Mixtures of fatty acid ethyl esters were produced by lipase-catalyzed ethanolysis of milk fat triglycerides. Three commercial immobilized lipases (Lipozyme TL, Lipozyme RM, and Novozym 435) were tested in different reaction conditions with the aim of maximizing the conversion of the short-chain fatty acid fraction of milk fat to flavor ethyl esters. The influence of the reactants molar ratio was investigated, as well as three different reaction media, that is, hexane, CO(2)-expanded liquid (GXL), and the solvent-free mixture. Novozym 435 showed the highest activity in all conditions. This lipase also exhibited selectivity for short-chain fatty acids, which, at short reaction times, resulted in a product mixture richer in short-chain fatty acids than the original milk fat. The highest selectivities were obtained in hexane and in CO(2)-expanded liquid fat, at low ethanol to fat ratios. Using dense CO(2) as the reaction cosolvent is attractive because it results in the largest short-chain fatty acid enrichment in the product mixture, while leaving no residues in the product.

The overall decline in milk fat consumption experienced in the last decades has promoted global research eVorts seeking for alternate uses of this valuable natural fat. Milk fat possesses a pleasant Xavor and a rich chemical composition, including a range of bioactive, health beneWcial minor components. The main drawbacks of milk fat from the consumer point of view are its poor spreadability at refrigeration temperature and its high content in saturated fatty acids, which raises health concerns. However, the rich fatty acid composition of milk fat could be utilized for the production of a wide range of added-value derivatives in the food and cosmetic industries, including nutritionally enhanced modiWed fats, food emulsiWers, Xavors, and tailor-made lipids. A promising strategy for the revalorization of milk fat encompasses the isolation and commercialization of the valuable minor components of milk fat, coupled with a broader utilization of physically or nutritionally improved milk fat fractions and derivative products.

We propose a novel process for the production of a DAG-rich acylglycerol mixture derived from milk fat. This product has potentially interesting nutritional properties, derived from both its high content of DAG and of short-chain fatty acids (FAs). The proposed process consists of three steps: lipase-catalysed partial ethanolysis of milk fat, extraction of the by-product fatty acid ethyl esters (FAEEs) using supercritical carbon dioxide (SC-CO 2 ) and isomerization of DAG to increase the proportion of 1,3-DAG. The experimental investigation of the process steps was done using milk fat and trilaurin. Several lipases were tested for maximizing the percentage of DAG in the acylglycerol mixture produced by ethanolysis. The selectivity of the chosen lipase was such that the produced AG mixture was enriched in short-chain FAs in relation to the original milk fat. FAEEs were completely extracted from the ethanolysis mixture by SC-CO 2 . In the final process step, we explored the reaction conditions for facilitating acyl migration in the DAG mixture, so that the equilibrium proportion of 1,3-DAG (64%) was attained. Our results set the basis for the development of a simple process for the production of a DAG-rich milk fat analogue.

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