Author(s): JW Finley, WF Shipe
Organoleptic evaluation of centrifugal fractions of unexposed and light-exposed milk indicates that a low density lipid-protein fraction is a principal source of light-induced flavors in milk. The protein portion of the fraction appeared to undergo a partial degradation resulting in losses of tryptophan, tyrosine, lysine, cysteine and methionine. The lipid portion was partially oxidized as indicated by decreased oleic and linoleic acid and production of a series of 2,4-dinitrophenylhydrazine reacting products. The light-induced changes in the lipid portion were different from those induced by addition of copper ions to milk.