Requirements in terms of water activity (a,) for the growth, sporulation, and germination of Clostridium perfringens were determined. Strain A48 was used in all phases, and in addition either NCTC 8239 or NCTC 8797 was used for growth, sporulation, and germination studies. The desired a, of the test media was obtained by the addition of one of three solutes: glycerol, sucrose, or sodium chloride. The freezing point depression method was used to determine the a,. The basal medium for growth and germination was Fluid Thioglycollate Medium. It had an a, of 0.995 and produced maximum growth and fastest growth rate among the six levels of a, tested. The lowest a, supporting growth and germination of C. perfringens was between 0.97 and 0.95 in the test media made with sucrose or sodium chloride and 0.93 or below in the test media adjusted with glycerol. Spore production by C. perfringens in Ellner's or modified medium required a higher a, than growth. An understanding of the influence of the available water in foods on the growth, sporulation, and germination of Clostridium perfringens may aid in control of this microorganism as a cause of foodborne illness. The available water activity (a,) in a food is affected by all of the constituents which have an affinity for water. These will include those which can be metabolized by the organism as well as those which cannot. In addition, food processing may alter the available water. Gough and Alford (5) tested the effects of NaCl, NaNO3, and NaNO2 on growth, survival, and heat resistance of several strains of C. perfringens. Growth occurred in concentrations of these salts which were higher than those used in the normal curing of meat. A NaCl concentration of 6% (w/v) in Fluid Thioglycollate Medium was required to inhibit growth significantly. The
Requirements in terms of water activity (a w ) for the growth, sporulation, and germination of Clostridium perfringens were determined. Strain A48 was used in all phases, and in addition either NCTC 8239 or NCTC 8797 was used for growth, sporulation, and germination studies. The desired a w of the test media was obtained by the addition of one of three solutes: glycerol, sucrose, or sodium chloride. The freezing point depression method was used to determine the a w . The basal medium for growth and germination was Fluid Thioglycollate Medium. It had an a w of 0.995 and produced maximum growth and fastest growth rate among the six levels of a w tested. The lowest a w supporting growth and germination of C. perfringens was between 0.97 and 0.95 in the test media made with sucrose or sodium chloride and 0.93 or below in the test media adjusted with glycerol. Spore production by C. perfringens in Ellner's or modified medium required a higher a w than growth.
SUMMARY— Reductions in numbers but no depression of respiration of 4 Salmonellaserotypes over a 7.0‐hr period was noted when they were incubated in the presence of anthocyanin pigments, malvidin‐3.5diglucoside or cyanidin chloride. At certain concentrations of these pigments in the presence of glucose, stimulation of the respiration of some serotypes was evident. Slight reductions in cell numbers were noted as concentrations of malvidin‐3,5‐diglucoside increased. Comparable counts were obtained upon plating the cells on minimal and complete media, indicating lack of metabolic damage to those cells present. An enzyme assay utilizing the respiration of Saccharomyces cerevisiae var. ellipsoideus indicated the possibility of an anthocyanase in the cells which had been preincubated in the presence of the diglucoside of malvidin without glucose but not with glucose. If this observation were substantiated, it would indicate the production of a glucose‐repressible anthocyanase. No evidence was obtained to indicate utilization of the aglycone by any of the 4 serotypes.
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