Uticaj parametara osmotske dehidratacije na kinetiku, funkcionalne i antioksidativne karakteristike lista koprive (Urtica dioica) / The effects of osmotic dehydration parameters on the kinetics, functional and antioxidant characteristics of nettle leaf (U

The osmotic dehydration of the nettle leaf into two different osmotic media was studied in this dissertation: 1. Aqueous solution of sucrose and sodium chloride and 2. Sugar beet molasses. The effects of the process temperature (20 °C, 35 °C and 50 °C) and the immersion time (30, 60 and 90 min) on water loss, solid gain, dry matter content, water activity, microbial changes, mineral composition (Ca, Mg, Na, K, Fe, Cu, Zn, Mn, Co) and the change in the antioxidant activity during osmotic dehydration of the nettle leaf were studied in this investigation. It has been proved that the increase in temperature and the prolonging of process time, accelerate the mass transfer, i. e., the migration of the water molecules from the treated plant material to the surrounding osmotic solution, and also the penetration of the molecules from the osmotic solution into the treated plant tissue. The reduced aw values in all tested samples indicate the positive effect of osmotic dehydration on the microbiological stability of the treated nettle leaf. The obtained results showed a significant improvement in the mineral composition of the nettle leaf dehydrated in sugar beet molasses, while the decrease in the mineral content was observed in the samples treated with sucrose and sodium chloride solution. Contrary to the sucrose and sodium chloride solution, which negatively affected the overall antioxidative effect of osmotically dehydrated samples, sugar beet molasses contributed to an increase in antioxidantity, being a rich source of natural antioxidants, and it also improves the functional quality of the dehydrated product. Statistical analysis of the obtained experimental results showed that optimal process parameters in terms of process efficiency, as well as microbiological, nutritive and functional quality of the osmotically dehydrated leaf net, could be reached after 60 min of osmotic treatment, at a temperature of 50 °C, using sugar beet molasses as an osmotic solution.