Populations and frequency of occurrence of yeasts in frozen apple, cherry, grape, orange, and pineapple juice concentrates were determined. Total yeast populations ranged from log10 < 1.00 to 5.41 CFU/ml of diluted (1:4) concentrate and increased to 2.42–7.34 CFU/ml after 24 h of incubation at 25°C. One hundred fifty-four isolates from 33 samples of fruit juice concentrates represented 21 species and 12 genera. The most frequently isolated species were Saccharomyces cerevisiae (24.7% of isolates), Candida stellata (22.1%), and Zygosaccharomyces rouxii (14.3%), followed by, in decreasing order of frequency, Torulaspora delbrueckii, Rhodotorula mucilaginosa, Issatchenkia orientalis, Hanseniaspora occidentalis, Lodderomyces elongisporus, Kluyveromyces thermotolerans, Hanseniaspora guilliermondii, Candida glabrata, and Pichia anomala, each representing 3–8% of isolates. Candida magnoliae, Candida maltosa, Candida parapsilosis, Candida tropicalis, Clavispora lusitaniae, Cryptococcus humicolus, C. laurentii, Pichia membranaefaciens, and Sporidiobolus salmonicolor were represented by single isolates. Populations in various samples consisted of 24–100% S. cerevisiae, 52–100% C. stellata, and 3–56% for Z. rouxii. S. cerevisiae and Z. rouxii were isolated, respectively, from five and four types of fruit concentrates investigated. This may be the first observation of this high frequency of C. stellata in juice concentrates.
1Permanent address: Department of Microbiology, University of Horticulture and Food Industry, Budapest. Hungary.