Utilizing acidic sprays for eliminating Salmonella enterica on raw almonds

In-shell or shelled almonds inoculated with Salmonella were sprayed with water, acetic acid, citric acid, acidified sodium chlorite, peroxyacetic acid, or a mixture of citric, hydrochloric, and phosphoric acids before testing for Salmonella on xylose-lysine-deoxycholate (XLD) agar and tryptic soy agar (TSA). Spraying acids on in-shell almonds reduced about 0.48 to 1.88 and 0.22 to 0.67 log colony-forming units (CFU)/g of Salmonella on XLD agar and TSA counts, respectively, on the in-shell almonds but had no effect on the edible portion of the almonds (shelled almonds). When spraying acids on shelled almonds, a single spray application (1.6 mL acid solution/25 g of shelled almonds) with 1 min holding caused 0.72 to 1.93 and 0.38 to 1.35 log CFU/ g reductions of Salmonella counts on XLD agar and TSA, respectively. Increasing the holding time to 5 min did not enhance the reductions. When spraying shelled almonds, increasing the number of application (1 to 3 times) enhanced Salmonella reduction. Except for the peroxyacetic acids, increasing total holding time (5 to 120 min) improved the efficacies. Furthermore, increasing acid concentrations improved the efficacies of acetic, citric, and peroxyacetic acid treatments. Estimated 5-log reductions on both TSA and XLD counts can be achieved under laboratory conditions using 10% citric acid by (1) the combination of shelling, 1 spraying, and 3 d of storage, (2) the combination of shelling, 2 sprayings, and 1 d of storage, or (3) the combination of shelling and 3 sprayings. Acidic sprays may be utilized for enhancing the microbiological safety of raw nuts.