Effectiveness of Superheated Steam and Gas Catalytic Infrared Heat Treatments to Inactivate Salmonella on Raw Almonds Md. Latiful Bari, 1 Daisuke Nei, 1 Itaru Sotome, 1 Ikuo Y. Nishina, 2 Fumiyo Hayakawa, 1 Seiichi Isobe, 1 and Shinnichi Kawamoto 1 Abstract The majority of the almond-related outbreaks have been associated with Salmonella. Therefore, it is necessary to find an effective method to inactivate these organisms on the raw almond before distribution in the market. This study was conducted to assess the effectiveness of superheated steam (SHS) treatments followed by catalytic infrared (IR) heat treatment to inactivate Salmonella populations on raw almond and to determine the effect of these treatments on the quality of raw almond. It has been found that SHS treatment for 70 seconds followed by catalytic IR heat treatment for 70 seconds was able to reduce 5.73  0.11 log CFU=g Salmonella population, and no survivors were found in the enrichment medium. The overall visual quality parameters of both treated and nontreated almonds were found within the acceptable limit. Therefore, SHS treatments for 70 seconds followed by catalytic IR heat treatment for 70 seconds could be an effective decontamination method for raw almonds. Introduction R ecent outbreaks of salmonellosis in raw almonds have shown that even low moisture levels will not completely protect a product from contamination with food- borne pathogens. The outbreaks of 2000–2001 and 2003–2004 of Salmonella Enteriditis related to raw almonds resulted in considerable concern for the industry and regulators. Since then, Salmonella Enteriditis PT30 has been found in almond production orchards and in almonds leaving the huller= sheller (Uesugi et al., 2007), which lead to a mandatory pas- teurization program effective from September 1, 2007, that can achieve a 4-log reduction of Salmonella in almonds (Al- mond Board of California, 2009). Therefore, there is a great interest in developing new technologies that can improve the microbial safety of almonds without compromising their quality as a raw product. Many researches have been done to eliminate Salmonella from the almond surface, including propylene oxide treat- ment (Danyluk et al., 2005), various heat processes involving steam (Lee et al., 2006) and infrared (IR) heat ( Mata-Protuguez et al., 2002; Ingemanson, 2005; Brandl et al., 2008), ionizing radiation (Prakash et al., 2009), electrolyzed water along with IR heating (Bari et al., 2009), chlorine dioxide (Wihodo et al., 2005), and citric acid spray (Pao et al., 2006). However, to date, Food and Drug Administration has approved oil roasting, dry roasting, blanching, steam processing, and propylene oxide processes as acceptable forms of pasteurization for almonds (Almond Board of California, 2009). Superheated steam (SHS) pasteurization is an emerging technology that has the potential to replace commonly used heat treatment. SHS has various advantages over other heat- ing system, including high heat transfer rate due to conden- sation and gas radiation, accelerated drying rate, and an oxygen-free environment. During SHS heating of food mate- rials, condensation followed by evaporation of moisture on the materials was observed and this reverse process of mois- ture transfer produced characteristic food-processing prop- erty of SHS (Konishi et al., 2004; Iyota et al., 2005). A new oven system has been developed using SHS containing micro droplets of hot water for wide application of this technology. In this system, mixture of SHS and hot water has been achieved by spraying pressurized boiling water. A number of products have been processed with SHS, including Asian noodles (Markowski et al., 2003), brewers’ spent grain and distillers’ spent grain (Tang et al., 2005), sugar-beet pulp (Tang et al., 2000), potato (Sotome et al., 2009), potato chips (Caixeta et al., 2002), lumber (Woods et al., 1994), wood pulp and paper (Douglas, 1994), coal (Potter and Beeby, 1994), and sludge (Franics and Di Bella, 1996). Brandl et al. (2008) reported that substantial reduction of Salmonella population occurred with IR heating. Therefore, in 1 National Food Research Institute, Tsukuba, Japan. 2 Satake USA Inc., Stafford, Texas. FOODBORNE PATHOGENS AND DISEASE Volume 7, Number 7, 2010 ª Mary Ann Liebert, Inc. DOI: 10.1089=fpd.2009.0500 845