There is a growing demand for delivery of antioxidants through functional foods with the concomitant challenge of protecting their bioactivity during food processing and subsequent passage through the gastrointestinal tract. This study focuses on the retention of antioxidant activity of polyphenolic antioxidants after encapsulation/spray-drying. The polyphenolic compounds present in grape-seed extract (GSE), apple polyphenol extract (APE) and olive-leaf extract (OLE) were analysed by chromatographic methods. Catechin, epicatechin and gallic acid were identified in GSE and APE. Oleorupein is the major compound found in OLE. Total polyphenol content was found to be the highest in APE followed by GSE and OLE. These extracts were encapsulated using protein-lipid emulsions and subsequently spray-dried. Optical microscopy and particle size distribution analysis indicated the sphericity and uniform size distribution pattern of the dry particles. Radical scavenging activity studies demonstrated significant retention of antioxidant activity after the encapsulation and spray-drying process.

Water-soluble chitosan was processed using ultrasonication, microfluidisation and homogenisation to modify its physicochemical properties. The effect of using sonicated chitosan on formation of chitosan-glucose conjugates was investigated. Untreated and sonicated chitosan conjugates were prepared under varying reaction conditions (such as ratios of reactants, pH and temperature). The conjugates formed were evaluated for colour development and antioxidant activity. For both untreated and sonicated chitosans, the reactivity was found to be higher at pH 6.0/121°C than at pH 4.9/121°C. The reactivity was found to be lower at 105°C at both pH conditions than at 121°C. This clearly demonstrated the greater reactivity at higher temperature irrespective of the reaction pH. Antioxidant activity studies indicated that the conjugates formed at 121°C had higher activity. Although sonication of water-soluble chitosan led to slightly enhanced viscosity indicating higher reactivity, it did not improve the antioxidant activity.