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.