Ohmic Heating under Vacuum Integrated with Vacuum Cooling: Pre-cooking and Cooling Beef Meatballs

Abstract In this study, an ohmic heating pre-cooking (OHPC) process under vacuum integrated with a subsequent vacuum cooling (VC) was designed for pre-cooking and cooling meatballs. OHPC was conducted at three different voltage gradients (10, 15, and 20 V/cm) under atmospheric pressure or vacuum (600 mbar). Conventional pre-cooking (CPC) was performed in a convection oven. All beef meatballs were subjected to VC at 10 ± 2 mbar immediately after pre-cooking. This study is the first to innovate a system that combines direct ohmic heating under vacuum conditions with VC, investigating its effect on the quality properties of beef meatballs. Initially, the fat and salt contents of meatballs were optimized to achieve maximum electrical conductivity (EC) during ohmic heating. The effect of the integrated process on some quality and process parameters including physicochemical, textural, sensory, and microbiological properties of beef meatballs with optimum fat and salt contents were determined. The maximum effective EC of meatballs was 0.706 S/m at the optimum fat (12.20%) and salt contents (1.85%). OHPC (the highest value of 3.1 min) resulted in shorter pre-cooking time than CPC (11.8 min) ( p < 0.05). Under various OHPC conditions, cooking loss varied from 8.40 to 15.67%, which were significantly lower than those of CPC (22.13%) ( p < 0.05). Throughout the cold storage of meatballs, OHPC under vacuum exhibited a significant reduction in total mesophilic aerobic bacteria (TMAB) counts ( p < 0.05). Compared to CPC, OHPC achieved over 90% energy savings based on total energy consumption ( p < 0.05). The sensory juiciness scores of meatballs pre-cooked using OHPC under vacuum (7.41–7.89) were significantly higher than those pre-cooked using CPC (6.20) ( p < 0.05). These results suggested that integrating the OHPC process under vacuum with VC holds significant industrial potential for the pre-cooking of meatballs.