Production of Italian Dry Salami. I. Initiation of Staphylococcal Growth in Salami Under Commercial Manufacturing Conditions

Abstract

Three strains of Staphylococcus aureus (S-6, 137 and 472) were inoculated, in duplicate, into Italian-style dry salami made with finished product as starter and processed under commercial manufacturing conditions. Five levels of S. aureus ranging from 2.2 × 102 - 1.8 × 107 cells/g were used. A fourth strain (264) was inoculated at a level of 105 cells/g. All strains of S. aureus grew at every level of inoculation, but the amount of growth was dependent on inoculum size. Strains S-6 and 472 increased in number by 1.2 – 2.9 logs (mean 2.14) at inoculum levels of 2.3 × 102 – 2.5 × 103 cells/g, and by 2.1 – 3.2 logs (mean 2.66) at inoculum levels of 3.7 × 104 – 6.6 × 105 cells/g. Strain 137 was very sensitive to salami environment and only increased by 0.47 – 1.86 logs (mean 1.23) even at the greatest inoculum level. Strain 264 increased in numbers by 1.5 logs in the presence of 5 × 105 inoculated lactobacilli/g and by 2.5 logs in the presence of 6 × 104 naturally occurring lactic acid bacteria. Staphylococci occurring naturally in salami mix were unable to grow to levels greater than 2 × 104 cells at any time during processing of experimental sausages. Thermonuclease was detected only in salamis inoculated with strains S-6 and 472 at initial levels of greater than 3.7 × 104 cells/g and only when growth reached levels greater than 107 cells/g. No enterotoxin was detected in any of the inoculated samples. Development of regression equations allowed description of the growth of inoculated S. aureus in the salami during manufacturing as affected by a number of variables.