Physicochemical, microstructural, and microbial qualities of dehydrated Tuna chunks: Effects of microwave power and drying methods

Abstract

Boneless Tuna chunks were marinated using spices and were dried in a microwave vacuum dryer at different powers (600 W [T1], 650 W [T2], and 700 W [T3]) for 2 hr. Another two batches were prepared by hot air drying (55 ± 5°C) (HAD) and sun drying (SD) to a comparable moisture content obtained by sample T2. The moisture content was 44.69 g/100 g, 39.26 g/100 g, 24.40 g/100 g, 32.80 g/100 g, and 38.45 g/100 g for T1, T2, T3, SD, and HAD, respectively. Increasing microwave power level resulted in reduced moisture content and water activity in dried tuna chunks. Analysis of SEM indicated a tough morphology in SD and HAD whereas a smooth morphology in microwave vacuum dried samples. Results of FTIR analysis indicated higher protein denaturation with an increase in microwave power. Oxidation of lipids increased significantly (p < .05) with microwave power as displayed by higher peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) values in T3 and T2 samples. Microbial spoilage was faster in T1 samples compared to T2 and T3. On the other side, sun-dried and hot air-dried samples have shown poor rehydration and color attributes but better oxidative stability than microwave vacuum dried samples.