Sheep milk yogurt from a short food supply chain: study of the microbiological, chemico-physical and organoleptic parameters in relation to shelf-life

  • Nicla Marri Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.
  • Virginia Carfora Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.
  • Daniela Patriarca Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.
  • Maria Cristina Veschetti Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.
  • Giuseppina Giacinti Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.
  • Gilberto Giangolini Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.
  • Simonetta Amatiste | simonetta.amatiste@izslt.it Centro di Referenza Nazionale per la qualità del latte e dei derivati ovini e caprini, Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, Roma, Italy.

Abstract

Aim of this work was to analyse some microbiological, chemico-physical and organoleptic parameters of sheep milk yogurt during and after its declared shelf-life. Five samples of a sheep’s milk yogurt of the same lot, collected from a short supply chain ovine dairy farm of the Roman province, were analysed. Declared shelf-life of the product was 30 days. The products were examined at 2, 14, 30, 35 and 40 days from the production date, performing the following microbiological analyses: enumeration of i) colony-forming units characteristic of the yogurt, ii) Enterobacteriaceae, iii) yeasts and/or moulds at 25°C. Microbiological identification was performed by miniature biochemical tests and for the lactic acid bacteria also by PCR. At every test interval, evaluation of organoleptic parameters and pH was also performed. The analysed product maintained an almost constant amount of lactic acid bacteria until the end of the declared shelf-life. Concerning lactic acid bacteria, a 100% concordance of the results observed by using biochemical identification methods and PCR assays was obtained. After 14 days from the production, the presence of yeasts (Candida famata) was revealed, while the presence of moulds was detected after 30 days. Ralstonia picketii, an environmental microorganism, was also isolated. The results obtained in this study indicate that yogurt spoilage is mainly due to the growth of specific microorganisms of spoilage, such as yeasts and moulds.

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Published
2014-08-28
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Original Articles
Keywords:
Yogurt, Sheep milk, Shelf-life, Lactic acid bacteria, Specific spoilage organisms
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How to Cite
Marri, N., Carfora, V., Patriarca, D., Veschetti, M. C., Giacinti, G., Giangolini, G., & Amatiste, S. (2014). Sheep milk yogurt from a short food supply chain: study of the microbiological, chemico-physical and organoleptic parameters in relation to shelf-life. Italian Journal of Food Safety, 3(3). https://doi.org/10.4081/ijfs.2014.1695