough, and bulgur flour; with rock salt also added. During storage, an additional yeast-mediated fermentation can occur, causing changes in organoleptic properties, as evidenced by the microbe-mediated release of gases. Here, we characterise şalgam as a microbial habitat, identify the yeasts that cause spoilage, and characterise yeast-induced changes of the şalgam. The total acidity of the spoiled şalgam, in terms of lactic acid, ranged from 5.33 to 8.36 g/L with pH values from 3.86 to 4.10. Nine different spoilage fungi were isolated and then identified using molecular techniques (combination of PCR-RFLP of the 5.8 S-rRNA region and sequencing of the D1/D2 domain of the 26 S-rRNA gene). The highest frequencies of species were for the (apparently dominant) Saccharomyces cerevisiae, Galactomyces candidum, and Pichia kudriavzevii. Notably, two of these yeasts-P. kudriavzevii and Saccharomyces cerevisiae-are known to be acid-tolerant, have a robust stress biology, and can dominate various microbial habitats including those of fermented foods and drinks. Şalgam is a nutrient-rich, high-water-activity habitat that can favour the growth of various microbes and becomes less acidic (so more ecologically open) after the proliferation of yeasts.