Effect of a high-temperature stress on endo- beta -mannanase and alpha - and beta -galactosidase activities during tomato fruit ripening.
Sozzi, G. O.; Cascone, O.; Fraschina, A. A.;
Postharvest Biology and Technology Year: 1997 Vol: 9 Issue: 1 Pages: 49-63 Ref: 42 ref.
1997
บทคัดย่อ
Patterns of alpha - and beta -galactosidase ( alpha - and beta -Gal) and endo- beta -mannanase activity were followed in detached tomato cv. Gedera 190 fruits, and the degree of inhibition of activity at high temperatures was evaluated. The potential resumption of enzyme activity when fruits were transferred to a room-temperature environment was also studied. Mature-green fruits were incubated at: (a) 36 deg C for 2 days, (b) 40 deg for 2 days, or (c) 40 deg for 2 days + 36 deg for another 2 days. After heat treatments, fruits were transferred to 21 deg in the dark. Control fruits were stored at 21 deg . In the control fruits, activity was higher for alpha -Gal than for beta -Gal and revealed slightly increasing patterns towards the red-ripe stage. Endo- beta -mannanase activity was not detected in mature-green fruits but appeared at the breaker stage and rose rapidly, reaching constant values at the red-ripe stage. The firmness and enzymatic activities of fruits initially treated at 36 deg for
2 days were similar to those of controls. Galactosidase activity decreased in tomatoes incubated at 40 deg for 2 days; in those whose heat treatment was extended another 2 days at 36 deg , alpha - and beta -Gal reached a minimum of 1/5 and 1/25, respectively, of the initial activity on the fourth day. Endo- beta -mannanase activity could be detected only 6 days after the fruits had been transferred to 21 deg and increased slowly up to 24% of that attained by controls. alpha -Gal showed a low rate of recovery but beta -Gal activity recovered after 16 days at 21 deg . It was concluded that these enzymes could have an active role in the fruit softening process.