Rehydration of Apple Dried by Different Methods

Figures & data

Figure 1 Experimental stand for measuring cubes height during rehydration. 1—rehydrated material; 2— vessel with water; 3—perforated plate; 4—minimal displacement gauge; 5—computer.

Table 1 Characteristics of dry materials.

Property	Convective drying	Freeze-drying
Initial dry matter, %	10.87	10.53
Initial water content, g/g d.m.	8.20	8.50
Final dry matter content, %	93.45	95.24
Final water content, g/g d.m.	0.0701	0.0500
Initial volume, cm^3	1	1
Final volume, cm^3	0.33	1
Water activity
raw material	0.98	0.98
dry cubes	0.14	0.07
After storage over CaCl2
water content, g/g d.m.	0.0150	0.0151
water activity	0.037	0.033

Figure 2 Increase in mass of dried apple during rehydration.

Figure 3 Soluble losses during rehydration of dried apple.

Table 2 Rehydration indices for dried apple.

Index	Convective dried	Freeze-dried
WAC	0.3816	0.8268
DHC	0.1692	0.1121
RA	0.0646	0.0927
WAC = water absorption capacity; DHC = dry matter holding capacity; RA = rehydration ability.

Figure 4 Swelling of dried apple during rehydration.

Figure 5 Water in pores and capillaries in relation to total volume increase of convective dried apple cubes.

Figure 6 Changes in height of convective dried apple cube during rehydration.

Figure 7 Changes in height of freeze-dried apple cube during rehydration.