The Effects of NaCl and Temperature on Growth and Survival of Yeast Strains Isolated from Danish Cheese Brines
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The Effects of NaCl and Temperature on Growth and Survival of Yeast Strains Isolated from Danish Cheese Brines Ling Zhang1 · Chuchu Huang1 · Agnete Harboe Malskær1 · Lene Jespersen1 · Nils Arneborg1 · Pernille Greve Johansen1 Received: 27 March 2020 / Accepted: 25 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Yeasts play an important role in cheese making, by contributing to microbial community establishment and improving flavor. This study aimed at investigating the impact of NaCl and temperature on growth and survival of 20 strains belonging to the yeast species Candida intermedia (2 strains), Debaryomyces hansenii (11), Kluyveromyces lactis (1), Papiliotrema flavescens (1), Rhodotorula glutinis (1), Sterigmatomyces halophilus (2) and Yamadazyma triangularis (2) isolated from Danish cheese brines. All yeasts could grow in Malt Yeast Glucose Peptone (MYGP) medium with low NaCl (≤ 4%, w/v) concentrations at 25 °C and 16 °C. Further, none of the strains, except for one strain of D. hansenii (KU-9), were able to grow under a condition mimicking cheese brine (MYGP with 23% (w/v) NaCl and 6.3 g/L lactate) at 25 °C, while all yeasts could grow at 16 °C, except for the two strains of C. intermedia. In the survival experiment, D. hansenii, S. halophilus and Y. triangularis survived in MYGP with 23% (w/v) NaCl throughout 13.5 days at 25 °C, with Y. triangularis and S. halophilus being the most NaCl tolerant, while the remaining yeasts survived for less than 7 days. These results enable the selection of relevant yeasts from cheese brines for potential use in the cheese industry.
Introduction Salting of most semi-hard cheeses is performed by immersion into brines with about 19–21% NaCl (w/w) at 10–14 °C for only a few hours or several days [1]. The pH of the brine is typically adjusted to 5.2–5.3 that is close to the cheese pH. Currently, cheese brines are rarely renewed but salt is added regularly to replenish the salt, which has diffused into the cheeses. The salt ions ( Na+ and C l−) diffuse from the brines into the cheese blocks by osmotic pressure, which results in reverse diffusion of low molecular mass water soluble compounds into the brines [2, 3]. After brining, NaCl concentration on the surfaces of Danish semi-hard Danbo cheese starts at 8.2% (w/w), but due to migration it levels out at 2.6% (w/w) after 7 days of ripening [4]. Besides being important
Ling Zhang and Chuchu Huang contributed equally to this paper. * Pernille Greve Johansen [email protected] 1
Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 26, 1958 Frederiksberg C, Denmark
for the structure and flavor of the cheeses, the brining highly affects the microbial growth [5–8]. After having been used for several batches, cheese brine with plentiful nutrients becomes a natural medium for a complex microbiota [9]. The microbial diversity and abundance in brines usually increase during long periods of utilization [2]. Recently, several studies have revealed
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