The Effect of Grinding Techniques on the Microstructural Properties of Purslane (Portulaca oleracea L.) Powder, Its Total Phenolics Before and After In Vitro Simulated Gastrointestinal Digestion, and Its Antioxidant Capacity

Purslane (Portulaca oleracea L.) is a plant recognized as a valuable source of nutrients and bioactive compounds such as omega-3 fatty acids, antioxidants, vitamins, and minerals. This study investigates the effects of grinding techniques (knife, ball, and planetary ball mill) on the properties of purslane powder (surface microstructure, particle size distribution, and color), their influence on the phenolic content in the extracts of purslane powder before and after in vitro simulated digestion process, and the antioxidant activity of the purslane extracts. The results showed that applied grinding techniques affected the particle size distribution and surface morphology of the powder, which in turn influenced the gastrointestinal stability of the dominant phenolic compounds in purslane powder extracts. The powder obtained via ball milling, characterized by the highest proportion of fine particles (x < 100 µm), showed the highest content of total phenolics (656 mg GAE/L). Ball milling resulted in high preservation of the dominant phenolic acids in the powder extract after simulated gastric and intestinal digestion (83.55% and 69.42%) and high free radical scavenging activity (DPPH and ABTS) and ferric reducing power (FRAP). The results obtained emphasize the nutritional and biological benefits of purslane in the form of a fine powder.