Characterization of ohmic heating and sous-vide treatment of scallops: Analysis of electrical conductivity and the effect of thermal protein denaturation on quality attribute changes

A 20 kHz ohmic heating (OH) and two sous-vide (SV) treatments of scallop muscles were characterized, and their effects on thermal protein denaturation (TPD) and quality attribute changes were evaluated. TPD was analyzed by differential scanning calorimetry and estimated by kinetic analysis for several thermal schedules with a dynamic method. The OH process was evaluated by analyzing the electrical conductivities (ECs) between the frequencies of 50 Hz and 20 kHz, temperatures from −20 °C to 65 °C, and effects of parallel and series current directions. The increase of frequency and temperature caused a drop in the resistance of scallop muscles and an increase in the heating rate. Thereby, the process time decreased. OH obtained a lower quality attribute change in scallops in comparison with SV, owing to higher water retention within the muscle. OH significantly reduced the time of exposure to high temperatures, which in turn reduced the degree of actin denaturation. The application of OH as an alternative to the sous-vide (SV) technique for scallop muscles has been explored assuming that OH could benefit the processed samples by providing better temperature uniformity and a reduction in the processing time, which avoids unnecessary damage to quality attributes. In this study, these assumptions were confirmed with a higher retention of quality attributes in scallops, where OH > novel SV > traditional SV. These results have the potential to promote the utilization of OH systems in central kitchens, gourmet restaurants, and catering instead of SV treatments based not only on the improved quality of the processed foods but also by a considerable reduction in the processing time and probably energy consumed. However, for the application of any of the two treatments, first they should be validated for product safety. The employed TPD approach, can also be used for the analysis of other thermal treatments, allowing the evaluation of the changes in quality attributes within the temperature range of protein denaturation.