The Effects of Stress Factors on the Growth of Spoilage Yeasts Isolated From Apple-Related Environments in Apple Juice

This study aimed to evaluate the effects of temperature, pH, sugar content and antimicrobial components on the growth of 11 yeast isolates in apple juice (12 degrees Brix, pH 4.0). The results showed that reduction of the storage temperature to 4C could achieve a complete inhibition of test strains, and the temperature required to kill all the initial yeast inoculum (10(3)cfu/mL) within 20min ranged from 46 to 55C, depending on the isolate. However, high sugar content enabled test strains to survive in what would have been a lethal treatment. A pH value below 2.0 had a significant inhibitory effect on the growth of test strains. Increasing the sugar content of apple juice was not enough to completely avoid the spoilage caused by the test strains, especially Zygosaccharomyces rouxii. Addition of antimicrobial components (4.0mM sorbic acid, 1.5mM cinnamic acid, 20mM vanillin, 10mM ferulic acid or 12mM p-coumaric acid) was an applicable strategy to prevent the spoilage in apple juice spawned by the test strains.