To enzymatically synthesize aroma acetoin fatty acid esters, useful as flavor and fragrance ingredients in foods. Immobilized Candida antarctica lipase B (CALB), performed significantly better than lipases from Rhizopus niveus and Candida rugosa in carrying out the esterification of acetoin and fatty acids. C-4-C-12 straight chain fatty acids were suitable acyl donors and CALB had a strong preference for longer straight chains up to ten carbon atoms. Higher temperatures, 40-60 A degrees C, and higher acetoin/fatty acid molar ratios favored the conversion. The maximum yield of acetoin octanoate obtained was (51 +/- A 1) % after 24 h reaction time in hexane with 0.25 M octanoic acid, 5:1 excess acetoin and an enzyme concentration of 6 g/mol fatty acid at 60 A degrees C. The enzyme activity declined at a steady rate during reuse at 60 A degrees C and after the 10th cycle, 65 % of initial activity was still be retained. This is the first report of acetoin fatty acid ester synthesis by biological method and CALB has been shown to be effective for the lipase-catalyzed esterification of acetion and C-4-C-12 straight chain fatty acids.