INVESTIGADORES
PONCE Nora Marta Andrea
artículos
Título:
Chemical and biochemical changes of pumpkin (Cucumis moschata, Duch.) tissue in relation to osmotic stress
Autor/es:
DE ESCALADA PLA M.F.; PONCE NORA M.A.; WIDER, E. A; STORTZ, CARLOS A.; ROJAS, ANA M.; GERSCHENSON, LÍA NOEMÍ
Revista:
JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE
Editorial:
John Wiley
Referencias:
Lugar: Hoboker, NJ; Año: 2005 vol. 85 p. 1852 - 1860
ISSN:
0022-5142
Resumen:
Chemical and biochemical changes of pumpkin (Cucumis moschata, Duch) tissue in relationto osmotic stress were studied and related to tissue textural behavior. Turgor pressure of raw tissue wasadjusted by immersion in hypotonic (0.0 molm−3), isotonic (250 molm−3) and plasmolyzing (1050 molm−3)buffered (20molm−3 potassium phosphate, pH 6.8) solutions of poly(ethylene glycol) 400 (PEG). It wasfound that a substantial proportion of polysaccharides located in the cell wall (CW)–middle lamellae (ML)of studied tissue was water extractable. This proportion decreased when CW-stretch increased. Ionicallybound peroxidase (POX) presented an increased activity in swollen and isotonic tissue, probably associatedto oxidative cross-linking of extensin located in the CW of this tissue, as a response to stress promotedby cut, immersion and turgor pressure change. The resistance of CW to elongation when equilibratedin hypotonic medium, might be ascribed to reinforcement of the CW by the oxidative cross-linking ofextensin, with simultaneous formation of pectin-in-extensin entanglements. Plasmolyzed tissue whereCW is relaxed, showed pectin–rhamnogalacturonan degradation. The water-soluble fraction (WSF) wasshown to be a negative function of CW stretching and infinite force of relaxation.