Direct Recovery of Off Flavors From Foam-Dried Whole Milk

Off-flavor compounds were obtained by a short-path migration at 1 μ pressure to a liquid nitrogen-cooled condenser, from dried milk warmed to 40C or less for 3 hr. Milks reconstituted from stale and oxidized powders, both before and after treatment, and market milk, both with and without the condensed volatiles, were evaluated by a five-man taste panel. The volatile flavors were oxidized, stale, unclean, astringent, and foreign. As with the author's earlier findings with regard to added ketones, the procedure is made more effective by first freeing the fat in the powder. Compounds recovered from a slightly stale dried milk gave a stale flavor to control milk, but their removal did not improve the residual powder. Compounds recovered from a strongly oxidized dried milk gave an oxidized flavor to control milk and their removal definitely improved the flavor of the residual powder. From four experiments with high free-fat oxidized dried milk, the average scores were: powder control—27.2; powder residue (powder control less volatiles)—30.7; milk control—37.8; milk plus volatiles—28.8.