Standardization of process parameters for microwave assisted convective dehydration of ginger

Abstract

Ginger (Zingiber Officinale, Cv. Suprava) slices (4 mm thick) were dehydrated at 25°, 40°, 50°and 60°C with three different microwave power levels, viz. 120, 240, and 360 W in microwave assisted convective dryer up to 0.07 g moisture/g dry solid to observe the feasibility of microwave assisted convective drying for ginger. The samples were also dried without application of microwaves (0 W) at the above air temperatures. The final product quality was compared in terms of rehydration characteristics, oleoresin and volatile oil contents, hardness, color and organoleptic quality. The maximum rehydration ratio of 3.86±0.06 was obtained at 50°C without application of microwaves and was followed by 120 W-40°C combination treatment (3.64±0.15). The minimum rehydration ratio was 2.34±0.20 for 360 W with 60°C. The yield of oleoresin content was higher for 120 W as compared to other power levels, which ranged between 5.12±0.85% and 6.34±0.89%. The maximum retention of oleoresin was observed in case of 120 W-40°C. The samples dried with microwave power level of 120 W also gave better yields of volatile oil as compared to other power levels. The best color was observed at 120 W-50°C and 120 W-60°C conditions with Hunter 'a' (redness) values at 0.50±0.03 and 0.35±0.03, respectively. The sensory analysis also indicated that drying at 120 W-50°C and 240 W-50°C combinations gave the most acceptable quality product. Drying ginger with 120 W-50°C combination helped in a saving of 53% and 44% in drying time as compared to hot air drying at 50°and 60°C, respectively. Drying at 240 W-50°C also gave a reasonably acceptable quality product with a net saving of 91% and 89% in drying time as compared to hot air drying at 50°and 60°C, respectively. However, on the basis of rehydration characteristics, the acceptable process conditions were hot air drying at 50°or 60°C, or with the 120 W-40°C combination.

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

“…After 30 min of rehydration, RR of chunks dried at 700 W started declining and remained lower to that of the chunks dried at 650 W. Similar to our finding, Mohanta et al. (2014) also observed less rehydration ability in ginger slices when the microwave power increased from 120 W because of shrinkage of cell structure caused by faster drying rate.…”

“…RR of chunks dried at 600 W was the lowest among all samples owing to its higher moisture content and a tight microstructure which limits further diffusion of moisture into the muscle. After 30 min of rehydration, RR of chunks dried at 700 W started declining and remained lower to that of the chunks dried at 650 W. Similar to our finding, Mohanta et al (2014) also observed less rehydration ability in ginger slices when the microwave power increased from 120 W because of shrinkage of cell structure caused by faster drying rate.…”

“…Plenty of literature proves that the drying rate increases with an increase in microwave power (Chahbani et al, 2018;Doymaz et al, 2015). Ganesapillai et al (2012) observed a threefold reduction in the drying time of ginger slices when the microwave power was increased from 100 to 300 W. Similarly, by increasing the power from 120 to 240 W, 80% reduction in drying time of ginger slices was recorded by Mohanta et al (2014). In our study, though the drying time was kept constant for the microwave vacuum process, an increase in power lead to significant variation in the moisture content of the dehydrated sample.…”

Artificial neural network modelling approach of drying kinetics evolution for hot air oven, microwave, microwave convective and freeze dried pineapple

“…MWC being the fastest drying method employed for pineapple slices in this study, resulted in irreversible cellular shrinkage, which may responsible for hindrance in water uptake during rehydration operation. Mohanta et al [26] observed similar rehydration characteristics for microwave convective dried ginger. An increase in RR was noted with increasing rehydration temperature from 20 to 80 °C, this may be supported by the fact that with a rise in temperature, moisture also penetrated to the dried product at a higher rate.…”

Comparative Study of the Effect of Five Drying Methods on Bioactive Compounds, Antioxidant Potential and Organoleptic Properties of Zingiber officinale (Ginger) Rhizome

“…These results confirm a denaturation of ginger characteristics when using this drying method at a high-power level. Testing a microwave assisted convective dryer at power level up to 240 W, Mohanta et al [33] rather obtained accepted infusions. This power level is therefore a key parameter to take into consideration when performing such treatment.…”