Spoilage Potential of Contaminating Yeast Species Kluyveromyces marxianus, Pichia kudriavzevii and Torulaspora delbrueckii during Cold Storage of Skyr

Abstract

This study investigated the spoilage potential of yeast strains Kluyveromyces marxianus (Km1, Km2 and Km3), Pichia kudriavzevii Pk1 and Torulaspora delbrueckii Td1 grown in skyr in cold storage. Yeast strains were isolated from skyr and identified by sequencing of the 26S rRNA gene. K. marxianus yeasts were grown in skyr to high numbers, generating large amounts of volatile organic compounds (VOC) associated with off-flavours, among them were alcohols (3-methyl-1-butanol, 2-methyl-1-propanol and 1-hexanol), esters (ethyl acetate and 3-methylbutyl acetate) and aldehydes (hexanal, methylbutanal and methylpropanal). Growth of P. kudriavzevii Pk1 led to moderate increases in several alcohols and esters (mostly, 3-methyl-1-butanol and ethyl acetate), whereas only minor shifts in VOCs were associated with T. delbrueckii Td2. The levels of the key aroma compounds, diacetyl and acetoin, were significantly decreased by all K. marxianus strains and P. kudriavzevii Pk1. In contrast to the other yeast species, K. marxianus was able to utilize lactose, producing ethanol and carbon dioxide. Based on the overall results, K. marxianus was characterised by the highest spoilage potential. The study revealed the differences between the yeast species in fermentative and spoilage activities, and clarified the role of yeast metabolites for off-flavour formation and quality defects in skyr during cold storage.

Antifungal activity of protective cultures against the yogurt drink‐specific spoilage yeasts

“…Meanwhile, sample 2, showing similar enumeration results but a very low gas formation, was dominated by P. kudriavzevii . Gas production by these two microorganisms in this project is also in agreement with a previous study (Srimahaeak et al., 2022).…”

“…In spite of the fact that a variety of microorganisms especially spore‐forming bacteria that are able to stand the two‐step pasteurization were identified in this project and other studies, it was shown here that yeasts as the post‐pasteurization contaminants were the most dominant isolates in non‐carbonated and pasteurized industrial yogurt drink. With respect to the present results, C. parapsilosis was previously reported to be responsible for the spoilage in yogurt drink, in addition to K. marxianus and P. kudriavzevii indicated as the spoilage agents in an Icelandic dairy product called skyr (Anari et al., 2022; Srimahaeak et al., 2022).…”

Update of the list of qualified presumption of safety (QPS) recommended microbiological agents intentionally added to food or feed as notified to EFSA 17: suitability of taxonomic units notified to EFSA until September 2022

“…However, the isolates had not caused disease and the species identification is uncertain. Srimahaeak et al (2022) demonstrated a dairy products spoilage potential of three K. marxianus strains isolated from skyr (an Icelandic dairy product similar to yoghurt).…”

“…Srimahaeak et al. ( 2022 ) demonstrated a dairy products spoilage potential of three K. marxianus strains isolated from skyr (an Icelandic dairy product similar to yoghurt).…”

Advances in the Application of the Non-Conventional Yeast Pichia kudriavzevii in Food and Biotechnology Industries

“…P. kudriavzevii has been isolated from several indigenous fermented milk products from different areas, although it was reported to be lactase-negative [ 38 , 39 , 40 , 41 ]. Several studies highlighted the spoilage potential of P. kudriavzevii because of its film-forming property under acidic conditions, and the release of alcohols and esters thought to be associated with off-flavors of fermented milk beverages [ 42 , 43 ]. On the other hand, P. kudriavzevii from a traditional fermented cow milk in Colombia was reported to produce peptides with Angiotensin I converting enzyme (ACE) inhibitory activity, which has the effect of lowering blood pressure [ 44 ].…”