Enzymatic and chemical conversions taking place during in vitro gastric lipid digestion: The effect of emulsion droplet size behavior

This investigation reports the effect of droplet size behavior on the overall lipolysis profile and molecular lipolysis mechanisms under in vitro gastric conditions. O/W emulsions (5% triolein, 1% sodium taurodeoxycholate) with different initial droplet sizes (fine: 0.58 mu m; medium: 1.82 mu m; and large: 4.00 mu m) were subjected to static in vitro digestion. For the first time, multiple lipolysis products including diolein and monoolein regioisomers were quantified within a single HPLC run. An inverse relation was found between the droplet size and the initial rate and final extent of lipolysis based on the digested triolein. Furthermore, a mechanistic gastric lipolysis model was established based on a reaction scheme including enzymatic and chemical isomerization conversions. The estimated rate of the sn-1/3 hydrolysis was around two- to thirty-fold faster compared to the rates of sn-2 cleavage and isomerization, respectively. These findings resulted in a profound insight in in vitro gastric molecular lipolysis mechanisms.