Heat resistance of the spoilage yeastsCandida pelliculosaandKloeckera apisand pasteurization values for some tropical fruit juices and nectars

Spoilage yeasts, identified asCandida pelliculosaandKloeckera apis, were isolated from fermented pasteurized pineapple juice, guava and passion fruit nectars, and studied for their heat resistance in relation to the pasteurization process of the beverages. The decimal reduction times (DT) obtained between 55 and 60°C forK. apisvaried from 1.41 to 2.49 min, and those forC. pelliculosaobtained between 60 and 75°C varied from 1.03 to 4.90 min depending upon the beverage and the tested temperatures.C. pelliculosaseemed to be more heat resistant thanK. apis. Thez-values or the increase in temperature needed to reduce theDTby 10, determined between 60 and 75°C forC. pelliculosa, were 31.75±0.03°C (r2=0.91) in pineapple juice, 27.70±0.04°C (r2=0.90) in passion fruit nectar and 34.84±0.02°C (r2=0.998) in guava nectar. ForK. apis, thez-values determined between 55 and 60°C were 21.88±0.07°C (r2=0.97) in pineapple juice, 22.73±0.04°C (r2=0.99) in guava nectar and 29.07±0.01°C (r2=0.999) in passion fruit nectar. The minimal pasteurizing valuesPTzwere determined forC. pelliculosaat 70°C and at 75°C, at a pasteurization efficiency (logN0/N) of 9. In pineapple juice,Pz70=27.91 min andPz75=13.5 min would have be applied to destroy almost any vegetative forms of the yeast. In passion fruit nectar,Pz70=20.25 min andPz75=9.27 min, and in guava nectarPz70=16.83 min would have be applied.