F. Artes et Mc. Salmeron, QUALITY ATTRIBUTES, PECTOLYTIC ENZYME-ACTIVITIES AND PHYSIOLOGICAL-CHANGES DURING POSTHARVEST RIPENING OF NECTARINE, Journal of food quality, 19(6), 1996, pp. 491-503
The postharvest ripening at 20C and 90-95% RH for 10 days of 'Armking'
nectarine grown in a greenhouse was investigated over two seasons. Fi
rmness, titratable acidify, ascorbic acid, pH and maturity index were
all adequate to stablish the rate of ripening. However, soluble solids
content and reducing and non-reducing sugars showed no significant ch
anges. It took about 10 days for very early ripening fruit (100 g weig
ht and 82 N firmness) and 6 days for normal early ripening fruits (115
g weight and 46 N firmness), both harvested at preclimacteric stage,
to become eating ripe (near 20 N). Total weight loss and decay after 1
0 days was approximately 11%. During ripening there was a temporal coi
ncidence among higher rates of ethylene production, higher pectinmethy
lesterase (PME) and polygalacturonase (PG) activities, lower firmness
and acidity and higher maturity index. PME and PG activities increased
during ripening, with a highly negative linear correlation between ac
tivities of the two enzymes and firmness. In very early ripening fruit
, PME activity was more closely related to softening than PG, whereas
in normal early ripening fruit, PG activity was slightly more closely
linked to the loss of firmness than PME.