Inhibitory Effect of Yucca Extract on the Growth of Film-Forming Yeasts Isolated from Ume-Zuke, Salted Japanese Apricot Fruit

Abstract

The inhibitory effects of Yucca extract (YE) and various additives on the growth and film-formation of 20 strains of film-forming yeasts belonging to 4 genera isolated from ume-zuke, a salted Japanese apricot (Prunus mume) fruit product were studied. The minimum inhibitory concentrations (MIC) of YE against the isolated film-forming yeasts were 100 μg /ml for Pichia anomala, 200-400, μg /ml for Kloeckera apiculata and Candida guilliermondii, and 1000 μg/ml for Debaryomyces hansenii. Deb. hansenii and C.gnillemmondii could tolerate YE relatively well, but the former was sensitive to thiamine dilaurylsulfate, sulfur dioxide, and sodium benzoate, and the latter to sodium cinnamate. Deb. hansenii was more susceptible to the organic acid concentration, as well as to a low pH (below 2.0), and a high storage temperature (above 30°C). The inhibitory effects were enhanced and showed a broad antimicrobial spectrum when YE was used in combination with various additives (thiamine dilaurylsulfate, potassium sorbate, sulfur dioxide, sodium benzoate, sodium cinnamate, and sodium acetate). From the results, YE is considered to be effective for the preservation of ume-zuke.