Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2008
Publication Date: 5/16/2008
Citation: Brandl, M., Pan, Z., Huynh, S., Zhu, Y., Mc Hugh, T.H. 2008. Reduction of Salmonella Enteritidis Population Sizes on Almond Kernels with Infrared Heat. Journal of Food Protection. 71(5)-897-902
Interpretive Summary: Food-borne illness caused by Salmonella enterica has been linked traditionally to raw almonds. We have investigated the efficacy of infrared (IR) heating for decontamination of raw almonds. Raw almond kernels were treated with infrared heat under various conditions of time and temperature. Our results demonstrate that short time exposures of kernels to infrared heat combined with holding at warm temperature for 60 min effected over 7.5-log10 kill of Salmonella Enteritidis on kernels inoculated in the laboratory. In addition, the kernels retained their macroscopic quality of color, skin integrity, and meat texture. Our study reveals that IR heating is an effective dry nonchemical pasteurization process for raw almonds.
Technical Abstract: Catalytic infrared (IR) heating was investigated to determine its effect on Salmonella enterica serovar Enteritidis population sizes on raw almond kernels. Using a double-sided catalytic infrared heating system, a radiation intensity of 5458 W/m2 caused a fast temperature increase at the kernel surface and minimal temperature differences between the top and bottom kernel surfaces. Exposure of dry kernels to IR heat for 30, 35 and 45 sec resulted in maximum kernel surface temperatures of 90, 102, and 113ºC, and when followed by immediate cooling at room temperature, yielded a 0.63-, 1.03-, and 1.51-log10 reduction in S. enterica population sizes, respectively. The most efficacious decontamination treatment consisted of IR exposure followed by holding of the kernels at warm temperature for 60 min and effected a greater than 7.5-log10 reduction in S. enterica on the kernels. During that treatment, the kernel surface temperature rose to 109ºC and gradually decreased to 85ºC. Similar IR and holding treatments with lower maximum kernel surface temperatures of 104ºC and 100ºC yielded reductions of 5.3-log10 and 4.2-log10 cfu/g kernel, respectively. During these treatments, moisture loss from the kernels was minimal and did not exceed 1.06%. Macroscopic observations suggested that kernel quality was not compromised by the IR-holding combination treatment, as skin morphology, meat texture and kernel color were indistinguishable from those of untreated kernels. Our studies indicate that IR heating technology is an effective dry pasteurization for raw almonds.