P2-05 Moisture Equilibration and Product Fabrication Methods Affect Measured Thermal Resistance of Salmonella Enteritidis PT30 on/in Whole Almonds, Almond Meal, and Almond Butter

Tuesday, August 2, 2016
America's Center - St. Louis
Pichamon Limcharoenchat, Michigan State University, East Lansing, MI
Michael James, Michigan State University, East Lansing, MI
Nicole Hall, Michigan State University, East Lansing, MI
Bradley Marks, Michigan State University, East Lansing, MI
Introduction: Recent work has suggested that changing the structure of low-moisture food products, with equivalent composition, may affect the thermal resistance of Salmonella in/on those products; however, the underlying effects of sample preparation (equilibration and fabrication) have not been systematically evaluated.

Purpose: The objective was to quantify the effect of product equilibration and fabrication on Salmonella thermal resistance on/in multiple almond products.

Methods: Whole raw almonds were inoculated with Salmonella Enteritidis PT30 (~108 CFU/g) and equilibrated (3-10 days) to 0.25, 0.45, or 0.65 aw (triplicate tests). Inoculated and equilibrated almonds were individually vacuum-packed in plastic bags or fabricated into meal and butter that was loaded into aluminum test cells (~1 g samples). Samples were heated in an isothermal water bath (80°C), pulled at multiple intervals, cooled in an ice bath, diluted in peptone water, and plated on modified trypticase soy agar to enumerate survivors.

Results: Although aw of almonds appeared to reach equilibrium after 3-5 days (by aw meter readings), the moisture content (mc) of the meal and butter fabricated from that product were significantly (P < 0.05) lower or higher than the almond mc for adsorbing (0.65 aw) and desorbing (0.25 aw) conditions, respectively, indicating that full equilibration had not been achieved. However, for 0.25 aw, after 8-10 days of equilibration, the resulting meal and butter were at the same mc as the almonds, but aw was higher (P < 0.05) for meal (0.29) than butter (0.22) and almonds. Subsequently, the D80°Cvalue on whole almonds (19.7 min) was lower (P < 0.05) than in meal (50.8 min) and butter (48.3 min).

Significance: Equilibration state impacted aw changes in fabricated almond products, and product structure may be significantly important when applying inactivation parameters to process validations.