D-aspartate and D-glutamate in microwaved versus conventionally heated milk.
OBJECTIVE
It has been reported that microwave heating of infant formulae can isomerize and racemize amino acids in the milk proteins, causing toxicity or affecting the nutritional value of the milk formulae. Therefore, we investigated whether microwave heating vs conventional heating would produce any D- enantiomers of aspartic acid (Asp) and glutamic acid (Glu) in milk.


METHODS
Whole and skim milk samples were heated for 10 minutes in either a microwave oven at medium power or on a hot water bath at 80 degrees C. D-Asp and D-Glu were determined by high performance liquid chromatography.


RESULTS
Unheated (control) samples were found to contain 0.40-0.45% D-Asp and D-Glu, inherent from the original pasteurizing process. Both conventional heating and microwave heating induce < 0.25% more racemization when compared to the control samples.


CONCLUSIONS
Within experimental error, there is no significant difference in the levels of these D-amino acids between the conventionally heated and microwave heated milks, thus having no significant effect on the nutritional value of the milk proteins.
Petrucelli
L
L
Department of Chemistry, Barry University, Miami Shores, Florida 33161.
Fisher
G H
GH
D000818:Animals; D001224:Aspartic Acid / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D005971:Glutamates / Q000032:analysis*; D018698:Glutamic Acid; D006358:Hot Temperature; D008872:Microwaves; D008892:Milk / Q000737:chemistry* / Q000528:radiation effects
D005971:Glutamates; D001224:Aspartic Acid; D018698:Glutamic Acid