Impact of particle size on functional, physicochemical properties and antioxidant activity of cladode powder (Opuntia ficus-indica)

Particle size is an important quality parameter of pharmaceutical and processed food products. The present study aimed at evaluating the effect of powder fractionation on the functional, physicochemical properties and antioxidant activity of cladode powder with particle size ranging from < 45 to 500 mu m. Granulometric study presented bimodal granules' volume distribution explaining the irregular shape of particles. The results indicated that functional properties were significantly (p < 0.05) affected by particle size distribution and the critical fraction size was 63-80 mu m. Scanning electron microscopy showed that morphology of cladode powder granules was highly related to the grinding treatment. Physicochemical analysis showed that ash content and soluble solids were more affected contrary to moisture, pH and titratable acidity. Chlorophylls (a, b) and carotenoids content of fractionated powder were affected significantly unlike color (b* value). The granulometric classes (80-100 mu m) had the highest polyphenol and flavonoids content (605.30 mg GAE/100 g and 476.33 mg CE/100 g respectively). Two fractions "100-200 mu m" and "80-100 mu m" exhibited a high rise in the antioxidant activity as determined by the DPPH, ABTS and FRAP essays compared to other fractions. The chemical composition and bioactive compounds analysis of cladode powder confirmed a differential distribution of chemical composition and bioactive compounds according to particle size.