Long-term kinetics of Salmonella Typhimurium ATCC 14028 survival on peanuts and peanut confectionery products

Due to recent large outbreaks, peanuts have been considered a product of potential risk for Salmonella. Usually, peanut products show a low water activity (a(w)) and high fat content, which contribute to increasing the thermal resistance and survival of Salmonella. This study evaluated the long-term kinetics of Salmonella survival on different peanut products under storage at 28 degrees C for 420 days. Samples of raw in-shell peanuts (a(w) = 0.29), roasted peanuts (a(w) = 0.39), unblanched peanut kernel (a(w) = 0.54), peanut brittle (a(w) = 0.30), pacoca (a(w) = 0.40) and pe-de-moca (a(w) = 0.68) were inoculated with Salmonella Typhimurium ATCC 14028 at two inoculum levels (3 and 6 log cfu/g). The Salmonella behavior was influenced (p<0.05) by a(w), lipid, carbohydrate and protein content. In most cases for both inoculum levels, the greatest reductions were seen after the first two weeks of storage, followed by a slower decline phase. The lowest reductions were verified in pacoca and roasted peanuts, with counts of 1.01 and 0.87 log cfu/g at low inoculum level and 2.53 and 3.82 log cfu/g at high inoculum level at the end of the storage time. The highest loss of viability was observed in pe-de-moca, with absence of Salmonella in 10-g after 180 days at low inoculum level. The Weibull model provided a suitable fit to the data (R-2 >= 0.81), with delta value ranging from 0.06 to 49.75 days. Therefore, the results demonstrated that Salmonella survives longer in peanut products, beyond the shelf life (>420 days), especially in products with aw around 0.40.