Effective Moisture Diffusivity of Onion Slices undergoing Infrared Convective Drying

Moisture content of soybean kernel at harvest time is too high for storage, and needs to be reduced. In this research, drying characteristics, quality and energy requirement for microwave-fluidized bed drying of soybean kernels were studied. The results showed that air temperature (80-140°C), velocity (1.8-4.5 m/s) and microwave power (200-500 W) significantly influenced drying time, moisture diffusivity, rehydration capacity, cracking, and specific energy consumption (P≤0.05). Among the applied models, Page's model has the best performance to estimate the microwavefluidized bed drying behavior of the soybean kernels. Moisture diffusivity values increased (6.25×10 −10 to 42.14×10 -10 m 2 /s) as the air velocity decreased and air temperature and microwave power increased. Activation energy was foundto be between 3.33 and 17.70 kJ/mol. Minimum cracking percentage of soybean kernels (12.96 %) was obtained at 80°C, 1.8 m/s and 200 W treatments. The increase in microwave power and decrease in air velocity level decreased the rehydration capacity. Specific energy consumption varied from 50.94 to 338.76 MJ/kg water and the lowest specific energy consumption were obtained at 80°C, 4.5 m/s and 500 W.

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“…An analytical solution of Eq. (8) can be derived by making the following assumptions (Pathare and Sharma 2006;Caglar et al 2009):…”

Section: Moisture Diffusion Modelmentioning

confidence: 99%

Effects of microwave - fluidized bed drying on quality, energy consumption and drying kinetics of soybean kernels

2014

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“…To counter these disadvantages, drying methods viz. freeze drying, infrared drying, and vacuum drying alone or as multimode combination has been experimented (Kumar Parveen et al 2005;Sharma et al 2005;Pathare and Sharma 2006;Mongpraneet et al 2002). The technologies improved the quality of end product but involve high processing cost.…”

Section: Introductionmentioning

confidence: 99%

A less energy intensive process for dehydrating onion

et al. 2013

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Onion powder has an extensive demand and wide application worldwide as flavour additive in convenience foods and medicinal products. Conventionally onion powder is prepared by hot air drying of onion slices followed by grinding. Convective air drying when used alone demands longer drying time and thus has a high expense of energy. As bulk of onion is water (82-87 %), removal of moisture prior to drying can reduce moisture loading on dryer and hence the energy consumption. Keeping this in view, onions were partially dewatered using centrifugal force before convective drying. The effect of partial mechanical dewatering and drying air temperature was studied on drying time, specific energy consumption and onion powder quality (colour and flavour). The combination process was also optimized to achieve increased drying rate and product quality comparable to products obtained using convective drying alone. Onions subjected to 60 % partial mechanical dewatering and hot air drying at 70°C exhibited significantly (p≤0.5) shortened drying time, decreased energy consumption and maintained colour and flavour of the dried product.

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“…Combined mode drying like convective-microwave (Andres et al, 2004;Araszkiewicz et al, 2007;Kowalski and Rybicki, 2004) and microwavevacuum (Giri and Prasad, 2007) have been successfully employed in order to improve the effectiveness of drying. In the recent past, a few studies on the application of IR for combined mode drying of food materials have been reported (Afzal et al, 1999;Mongpraneet et al, 2002;Hebbar et al, 2004;Jain and Pathare, 2004;Praveenkumar et al, 2005;Pathare and Sharma, 2006;Swasdisevi et al, 2007;Reyes et al, 2008;Mihoubi et al, 2009;Kowalski and Rajewska, 2009). During combined IR and hot air drying, the rapid heating of food materials by IR radiation (due to high heat density and depth of penetration) increases the rate of moisture migration towards the surface, while the convective air-1) Mass transfer is by diffusional mechanism 2) Moisture is initially (t=0) distributed uniformly throughout the mass of a sample 3) Mass transfer is symmetric with respect to the centre 4) Resistance to mass transfer at the surface is negligible compared with internal resistance of the sample…”

Section: Introductionmentioning

confidence: 99%

Hot Air Assisted Infrared Drying of Vegetables and Its Quality

Vishwanathan

Hebbar

Raghavarao

2010

FSTR

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Hot air assisted infrared (IR) drying of potato and carrot is carried out and product quality is compared with hot air dried samples. The synergistic effect of hot air and IR during combined mode (hot air assisted IR) drying reduced the processing time by nearly 48% as compared to hot air drying alone, besides improving the quality of products. Higher rehydration ratio and lower browning index values are observed for combined mode dried products. Photomicrographs of dehydrated carrot and potato showed superiority of product structure for combined mode dried products. The IR dried carrot had higher (by 17%) retention of carotenoid than hot air dried sample. The processing conditions such as velocity and temperature of air affected the drying characteristics during combined mode drying. Higher values of effective diffusivity of water are observed with combined mode drying.

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Effective Moisture Diffusivity of Onion Slices undergoing Infrared Convective Drying

Cited by 124 publications

References 9 publications

Effects of microwave - fluidized bed drying on quality, energy consumption and drying kinetics of soybean kernels

Effects of microwave - fluidized bed drying on quality, energy consumption and drying kinetics of soybean kernels

A less energy intensive process for dehydrating onion

Hot Air Assisted Infrared Drying of Vegetables and Its Quality

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