Changes in cell wall composition associated to the softening of ripening papaya: evidence of extensive solubilization of large molecular mass galactouronides.
Papaya (Carica papaya) is a climacteric fruit that undergoes dramatic pulp softening. Fruits sampled at three different conditions (natural ripening or after exposition to ethylene or 1-methylcyclopropene) were used for the isolation of cell wall polymers to find changes in their degradation pattern. Polymers were separated according to their solubility in water, CDTA, and 4 M alkali, and their monosaccharide compositions were determined. Water-soluble polymers were further characterized, and their increased yields in control and ethylene-treated fruit, in contrast to those that were treated with 1-MCP, indicated a strong association between fruit softening and changes in the cell wall water-soluble polysaccharide fraction. The results indicate that the extensive softening in the pulp of ripening papayas is a consequence of solubilization of large molecular mass galacturonans from the pectin fraction of the cell wall. This process seems to be dependent on the levels of ethylene, and it is likely that the releasing of galacturonan chains results from an endo acting polygalacturonase.
Shiga
Tânia Misuzu
TM
Laboratorio de Quimica, Bioquimica e Biologia Molecular de Alimentos, Departamento de Alimentos e Nutricao Experimental, FCF, Universidade de Sao Paulo, Avenida Lineu Prestes 580, Bloco 14, CEP 05508-900, Sao Paulo, SP - Brazil.
Fabi
João Paulo
JP
do Nascimento
João Roberto Oliveira
JR
Petkowicz
Carmen Lúcia de Oliveira
CL
Vriesmann
Lúcia Cristina
LC
Lajolo
Franco Maria
FM
Cordenunsi
Beatriz Rosana
BR
D029441:Carica / Q000737:chemistry* / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry* / Q000378:metabolism; D005511:Food Handling; D008970:Molecular Weight; D010368:Pectins / Q000737:chemistry* / Q000378:metabolism; D012995:Solubility
D010368:Pectins; C003181:polygalacturonic acid