During dewatering and impregnation soaking (DIS), transfer of water and of natural compounds from the product to the hypertonic solution occurs, however, few studies have been carried out to identify and quantify the losses of these compounds. Thus, this work reports on the losses of vitamin C and of the following minerals: Na, K, Ca, Mg, Zn and Mn, in red guavas submitted to the combined process of DIS (at 50 ºC for 2 hours) and convective drying (at 60 ºC and air velocity of 1.25 m/s, to a final moisture content of 20% w.b.). Studies were carried out employing two types of solutes: sucrose (in 0.4 and 0.5 g.mL-1 solutions) and liquid invert sugar (in a 41% w/w solution and as an undiluted syrup). Also, a test was performed using a solution comprised of 0.3 g.mL-1 sucrose and 0.2 g.L-1 sucralose. The control treatment consisted of drying guava solely in the convective drier. The effect of storage conditions on the stability of ascorbic acid was assessed after 60 days at 7 and 25 ºC. Results indicated reductions in the range of 20 to 64% in the amounts of the minerals studied at the end of the DIS process, as compared to the amount found in fresh fruits, and negligible losses of vitamin C, except in the treatment with undiluted liquid invert sugar. Convective drying promoted losses of vitamin C in the range of 32 to 68%. The ranges of vitamin C loss in storage at 7 and 25 ºC were 58 to 82% and 70 to 86%, respectively.
Psidium guajava L.; minerals; vitamin C; osmotic dehydration
