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Factors Influencing the Dry Heat Sensitivity of S almonella enterica on Alfalfa Sprouting Seeds
Author(s) -
Neetoo Hudaa,
Chen Haiqiang
Publication year - 2014
Publication title -
journal of food safety
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.427
H-Index - 43
eISSN - 1745-4565
pISSN - 0149-6085
DOI - 10.1111/jfs.12127
Subject(s) - sprouting , food science , horticulture , contamination , inoculation , germination , strain (injury) , chemistry , water activity , outbreak , biology , zoology , water content , ecology , geotechnical engineering , virology , engineering , anatomy
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 S almonella on alfalfa seeds as affected by the water activity of seeds, inoculum strain(s) of S almonella , storage temperature of seeds and heat treatment duration. Thermal inactivation of S almonella at 65 C 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 S almonella in seeds with an elevated water activity of 0.6, but not for seeds with a water activity of 0.3–0.5. S almonella DT104 and a cocktail of four typical strains of S almonella were more heat resistant than S almonella S enftenberg 775 W regardless of the storage temperature. Heat treatment (65 C ) of durations ranging from 8 to 48 h of seeds (a w ∼0.6), previously kept at freezing or refrigeration temperatures, resulted in complete elimination of S almonella irrespective of the strains tested. Freezing of seeds (a w ∼0.6) followed by heating at 65 C for 6–8 h did not significantly reduce the germinability of seeds although the yield was significantly impaired ( P < 0.05). Practical Applications Sprouts have been implicated in the outbreaks of salmonellosis where seeds were found to be the likely source of contamination. The effect of water activity, inoculum strain(s) of S almonella , storage temperature and treatment duration on the lethality of the heat treatment of seeds was investigated. A decrease in the seed water activity from 0.6 to 0.3 resulted in a considerable decrease in the efficacy of the thermal treatment. There was an appreciable difference in the extent of heat inactivation of the different strains, suggesting the importance of using strain cocktails in inactivation studies. Storage of seeds (a w of 0.6) at freezing temperature followed by heating at 65C for 6–8 h reduced the load of S almonella to undetectable levels although the sprouting yield was greatly reduced. Findings from this study highlight the important intrinsic and extrinsic parameters that need to be optimized for effective pathogen load reduction and viability retention of seeds.