Utilização da nisina na destribuição termica de Bacillus stearothermophilus em homogeneizado de cogumelos pH 6,2

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The present work intended to establish the microbiological parameters for process using nisin as a thermal adjuvant in a homogenate of mushrooms in brine 1.5 per cent (p/v) pH 6.2 (HM). The HM simulates a low-acid processed product. The target microorganism for the thermo-chemical destruction was Bacillus stearotherraophilus FS 1518. The spore suspension was obtained from a stock suspension and produced in Nutrient Agar (NA) supplemented with 5 ppm of Manganese Sulfate (PFLUG, 1982). This methodology showed to be more efficient than the one standardized by KIM &NAYLOE (1966). It was determined the optimum conditions of activation for germination on the subculture medium studied. It was found that the optimum activation time was 5 minutes at boiling temperature. Nutrient Broth was chosen as the culture medium to study the effect of nisin on the germination and post-germinative growth, because it showed to be the most adequate to the spectrophotometry method of absorbance reduction. It was observed that nisin does not inhibit germination of such spores. Its inhibiting action occurs after the germination phase. Nisin Minimum Inhibitory Concentration (MIC) for B. stearothermophilus FS 1518 in apopulation of 106 CFU/ml was 50 UI/ml. Half of this MIC was added to the HM medium previously innoculated with the spores to determine its thermo-chemical resistance. The thermo-chemical resistance reduction using HA medium for subculturing was 19, 36 and 44 per cent for temperatures of 125, 121 and 118°C, respectively. The Z-value found was 11.66 and 9.15"C with and without nisin, respectively. The sterilization value required (F) to cause 5 decimal reduction on the initial population of 7000 spores per 250 g of product decreased approximately 36 per cent at 121ºC with nisin. These data prove the efficiency of nisin in reducing the thermal resistance of such spores when inoculated in HM medium, and it also provides the F-value for processing the product in the studied conditions.

ASSUNTO(S)

cogumelos nisina bacillus (bacteria)

ACESSO AO ARTIGO

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