High-quality dehydrated vegetables

Torreggiani, D. and Bertolo, G. 1999. High quality fruit and vegetable products using combined processes. In Osmotic Dehydration and Vacuum Impregnation Application in Food Industries (P. Fito, A. Chiralt, J.M. Barat, W.E.L. Spiess, and D. Behsnilian, eds), pp. 3-9. Tech-nomic Publishers Lancaster, PA. 

Chemistry and Processing of High-Quality Dehydrated Vegetable Products... 

Process Development for High Quality Dehydrated Diced Vegetables... 

G. Donsi, G. Ferrari, R. Nigro, and P.-Di. Matteo, Combination of mild dehydration and freeze drying processes to obtain high quality dried vegetable and fruits. Food Bioprod. Process., 76(C4) 181-187(1998). 

Dehydration is performed in a conveyor or tube dryer at 55-60 °C to a residual moisture content of 4-8%. Liquid or paste forms, such as tomato or potato mash, are dried in a spray or drum dryer or, in the case of some special products, in a fluidized bed dryer. Dehydration by freeze-drying provides high quality products (good shape retention) with a spongy and porous structure that is readily rehydrated. Some vegetables used in soup powders, e. g., peas and cauliflower, are prepared in this way. For production of dehydrated potato products (Fig. 17.4), tubers are peeled, cleaned, sliced into strings or chips or diced and, after... 

Osmotic dehydration, both at atmospheric pressure or preceded by the application of subatmospheric pressure for a short time, has been proposed in the production of minimally processed fruits and vegetables, which are convenient, ready-to-eat, high-moisture but ambient stable foods. The consumer prefers minimally processed foods, as these foods have appealing fresh-like characteristics and thus superior sensory quality. However, at the same time, these foods must be microbiologically safe and stable. These somewhat conflicting goals are achievable by the application of... 

Dalla Rosa, M., Bressa, F., Mastrocola, D., and Pittia, P. 1995. Use of osmotic treatments to improve the quality of high moisture minimally processed fruits. In Osmotic Dehydration of Fruits and Vegetables (A. Lenart and P.P. Lewicki, eds), pp. 69-87. Warsaw Agriculture Univ. Press, Warsaw, Poland. 

Osmotic pretreatment before microwave-assisted air drying increase the final overall quality of the product [187]. Fruits and vegetables treated by osmosis can be further dehydrated in a convection dryer to lower the water activity to the level of 0.65-0.90. At those water activities, water content in the material is still high and the product presents such organoleptic attributes as chewiness, softness, elasticity, and plasticity [76,188-190], The product has a natural color, well-preserved flavor, and high retention of vitamins [132], Its shrinkage is much smaller when compared with that observed in convection-dried products at the same water activity. 

Water is present in most natural foods, at levels up to 90-95% w/w in some fruits (oranges) and vegetables (tomatoes). Most beverages contain high proportions of water. Water exists in foods in various forms free water, water droplets, water adsorbed on a surface, chemically bound water, crystal water, and composition water. Often water is removed from processed foods to improve their keeping quality or to reduce their weight and volume. In most cases, however, part of this water is extremely difficult to remove, so even dehydrated foods may contain 2-3% residual water. The physics of water, as a pure substance and as part of biological systems, has been studied by many workers [16-18] the basic phenomena are described in a volume edited by Franks [19]. 

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