Effects Of Ultraviolet Irradiation On The Physicochemical And Functional Properties Of Selected Food Biopolymers
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Date
2011-01
Authors
Kuan, Yau Hoong
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Publisher
Universiti Sains Malaysia
Abstract
The application of food biopolymers can be diversified with chemical, enzymatic or physical modifications. This thesis addressed the use of ultraviolet (UV) irradiation to modify the functional properties of selected food biopolymers. These food biopolymers include food proteins derived from plant sources, specifically soy protein isolate (SPI) and wheat gluten (WG) as well as food proteins derived from animal sources, specifically egg white protein (EW) and sodium caseinate (SC). Other than this, food biopolymer from polysaccharides, specifically gum arabic (GA) was also selected. In this study, the effects of UV irradiation on the physicochemical and functional properties of selected food biopolymers were investigated, particularly on the emulsifying and foaming properties. All the samples were treated with UV irradiation for 30, 60, 90 and 120 min. However, the WG and SC samples were subjected to extended UV irradiation for 4 and 6 h as no difference was found on the initial UV exposure time. For GA, the sample was also treated with formaldehyde for comparison.
For plant proteins, UV-irradiated SPI and WG samples exhibited insignificant (P > 0.05) colour changes compared with control sample. For SPI samples, total free amino group, Sodium Docecyl Sulfate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Fourier Transform Infrared Spectroscopy FTIR
analyses indicated that UV irradiation could induce protein cross-linking; this effect was enhanced upon increasing the UV exposure time. UV irradiation induced cross-linking was then given rise to an increased (P < 0.05) apparent viscosity. All irradiated SPI samples exhibited better emulsification and foaming properties than un-irradiated samples. On the other hand, for WG samples, changes were not detectable based on results obtained from total free amino group, SDS-PAGE, apparent viscosity profiles as well as emulsification and foaming properties. However, based on the results obtained from FTIR analysis, changes were detected on the alteration of amides in the WG sample treated with extended irradiation time. Therefore, it is believed with prolonged irradiation time, cross-linking would occur on WG samples and subsequently improve the emulsification and foaming properties.
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Keywords
The use of ultraviolet (UV) irradiation to modify , the functional properties of selected food biopolymers