Carrots osmotic dehydration

During osmotic dehydration of apple, pumpkin, and carrot in sugar solution at 30 °C, the rate of water loss was 5-10 times higher than the rate of solid gain and depended on advancement of the dewatering process (Kowalska and Lenart, 2001). Under the same dewatering conditions, pumpkin and carrot reached smaller water contents than apple (Figure 3). 

FIG. 3 Water loss (WL) and solid gain (SG) expressed on initial dry matter (idm) of strawberry (ST) slices (Brambilla et al., 2000) and apple (AP), carrot (CA), and pumpkin (PU) cubes (Kowalska and Lenart, 2001) after 60 min osmotic dehydration in a 60% (w/w) sucrose solution at 30 °C at atmospheric pressure. 

FIG. 4 Effects of varying raw material treatments prior to osmotic dehydration on moisture (MC) and solid (SC) content expressed on initial dry matter (idm). Potato slices, high hydrostatic pressure (Rastogi et al., 2001) carrot slices, PFE (Rastogi et al., 1999) bell pepper disks, PFE (Ade-Omowaye et al., 2002b) and apple slices, edible coatings (Lenart and Dabrowska, 1998). 

Rastogi, N.K., Eshtiagi, M.N., and Knorr, D. 1999. Accelerated mass transfer during osmotic dehydration of high intensity electrical field pulse pretreated carrots. J. Food Sci. 64, 1020-1023. 

Rastogi, N.K. and Raghavarao, K.S.M.S. 1997. Water and solute diffusion coefficients of carrot as a function of temperature and concentration during osmotic dehydration. J. Food Engineer. 34, 429-440. 

Lenart and Lewicki have shown that the thickness of the material shonld not exceed 10 mm [71,72]. Taking into account further processing following osmotic dehydration and use of the product, they considered a cube with a side dimension close to 10 mm as an optimal size and shape for most materials. Lewicki et al. [73-77] and Lerici et al. [78] dehydrated apples, carrots, and potatoes as cubes of 8-10 mm on a side. Flink, as well as Simal et al. [20], likewise used this shape in most of his studies [79],... 

High-intensity electric field pulses accelerated osmotic dehydration of carrot [18], A Fickian diffusion coefficient for water and solute increased exponentially with electric field strength. This effect was attributed to increased cell wall permeability, which was also manifested by the softening of product. 

Solutions of sugars are mostly used to dehydrate fruits and glycerol, starch syrup, and sodium chloride are used for vegetables [62,73,91,99]. Sucrose is the most frequently used substance [17,65,100-104]. The control of pH of sucrose solution is recommended for banana slices osmotic dehydration [105]. It was also shown that control of pH of sucrose solution affects the course of osmotic dehydration of apple and carrot [106]. Addition of ascorbic acid to sugar solution is practiced to minimize browning of fruit pieces during osmotic process [72]. Sucrose can be substituted in part by lactose [15]. 

FIGURE 32.11 The effect of the kind of material on the course of osmotic dehydration in saccharose solution at 20°C. (1) apple (2) carrot. 

K.-S. Youn and Y.-H. Choi, Mass transfer characteristics in the osmotic dehydration process of carrot, Korean J. Food Sci. TechnoL, 27(3) 3 1 (1995) (FSTA 1996-12-10076). 

Amami, E., Fersi, A., Khezami, L., Vorobiev, E., Kechaou, N., 2007. Centrifugal osmotic dehydration and rehydration of carrot tissue pre-treated by pulsed electric field. LWT-Food Sci. Technol. Res. 40 1156-1166. 

Accelerated mass transfer during osmotic dehydration of high intensity electrical field pulse pretreated carrots. f Food Sci. 64 1020-1023. 

P.P. Lewicki, A. Lenart, and M. Malkowska, Diffusive movement of substance in the carrot dehydrated osmotically in the sodium chloride solution, Ann. Warsaw Agric. Univ., Food TechnoL Nutr., 77 45 (1987). 

J.M. Flink, Dehydrated carrot shces influence of osmotic concentration on drying behaviour and product quahty. Food Proc. Eng., 7 412(1980). 

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