Abu-Bakr Ali Abu-Goukh

Compositional changes during guava fruit ripening

Abstract Compositional changes of fruit pulp and peel during ripening of white- and pink-fleshed guava fruits were studied. The white and pink guava fruits exhibited a typical climacteric pattern of respiration. Fruit tissue firmness decreased progressively, in a similar manner, in both guava fruit types. Total soluble solids (TSS) and total sugars increased in pulp and peel of both guava types with decrease in flesh firmness. More increase in total sugars was observed after the climacteric peak of respiration. Reducing sugars and titratable acidity increased up to the full-ripe stage and then decreased. Ascorbic acid and phenolic compounds decreased continuously during ripening of the two types. The peel showed higher values of ascorbic acid, total protein and phenolic compounds than the plup. The white-fleshed guavas had higher levels of TSS, total sugars, reducing sugars. titratable acidity, phenolic compounds and ascorbic acid content then the pink-fleshed fruits.

Changes in pectic enzymes and cellulase activity during guava fruit ripening

Changes in activities of the cell wall degrading enzymes, pectinesterase (PE), polygalacturonase (PG) and cellulase, were studied during the ripening of white- and pink-fleshed guava fruit types. PE activity increased in both guava types up to the climacteric peak of respiration (flesh firmness of 1.21 kg/cm2) and subsequently decreased. Activities of PG and cellulase increased progressively during the ripening of both guava fruit types with a high correlation between the increase in the activity of the two enzymes and the loss of fruit flesh firmness.

Effect of ethrel in aqueous solution and ethylene released from ethrel on mango fruit ripening

Summary The effect of ethrel in aqueous solution and ethylene released from ethrel was evaluated on fruit ripening of ‘Kitchner’, ‘Dr Knight’ and ‘Abu-Samaka’ mango. Ripening was enhanced in all treated fruits of the three cultivars at all concentrations used. The ripening rate progressively increased with increase in concentration. Ethylene released from ethrel was more effective in triggering fruit ripening than dipping fruits in aqueous solution of ethrel. Depending on concentration and cultivar, ripening was 1–3.d faster in fruits dipped in 500 and 1000 ppm ethrel and 1–5.d earlier in fruits treated with 250, 500 and 1000 ppm ethylene released from ethrel, compared with untreated fruits. The effect on fruit ripening was indicated by enhanced climacteric peak, increased skin colour, increased total soluble solids and decreased flesh firmness.