, 2009), and irradiation ( Mexis et al., 2009, Narvaiz et al., 1992 and Prakash et al., 2010). Compared Selleckchem Sunitinib to hydro, thermal, and chemical methods, ionizing radiation has the advantage of retaining the functional quality of nuts. However, radiation efficacy varies among studies due to different sample conditions during treatment. Although low water activity (aw) is one key to controlling microbial growth, it actually presents a significant impediment to microbial inactivation. According to Laroche et al. (2005), the thermal inactivation rates for Saccharomyces cerevisiae and Lactobacillus plantarum are not monotonically dependent on initial aw (0.10–0.70).

Additionally, the effect of aw on thermal resistance of Salmonella Typhimurium varied with solute type (glycerol, sucrose, glucose, or polyethylene glycol) ( O’Donovan-Vaughan and Upton, 1999). Given that the surrounding humidity can alter the surface aw of nuts during processing and storage, it is important to quantify inactivation rates as a function of this critical variable. Therefore, the objectives of this study were to: (1) quantify the relationship between aw and the D10-value for low-energy X-ray inactivation of Salmonella on almonds and walnuts, (2) quantify post-irradiation survival of Salmonella on nuts during storage, and (3) determine the impact of X-ray irradiation on the sensory quality. Shelled

raw whole almonds (Nonpareil) and walnuts (Juglans regia) from the 2009 crop were purchased in a single lot of each from retail sources located in California. Upon acquisition, 200 g of each nut type were vacuum-packaged and stored at 4 °C until testing. PLX-4720 concentration Kernel and bulk density were measured in a graduated cylinder nearly using the platform scale method (AOAC 971.25) ( AOAC, 2000). For moisture content determination, samples were ground using a IDS55 coffee bean grinder (Mr. Coffee, Cleveland, OH) for ~ 30 s, and ~ 2 g (5 replications) was dried in an oven at 102 °C to constant weight (~ 48 h). An FP-200 Nitrogen Analyzer (Leco Corp., St. Joseph, MI: compliance with AOAC 990.03) was used for protein

analysis, and a Soxhlet fat extractor was used according to AOAC 948.22 ( AOAC, 2000) for total fat content. Salmonella Enteriditis PT30 (SE PT30), originally isolated from raw almonds implicated in the 2000 and 2001 outbreaks, was previously obtained from Dr. Linda Harris (University of California — Davis) and preserved at − 80 °C in Tryptic Soy Broth (TSB) (Difco, Becton Dickinson, Sparks, MD) containing 20% glycerol. To compare serovars, three strains of Salmonella Tennessee (S13952, S13972, and S13999) were obtained from the Food Science and Human Nutrition culture collection at Washington State University (Pullman, WS) and preserved under the same condition as SE PT30. The inoculation procedure of Danyluk et al. (Danyluk et al., 2005) was followed with slight modifications.