Keywords: conservation, refrigeration, internal browning, polyphenoloxidase, phenylalanine-ammoniumlyase.
The relationships of fertilization to quality and susceptibility to internal browning of Zacatecas-type local race peach fruits under cold storage were studied. The research was conducted in an orchard with 10-year-old seedling trees. Six fertilization treatments were evaluated: T1, 100-20-00; T2, 150-50-80; T3, 200-20-100; T4, 100-20-00+F; T5, 150-50-80+F; T6, 200-20-100+F (kg·ha-1 of N, P2O5, and K2O for T1, T2 and T3 and kg·ha-1 of N, P2O5 and K2O plus foliar application of Poliquelâ for T4, T5 and T6). Parameters evaluated were firmness, color, titratable acidity, total soluble solids, and ethanol and acetaldehyde content. Total phenols, polyphenoloxidase, and phenylalanine-ammonialyase. Soil fertilization with the lowest nitrogen content plus foliar application increased flesh firmness, which persisted during storage at 5 ºC as well as later at room temperature. Foliar applications with high potassium content improved fruit color. Soil fertilization with higher nitrogen content reduced fruit firmness, while potassium increased phenol content. Foliar fertilization improved fruit color and increased the activity of phenylalanine-ammoniumlyase and reduced polyphenoloxidase. Both soil and foliar applications significantly changed total soluble solids, malic acid and ethanol. Higher nitrogen fertilization increased acetaldehydes. Fruits stored under refrigeration, as well as those later exposed to room temperature, ripened normally.