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Food Dehydration
Published in Dennis R. Heldman, Daryl B. Lund, Cristina M. Sabliov, Handbook of Food Engineering, 2018
Martin R. Okos, Osvaldo Campanella, Ganesan Narsimhan, Rakesh K. Singh, A. C. Weitnauer
Drum drying involves heat transfer from condensing steam through the metal drum to the product layer. The rate of heat transfer depends on the resistance to the removal of water at lower moisture contents and product characteristics. When the time to remove the last few percent moisture becomes too great to be practical, the drum dryer can be used as a predryer for a more suitable drying technique. The capacity of the dryers often increase dramatically in these instances. Maximum evaporation rates for drum dryers can be as high as 18.5 lb/h/ft2. This rate is attained with dilute solutions which evaporate easily. The heat transferred varies over the surface area of the drum. For example, the drum surface between the knife scraper and the feed applicator is not utilized. No heat is transferred at this point except for radiation loss. This is where the drum temperature is at its maximum. Once the wet feed material is applied, the surface temperature drops rapidly. Depending on the product’s coefficient of heat transfer, the temperature will remain at or below the steam temperature. At the point of product removal, heat transfer rates are low due to the resistance of the dry product. The product will be approaching the drum temperature and the temperature difference will be quite small. The temperature of the drum surface of a double-drum dryer used for drying milk was studied by Roeser and Mueller (1930). The temperature of the milk was within 3°F of the metal temperature at the point of product removal. Calculations have shown that the overall heat transfer is 360 Btu/hr/ft2°F in the area between the drums of a double-drum dryer, and 220 Btu/hr/ft2°F close to the knives (Van Marle, 1938).
Drying of Fruits and Vegetables
Published in Arun S. Mujumdar, Handbook of Industrial Drying, 2020
K. S. Jayaraman, D. K. Das Gupta
Drum drying is an important and inexpensive drying technique suitable for a wide range of products—liquid, slurry, and puree. The material to be dried is applied as a thin layer to the outer surface of a slowly revolving hollow drum (made of iron or stainless steel) heated internally by steam (24). The principle and types of drum dryers have been discussed by a number of authors (20,22,24,25).
Drying of Agricultural Crops
Published in Guangnan Chen, Advances in Agricultural Machinery and Technologies, 2018
D. M. C. C. Gunathilake, D. P. Senanayaka, G. Adiletta, Wiji Senadeera
Drum drying is a method used for drying out liquids from raw materials. In the drum drying process, pureed raw ingredients are dried at relatively low temperatures over rotating, high-capacity drums that produce sheets of drum-dried product. This product is milled to a finished flake or powder form and this operation is similar to a cloth dryer.
Sorption isotherms, glass transition and storage stability of drum-dried mango peels obtained with and without process additives
Published in Drying Technology, 2023
Paula Ramos Antoniolli, Cristhiane Caroline Ferrari, Daniele Fidelis Borges, Sílvia Pimentel Marconi Germer
Few studies pointed out the application of drum-drying to by-products of fruit processing. [5–7] Troiani et al.[5] demonstrated the technical feasibility of drum-drying mango peels (Palmer variety) using process additives (corn starch/glyceryl monostearate). Drum-drying is a well-suited process for drying purees, presenting, in a continuous process, high drying efficiency and high production capacity.[8] Additives, such as starches, gums, and pectins, are used in concentrations ranging from 3 to 20% d.b., playing a role in helping to form and detach the film from the heated cylinder. Additives can also impart higher stability to the product, protecting nutrients and increasing the glass transition temperature. Despite that, additives have been partially avoided in some food formulations, aiming a clean label market. Troiani et al. [5] developed a product with high potential for use as ingredient, rich in nutrients (fibers, phenolics, vitamins, and minerals), presenting interesting technological properties (hygroscopicity, water incorporation index, oil incorporation index) for different food formulations.
Valorization of fruits, vegetables, and their by-products: Drying and bio-drying
Published in Drying Technology, 2022
Choon Hui Tan, Ching Lik Hii, Chaleeda Borompichaichartkul, Puttapong Phumsombat, Ianne Kong, Liew Phing Pui
Another method for producing fruit powders is drum drying (e.g., double drum dryer).[57] The double drum dryer is constructed using two metallic cylinders of the same diameter that rotate just next to each other. The cylinders will achieve high temperatures and transfer the heat to the products, drying quickly. Despite high temperatures, it is also an economically viable drying method.[58,59] Drum drying has several advantages, including high profitability, energy efficiency, and versatility for multiple productions. Furthermore, the equipment is simple to operate, maintain, and clean. Because the exposure to high temperatures is limited to a few seconds, drum drying is appropriate for many heat-sensitive products, such as retaining the bioactive compounds in food products. Gums, starches, pectins, and maltodextrins are used as process additives in the drum drying of fruit purees. It serves to improve the thermoplastic properties of the materials and the hygroscopic properties of the powders.[57] The concentration varies from 1% to 20% (dry basis) depending on the fruit. Table 5 shows the application of the drum drying method on different food products.
Stability of mango flakes obtained by drum drying with different additives
Published in Drying Technology, 2020
Maira Akemi Casagrande Yamato, Vanessa Martins da Silva, Elaine de Cássia Guerreiro Souza, Cristhiane Caroline Ferrari, Silvia Pimentel Marconi Germer
Drying tests were performed in a rotary single cylinder dryer (Richard Simon & Sons, D139, Nottingham, England), with a total drying area of 0.5 m2. Two experiments, one with starch (3% d.b.) and another with maltodextrin 10 DE (3% d.b.), were carried out with approximately 12 kg of mango pulp, both with 0.5% dry basis of GMS. The thawed pulp was homogenized in a colloidal mill (Meteor, REX 2-AL, São Paulo, Brazil). The conditions of drum drying were fixed in accordance with a previous study:[12] clearance of 0.15 mm (between the heating and applicator cylinder), pool level of 400 mL, residence time of 20 seconds, and process temperature of 135 °C. The dried product, obtained as a film, was flocculated (Fabbe, S508, São Paulo, Brazil) using a 2.5-mm sieve.