Fruits contain an abundant amount of polyphenolic compounds that have antioxidant properties. These compounds have shown the ability of... Show moreFruits contain an abundant amount of polyphenolic compounds that have antioxidant properties. These compounds have shown the ability of reducing the risk of major degenerative diseases, relief from allergies/asthma, weight loss and improved circulation. Dairy proteins have numerous benefits as enhancing muscle formation, weight and blood pressure control, beneficial effect in bone and dental health and protection against toxins, bacteria, and viruses. The combination of both fruit and dairy in commercial or homemade mixtures, such as smoothies, is readily available and popular. But in fact, the interactions which happen between proteins and fruit antioxidants could affect the availability and potential activity of antioxidants. This thesis will focus on the interaction of dairy proteins with antioxidant from freeze dried strawberry and measure the availability of the antioxidant capacity. Freeze dried strawberry powder at different concentrations (1.64%, 3.28% and 6.56%) was mixed with four types of proteins at different concentration to demonstrate the interaction over a range. The proteins used were skim milk powder (6.89%), whey from bovine milk (0.51%), casein from bovine milk (2.04%), and albumin from bovine serum (2.55%). The antioxidant content was measured by several analytical techniques using LCMS/MS, Oxygen Radical Absorbance Capacity (ORAC) assay and Folin-Ciocalteu assay. SDS-PAGE was used to examine the change of protein molecular weight before and after the reactions. The binding interaction resulted in significantly reduced ORAC and Folin- Ciocalteu assay values compared to the respective non-protein strawberry mixtures (P<0.001 and P<0.05). The SDS-PAGE images between protein strawberry mixtures and non-protein strawberry mixtures showed similar results. The (+)-catechin, cyanidin-3-O glucoside, pelargonidin-3-O-glucoside and kaempferol-3-coumaroylglucoside content were significantly reduced when comparing skim milk based strawberry powder mixtures and non-protein strawberry mixtures (P<0.05). This research indicates the binding interaction between dairy protein and freeze dried strawberry powder reduces the antioxidant activity of the freeze dried strawberry powder. M.S. in Food Safety and Technology, May 2012 Show less
