Veterinarska stanica, Vol. 51 No. 6, 2020.
Original scientific paper
https://doi.org/10.46419/vs.51.6.4
Molecular identification of yeast from raw milk and traditionally produced cottage cheese
Manuela Zadravec
orcid.org/0000-0003-4382-4424
; Croatian Veterinary Institute, Zagreb, Croatia
Vesna Jaki Tkalec
; Veterinary Institute Križevci, Croatian Veterinary Institute, Križevci, Croatia
Sanja Furmeg
; Veterinary Institute Križevci, Croatian Veterinary Institute, Križevci, Croatia
Maja Kiš
; Veterinary Institute Križevci, Croatian Veterinary Institute, Križevci, Croatia
Mario Mitak
orcid.org/0000-0002-3870-2740
; Croatian Veterinary Institute, Zagreb, Croatia
Tomislav Mikuš
orcid.org/0000-0003-1388-2404
; Faculty of Veterinary Medicine, University of Zagreb, Croatia
Abstract
Yeasts are a common contaminant of dairy products, but they can also be used as a starter culture to improve the characteristics of the final product. Their presence in an increased number causes undesirable changes in dairy products, such as an unpleasant appearance, acrid smell and foul taste. The classical identification of yeasts based on morphological and biochemical properties is slow and unreliable. The aim of this study was to identify isolated yeasts from 30 dairy products, and to determine if they belong to desired or undesirable species. Isolated yeasts were identified by sequencing the D1/D2 domain of the gene 28S rRNA. The obtained sequences determined that the isolated yeasts belong to the species: Kluyveromyces marxianus, Candida tropicalis, Trichosporon coremiiforme, Rhodotorula mucilaginosa, Trichosporon ovoides, Pichia kudriavzevii, Issatchenkia orientalis, which are considered contaminants, and Debaryomyces hansenii, a species that can be used as a starter culture. Since yeasts are not thermoresistant microorganisms, they should be removed during pasteurization. However, milk is not heat-treated in traditional cheese-making
production, thus increasing the risk of yeast in the final product. These isolated species are very often found in the environment and/or on humans and animals therefore, it can be concluded that the majority of yeast contamination occurs as a result of inadequate hygiene.
Keywords
milk; cottage cheese; dairy; yeasts; molecular identification
Hrčak ID:
238438
URI
Publication date:
1.10.2020.
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