The Growth of Yeasts in Grape Juice Stored at Low Temperature

Fruit juices are usually stored at low temperatures to retain their wholesome, fruity character for long periods of time.In the bulk storage of grape juice at 22 to 28 F (-5.5 to -2.2 C), the quality of the prod- uct may remain materially unchanged for periods of 1 year or more.Even with the most careful operations, however, yeast contamination of grape juice may occur and may lead to considerable loss. (Pederson et al., 1959a).Safe yeast inhibitory agents which will not alter flavor nor produce other deleterious effects would interest the fruit juice industry.It is desirable to use a minimum of any fungistatic agent.Since grape juice is stored at temperatures approaching the minimal temperature range for growth of yeasts, concentra- tions of fungistatic acids lower than those ordinarily used may be effective. MATERIALS AND METHODSIn a preliminary survey using 13 different chemicals, it was observed that, sorbic, benzoic, salicylic, and ricinoleic acids were effective fungicides only in rela- tively high concentrations.Hypochlorites and certain quaternary ammonium compounds were far more effective.Since grape juice is pasteurized and cooled before its storage, an effective fungistat rather than a fungicide is desired.In a series of three preliminary studies, sorbic, ben- zoic, salicylic, caprylic, capric, and ricinoleic acids ex- hibited some fungistatic effect upon various yeasts inoculated into grape juice stored at 1.1 C. Yeast inhibition was observed in Concord and Niagara grape juices treated with only 0.005 per cent of acid.The degree of inhibition, however, was markedly reduced when the juice was held at 18 C or higher.Although capric and caprylic acids seemed to be slightly more effective than sorbic and benzoic acids, they possess the disadvantage of imparting an undesirable flavor.Following these observations, four series of juices were packed, two inoculated packs in 4-ounce bottles incubated in the laboratory cold room at 1.1 C and two uninoculated packs in 50 gallon barrels incubated