The interacting effects of ascorbic acid and metal ions on carotene oxidation were studied in an aqueous carotene-linoleate solution at pH 7. Ascorbic acid at concentrations up to 10W3M was a prooxidant. Fe3+ and, to a lesser extent CoZ+, acted synergistically with ascorbic acid, the prooxidant effect increasing with metal concentration. Cu*+ formed a prooxidant system with ascorbic acid only at low metal concentration, but as the copper concentration was raised, inversion of activity occurred and the copper-ascorbic acid system exerted a stabilizing action on carotene. Prooxidant effects were enhanced and antioxidant effects weakened in the presence of added lmoleate hydroperoxides. The latter were unstable in the presence of ascorbic acid and especially ascorbic acid + Cu '+. Ascorbic acid itself became unstable in the presence of Cu *+ Oxygen depletion, brought about by the rapid . oxidation of ascorbic acid, may be partly responsible for the carotenestabilizing effect of the Cu*+ -ascorbic acid couple. It is postulated that additional stabilization results from the radical-scavenging properties of copper or of a copper chelate formed by ascorbic and/or dehydroascorbic acid.

No abstract

The activity of aqueous extracts from red pepper fruits (Capsicum annuum L.) toward the oxidation of carotene presence of linoleate was measured by a calorimetric method. Highest activities were achieved by using as extractant distilled water or Tris buffer at pH 7.0, whereas solubilization of carotene-bleaching factors by Triton X-100 or preparation of acetone powder from pepper fruit extracts resulted in losses in carotene-oxidizing activity. After dialysis, ammonium sulfate precipitation and chromatographic purification on Ecteola and Sepharose 6-B, a proteinous carotene-oxidizing fraction was obtained which exhibited properties similar to those of a peroxidase, i.e., high specific activity toward guaiacol oxidation in the presence of hydrogen peroxide, precipitation with ammonium sulfate between 60 and 95% saturation, change in spectral absorbance upon addition of cyanide, inhibition of carotene bleaching activity by KCN, and typical changes in carotenebleaching activity with pH and protein concentration.

The content of a-tocopherol in pepper fruits (Capsicum annuum L.) and its stability during dehydration and storage were determined. Our data show that the three pepper varieties used in this study, regardless of stage of maturity, contained from 9000 to 10000 pg of a-tocopherol/g of oil (oleoresin). The a-tocopherol content in the fresh pepper and its dry matter was found to depend on the content of lipids which in turn depends on ripening stage and genetic variety factors. During dehydration the loss of a-tocopherol in red pepper fruits was less than 5%. The a-tocopherol was found to be unstable in powdered pepper stored a t low water activity, a,, but very stable at high a,. The large amount of a-tocopherol found in the fresh ripe fruits, ca. 3-10 mg/100 g, indicates that this vegetable could become an important source of vitamin E in the human diet.