Survey of the physiological properties of the most frequent yeasts associated with commercial chilled foods.

A comparative analysis of the initial and final population of yeasts, lactic acid bacteria and psychrotrophic bacteria, in a number of chilled foods, varying in ingredients, physico-chemical characters and origin, gave evidence that yeasts could play a significant role in the spoilage. The yeast populations appeared to be unexpectedly uniform and comprised principally strains of Yarrowia lipolytica, Debaryomyces hansenii and Pichia membranaefaciens. A survey of 62 isolates, comprising physiological characteristics such as growth temperatures, proteolytic and lipolytic activities, hydrophobicity, aw and preservative tolerance, in addition to organic acid production, indicated that these dominant species have very few common characters and that they are endowed with a spoilage potential probably linked to different physiological properties. The isolates of Y. lipolytica exhibited the strongest proteolytic and lipolytic activities and a pronounced hydrophobicity while D. hansenii isolates were characterized by a high growth rate at low temperature and at intermediate aw. P. membranaefaciens isolates showed a remarkable tolerance to acetic acid as a sole selective factor. A hypothesis of separate growth loci, in multicomponent or polyphasic food systems, was formulated.