QUANTITATIVE EVOLUTION OF SUGARS IN BANANA FRUIT RIPENING AT NORMAL TO ELEVATED TEMPERATURES

We have confirmed that the 3 main sugars of banana fruit are fructose, glucose and sucrose. In both the pulp and peel of bananas ripened at 20 and 30°C sucrose is the predominate sugar in the pre and climacteric stages; in the post-climacteric period, glucose and fructose are the predominate sugars. Ethylene treatment applies prior to the onset of the climacteric increased the sucrose concentration at the peak by 8% in comparison to the controls.

There is a noticeable suppression of sucrose concentrations in bananas ripening at 40°C but fructose and glucose remained unaltered. At 45°C ethylene treatment influenced glucose and fructose; at 50°C total sugar increase is less than 1.5%. Thermal inactivation of the sucrose synthesizing enzymes is probably the cause of the lack of sucrose in bananas ripened at 40°C. Furthermore, since ethylene was shown to have an effect on glucose and fructose synthesis during ripening at 45°C, it may indicate that ethylene provides some thermal protection or can replace a cofactor in some way.