Polyphenols and vascular streaking in cassava

Se investigaron las causas de la deterioracion vascular en raices de 6 var. de yuca que incluyeron una var. local (M4) y 5 hibridos, H226, H1687, H165, H2304 y H97, desarrollados en el Central Tuber Crops Research Institute, Trivandrum, India. Se estudio el contenido total de fenol y los cambios en la acidez titulable de estas var. durante 6 dias consecutivos de almacenamiento. En todas las var. se noto una disminucion en los fenoles totales durante el segundo y el tercer dia de almacenamiento y un ligero incremento al cuarto dia. Hubo un incremento concomitante en la actividad de la oxidasa de polifenol durante el segundo dia y una deterioracion vascular simultanea. Cuando la deterioracion en las raices almacenadas alcanzo el 50-60 por ciento se observo un incremento repentino en los valores fenolicos. Hubo una tendencia similar en la acidez titulable. Las raices tratadas con los inhibidores/inactivadores de la oxidasa de polifenol, acido ascorbico, glutacion y cianuro de potasio en concn. de 4 x 10(-3), 5 x 10(-3) y 5 x 10(-3)M, resp., durante 8 horas, no mostraron sintomas de deterioracion vascular. Los polifenoles pueden oxidarse enzimaticamente hasta constituir quinonas altamente reactivas, que pueden formar complejos coloreados con los aminoacidos y con otras micromoleculas de las celulas. Estos complejos, depositados en los tejidos vasculares, producen el fenomeno de decoloracion azul. (RA-CIAT) spa

The causes of vascular deterioration of roots were studied using 6 cassava var.: local var. M4 and 5 hybrids, H226, H1687, H165, H2304, and H97 developed at the Central Tuber Crops Research Institute, Trivandrum, India. Total phenol content and the changes of titrable acidity of these var. were studied for 6 consecutive days of storage. In all var., a decrease in total phenols was noticed during the 2nd and 3rd days of storage with a slight increase during the 4th day. There was a concomitant increase in polyphenol oxidase activity during the 2nd day of storage, with the simultaneous occurrence of vascular streaking. As the deterioration in storage roots reached 50-60 percent, a sudden increase in phenolic values was observed. A similar trend was observed for titrable acidity. Roots treated with inhibitors/inactivators of polyphenol oxidase (ascorbic acid, glutathione, and potassium cyanide at concn. of 4 x 10(-3), 5 x 10(-3), and 5 x 10(-3) M, resp.) for 8 h did not show symptoms of vascular deterioration. Polyphenols may be enzymically oxidized to highly reactive quinones, which may form colored complexes with amino acids andother micromolecules of the cells. These complexes, on deposition in the vascular bundles, produce the phenomenon of blue discoloration. (CIAT) eng