Evaluation of Enterococcus faecium NRRL B-2354 as a potential surrogate of Salmonella in packaged paprika, white pepper and cumin powder subjected to radio frequency heating

This study aimed to (1) determine the thermal resistance (D and z values) of Salmonella and Enterococcus faecium NRRL B-2354 as a promising surrogate for thermal validation studies using paprika, white pepper, and cumin powders, and (2) determine the efficacy of RF on the inactivation of both microorganisms in packaged samples. Samples of paprika, white pepper, and cumin powders with initial water activity levels () of 0.45 ± 0.05 were inoculated with Salmonella cocktail (S. Typhimurium, S. Agona, S. Montevideo, and S. Tennessee) and E. faecium NRRL B-2354 at approximately 8.5 log CFU/g. Inoculated samples were loaded in the thermal death time (TDT) cells and subjected to isothermal treatment in a water bath at 70, 75 and 80°C. Samples (20 g) were also sealed in small polystyrene petri dishes and subjected to RF heating in a 27.12-MHz, 6-kW pilot scale RF unit with 105 mm electrode gap until the temperature at the geometric center reached 80°C. The survival of both bacteria was enumerated and converted to log CFU per gram. The change in color of RF heated samples was also evaluated to assess the impact of RF heating on the product quality. Results showed that the thermal resistance of E. faecium at inactivation temperatures is higher than Salmonella in all three spices. Both microorganisms had less thermal resistance in paprika than other spices. Thevalues of Salmonella and E. faecium were determined to be 1.21 and 1.82 min in paprika, 2.85 and 5.27 min in white pepper, an...
Source: Food Control - Category: Food Science Source Type: research