Oxidative stability in emulsions prepared with faba bean proteins

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Title: Oxidative stability in emulsions prepared with faba bean proteins
Author: Liu, Chang
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Food and Environmental Sciences
Publisher: Helsingfors universitet
Date: 2015
Language: eng
URI: http://urn.fi/URN:NBN:fi:hulib-201512143998
Thesis level: master's thesis
Discipline: Food Science
Food Science (Food Safety)
Food Science
Abstract: The literature review related to faba bean proteins, the mechanism of protein oxidation and detection methods for protein oxidation as well as the relationship between lipid and protein oxidation. Native faba bean, faba bean treated by oven and microwave, as well as soy protein isolate were used as materials. The materials differed in their lipoxygenase activity. Oil-in-water emulsions were made of 10% purified (removal of antioxidants) rapeseed oil and 3% water soluble proteins that were extracted from flour samples. The emulsions were prepared by homogenizing using microfludizer. Oxidation took place in the oven at 37 °C in the dark with constant stirring by magnet stirrers. Sampling for measurements was carried out on day 0, 1, 4 and 7 from each replicate. Oxidative stability of was monitored by following lipid oxidation as formation of conjugated dienes and hexanal, and by following protein oxidation by measuring loss of tryptophan, formation of carbonyls and dityrosine through fluorescence detections both in the lipid phase and in the continuous phase. In this study, the degree of protein oxidation was generally consistent with corresponding lipid oxidation. Generally, the degree of protein oxidation in lipid phase of emulsions was higher than that in continuous phase, although the protein content was far less in the lipid phase. Both results implied co-oxidative relationship between lipid and protein oxidation. In addition, the results showed that thermal treatment or microwave irradiation can not only result in retarding or decreasing lipid oxidation by lowing lipoxygenase (LOX) activity, but also affect protein oxidation via lipid oxidation and the conformational changes of proteins.
Subject: faba bean
protein oxidation
lipid oxidation
fluorescence spectroscopy

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