Lipase-catalyzed modification of milk fat: A promising way to alter flavor notes of goat milk products

The rancid and tart off-flavor of goat milk limits the popularization of its associated products. In this study, a two-step enzymatic catalysis method was proposed to generate new aromatic notes that could alter the negative flavor perception of goat milk products. The goat milk fat was first hydrolyzed to prepare fatty acids (FFAs) as substrates, and then esterification was carried out for the synthesis of esters with pleasant notes. In the first step, the FFAs were sufficiently released, accounting for 97.5% of the volatile fraction. In the final reconstituted goat milk product, esters with sweet, floral, and fruity-like notes occupied more than 65% of the total volatile compounds, while the abundance of fatty acids characterized by unpleasant odor decreased by 75%. Especially, 4-methyloctanoic acid, one of the FFAs responsible for the "goaty" flavor, was not detected under the substrate molar ratio of 0.4. Moreover, the performance of four commercial lipases was investigated and compared during the first step. Lipozyme TL IM was the most efficient in the catalysis of lipid hydrolysis at 60 °C and pH 8.0. The two-step lipase-catalyzed product provided a sweet and fruity note to goat milk products and reduced the intensity of the unpleasant "goaty" flavor.