Synthesis and microencapsulation of structured lipids containing long-chain polyunsaturated fatty acids for possible application in infant formulas
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It has been well established that lower fat absorption in infants, fed with formula, is due to the difference between the regiospecificity of the palmitic acid in the vegetable oil blend versus that present in human milk fat (HMF). In HMF, most of the palmitic acids are esterified at the sn-2 position of the triacylglycerols (TAGs). However, in vegetable oil, they are predominantly present at the sn-1, 3 positions. Structured lipids (SLs), with fatty acid profiles and positional distributions similar to HMF, were developed via a single step enzymatic modification of either palm olein or tripalmitin. These SLs also were also enriched with long-chain polyunsaturated fatty acids (LCPUFAs), such as docosahexaenoic (DHA) and arachidonic (ARA), which are important for infant brain and cognitive development. SL from modified tripalmitin contained 17.69% total ARA, 10.75% total DHA, and 48.53% sn-2 palmitic acid. Response surface methodology was employed to study the effect of time, temperature, and substrate molar ratio on the incorporation of palmitic acid at the sn-2 position, and the total incorporation of LCPUFAs. Physicochemical properties of SLs were characterized for TAGs molecular species, melting and crystallization thermograms, and fatty acid positional distribution. SLs in powdered form were obtained by microencapsulation, using Maillard reaction products (MRPs) of heated protein-polysaccharide conjugates as encapsulants, followed by spray-drying. SL-encapsulated powders had high microencapsulation efficiency and oxidative stability. Infant formula prepared with microencapsulated SL in a dry-blending method, had a better oxidative stability and color quality than the formula prepared with non-microencapsulated SL in a wet-mixing/spray-drying method.