Synergistic decontamination of Salmonella spp. in raw almonds using phytic acid and drying as an eco-friendly alternative to propylene oxide

초록

Multistate Salmonella outbreaks involving raw almonds have led to U.S. FDA regulations requiring a minimum 4-log reduction in Salmonella during manufacturing processes. While propylene oxide fumigation is a common industrial pasteurization method, given the growing public concern about the use of synthetic chemicals, alternative methods with significant efficacy and minimal quality deterioration are needed. This study aimed to develop eco-friendly decontamination technology for raw almonds that includes natural-borne substance treatment and drying. The bactericidal effects of phytic acid (1, 2, 3 % (v/w)) and/or drying (6, 8 h at 75 °C) were investigated on Salmonella spp. (S. Enteritidis ATCC 13076, S. Enteritidis PT30, and S. Typhimurium DT104; ca. 3–4 or 6–7 log), which were artificially inoculated in raw almonds at moderate (ca. 3–4 log) or high (ca. 6–7 log) inoculum levels. Additionally, an enrichment test was conducted to validate the recovery of injured cells after treatment. The physicochemical, textural, and sensory attributes (color, pH, water activity, hardness; appearance, color, odor) of untreated/treated almonds were further analyzed. All individual treatments of 1–3 % phytic acid or 6–8 h of drying resulted in low antibacterial efficacies (< 1.0 log reduction from high inoculum and <2.1 log reduction from moderate inoculum; P < 0.05). For the high inoculum, 3 % phytic acid treatment followed by 8 h of drying achieved a >6.2 log reduction in Salmonella spp. in raw almonds (P < 0.05), and most of the injured bacterial cells (83.3 %) showed no recovery after enrichment. The equivalent treatment of almonds at a moderate inoculum level completely eliminated Salmonella spp. (> 3.1 log reduction; P < 0.05) without recovery. Moreover, the panelists indicated no significant differences (P > 0.05) in the tested sensory attributes (appearance, color, and odor) between the optimal treatment and the control, although some physicochemical properties were slightly affected. The results of this study suggest a novel decontamination method using a natural-borne substance that exerts a synergistic effect with drying against Salmonella spp. in raw almonds and ensures minimal deterioration in food quality. The developed method is expected to replace synthetic chemical decontamination methods in nuts and other low-moisture food industries. © 2024

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