Evolution of Soluble Sugars During Ripening of Papaya Fruit and its Relation to Sweet Taste

Abstract

Fruit ripening is closely associated with compositional and structural changes which can occur before or after harvesting. In papaya fruit, the period of sugar synthesis and accumulation remains poorly understood. The correlation between soluble sugar content and sweetness during papaya ripening was investigated in this study. Soluble sugars accumulated mainly when the papaya fruit was still attached to the plant. After harvest, however, there was still sucrose synthesis, and the sucrose-phosphate synthase activity was highly correlated to the sucrose content, indicating the importance of this enzyme in the process. Sensory analysis showed that there was a dissociation between sugar content and sweet sensory perception, while the pulp softening showed high correlation with the sweetness process, probably due to the easier release of cellular contents in the fully ripened tissue.

The role of hydrolases in the loss of firmness and of the changes in sugar content during the post-harvest maturation of Carica papaya L. var solo 8

“…Other studies showed a decrease of galactose and an increase of glucose due to the degalactosylation of polysaccharide chains in apples, strawberries, tomatoes, and in germinating seeds (Ignacio et al 2011;Brett and Waldron 1996;Pressey 1983). This rapid metabolization of galactose explains why Gomez et al (2002) did not find free galactose in ripped papayas. In fact, they determined that galactose was the main source of carbon during the synthesis of sucrose and that the resulting product was greatly used in the climacteric respiration.…”

“…This result indicates a depletion of the substrates necessary for these enzymatic reactions. Moreover, sugars were the first substrate used for respiratory metabolism in papaya (Gomez et al 2002;Sharma et al 2008) and in peach (Chen et al (2006). Indeed, Harold et al (2011) indicated that respiration is a property of all living cells tissues and is the center of the metabolic processes of development, maturation and senescence of fruit.…”

“…We agree with these authors that the loss of firmness in the papayas is due to the enzymatic degradation of the cell wall, in association with the respiratory activity, the synthesis and the action of ethylene. The increase of the respiratory activity is accompanied by the increase of sugar as substrate for several metabolic processes (Gomez et al 2002;Sharma et al 2008). In general, the amount of reducing sugars and dry soluble extracts (Table 1) of Carica papaya L. var solo 8 increases during storage.…”

“…However, the total sugars concentration (Table 1) increases initially, then, decreases slightly during the maturation. This reduction of total sugars content is due to the increasing use of the saccharose during the climacteric respiration as indicated by Gomez et al (2002) in their work on the evolution of soluble sugars throughout the maturation of papaya solo. They also showed that the accumulation of soluble sugars in papayas was mostly done when the fruit was still attached to the plant.…”

“…On the other hand, papaya, which is also a climacteric fruit does not accumulate starch during it development (Gomez et al 2002). The respiration which implies the use of a considerable amount of sugar as substrates for several metabolic processes increases during the storage of the fruit at ambient temperature.…”