Determination of the Relationship between the Granulometry and Release of Polyphenols Using LC-UV, and Their Antioxidant Activity of the Pulp Powder of the Moroccan Argan Tree, “Argania spinosa L.”

The bioavailability of cosmetic, pharmaceutical, nutraceutical, and food preparations depends, among other factors, on the galenic form and the control of the granulometric structure of powders. The present study aimed to evaluate the effect of argan pulp powder particle size on functional, physicochemical properties, and antioxidant bioactivity. The particle size study revealed a unimodal particle volume distribution, explaining the regular particle shape. The results relating to functional properties indicated that the critical fraction was in the range of 50–125 µm. However, the study of the particles in each class, evaluated via SEM, showed that the morphology of the pulp powder was strongly dependent on the degree of grinding. The classes in the range of 50–125 µm had the highest polyphenol content, while those of <25 µm had the highest flavonoid content (893.33 mg GAE/100 g DW and 128.67 mg CE/100 g DW, respectively). Molecular analysis via LC and GC-MS showed that particle size had a significant effect on the release of bioactive molecules. ABTS, DPPH, and TAC tests showed that the fraction, ‘‘50–125 µm’’, had the highest antioxidant activity. However, the FRAP test showed highest antioxidant activity for particles of <25 µm. The analysis of the bioactive compounds of the argan pulp powder confirmed a differential distribution, depending on the size of the particles.