The Role of Gastric Lipase and Pepsin in Lipid Digestion of a Powder Infant Formula Using a Simulated Neonatal Gastric System

This study has sought to determine the impact of interfacial dynamics on the in vitro lipid digestion of a commercial infant formula; in particular, the specific role of interfacial proteolysis on the subsequent rates of reaction of droplet lipolysis. A powder infant formula was used as the as a protein-stabilised emulsion substrate during simulated infant gastric digestion at different pH level 3.5, 4.5 and 5.5. The digestate was treated with a fungal lipase and porcine pepsin (used to analogue human gastric lipase and pepsin) respectively and in a combined action. The study found that for fungal lipase treated digestate, the rate and extent of lipolysis were observed to be maxim at pH 5.5, in accordance with the optimal pH activity of the lipase. Findings also indicated that the proteinaceous interface did not appear to act as a barrier to lipolysis, since treatment with lipase and pepsin did not result in any significant increase in extent of lipolysis. However, it was observed that surface proteolysis did lead to alteration of the structural fate of the enzyme during digestion when compared to when the emulsion was digested solely by lipase. Findings suggest that lipolysis under these conditions may be independent of the structural dynamics of the emulsion during digestion, as observed within the context of this study design.