Peanut and tree nut butters have been implicated in Salmonella outbreaks in recent years. Previous studies investigated efficacy of thermal treatments to reduce Salmonella in multiple peanut butter formulations; however, evidence is lacking to support thermal treatment of tree nut butters. This study evaluated thermal treatments to reduce Salmonella in commercial nut butter formulations in final package. Formulations (n 5 6) were inoculated with a Salmonella cocktail and packaged in glass jars before thermal treatment (boiling waterbath, holding times: 0-90 min, >90 8C). Salmonella survivors were enumerated using standard dilution and plating on Hektoen Enteric Agar (37 8C, 24-48 hr). Low levels of survivors (<1 CFU/g) were quantified using a one-tube most probable number technique. Thermal treatments at >90 8C with a 30-min hold time effectively reduced >5 log CFU/g of Salmonella in tree nut formulations; however, holding times >60 min were required to achieve similar reductions in peanut butter. Practical applicationsThis study was designed to provide evidence to support a reconditioning proposal for the processing of tree nut butters that were linked to an outbreak of Salmonella Paratyphi L(1)tartrate(1).There were no previous reports in the scientific literature to demonstrate the efficacy of thermal treatment to inactivate Salmonella spp. in tree nut butters, including nut butters with more complex formulations. Ideally, reconditioning of contaminated product would not require repackaging of the products; therefore, this study was designed to determine treatment parameters that could be easily achieved with the product remaining in its original packaging. This report supports thermal treatment as an option for reconditioning contaminated tree nut butter products using a thermal process that is less intense than what would be necessary to reduce Salmonella spp. in peanut butter products. spreads, and pastes using conventional thermal inactivation study approaches (He et al., 2013;He, Guo, Yang, Tortorello, & Zhang, 2011;Keller et al., 2012;Li, Huang, & Chen, 2014;Shachar & Yaron, 2006). Time and temperature were consistently verified as critical parameters; however, heat resistance of Salmonella spp. was significantly influenced by product formulation (He et al., 2011;Kataoka et al., 2014;Li et al., 2014;Ma et al., 2009;Shachar & Yaron, 2006). Reduced fat formulations with increased carbohydrate content required significantly longer treatment times (15-45 min) at 90 8C to achieve a 5-log reduction of Salmonella spp. compared to standard formulations (10-25 min) (He et al., 2011;Li et al., 2014). Given the variability in thermal resistance of Salmonella spp. in different peanut butter product formulations and the diversity of commercial nut butter products in the marketplace, there is a lack of evidence to critically evaluate processing or reconditioning proposals for products other than basic peanut butter formulations. | I NTR OD U CTI ONIndustrial application of thermal processing is further compli...

The U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) guidance encourages jerky processors to use a single lethality step that will achieve a 5-log reduction of Salmonella. Many processors rely on internal temperature-time combinations recommended in this guidance. However, the efficacy of convective heating is highly dependent on relative humidity (RH). RH recommendations are vague because of variability in processing conditions and limited available data. This study was conducted to establish processing conditions for an entry-level commercial dehydrator (Harvest Saver R5A) to achieve a 5-log reduction of Salmonella. Unseasoned, unmarinated top round beef strips (65 mm thick) were inoculated with Salmonella (>7 log CFU/g) and processed with the chamber temperature set to 82.2°C for a total cook time of 60 min with the intake closed (closed oven). Modifications (product load and fan speed) were made in subsequent trials to improve lethality. After incubation at 37°C for 24 to 48 h, surviving Salmonella populations were enumerated on tryptic soy agar. In trial A, the maximum fan speed (2.5 m/s) with 30 kg of product resulted in 45 to 48.5% RH at 60 min, and a 5-log reduction of Salmonella was achieved in only 35.5% of the meat samples (54 of 152 samples). Increasing the product load by 40% (42 kg; trial B) increased RH in the chamber (57 to 85%) and resulted in improved lethality; a 5-log reduction was achieved in 95.0% of samples (131 of 138 samples). Because samples with reduced lethality were located on the windward side of the chamber, the fan speed was reduced (0.9 m/s; trial C1) to increase the RH, resulting in a 5-log reduction in 100% of the samples (138 of 138 samples). A replicate trial (trial C2) was conducted, and a 5-log reduction again was achieved in 100% of the samples. All trials exceeded recommendations by the FSIS; however, adequate Salmonella reduction was achieved only when the RH was >65% throughout. Product load and fan speed are practical parameters for processors to manipulate to increase the RH in closed systems and thus improve Salmonella lethality.