HEAT PENETRATION CHARACTERISTICS OF SMOKED TUNA IN OIL AND BRINE IN RETORT POUCHES AT DIFFERENT ROTATIONAL SPEEDS

Abstract

ABSTRACT Yellowfin tuna (Thunnus albacares) steaks were light smoked using coconut husks and packed in indigenously developed retort pouches of size 17 cm × 11 cm, having a configuration of 12.5-µm polyester/12.5-µm aluminum foil/80-µm cast polypropylene. Hot refined sunflower oil and 2% brine solution were used as the filling medium. Processing was done to an Fo value of 10 in an overpressure autoclave with a facility for rotation. Heat penetration characteristics of the product were studied using an Ellab CTF 9008, an Fo-cum-cook value integrator. Different batches of tuna were processed in oil and brine media to an Fo value of 10 at 2, 4, 6 and 8 rpm, and compared the results with that obtained from a stationary retort. Increase in speed of rotation gave a reduction in total process time and a lower cook value. Heat penetration was lowest for the stationary retort and increased with the speed of rotation in both the oil and brine media. Heat penetration was faster in the brine medium for the same rotation speed and stationary retort when compared with that in the oil medium. PRACTICAL APPLICATIONS The study shows that heat penetration was faster in brine- than in oil-packed tuna because of the higher viscosity of the oil, which prevents rapid convection movement within the pouches. Because the retort pouch has a thinner profile than cans, heat penetration is faster during rotation, heat-induced Maillard reaction will be less, and the product will have better sensory attributes and nutritional properties. By rotation, the process time can be reduced, which can save time, fuel and energy and also obtain products with better nutritional value, color, taste and flavor.