Combined Convective and Microwave Drying of Grapes

Tulasidas, T.N.

doi:10.1080/07373939508917001

Cited by 22 publications

(10 citation statements)

References 33 publications

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“…A high voltage transformer was incorporated in the circuit to supply current to the anode of the magnetron separately. A 270 V (AC)/15 A variac was also placed on the primary side of the high voltage transformer, to vary the anode current, thus varying the output power of the magnetron between 0 and 800 W. The output power of magnetron was measured by calorimetric method [10]. A container made of polycarbonate with provision to spread pomegranate arils sample over glass petridish was placed inside the microwave oven cavity.…”

Section: Microwave-vacuum Dryingmentioning

confidence: 99%

Optimization of microwave-vacuum drying of pomegranate arils

2014

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Pomegranate arils (Punica granatum L.) were dried in a microwave-vacuum drier up to a final moisture content of around 5-6 % (d.b.). The effect of microwave power level (25-95 W), vacuum pressure (25-195 mm Hg) and sample mass (65-235 g) on drying efficiency and some quality attributes (color, texture, rehydration ratio and sensory score) of dried pomegranate arils were analyzed by means of response surface methodology. A rotatable central composite design was used to develop models for the responses. Analysis of variance showed that a second order polynomial model predicted well the experimented data. All three process parameters microwave power, vacuum pressure and sample mass strongly affected quality attributes of dried pomegranate arils and drying efficiency. A lower vacuum pressure during drying resulted in better quality products. Optimum drying conditions of microwave power level of 80 W, vacuum pressure of 60 mm Hg and sample mass of 193.7 g were established for microwave-vacuum drying of pomegranate arils. Separate validation experiment was conducted at the derived optimum conditions to verify the predictions and adequacy of the models.

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Section: Microwave-vacuum Dryingmentioning

confidence: 99%

Optimization of microwave-vacuum drying of pomegranate arils

2014

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“…These combined methods are reported to have good potential for high speed and high quality drying. Microwave assisted convective dehydration has been found to be successful for some food products like corn (Gunasekaran 1990), grapes (Tulasidas et al 1993), potato (Bouraoui et al 1994), banana (Maskan 2000), carrot cubes (Prabhanjan et al 1995), button mushroom (Kar et al 2004), garlic (Sharma and Prasad 2001), various medicinal plants (Ren and Chen 1998), apple (Zhenfeng et al 2010), pineapple (Botha et al 2011), etc. It has been observed that the final product has a better color and rehydration ratio.…”

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confidence: 99%

Standardization of process parameters for microwave assisted convective dehydration of ginger

et al. 2011

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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.

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“…Using solar energy as the heating generator, combined with some thermalenergy supplied dryer have been widely developed. Besides, microwave drying [56][57][58], vacuum pulsed drying, as well as combination of different drying methods also used for grape drying [59]. Heat pump dryer is also been developed due to its' improved efficiency, accurate control of drying conditions, wide range of drying conditions, better product quality, and increased throughput [60][61][62].…”

Section: Mechanical Dryingmentioning

confidence: 99%

Grape Drying: Current Status and Future Trends

Wang¹,

Mujumdar²,

Mu³

et al. 2016

Grape and Wine Biotechnology

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With high moisture and sugar content, fresh grapes respire and transpire actively after harvest, which contribute to quality loss. Drying can process grapes into raisins for longer shelf-life as well as dehydrated grapes, which can be used for wines or juice production. The pre-treatments, drying method and drying conditions, can significantly influence the quality of final products. In this chapter, firstly, different pretreatments as a necessary operation previous to the drying of grapes into raisins is introduced. These pre-treatments include chemical pre-treatment, physical pretreatment, and blanching. In addition, the quality and drying characteristics of different pre-treatments is summarized too. Secondly, the current status of different technologies for grape drying and their effects on drying kinetics and quality attributes of seedless grapes are described to highlight the advantages and disadvantages of each drying method. These drying methods include the traditional open sun drying, shade drying, hot-air drying, freezing drying, microwave drying, as well as the vacuum impulsed drying. Thirdly, influences of drying on bioactive substances (flavonoids, phenolics, anthocyanin, and resveratrol) and antioxidant capacity of grape by-products including seed, skin, stem, and stalk are also examined. Finally, the future research trends of grape and its by-product drying are indentified and discussed.

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Combined Convective and Microwave Drying of Grapes

Cited by 22 publications

References 33 publications

Optimization of microwave-vacuum drying of pomegranate arils

Optimization of microwave-vacuum drying of pomegranate arils

Standardization of process parameters for microwave assisted convective dehydration of ginger

Grape Drying: Current Status and Future Trends

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