Enhancement of water removing and the quality of fried purple-fleshed sweet potato in the vacuum frying by combined power ultrasound and microwave technology

Abstract

The combination of ultrasound and microwave in vacuum frying system was investigated to achieve higher drying efficiency and quality attributes of fried products. Purple-fleshed potato were used as test specimen and different power levels of microwave (0 W, 600 W, 800 W) and ultrasound (0 W, 300 W, 600 W) during vacuum frying. Drying kinetics, dielectric properties, moisture state variation and quality attributes of fried samples were measured in a vacuum frying (VF), and an innovatively designed ultrasound and microwave assisted vacuum frying (USMVF) equipment. The USMVF process markedly increased the moisture evaporation rate and effective moisture diffusivity compared to VF process. The oil uptake was reduced by about 16-34%, the water activity and the shrinkage was lowered, the texture (crispness) and the color of fried samples were greatly improved. The higher ultrasound and microwave power level in USMVF made a greater improvement. The total anthocyanin levels and retention of fried purple-fleshed potato chips was the highest (123.52 mg/100 g solids and 79.51% retention, respectively) among all treatments in US600M800VF process. The SEM analysis revealed a more porous and disruption microstructure in USMVF sample.

The synergistic effect of ultrasound and microwave on the physical, chemical, textural, and microstructural properties of vacuum fried Chinese yam ( Dioscorea polystachya )

“…Moreover, the ultrasound was reported to increase the heat transfer rate during frying because of micro‐vibrational effect and microstreaming effect (Kadam, Tiwari, & O'Donnell, ). Therefore, the frying process was accelerated at constant microwave power when ultrasound power was increased from 300 to 600 W. This result was in accordance with earlier work of combined ultrasound and microwave vacuum frying of purple‐fleshed chips (Su, Zhang, Bhandari, et al, ). This result can also be explained from the SEM analysis as shown in Figure .…”

“…The oil content was found to decrease (40.29%) significantly ( p < 0.05) from 17.67% to 10.55% when ultrasound and microwave powers were increased from 300 to 600 and 1,800 to 3,000 W, respectively. Similar results were reported in a study of application of ultrasound and microwave in vacuum frying of purple‐fleshed sweet potato (Su, Zhang, Bhandari, et al, ). Quan et al () also observed similar effect of microwave on French fries with lower oil content.…”

“…From Figure a,b, when the ultrasound power was kept constant and microwave power was increased from 1,800 to 3,000 W, the moisture removal rate was significantly ( p < 0.05) increased. It was reported that heat penetration and heat transfer was increased by microwave in vacuum frying of potato (Su et al, ) and purple‐fleshed sweet potato (Su, Zhang, Bhandari, et al, ). It could be deduced from the results that when the ultrasound power was increased from 300 to 600 W, the frying time was found to reduce due to faster removal of moisture.…”

“…Su, Zhang, Zhang, Liu, and Adhikari () studied the effect of ultrasound–microwave‐assisted vacuum frying of potato chips at different temperature of frying. Moreover, Su, Zhang, Bhandari, and Zhang () studied the enhancement of drying and quality parameters of purple‐fleshed sweet potato during vacuum frying using ultrasound and microwave as energy sources. Similarly, Devi, Zhang, and Law () reported the quality of mushroom chips and Islam, Zhang, and Fan () studied drying kinetics and physical properties of edamame, whereas Faruq, Zhang, and Fan () studied the modeling and dielectric properties of ultrasound microwave combined vacuum frying of apple slices.…”

The impacts of vacuum microwave drying on osmosis dehydration of tilapia fillets

“…Due to the rapid evaporation of surface moisture, internal moisture transferred to the fillets' surfaces with the water gradient, which was consistent with the relatively high shrinkage ratio and rehydration rate of HAD. The changes in cell structure were attributed to the moisture evaporation by the additional microwave heated (Su, Zhang, Bhandari, & Zhang, ). Figure b shows that the microscopic holes formed during the VMD process were bigger than those formed during the other processes.…”