Effect of acid adaptation on inactivation of Salmonella during drying and storage of beef jerky treated with marinades

Abstract

This study evaluated the influence of pre-drying marinade treatments on inactivation of acid-adapted or nonadapted Salmonella on beef jerky during preparation, drying and storage. The inoculated (five-strain composite, 6.0 log CFU/cm 2) slices were subjected to the following marinades (24 h, 4 °C) prior to drying at 60 °C for 10 h and aerobic storage at 25 °C for 60 days: (1) no marinade, control (C), (2) traditional marinade (TM), (3) double amount of TM modified with added 1.2% sodium lactate, 9% acetic acid, and 68% soy sauce with 5% ethanol (MM), (4) dipping into 5% acetic acid and then TM (AATM), and (5) dipping into 1% Tween 20 and then into 5% acetic acid, followed by TM (TWTM). Bacterial survivors were determined on tryptic soy agar with 0.1% pyruvate and xylose–lysine–tergitol 4 (XLT4) agar. Results indicated that drying reduced bacterial populations in the order of pre-drying treatments TWTM (4.8–6.0 log CFU/cm 2)≥AATM≥MM>TM≥C (2.6–5.0 log CFU/cm 2). Nonadapted Salmonella were significantly ( P<0.05) more resistant to inactivation during drying than acid-adapted Salmonella in all treatments. Bacterial populations decreased below the detection limit (−0.4 log CFU/cm 2) as early as 7 h during drying or remained detectable even after 60 days of storage, depending on acid adaptation, pre-drying treatment, and agar media. The results indicated that acid adaptation may not cause increased resistance of Salmonella to the microbial hurdles involved in jerky processing and that use of modified marinades in manufacturing jerky may improve the effectiveness of drying in inactivating Salmonella.