Food Research Institute

Buljeta, I. – Vukoja, J. – Pichler, A. – Šimunović, J. – Kopjar, M.
Encapsulation of gallic acid on pectin: antioxidant activity, alpha-amylase and alpha-glucosidase inhibitory activity of complexes
Journal of Food and Nutrition Research, 61, 2022, No. 3, s. 242-250

Mirela Kopjar, Department of Food Technologies, Faculty of Food Technology Osijek, Josip Juraj Strossmayer University, F. Kuhača 18, 31000 Osijek, Croatia. E-mail: mirela.kopjar@ptfos.hr

Received 16 February 2022; 1st revised 23 June 2022; accepted 25 June 2022; published online 18 July 2022.

Summary: Gallic acid is a phenolic acid with reported health-promoting properties such as antioxidant, antimicrobial, anticancer, antihyperglycaemic activities. Bioactive compounds, such as polyphenols, are prone to degradation during food processing, but their preservation could be achieved by encapsulation. The main objective of the present study was to encapsulate gallic acid by freeze-drying, using pectin as wall material. Various concentrations of pectin (25 g·l^-1, 50 g·l^-1, 75 g·l^-1 and 100 g·l^-1) were used for sample preparation. Additionally, the influence of complexation duration (10 min or 30 min) was also evaluated. The highest content of gallic acid (3.633 g·kg^-1) was achieved in the complex where 25 g·l^-1 of pectin was used with complexation of 30 min. The same complex possessed the highest antioxidant activities determined by 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical-scavenging assay, 2,2-diphenyl-1-picrylhydrazyl scavenging capacity assay, cupric reducing antioxidant capacity and ferric reducing antioxidant power assays, as well as capability of inhibition of alpha-amylase and alpha-glucosidase. Concentrations of pectin higher than 25 g·l^-1, used for sample preparation, negatively affected gallic acid adsorption. Fourier transform infrared with attenuated total reflection spectroscopy analysis was conducted in order to confirm the binding of gallic acid onto pectin. From infrared spectra, it could be observed that band intensity changed and shift of bands occurred when gallic acid was present in the complex.

Keywords: gallic acid; pectin; freeze-drying; encapsulation; antioxidant activity; enzyme inhibition, infrared spectra

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