title: Drying and decontamination of raw pistachios with sequential infrared drying, tempering and hot air drying.
abstract: Pistachio nuts have been associated with outbreaks of foodborne disease and the industry has been impacted by numerous product recalls due to contamination with Salmonella enterica. The current hot air drying of pistachios has low energy efficiency and drying rates, and also does not guarantee the microbial safety of products. In the study described herein, dehulled and water-sorted pistachios with a moisture content (MC) of 38.14% (wet basis) were dried in a sequential infrared and hot air (SIRHA) drier to <9% MC. The decontamination efficacy was assessed by inoculating pistachios with Enterococcus faecium, a surrogate of Salmonella enterica used for quality control in the almond industry. Drying with IR alone saved 105min (34.4%) of drying time compared with hot air drying. SIRHA drying of pistachios for 2h with infrared (IR) heat followed by tempering at a product temperature of 70°C for 2h and then by hot air drying shortened the drying time by 40min (9.1%) compared with drying by hot air only. This SIRHA method also reduced the E. faecium cell population by 6.1-logCFU/g kernel and 5.41-logCFU/g shell of pistachios. The free fatty acid contents of SIRHA dried pistachios were on par with that of hot air dried samples. Despite significant differences in peroxide values (PV) of pistachio kernels dried with the SIRHA method compared with hot air drying at 70°C, the PV were within the permissible limit of 5Meq/kg for edible oils. Our findings demonstrate the efficacy of SIRHA drying in achieving simultaneous drying and decontamination of pistachios.
authors.affiliation: Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Chandrasekar
authors.initials: C
authors.lastname: Venkitasamy
authors.affiliation: Produce Safety and Microbiology Research Unit, WRRC, USDA, ARS, 800 Buchanan St., Albany, CA 94710, USA.
authors.forename: Maria T
authors.initials: MT
authors.lastname: Brandl
authors.affiliation: Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; Department of Food Science and Engineering, Northwest University, 229 Taibai N Rd, Beilin, Xi'an, Shaanxi, China.
authors.forename: Bini
authors.initials: B
authors.lastname: Wang
authors.affiliation: Healthy Processed Foods Research Unit, WRRC, USDA, ARS, 800 Buchanan St., Albany, CA 94710, USA.
authors.forename: Tara H
authors.initials: TH
authors.lastname: McHugh
authors.affiliation: Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Ruihong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Biological and Agricultural Engineering, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA; Healthy Processed Foods Research Unit, WRRC, USDA, ARS, 800 Buchanan St., Albany, CA 94710, USA. Electronic address: zlpan@ucdavis.edu.
authors.forename: Zhongli
authors.initials: Z
authors.lastname: Pan
mesh_terms: D003666:Decontamination / Q000379:methods*; D003890:Desiccation / Q000379:methods*; D016984:Enterococcus faecium; D005230:Fatty Acids, Nonesterified / Q000737:chemistry; D006358:Hot Temperature; D007259:Infrared Rays; D027927:Pistacia / Q000382:microbiology*; D010938:Plant Oils / Q000737:chemistry; D019779:Salmonella enterica; D014867:Water
chemical_list: D005230:Fatty Acids, Nonesterified; D010938:Plant Oils; D014867:Water
keywords: Contamination; Foodborne pathogen; Moisture content; Oil; Pistachios; Processing; Sanitization