P1-82 Comparing the Effect of Product Structure on Thermal Resistance of Salmonella Enteritidis PT30 on/in Almond and Wheat Products

Sunday, July 26, 2015
Exhibit Hall (Oregon Convention Center)
Pichamon Limcharoenchat, Michigan State University, East Lansing, MI
Bradley Marks, Michigan State University, East Lansing, MI
Elliot Ryser, Michigan State University, East Lansing, MI
Michael James, Michigan State University, East Lansing, MI
Nicole Hall, Michigan State University, East Lansing, MI
Introduction: Low-moisture pasteurization processes must be validated to ensure efficacy. Although product characteristics are known to affect Salmonella thermal resistance, the impact of product structure is not well known or reported.

Purpose: The objective was to quantify the effect of structure on thermal resistance of Salmonella Enteritidis PT30 on/in multiple almond and wheat products.

Methods: Raw almonds, surface-damaged almonds, blanched almonds, and whole wheat kernels were surface-inoculated with Salmonella Enteritidis PT30 (~108 CFU/g). Almond meal, almond butter, wheat meal, and wheat flour were fabricated by grinding the same raw almonds or wheat kernels in a food processor, and inoculated with the same Salmonella (~108 CFU/g). All inoculated products were equilibrated to ~0.4 water activity (aw) in controlled-humidity chambers. The inoculated whole almond and wheat kernels (vacuum-packaged in thin layer plastic bags) and fabricated samples (in aluminum test cells, sample thickness < 1 mm) were heated (in triplicate) in an isothermal water bath (80°C),  pulled at multiple intervals, cooled in an ice bath, diluted in peptone water, and plated on modified tryptic soy agar to enumerate survivors.

Results: Salmonella thermal resistance (D80°C) was greater (P < 0.05) on/in all the almond products than on/in the wheat products. The D80°C values on raw, damaged, and blanched almonds were statistically equivalent, but significantly less (P < 0.05) than in almond meal and butter of equivalent composition. Moreover, the D80°C value in wheat meal was significantly higher (P < 0.05) than on/in whole wheat surface and flour.

Significance: Product structure can affect Salmonella thermal resistance; however, that effect differs by product. The high oil content in the almond products may have caused the difference, as compared to the wheat products.  In either case, knowledge of structure effects on thermal resistance is important to ensure accurate validation of pathogen intervention processes.