Effect of Pollution of Air with Ozone on Flavor of Spray-Dried Milks

Abstract

In an investigation of seasonal variations in the flavor quality of milk powders manufactured in the Dairy Products Laboratory, we conducted a series of experiments in which low-heat, spray-dried milks were manufactured during a period of low background levels of ozone. The effect of ozone on the flavor of dried milks was ascertained by manufacturing, in each experiment, powders both with and without addition of ozone to the dryer air, and subsequently evaluating their flavor by a trained taste panel.Levels of ozone reported by others as occurring in the atmosphere of the Washington area during the warm weather months were sufficient to lower substantially the flavor score of dried milks. Skimmilk powders manufactured in air containing 32 ppb (parts per billion) ozone averaged 1.7 flavor points (on a ten-point scale) lower than those manufactured under a background level of 2 ppb. Under the same conditions, whole milk powders averaged 2.9 points lower than the control powders. Foaming heightened the damaging effect of ozone on flavor quality. Raising the ozone level from 32 to 52 ppb produced little or no further effect on the flavor of whole milk powder and only a questionable effect on the flavor of skimmilk powder.