Uticaj parametara osmotske dehidratacije na kinetiku, funkcionalne i antioksidativne karakteristike lista koprive (Urtica dioica)

Abstract

U ovoj disertaciji proučavana je osmotska dehidratacija lista koprive u dva različita osmotska rastvora: 1. vodenom rastvoru saharoze i natrijum hlorida i 2. melasi šećerne repe. Ispitivan je uticaj temperature procesa (20°C, 35°C i 50°C) i vremena imerzije (30, 60 i 90 min) na gubitak vode, priraštaj suve materije, sadržaj suve materije, vrednosti aktivnosti vode, mikrobiooške promene, promenu mineralnog sastava (Ca, Mg, Na, K, Fe, Cu, Zn, Mn, Co) i promenu antioksidativne aktivnosti, tokom osmotske dehidratacije lista koprive. Dokazano je da se povećanjem temperature i produženjem vremena trajanja procesa pospešuje prenos mase tj. migracija molekula vode iz tretiranog biljnog materijala u okolni rastvor, i prodiranje molekula rastvorene supstance iz osmotskog rastvora u tretirano biljno tkivo. Snižene aw vrednosti u svim ispitivanim uzorcima ukazuju na pozitivan uticaj osmotske dehidratacije na mikrobiološku stabilnost tretiranog lista koprive. Dobijeni rezultati su pokazali značajno poboljšanje mineralnog sastava lista koprive, dehidriranih u melasi šećerne repe, dok je kod uzoraka tretiranih u rastvoru saharoze i natrijumhlorida uočeno smanjenje sadržaja ispitivanih mineralnih materija. Nasuprot rastvoru saharoze i natrijum hlorida koji je uticao na opadanje ukupne antioksidativnosti osmotski dehidriranih uzoraka, melasa šećerne repe, kao bogat izvor prirodnih antioksidanasa, doprinosi povećanju antioksidativnosti i poboljšanju funkcionalnog kvaliteta dehidriranog produkta. Statističkom obradom rezultata, uočeno je da su optimalni procesni parametri u pogledu efikasnosti procesa, kao i mikrobiološkog, nutritivnog i funkcionalnog kvaliteta osmotski dehidriranog lista koprive, vreme trajanja procesa od 60 min, na temperaturi od 50°C, u melasi šećerne repe kao osmotskom rastvoru.

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.