FACTORS INFLUENCING THE DRY HEAT SENSITIVITY OF SALMONELLA enterica ON ALFALFA SPROUTING SEEDS

摘要

Sprouts have been implicated in several outbreaks of salmonellosis where the seeds were found to be the likely source of contamination. The aims of this study were to assess the efficacy of heat to eliminate Salmonella on alfalfa seeds as affected by the water activity of seeds, inoculum strain(s) of Salmonella, storage temperature of seeds and heat treatment duration. Thermal inactivation of Salmonella at 65C was less effective in seeds of reduced water activity of 0.3 or 0.5 compared with 0.6. Prior freezing of inoculated seeds enhanced heat inactivation of Salmonella in seeds with an elevated water activity of 0.6, but not for seeds with a water activity of 0.3-0.5. Salmonella DT104 and a cocktail of four typical strains of Salmonella were more heat resistant than SalmonellaSenftenberg 775W regardless of the storage temperature. Heat treatment (65C) of durations ranging from 8 to 48h of seeds (a(w) approximate to 0.6), previously kept at freezing or refrigeration temperatures, resulted in complete elimination of Salmonella irrespective of the strains tested. Freezing of seeds (a(w) approximate to 0.6) followed by heating at 65C for 6-8h did not significantly reduce the germinability of seeds although the yield was significantly impaired (P0.05).