In this doctoral dissertation, the application of subcritical water as a green medium for
the extraction and processing of natural materials is presented. The work is divided into three
main parts. In the first part, subcritical water is proposed as a solvent for the simultaneous
extraction of oil- and water-soluble phase from oily seeds. The extraction parameters, such as
temperature, time and material to solvent ratio that yield the highest amounts of both phases
are examined. The quality of both obtained phases is examined. The characteristics of oils
obtained using subcritical water is compared to that obtained using a conventional method.
The second part of this work proposes subcritical water as an efficient solvent for the
isolation of bioactive phenolic compounds from wood waste, that is produced by the forestry
industry. Different wood fractions are firstly extracted in batch-mode and the fraction with the
highest amounts of bioactive compounds is determined. Next, semi-continuous operation is
applied, where the effects of different extraction parameters are studied on the extraction yield
and quality of the extract. The effect of temperature and ethanol addition to the subcritical
water on the content of single phenolic compounds identified in the extracts is observed.
Lastly, the cost of manufacturing of such a product is estimated by evaluating the economics
of different pilot- and industrial-scale processes operating at optimal conditions determined
on the laboratory scale.
The last part proposes the use of subcritical water as an efficient hydrolytic medium
for glycoside bonded antioxidants, specifically those found in waste agro-industrial sources.
Effect of temperature, treatment time, concentration and the atmosphere used for establishing
the pressure in the reactor are first studied on a model glycoside compound - rutin and the
optimal combination of reaction parameters are established for the batch-mode reactor. The
degradation products of the model compound are identified and the concentration/time profiles
of their degradation are observed. Furthermore, the reaction kinetics explaining the
degradation of the rutin standard are evaluated. In the next step, the method is implemented
on a real glycosides-containing extract. The extract is hydrolyzed at conditions obtained from
the first step and the free aglycone is obtained at the highest yields possible. Lastly, the process
is upgraded to continuous operation and the final hydrolyzed high-purity product is recovered.Glavni namen te doktorske disertacije je bilo raziskati uporabnost subkritične vode kot
zelenega medija za izolacijo in procesiranje naravnih materialov. Delo sestoji iz treh delov.
Prvi del se osredotoča na uporabnost subkritične vode kot topila za sočasno ekstrakcijo v olju
in vodi topne faze iz oljnih semen. V ta namen smo študirali ekstrakcijske parametre, torej
vpliv temperature, časa in razmerja material/topilo na izkoristek obeh faz. Kvaliteto obeh faz
smo preverili. Kvaliteto olj pridobljenih s subkritično vodo smo primerjali z oljem
pridobljenim s konvencionalno metodo.
Drugi del te disertacije predlaga subkritično vodo kot efektivno topilo za izolacijo
bioaktivnih fenolnih spojin iz odpadnega lesa. V prvem koraku smo ekstrahirali različne
frakcije odpadnega lesa, ki nastanejo pri spravljenju lesa v gozdovih z uporabo šaržnega
sistema, z namenom najti najprimernejšo frakcijo za izolacijo. V drugem koraku smo uporabili
semi-kontinuirni ekstrakcijski postopek, kjer smo študirali vpliv ekstrakcijskih parametrov na
ekstrakcijski izkoristek in kvaliteto ekstrakta. Določili smo vpliv temperature in dodatka
etanola na hidrotemično degradacijo fenolnih spojin med samo ekstrakcijo. Na koncu smo
ocenili še ekonomičnost pilotnih in industrijskih procesov z različnimi kapacitetami
ekstraktorja, z namenom, približno ovrednotiti cene proizvodnje takšnega produkta.
Zadnji del te doktorske disertacije predlaga subkritično vodo kot efektiven reakcijski
medij za hidrolizo glikozidno vezanih antioksidantov najdenih v odpadkih
živilskopridelovalne industrije. Preučili smo vpliv temperature, časa, koncentracije in
atmosfere uporabljene za vzpostavitev tlaka v šaržnem reaktorju na potek hidrolize ter določili
optimalno kombinacijo le-teh za modelni glikozid - rutin. Določili smo produkte
hidroterminčnega razpada rutina ter degradacijske profile le-te v odvisnosti od časa. Poleg
tega, smo razvili tudi kinetični model, ki matematično opisuje razgradnjo rutina v kvercetin.
V naslednjem koraku smo metodo implementirali na realnem ekstraktu, ki vsebuje podobne
glikozide kakor modelna komponenta in skušali dobiti proste aglikone v največjem možnem
izkoristku. Na koncu smo izvedli hidrolizo tudi s kontinuirnim postopkom in skušali dobiti
končni hidrolizirani produkt visoke čistosti
