Microbial spoilage of dried prunes: III. Relation of equilibrium relative humidity to potential spoilage
AuthorsM. W. Miller
Authors AffiliationsM. W. Miller was Assistant Professor of Food Science and Technology and Assistant Food Technologist in the Experiment Station, Davis; Hirosato Tanaka was Research Assistant in Food Science and Technology, Davis.
Hilgardia 34(6):183-190. DOI:10.3733/hilg.v34n06p183. April 1963.
The soluble-solids content of fresh prunes was studied in fruits picked by hand at three stages of maturity. Although fruits were carefully sorted for uniformity of size and color, the soluble-solids content of individual fruits varied greatly at each stage of maturity.
Changes in the moisture content of dried prunes placed in atmospheres of various relative humidities at 20° and 30° C were followed for 25 weeks. Prunes attained equilibrium in 25 weeks in atmospheres of 76 per cent relative humidity or lower.
Dried prunes equilibrated in atmospheres of various relative humidities were inoculated with selected strains of Aspergillus glaucus, A. niger, Penicillium sp., and Saccharomyces rouxii. At 20° C the strains of A. glaucus and S. rouxii grew on prunes equilibrated at relative humidities as low as 76 per cent, but not at 69 per cent, in a four-month period. The strains of A. niger and of Penicillium sp. grew well on prunes equilibrated at 93 per cent relative humidity but failed to grow on those equilibrated at 87 per cent. At 30° C, only the strain of S. rouxii grew on prunes equilibrated at 85 per cent relative humidity. All strains tested, however, grew at 97 per cent.
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Microbial spoilage of dried prunes: I. Yeasts and molds associated with spoiled dried prunes
Microbial spoilage of dried prunes: II. Studies of the osmophilic nature of spoilage organisms