DEVELOPMENT OF DARK SKIN DISCOLORATION ON PEACH AND NECTARINE FRUIT IN RESPONSE TO EXOGENOUS CONTAMINATIONS

Dark skin discoloration development on peach and nectarine cultivars w as investigated in response to exogenous pH and metallic ions. The inf luence of skin abrasion and washing in combination with exogenous cont aminants was studied in a factorial design experiment by using skin di scs. Only abraded skin discs with and without washing developed discol oration after being exposed to high pH and different metallic ion conc entrations. Among the metallic ion contaminants studied (Fe, Al, Cu, S n, Zn, and Na), iron was the most effective in causing dark skin disco loration at physiological pH (3.5). Iron concentrations greater-than-o r-equal-to 10 ppm induced dark discoloration on abraded fruit skin. Da rk discoloration development produced by exposing the skin tissue to p H levels >6 was reversible, whereas the dark discoloration induced by iron and aluminum remained stable.