Microwave vacuum dried mackerel: Physico chemical qualities and evaluation of essential oils in inhibition of lipid oxidation

Abstract

Microwave vacuum drying is an emerging technology for drying food products. In the present study, Indian mackerel was dried in microwave vacuum drier and compared its physico chemical quality to mackerel dried in hot air oven. Effect of thyme and rosemary essential oils on inhibiting lipid oxidation during drying process was also evaluated. Brine salted mackerel was given dip treatment in 0.75 per cent thyme and clove leaf oil and dried in hot air oven and microwave vacuum drier . Control samples were also prepared by replacing essential oil solution with potable water. Moisture content of microwave vacuum dried and hot air dried samples was reduced to 30-32 per cent in 1.2 h and 12 h, respectively. Color and appearance of uncooked MVD sample was superior to that of HAD samples. Rehydration ability and water absorption index of MVD samples were slightly higher to that of HAD samples. HAD sample had more salt soluble and water soluble protein nitrogen fraction than MVD sample. Higher instrumental hardness values were observed for HAD samples. However, lipid oxidation was slightly higher in MVD samples compared to HAD samples with control having the higher TBARS and PV indices than essential oil treated samples. As per the results of PV and TBARS, thyme oil exhibited better antioxidant effect compared to clove leaf oil. The study demonstrated that fast drying can be achieved by microwave vacuum dryer and it can produce dried fish having better sensory and comparable physicochemical characteristics to that of conventionally dried products.