Regiospecific positioning of palmitic acid in triacylglycerol structure of enzymatically modified lipids affects physicochemical and in vitro digestion properties

Abstract

Tripalmitin‐(PPP, 81.2%), 1,3‐dipalmitoyl‐2‐oleoylglycerol‐(POP, 64.4%), 1,2‐dipalmitoyl‐3‐oleoylglycerol‐(PPO, 86.5%), and 1,3‐dioleoyl‐2‐palmitoylglycerol‐(OPO, 50.2%)‐rich lipids with different regiospecific positions of palmitic acid (P) were synthesized via acetone fractionation and lipase‐catalyzed acidolysis, and their physicochemical and hydrolytic characteristics were compared. Triacylglycerols (TAGs) with higher content of P, wherein P was at the sn‐1 (or 3) position, had higher melting points, crystallization temperatures, and packing densities of fat crystals compared to those with a lower content of P, and with P at the sn‐2 position. The in vitro digestion degree calculated as released fatty acid (FA) (%) at 30, 60, and 120 min was in the following order: OPO‐rich > PPO‐rich > POP‐rich lipids. At 120 min, in vitro digestion of the OPO‐rich lipid released 92.6% of fatty acids, resulting in the highest digestibility, while 89.7% and 87.2% of fatty acids were released from the OPO‐rich and PPO‐rich lipids, respectively. Over the digestion period, the TAG and monoacylglycerol (MAG) contents decreased, while the diacyl-glycerol (DAG) content initially increased and then decreased, and the 1,2‐DAG content exceeded the 1,3‐DAG content. Therefore, the content and stereospecific position of P attached to a specific TAG affected the physicochemical and in vitro digestion characteristics of the lipids.