Early spoilage in fresh cheese contributes to food loss and negativelyaffects consumer experience. Traditional preservatives, like sorbatesand propionates, are being removed due to consumer demand for cleanlabels. Protective cultures represent a potential clean label alternativefor spoilage control. The study objective is to investigate bacterial culturesefficacy in bio-preserving cottage cheese against post-processingyeast contamination. Cottage curd and dressing were sourced from amanufacturer in New York. Dressing was inoculated with 3 differentcommercial protective cultures (of Lactobacillus spp. designated PC1,PC2 and PC3) following manufacturer recommended dosage. Curd wasadded to dressing and mixed. A positive control (PC) with no protectiveculture was included. Eight genera of yeast previously isolatedfrom dairy processing environments (Pichia fermentans, Clavisporalusitaniae, Debaryomyces hansenii, D. prosopidis, Candida zeylanoides,Rhodotorula mucilaginosa, Meyerozyma guilliermondi and Torulasporadelbrueckii) were spotted on cheese surface at a rate of 100 cfu/5 g ofcheese. Samples were stored at refrigeration temperature (6 ± 2°C). Toenumerate yeast levels at 0, 7, 14 and 21 d post-inoculation, sampleswere homogenized in phosphate buffer saline, serially diluted, plated onpotato dextrose agar with chloramphenicol, and incubated at 25°C for 5d.Studies were performed in duplicate with technical replicates. Averageyeast counts were log-transformed, and JMP Pro was used to analyzedata using least squares method and Tukey’s test at significance level(P = 0.05). Negative control showed no growth throughout 21d. For P.fermentans, C. lusitaniae, D. hansenii, D. prosodies, C. zeylanoides andR. mucilaginosa, treatments showed no significant difference at 21d. ForM. guilliermondii, counts were ～1 log lower at 21d in PC1 versus PC,PC2 and PC3 (P < 0.05). Similarly, T. delbrueckii, counts were ～2 loglower at 21d in PC1 compared with PC, PC2 and PC3 (P < 0.05). Thestudy shows potential efficacy of PC1 against M. guilliermondii and T.delbrueckii in cottage cheese. The study demonstrates that protectivecultures potential to inhibit yeast in cottage cheese is strain selective.
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