Thermal Inactivation of Salmonella in Pâté Made from Chicken Liver

Abstract

ABSTRACT The effect of heating times and temperatures on inactivation of Salmonella in pâté made from chicken liver was evaluated. Raw chicken liver (ca. 1 kg) was blended in a food processor with two hard-boiled eggs (ca. 100 g total) plus a mixture of sautéed white onions (100 g), salt (5.0 g), black pepper (2.5 g), and butter (112 g). The tempered (ca. 15°C) raw pâté batter was inoculated with a nine-strain cocktail (ca. 6.5 log CFU/g) of Salmonella, and then ca. 25-g portions were aseptically transferred into sterile 50-mL polypropylene conical tubes. One set of tubes was completely submerged in a thermostatically controlled, circulating water bath set at 74.9°C and cooked to target instantaneous internal temperatures ranging from 60 to 73.9°C. An otherwise similar set of tubes was cooked at 60 to 73.9°C, with holding times of 3 to 30 min, in a water bath set at 1°C above each target endpoint cooking temperature. Regardless of the cooking process, when pâté was cooked to a target instantaneous internal temperature of 60 to 73.9°C, pathogen numbers decreased by ca. 1.9 to ≥6.4 log CFU/g; additional reductions of ca. 0.6 to 1.3 log CFU/g were observed when pâté was cooked to a target instantaneous internal temperature of 60 to 68°C and then held for 3 to 30 min. In related experiments, pâté was prepared as described above, but with inoculated chicken livers (500 g; ca. 5.5 log CFU/g) that were cooked in a frying pan maintained at ca. 140°C for 3 to 8 min with a mixture of sautéed onions, salt, black pepper, and butter and then blended with a hard-boiled egg. Pathogen numbers within liver cooked in a frying pan decreased by ca. 1.0 to 4.9 log CFU/g. Collectively, these findings may be useful for establishing cooking guidelines for pâté and thus for lowering the risk of illness if chicken liver is contaminated with Salmonella and the attendant batter is not handled or cooked properly. HIGHLIGHTS