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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Proteinase and phospholipase activities and development at different temperatures of yeasts isolated from bovine milk

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Author(s):
Melville, Priscilla A. [1] ; Benites, Nilson R. [1] ; Ruz-Peres, Monica [2] ; Yokoya, Eugenio [1]
Total Authors: 4
Affiliation:
[1] Univ Sao Paulo, Fac Vet Med & Zootechny, Dept Prevent Vet Med & Anim Hlth, BR-05508 Sao Paulo - Brazil
[2] Max Planck Vet Med Facil, Sao Paulo - Brazil
Total Affiliations: 2
Document type: Journal article
Source: JOURNAL OF DAIRY RESEARCH; v. 78, n. 4, p. 385-390, NOV 2011.
Web of Science Citations: 6
Abstract

The presence of yeasts in milk may cause physical and chemical changes limiting the durability and compromising the quality of the product. Moreover, milk and dairy products contaminated by yeasts may be a potential means of transmission of these microorganisms to man and animals causing several kinds of infections. This study aimed to determine whether different species of yeasts isolated from bovine raw milk had the ability to develop at 37 degrees C and/or under refrigeration temperature. Proteinase and phospholipase activities resulting from these yeasts were also monitored at different temperatures. Five genera of yeasts (Aureobasidium sp., Candida spp., Geotrichum spp., Trichosporon spp. and Rhodotorula spp.) isolated from bovine raw milk samples were evaluated. All strains showed one or a combination of characteristics: growth at 37 degrees C (99.09% of the strains), psychrotrophic behaviour (50.9%), proteinase production (16.81% of the strains at 37 degrees C and 4.09% under refrigeration) and phospholipase production (36.36% of the isolates at 37 degrees C and 10.9% under refrigeration), and all these factors may compromise the quality of the product. Proteinase production was similar for strains incubated at 37 degrees C (16.81% of the isolates) and room temperature (17.27%) but there was less amount of phospholipase-producing strains at room temperature (15.45% of the isolates were positive) when compared with incubation at 37 degrees C (36.36%). Enzymes production at 37 degrees C by yeasts isolated from milk confirmed their pathogenic potential. The refrigeration temperature was found to be most efficient to inhibit enzymes production and consequently ensure better quality of milk. The viability of yeasts and the activity of their enzymes at different temperatures are worrying because this can compromise the quality of dairy products at all stages of production and/or storage, and represent a risk to the consumer. (AU)