Pasting of G-Irradiated proteins from Vigna Subterranea in native starch models and the surface functional properties of the proteins
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Date
SEPTEMBER, 2009
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Abstract
This research was carried out to evaluate the surface functional properties of gamma irradiated Bambara groundnut protein isolates and to study their performance in modeled starch systems using the Brabender Viscoamylograph. Irradiation was done at five levels: 2.50, 5.00, 7.50, and 10.00kGy; while protein-starch admixtures in three combinations: 30P:70S, 50P:50S, 70P:30S were pasted. The results showed significant (p<0.05) effects of increasing irradiation doses on some protein related functional properties, while pasting characteristics of admixtures showed no dose-dependent significant (p<0.05) changes. Protein solubility decreased following irradiation, even though there were no significant differences (p<0.05) among samples. All samples readily solubilized at pH 8.00 with the non-irradiated (0.00kGy) showing the highest solubility value of 0.173g/ml. Increases in Water and Oil Absorption Capacities (WAC and OAC) were dose-dependent, with samples showing significant differences (p<0.05). The 10.00kGy samples recorded the highest values of 18.45% and 10.09% for WAC and OAC respectively. Foaming Properties increased across irradiation doses with some significant differences (p<0.05) among samples. However the 10.00kGy irradiated samples compared to Egg White, recorded lower values for foaming properties. Significant decreases (p<0.05) in Emulsifying Properties were recorded after irradiation, with the 2.50kGy sample recording the highest values of 45.83% and 73.33% for Emulsifying Activity and Emulsion Stability respectively. Pasting characteristics again increased significantly (p<0.05) with increasing starch:protein ratios. Correlation studies showed that the pasting properties were solely dependent on the starch concentration within the admixtures, indicating the insignificant contribution of modified Bambara groundnut proteins to the pasting properties of the blends. Enhanced surface functional properties of the gamma irradiated proteins makes them potential foaming, emulsifying, shelf life extension, and flavour retention agents. Admixtures may also serve as thickening agents for foods that require various degrees of viscosities.
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This thesis is submitted to the Department of Food Science and Technology in partial fulfilment for the requirement of the Master of Science (Msc.) degree in Food Science And Technology,