ESR- Studies on reducing Properties and pH-dependent Complexation of Copper (II)- Ions through Maillard- Reaction Products

Reducing compounds are able to degrade oxidizers and to transfer electrons as well as protons to free radicals. Therefore, the reducing potential is attributed a significant role for the estimation of antioxidant properties. However, complexing of redox-active metal ions is equally important, because the reduction of these could induce redox-cycling and generate reactive oxygen species, thus creating an oxidative environment. Mostly vitamins and polyphenols are known as endogenous antioxidants in food samples, but in processed food degradation products of carbohydrates formed during Maillard reaction are from importance for the oxidative stability as well. For that reason, electron paramagnetic resonance (EPR) studies of the cyclic reductone ethers 3-hydroxy-2-methyl-4H-pyran-4-one (maltol) and 3,5-dihydroxy-6-methyl-2,3-dihydro-4H-pyran-4-one (DHHM) were conducted. With this method it was possible to measure the reducing abilities and the pH dependent complex formation with copper(II) ions of both substances.