Effects of Added Copper on Concentrations of Volatile Materials Produced in Milk

Abstract

Analyzing the steam distillate from milk enabled measurement of increases in concentrations of n-hexanal, n-pentanal, propanal, acetaldehyde in raw, laboratory-pasteurized, and plant-pasteurized-homogenized milk exposed to 0 and 5 ppm added copper. Greatest changes were in the copper-treated laboratory-pasteurized milk and the least in Vacu-Therm pasteurized-homogenized milk. The 2-thiobarbituric acid values (TBA) in the exposed milk, laboratory pasteurized, .090; raw, .078; plant pasteurized, .056, reflected changes in volatile materials. Acetaldehyde concentrations increased about the same in whole pasteurized-homogenized milk as in skimmilk exposed to 1 or 2 ppm copper. The other carbonyl compounds increased consistently in whole milk, but little or none in skimmilk. Increases in concentration of the carbonyl compounds (other than acetaldehyde, acetone, and butanone) produced in pasteurized-homgenized milk exposed to 4 ppm copper for 44 h were reduced by adding 150 mg of ascorbic acid per liter of milk. However, the concentrations were greater in ascorbic acid-copper-treated milk than in milk not treated with copper. Adding the steam distillate from copper-oxidized milk produced the typical copper-oxidized flavor in good-flavored milk.