SUMMARY
The sporicidal activity of gaseous propylene oxide was determined at several concentrations and at low and high relative humidity (RH). At 37°C, 85% RH, and a concentration of 1250 mg/L, propylene oxide will kill 90% of a population of dry spores of B. subtilis var. niger in one hour. If RH is lowered to 25% under the same conditions, 90% of the spores are killed in 40 minutes. Microbial decontamination of several flaked or powdered foods with propylene oxide was determined in 4‐L rolling jars or in a 4‐cu‐ft revolving blender. The bacterial count of cereal flakes inoculated with dry spores of B. subtilis var. niger was reduced 95% in 4 hours at 37 and 55°C, hut further reduction in count was achieved only after prolonged holding times. Studies with cocoa powder showed that exposure to a propylene oxide concentration of l‐2% by weight of cocoa (or 1000‐2000 mg/L of space) at 37°C for 2‐3 hours reduced bacterial count by 50‐70% and thermophilic count by 50‐90%. Destruction of molds and vegetative bacteria in cocoa or other foods was 90‐99.9% under these conditions. Destruction of the microbial flora of cocoa was greater when the treated Cocoa was stored with some residual propylene oxide in bottles or plastic bags. Addition of liquid propylene oxide directly to small samples of cocoa gave good reduction of the microbial flora, but also some physical destruction of the contents.
Acidified (pH 2.8) ammonium persulphate (0.75%) was more effective than an acid wash at pH 2.8 or straight 0.75% ammonium persulphate in the disinfection of contaminated yeasts obtained from breweries. The contaminating bacteria in the samples of brewery yeast were isolated and grown in mixed fermentations with yeast. The data from disinfection trials with the contaminated yeasts showed that acidified ammonium persulphate provided the most effective treatment. The following patterns of bacterial resistance to the various treatments were noted: (a) lactobacilli tend to be resistant to disinfection with 0.75% ammonium persulphate; (b) acetic acid bacteria resist acid treatments, unless the pH is 2.4 or lower; and (c) flavobacteria are sensitive to acid washes and to treatments with ammonium persulphate, but the acidified ammonium persulphate killed this bacterial type more rapidly.
BRUCH, CAIRL W. (Wilmot Castle Company, Rochester, N. Y.), ANT) MIARTIN G. KOESTERER. Destruction of eniteric bacteria in liquid egg with ,B-propiolactone. Appl.
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