Determination of effects of ohmic heating process on fish paté quality parameters

In this study, quality changes in fridge conditions were investigated after ohmic and traditional heating of pate produced from smoked rainbow trout (Oncorhynchus mykiss, Walbaum, 1792). Ohmic heating was performed under 50 Hz operating frequency and 5 V/cm voltage gradient conditions, while traditional heating was carried out by placing the glass jar packed products in a water bath at a temperature of 98±1°C. Both heating operations were stopped when the product cold spot temperature were reached 78°C. Later on, the fish pate was packaged and stored at 4±1°C up to the end of the shelf life. During storage, quality characteristics of the pates were periodically checked by physical, chemical, microbiological and sensory analysis. Technological aspects of the two methods used for heating of the pate were also evaluated. During storage, TVB-N values of ohmic heated pates were changed between 12.19-20.58 mg/100g and TBA values of ohmic heated pates were changed between 0.60-1.07 mg malondialdehyde/kg, while TVB-N values of traditional heated pates were changed between 15.90-22.60 mg/100g and TBA values of traditional heated pates were changed between 0.65-1.55 mg malondialdehyde/kg. It was determined that TVB-N and TBA values showed statistically significant differences (p<0.05) depending on storage time and heating method. The L*, a* and b* values of pate before heat treatment were determined as 69.90±0.06, 3.69±0.06 and 21.34±0.06 respectively. It was determined that L* and a* values increased after heat treatment and b* values changed between 20.89-21.36. The total bacterial counts (TBS) of the pates after ohmic and conventional heating were determined as 2.28±0.02 and 2.32±0.02 log cfu/g respectively, and the total yeast-mold counts (TMK) were determined as 2.14±0.06 and 2.28±0.02 log cfu/g respectively. It was determined that there was no statistically significant difference (p>0.05) between TBS and TMK of the pates after ohmic and conventional heating. It was determined that the sensory properties of the ohmic heated pates were more appreciated and the loss of sensory properties of ohmic heated pates were occurred rapidly during storage. Ohmic heated pate samples on the 20th day of storage and conventional heated pate samples on the 32th day of storage, were determined as inconsumable in terms of sensory properties. During ohmic heating, the electrical conductivity of the fish pates ranged from 0.97 to 2.02 S/m. While fish pates were reached at 78°C in 1172.5±83.5 sec by conventional heating, 497±23 sec was sufficient for ohmic heating. At the end of the heat treatment, the efficiency of heating systems was determined % 89.89 for ohmic heating and % 9.25 for conventional heating. The ohmic heating system saved energy by reducing % 90 of consumed energy per unit compared to the conventional heating system.