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EFFECTS OF THERMAL STRESS AND REDUCED WATER ACTIVITY ON CONIDIA OF Aspergillus parasiticus
Author(s) -
ADAMS GARY H.,
ORDAL Z. JOHN
Publication year - 1976
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1976.tb00667.x
Subject(s) - conidium , agar , food science , chemistry , water activity , agar plate , sodium , sucrose , botany , horticulture , biology , microbiology and biotechnology , water content , bacteria , genetics , geotechnical engineering , organic chemistry , engineering
Conidia of Aspergillus parasiticus (an aflatoxin producer) were harvested from an agar medium, centrifuged, and resuspended in 0.05% Tween‐80. The suspension was subjected to a thermal stress of 51°C for up to 4 hr. Viability and thermal injury were evaluatd by the use of two plating media, yeast extract agar and yeast extract agar + 10% NaCl. Evidence of injury was demonstrated by the difference in colony counts on the two media. The number of injured cells increased as the heating time continued Colonies from injured conidia developed more slowly than colonies from unheated conidia. The effect of a reduced water activity (a w ) was evaluated by comparing the ability of unheated and heated conidia to grow in media of differing water activities. A most probable number technique was used to measure growth. Media of reduced a w limited the ability of injured conidia to outgrow as compared to unheated conidia. Continued storage of injured conidia in media of reduced a w eventually resulted in a loss of colony‐forming ability. Solutes used to lower a w were sodium chloride, glycerol, and sucrose.