PhD Oral Defense of Marya Aziz, Department of Food Science and Agricultural Chemistry
Commercial lipases, from porcine pancreas (PPL), Candida rugosa (CRL) and Thermomyces lanuginosus (Lipozyme TL IM), were investigated in term of their efficiency for the hydrolysis of safflower oil (SO) for the liberation of free linoleic acid (LA), used as a flavor precursor. Although PPL showed a high degree of hydrolysis (91.6%), its low tolerance towards higher substrate concentrations could limit its use for the SO hydrolysis. On the other hand, Lipozyme TL IM required higher amount of enzyme and additional reaction time to achieve its maximum degree of SO hydrolysis (90.2%). CRL was found as the most appropriate biocatalyst, with 84.1% degree of SO hydrolysis. The chromatographic analyses showed that the CRL-hydrolyzed SO was composed mainly of free LA. Using selected sources of LA as substrates, the synthesis of linoleic acid hydroperoxides (HPODs) by lipoxygenase (LOX) and their recovery were carried out. The investigated sources included pure (100%) and commercial (67%) LAs as well as SO and its hydrolyzed product. A model describing the commercial LA oxidation by LOX, based on Michaelis-Menten kinetics, was developed.