Volatile Flavor Compounds in Spray-Dried Skim Milk Powder

The volatile flavor compounds of skim milk powder have been investigated. Commercially processed spray-dried skim milk was homogenized with water, and the volatiles were isolated by simultaneous steam distillation-extraction under reduced pressure (SDE) using diethyl ether as solvent. The odor concentrate was analyzed by gas chromatography and gas chromatography-mass spectrometry. Among 196 individual peaks detected, 187 peaks were definitely or tentatively identified by mass spectrum and modified Kovats indices. Major compounds were 48 hydrocarbons, 18 aldehydes, 20 ketones, 21 alcohols, 29 fatty acids, 8 esters, 2 furans, 7 phenolic compounds, 10 lactones, and 14 nitrogenous compounds, which constituted over 99 % of total volatiles recovered. Most of them originated by breakdown of the major constituent of milk, especially fat to smaller, volatile chemicals or their secondary reaction, or by transfer from the forage.