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Thermal inactivation of Listeria innocua in salmon caviar by RF |
B. A. RASCO1, K. A. Starkweather1, J. Tang2, and B. G. Swanson1. (1) Dept. of Food Science & Human Nutrition, Washington State Univ., PO Box 646376, Pullman, WA 99164-6376, (2) Dept. of Biological Systems Engineering, Washington State Univ., PO Box 646120, Pullman, WA 99164-6120 There are no suitable pasteurization processes for salmon caviar that yield a product with an acceptable texture and high product quality. Important international markets for caviar require products to be pasteurized. The objective of this study was to evaluate RF pasteurization for salmon caviar. Chum salmon caviar (Oncorhynchus keta)(0.5 & 2.5% NaCl)was packaged in 4 oz glass hexagonal jars with metal lug-type closures. Thermal inactivation of Listeria innocua was determined (50 - 60°C). RF (27.12 MHz) and water bath processes were developed. Innoculated pack studies with Listeria innocua were conducted. Experiments were conducted to determine whether a pasteurized product with an aw>0.96 could be produced which would not support the growth of Clostridium sp.. Salmon caviar (0 - 13.7% water phase salt (WPS)) with 0 - 200 ppm sodium nitrite were innoculated with Clostridium sporogenes (PA 3679)@ 5,000 spores/ml; pasteurized (7D), and held for 3 hr at 70°C. Sporulation over a 2 week period at 37°C was determined by MPN. To assess the effect of thermal processing on product quality, the amount of force required to fracture fresh, and thermally treated caviar was determined by texture profile analysis (TPA). A 7D RF process at 60°C for RF processed product was 44.8 min, and for water bath pasteurized product, 88.8 min. Addition of sodium nitrite and high salt (13% WPS) did not inhibit germination of C. sporogenes. By Texture Profile Analysis, the average force required to fracture the sheath of a single caviar egg (2.5% NaCl) was 60 N for RF compared to 15 N for water bath pasteurized caviar suggesting that the RF process has less of an adverse affect on product quality. An RF process (7D) was developed which is significantly shorter than the current industrial processes and provides for an improved product texture. TPA results indicate that the characteristic "pop" of salmon caviar can be retained in an RF pasteurized product.
Session 42, Seafood Technology: Safety, Processing
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