SULFITE-MEDIATED DESTRUCTION OF BETA-CAROTENE

Sulfite-mediated β-carotene destruction was investigated in two systems. In the first system, which consisted of Mn2+, O2, glycine, and sulfite, over 90% of the β-carotene was destroyed in 15 s. Destruction occurred concurrently with the aerobic oxidation of sulfite and was effectively inhibited by the free radical scavengers α-tocopherol, l, 2-dihydroxybenzene-3, 5-disulfonic acid, and butylated hydroxytoluene. In the second system, which consisted of linoleic acid hydroperoxide and bisulfite, about 80% of the β-carotene was destroyed in 15 s; oxygen was not required. Destruction occurred concurrently with the disappearance of sulfite and hydroperoxide. The free radical scavengers α-tocopherol and butylated hydroxytoluene effectively inhibited the destruction of β-carotene, but the singlet oxygen quencher 2, 5-dimethylfuran was only slightly effective. Addition of metal chelators indicated metals were not participating in the reaction. This evidence indicates that in these two systems β-carotene was destroyed by free radicals, though via different mechanisms. A possible mechanism which accounts for such reactions is described. © 1979, American Chemical Society. All rights reserved.