Described are optical isomers of (+) &dgr;-decalactone and (+) &dgr;-dodecalactone which impart, augment and/or enhance the aroma and/or taste of consumable materials including foodstuffs, chewing gums, toothpastes, beverages, fragrance compositions, colognes and perfumed articles such as solid or liquid anionic, cationic, nonionic or zwitterionic detergents, fabric softeners and hair preparations. The optical isomers are produced by means of a two-phase, environmentally friendly fermentation process for producing high yields of (+) &dgr;-decalactone and (+) &dgr;-dodecalactone from the corresponding unsaturated starting materials. The (+) &dgr;-decalactone substantially has the structure: with a very minor amount of isomer having the structure: and an optical rotation of +53.64° ((&agr;D20=+53·64° ) ). The (+) &dgr;-decalactone, which is the subject of the invention, has an enantiomeric excess percent of 95.6 ([&egr;&egr;%=95.6]).