In this research, three various Mw of chitosan (CS)-gallic acid (GA) conjugates were synthesized, characterized, and used for improvement of physicochemical stability of β-carotene (BC) nanoemulsion (NE) by layer-by-layer technique. GA conjugation degrees were in the following order: HCS (125.6 mg/g) > MCS (102.3 mg/g) > LCS (74.6 mg/g) at GA:CS mass ratio of 0.5:1. Three varying Mw of CS-GA conjugates exhibited pronouncedly higher antioxidant abilities than native CS. For native CS, antioxidant abilities increased with the decrease of Mw. However, HCS-GA conjugate showed the highest antioxidant activity, due to the higher GA conjugation degrees and decreased intramolecular hydrogen bonds and crystallinity in HCS-GA conjugate. CS-GA conjugates substantially improved BC chemical stability in NE than CS and BC retentions were in the following order: HCS-GA (76.8%) > MCS-GA (68.3%) > LCS-GA (53.4%) after 30 days storage. The results obtained may provide some useful information for the applications of CS-GA conjugates for nutraceuticals stabilization in food systems.
Keywords: Antioxidant activity; Chitosan; Layer-by-layer technique; Molecular weight; Nanoemulsion; β-Carotene.
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