Structural changes and triacylglycerol lipolysis products of milk formula with large phospholipid-coated lipid droplets during in vitro digestion: Comparison with human milk and commercial standard formulas

Lipid digestion characteristics of a novel milk formula with large phospholipid-coated lipid droplets named Nuturis® (NF), four current standard formulas (CF1-4), and freshly expressed human milk (HM) were evaluated using a dynamic in vitro model of infant gastrointestinal digestion. Lipolysis degree (LD), triacylglycerol (TAG) lipolysis products including diacylglycerols, monoacylglycerols, and free fatty acids were determined. Structural changes including particle size distribution and microstructure of milk digesta were analyzed and compared. The LD of NF and HM showed no significant difference at 120 min of both gastric (G120) and intestinal digestion (I120). Compared to CFs, the lipolysis of NF was slower during gastric digestion while it caught up during the intestinal phase in which most of the lipolysis occurred. Milk lipolysis products are highly related to the milks initial TAG composition. Regarding structural changes during digestion, NF is closer to HM than CFs. In the gastric phase, NF and HM had constant particle size (∼5 μm) with mostly intact lipid droplet structures, while CFs started with smaller particles but flocculated to larger droplet aggregates (8–10 μm). Once the chyme had moved into the intestinal phase, the emulsion of all milks coalesced into large aggregates. This study showed that lipid digestion and structural changes of milk emulsions during digestion are highly dependent on the characteristics of the lipid droplets. In contrast to current standard formulas with small lipid droplets, milk formula with large phospholipid-coated lipid droplets and HM showed similar LD at the end of gastrointestinal digestion and droplet aggregation behaviors during digestion.