Free fatty acid release from vegetable and bovine milk fat-based infant formulas and human milk during two-phase in vitro digestion

Background: Bovine milk fat is increasingly used in infant formula (IF). The triacylglycerol (TAG) structure of bovine milk fat might be beneficial for digestion and absorption. We investigated the release of fatty acids (FAs) of IF containing different fat blends and compared this to human milk. Methods: Fresh human milk was sampled and two IFs were produced; one containing 100% vegetable fat (IF1) and one with 67% bovine milk fat and 33% vegetable fat (IF2). Using a static in vitro infant digestion model, consisting of a gastric and duodenal phase, the time dependent release of individual free fatty acids (FFA) was studied and analysed using GC-MS, and residual TAG levels were determined by GC-FID. Results: Human milk and the IFs showed comparable total FA release. In the gastric phase, 4-11% of lipolysis occurred, and mainly short (SCFA)- and medium chain fatty acids (MCFA) were released. In the duodenal phase, lipolysis proceeded with release of C4:0 but was marked by a fast release of long-chain fatty acids (LCFA). The digestion of the IFs resulted in different FFA profiles during and at the end of digestion. IF2 gave more release of C4:0-C11:0, which reflects the FA composition of bovine milk. Conclusion: The addition of bovine milk fat to IF resulted in a total FA release comparable to an IF with only vegetable fat and human milk. However, it did lead to a different time-dependent release of individual FAs, which might result in differences in absorption and other health effects in vivo.