Pre-cooking of meatballs by ohmic heating under vacuum and vacuum cooling

In this thesis, an ohmic heating pre-cooking (OHPC) process under vacuum integrated with a subsequent vacuum cooling was designed for meatballs, fat and salt contents of meatballs were optimized for the highest electrical conductivities during ohmic heating. Finally, the effect of the integrated process on some quality and process parameters of meatballs produced from chicken and beef with optimum fat and salt contents was determined. Optimum fat and salt contents for the maximum conductivities of both chicken (0.253 S/m) and beef meatballs (0.706 S/m) were 12.20 and 1.85%, respectively. Conventional pre-cooking (CPC) method was carried out in a convection oven, whereas OHPC was under atmospheric pressure and vacuum (600 mbar) at three different voltage gradients (10, 15 and 20 V/cm). Subsequently, meatballs were subjected to vacuum cooling process. In terms of pre-cooking times, a statistically significant difference was observed between CPC (17.7 and 11.8 min for chicken and beef meatballs, respectively) and OHPC (the highest values were 4.8 and 3.1 min, respectively) (p<0.05). In OHPC under different conditions, cooking loss values ranged from 0.83-5.65% for chicken and 8.40-15.67% for beef meatballs, which were significantly lower compared to CPC (11.05 and 22.13%, respectively) (p<0.05). In cold storage of chicken meatballs, except on the 21st day, TBARS values decreased in OHPC under vacuum compared to that under atmospheric pressure (p<0.05). The total color difference (ΔE*) values of chicken meatballs were significantly higher in CPC at different cold storage days (+4°C). In chicken meatballs, instrumental hardness values of OHPC under vacuum (51.75-126.58 N) were decreased compared to atmospheric conditions (77.23-158.75 N) (p<0.05). During frozen (-18°C) storage of beef meatballs, a significant decrease in total mesophilic aerobic bacteria counts were observed in OHPC under vacuum (p<0.05). Compared to CPC, OHPC resulted in energy savings of over 90% according to total energy consumptions (p<0.05). Sensory juiciness values (7.41-7.89) of meatballs pre-cooked by OHPC under vacuum were higher than those by atmospheric pressure (6.65-7.09). Results indicated that the integration of the OHPC process under vacuum followed by vacuum cooling might have a significant potential for the pre-cooking of meatballs.