Heat penetration characteristics and quality changes of Indian mackerel canned in brine at different retort temperatures

Abstract

Indian mackerel (Rastrelliger kanagurta) was processed in brine in indigenous polymer-coated tin-free steel cans to a common lethality value of 8 min at three different retort temperatures, namely 115, 121 and 130C. All the three batches were found to be commercially sterile upon testing using sodium thioglycollate broth. The heat penetration parameters were found to be significantly influenced by the retort temperature. The lag factor of heating (jh value) decreased, whereas the lag factor of cooling (jc value) increased with increase of retort temperature (P < 0.05). The heating rate index (fh value) showed a decreasing trend with increase of retort temperature. The total process time (TPT) taken to attain the targeted lethality decreased with increase in retort temperature. At 115, 121 and 130C, the targeted lethality value could be attained in 60, 33 and 15 min, respectively. Thermal processing mackerel at 121 and 130C helped in reducing the TPT by 45 and 75% as compared to those processed at 115C. Cook value (CV) maintained an inverse relationship with retort temperature. At 121 and 130C, the CV recorded was 36 and 55% lower than at 115C. CV to F0value ratios at 115, 121 and 130C were 15.25, 9.75 and 6.88, respectively. Mackerel samples processed at three retort temperatures were analyzed for their sensory qualities employing subjective and objective methods. Statistical analysis indicated the significance of retort temperature on the color and texture profile attributes, and the sensoryqualities of mackerel (P < 0.05). Analysis of Commission Internationale d’Eclairage lab values show that the L*value increased, while the a*value decreased with increase of retort temperature. The b*value did not show much difference with retort temperature. Instrumental analysis of texture showed that texture profile attributes and Warner–Bratzler shear force of mackerel muscle reduced with precooking and subsequent thermal processing. Among the thermally processed samples, better textural attributes were associated with samples processed at higher temperature. Sensory analysis revealed that all the sensory attributes except flavor are significantly affected by the retort temperature (P < 0.05).