COMBINED STRESS EFFECTS ON GROWTH OF ZYGOSACCHAROMYCES-ROUXII FROM AN INTERMEDIATE MOISTURE PAPAYA PRODUCT

Stress factors studied included 0.95 a(w) adjusted with sucrose and glyc erol, pH (4.0, 3.5, and 3.0), potassium sorbate (0, 500, 1000, and 1500 ppm) and sodium bisulfite (0, 100, and 150 ppm). These were tested on a strain of Zygosaccharomyces rouxii isolated from an intermediate moisture (IM) papaya product. Z. rouxii was very sensitive to SO2. A combination of 100 ppm SO2. 500 ppm sorbate and pH 4.0 is recommended to prevent spoilage of IM fruits by Z. rouxii. The minimum a(w) for growth in sucrose-glycerol broth was between 0.62 and 0.64 in the absence of antimicrobials and in the range of optimal pH for this yeast.