Effects of a novel three-step sous-vide cooking and subsequent chilled storage on the microbiota of beef steaks

Abstract

This study aimed to evaluate a novel three-step sous-vide (SV) method on bacterial growth and diversity, and its relationship to product storage life. Vacuum-packed naturally contaminated steaks were sequentially cooked at 39 °C (1 h), 49 °C (1 h), and 59 °C (4 h), then stored at −1.5 and 2 °C for 28 d, with a single-step SV at 59 °C for 4 h for comparison. None of the seven indicator bacteria tested proliferated (P > .05) after incubation at 39 or 49 °C; microbial diversity was also unaffected. Bacterial load was reduced (P < .05) by up to 5 log units with both (P > .05) SV methods. The odour of all steaks remained acceptable on d 28. Unexpectedly, during storage, Pseudomonas, not lactic acid bacteria, dominated the microbiota on steaks cooked by either SV method, likely due to the temperature shift-induced lag phase and/or heat sensitivity of psychrotrophic bacteria. In conclusion, the three-step SV did not lead to bacterial proliferation or compromise the storage life of cooked products.