The Effects of Heat Shock on the D-Values of <i>Listeria monocytogenes</i> on Selected Seafood Matrices

Abstract

With more ready-to-eat foods and increased shelf-lives, prevention of Listeria monocytogenes contamination has become a necessity for the food industry. This study examined the effects of sublethal heat treatment on the decimal reduction time (D-values) of three L. monocytogenes serotypes (1/2a, 1/2b, 4c), and non-pathogenic L. innocua . The D 70 (D-value at 70 ℃ ) values of heat-shocked (HS) and non-heat-shocked (NHS) Listeria grown in tryptic soy broth (TSB) were determined. The D 70 values of HS L . monocytogenes serotype 1/2a and L. innocua were significantly higher compared to NHS cultures, although by 48 h, the values returned to NHS levels. When HS and NHS 1/2a and 1/2b were inoculated on crab meat and cooked shrimp, the D 70 values of HS cultures were at least 2-fold higher, compared to when they were grown in TSB. This increase in heat resistance for the HS cultures may be attributed to the protective effect of the seafood matrix itself.