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Biomedical subjects

D F Splittstoesser

Publications and source records attributed to D F Splittstoesser.

15 recordsLinked to original sources
PubMed1996

Heat resistance of Escherichia coli O157:H7 in apple juice.

The objective was to determine the effect of cider composition on the heat resistance of Escherichia coli O157:H7. The average D52 value in a model Empire apple juice was 18 min with a z value of 4.8 degrees C. Increasing the Brix from 11.8 to 16.5 degrees had no effect on thermal resistance, while increasing L-malic acid from 0.2 to 0.8%, or reducing the pH from 4.4 to 3.6 sensitized the cells to heat. The greatest effect on heat resistance was afforded by the preservatives benzoic and sorbic acids: D50 values in ciders containing 1,000 mg/l were 5.2 min in the presence of sorbic acid and only 0.64 min in the presence of benzoic acid. Commercial apple juice concentrates yielded lower numbers of survivors than single-strength juices even though their higher sugar concentrations of about 46 degrees Brix increased heat resistance.

Benzoic Acid↗
PubMed1975

Influence of wine composition on the heat resistance of potential spoilage organisms.

Pasteurization studies were conducted on 29 yeast and five lactic acid bacteria. In general the yeasts were more heat resistant in wine than were the bacteria. The one exception was a strain of Lactobacillus fructivorans that gave an average D-value of 1.7 min at 60 C. Alcohol was the wine constituent that had the greatest effect on resistance; D-values for all test species were inversely related to the ethanol concentration. The response of organisms to other factors such as pH, sugar, and sulfur dioxide varied with the species.

Ethanol↗
PubMed1975

Utilization of brewery spent grain liquor by Aspergillus niger.

Aspergillus niger was found capable of rapidly converting about 97% of the sugar from brewery spent grain liquor to fungal mass. The yield of dry mycelium, based on the sugar consumed, was approximately 57%. This fungus produced 1.10% titratable acid calculated as citric acid and reduced the biochemical oxygen demand by 96%.

Aspergillus↗
PubMed1973

Some factors affecting the activity of diethylpyrocarbonate as a sterilant.

Quantitative data indicated logarithmic death in 5 degrees Brix Concord grape juice when concentrations of cells under 10(7)/ml were exposed to diethylpyrocarbonate (DEPC). Species differed considerably in their resistance; e.g., 50 ppm reduced the viable count of Saccharomyces cerevisiae over nine log(10) cycles, whereas 200 ppm reduced the count of Byssochlamys fulva ascospores by only about 1 log. DEPC lethality was enhanced by higher temperatures; destruction at 40 C was 10- to 100-fold greater than at 20 C. Studies on death rates showed that most yeasts and fungal spores were killed during the first hour of exposure, whereas 24 h or longer was needed for maximal destruction of several lactic acid bacteria. Repair of DEPC-induced damage was believed responsible for the slower death rates of the lactics.

Ascomycota↗
PubMed1971

Incidence of heat-resistant molds in eastern orchards and vineyards.

Over 70% of the samples of fruit, vegetation, and soil obtained in surveys of New York orchards and vineyards were contaminated with heat-resistant molds. The counts generally were low, under one per gram. Byssochlamys fulva was the most common isolate. Other isolates were identified as B. nivea, Paecilomyces varioti, Aspergillus fischeri, A. fischeri var. spinosus, A. fumigatus, Penicillium vermiculatum, and P. ochro-chloron.

Ascomycota↗
PubMed1971

Determination of hydrogen sulfide in fermentation broths containing SO 2 .

A procedure for the determination of hydrogen sulfide in fermentation broths containing up to 100 mug of SO(2) per ml is described. The method involves the sparging of H(2)S from the broth into a cadmium hydroxide absorption solution, the formation of methylene blue from the absorbed sulfide, and the measuring of this color spectrophotometrically. The use of cadmium hydroxide instead of zinc acetate, the common absorbent, substantially reduced the interference of SO(2) with the analysis.

Absorption↗
PubMed1970

Enumeration of byssochlamys and other heat-resistant molds.

Methods for the detection of low numbers of heat-resistant molds on fruits were studied by using cultures of Byssochlamys and a number of unidentified mold isolates. Ascospore dormancy had a marked effect on viable recoveries, and the medium in which ascospores were heated influenced activation rates. Best results were obtained when fruit homogenates were heated for 60 min at 70 C in Concord grape juice, followed by culturing on acidified Potato Dextrose Agar.

Journal Article↗
PubMed1968

Numerical taxonomy of catalase-negative cocci isolated from frozen vegetables.

Taxonomic data for 135 cultures of bacteria isolated from frozen snap beans and whole kernel corn were analyzed by computer. Of the isolates, 79% were grouped into five major clusters. Two of the groups consisted of leuconostocs, whereas the other three contained homofermentative types. The intergroup similarities suggested a generic level of similarity. Feature frequencies for the groups were calculated, and properties of the different groups are presented. Many of the isolates differed from described species.

Bacteria↗
PubMed1967

Numerical taxonomy of gram-positive and catalase-positive rods isolated from frozen vegetables.

One hundred isolates from peas, beans, and corn were compared with cultures of Corynebacterium, Microbacterium, and Arthrobacter by use of numerical taxonomic procedures. Six groups (clusters), representing 75% of the isolates, resembled Corynebacteriaceae. There was some doubt regarding the genera represented because the groups were not closely related to many of the known strains. The relationship of the different groups to each other, as well as a number of their properties, is presented.

Arthrobacter↗
PubMed1967

Irradiation of Composts Used in the Propagation of Agaricus bisporus.

Unpasteurized horse manure composts were given radiation doses of 0.1 and 1.0 Mrad in an attempt to increase mushroom yields by eliminating competing microorganisms. Yields were enhanced by 0.1 Mrad but were lower than those obtained with heat-pasteurized composts. Composts subjected to 1.0 Mrad gave the lowest yields, probably because of the generation of ammonia and other toxic compounds. Only temporary changes in the predominant microflora could be detected as a result of ionizing radiations.

Journal Article↗
PubMed1966

Effect of cations on activation of Bacillus popilliae spores.

Splittstoesser, D. F. (Cornell University, Geneva, N.Y.), and D. F. Farkas. Effect of cations on activation of Bacillus popilliae spores. J. Bacteriol. 92: 995-1001. 1966.-Cations affected the rate at which dormant Bacillus popilliae spores were heat-activated. Maximal rates were achieved in calcium solution at pH 7 or in tris(hydroxymethyl)aminomethane buffer at pH 9 to 10. A combination of calcium plus an alkaline pH, however, retarded activation. The rates also were markedly reduced by potassium and hydrogen ions but were not affected by sodium, cesium, or lithium. Divalent cations may be required for activation since ethylenediaminetetraacetic acid also inhibited, and potassium was shown to be competing with calcium for some active site.

Bacillus↗
PubMed1961

Studies on Media for Enumerating Enterococci in Frozen Vegetables.

A study was made of the relative sensitivity and specificity of presumptive and confirmatory media for the most probable number enumeration of enterococci in frozen vegetables. Azide dextrose broth yielded the highest numbers of confirmable enterococci and its sensitivity was shown to be comparable to nonselective media. The use of ethyl violet azide broth as a confirmatory medium resulted in a significant number of false positive tests. Growth in broth containing 6.5% sodium chloride incubated at 45 C for 2 days was found to be a more specific confirmatory test for enterococci.

Journal Article↗