Polygalacturonase activity and variation in ripening of papaya fruit with tissue depth and heat treatment

Abstract

1989. Polygalaeturonase aetivity and variation in ripening of papaya fruit with tissue depth and heat treatment -Physiol. Plant. 77; 93-98.Effects of tissue position (viz. outer vs inner mesocarp) and heat treatment (48°C, 20 min) on variations in polygalacturonase (EC 3.2.1.1.5 and EC 3.2.1.67) activity and ripening of fruits of Catica papaya L. ev. Backctoss Solo were investigated. Polygalaeturonase aetivity increased during ripening concotnitantly with an ineteasc in tissue softness and soluble polyuronide level. Throughout ripening, inner mesocarp tissue was softer and eontained higher polygalaeturonase activity than outer mesocarp tissue. Tittatable acidity as well as /i-galactosidase (EC 3.2.1.23) activity also increased during ripening; however, unlike polygalacturonase, their level or activity was lower in inner than in outer mesoeatp. Ascorbic acid could paitially account for the inerease in titiatable acidity during ripening but contributed very little to the differences in titratable aeid levels between outer and inner mesoearp. Heat treatment had no effeet on either fruit softness or tittatable aeidity, but it markedly redueed the increase in ascorbic acid and polygalacturonase activity during ripening. Ripening, as reflected by ehanges in tissue sottness and polygalacturonase activity, progressed outwatdly frotn the interior towatds the exterior of the fruit. The effect of heat treatment in supptessing polygalacturonase activity was relatively greater in inner than in outer mesocarp, suggesting that sensitivity of the enzyme to heat treatment may vary with stage of ripeness of the tissue.

The effect of antifungal hot-water treatments on papaya postharvest quality and activity of pectinmethylesterase and polygalacturonase

“…Jagtiani et al (1988) reported pH in papaya varying between 5.5 and 5.9, and TSS between 5.65 and 7.1%. Also, Lazan et al (1989) observed that hot water treatments at 48°C for 20 min, did not affect TA in papaya cv 'Backcross Solo' stored to 24-28°C.…”

“…However, they observed a significant PGactivity inhibition when the hot water treatments were applied at more advanced ripeness stages (quarter and half ripe). In addition, Lazan et al (1989) reported that the effect of heat treatments in suppressing PG activity was relatively greater in inner than in outer mesocarp, suggesting that sensitivity of the enzyme to heat treatments may vary with stage of ripeness of the tissue. It is well known that the ripening of papaya initiates at the inner area of the pulp and it is followed for the outer area.…”

“…For papaya cv 'Solo', the PG-activity inhibition has been correlated to delayed softening by Chan et al (1981) suggesting that PG activity is important during Decay and enzymatic activity of PME and PG in papaya fruit pulp treated with hot water at 55°C for 0, 3, 6, and 9 min. Vertical bars are the standard error of the mean of at least four replicates its softening process, although Lazan et al (1989) reported that the extent of tissue softening in cv 'Backcross Solo' during tissue ripening may not be dependent entirely on PG action. Because of the measured-in-pulp physico-chemical parameters (TSS, pH, TA, Firmness), and PME-, PGactivity were not significantly affected, it is observed that the tested AHWT had no effect on the overall ripening process of papaya fruit.…”

“…Furthermore, they alleviate some physiological disorders as chilling injury (McDonald et al 1993;Chan et al 1994). However, the excessive-heating effect on ripening (Paull 1994;Paull and Chen 1990) and on papaya-polygalacturonase activity has also been reported (Chan et al 1981, Lazan et al 1989. Chan et al (1981) observed a significant PG-activity inhibition when the hot water (HW) treatments of 46°C for, 40, 65 and 90 min were applied on Papaya cv Solo at their advanced ripeness stages (quarter and half ripe).…”

Influência da atmosfera modificada por filmes plásticos sobre a qualidade do mamão armazenado sob refrigeração

“…Este incremento pode ser devido à intensificação da atividade metabólica característica do pico climatérico do mamão, o que levaria à síntese de ácidos orgânicos [3,13].…”