Please use this blog to share your ideas and ask questions about postharvest handling practices (click on the hotlinks below).
Dr. Lisa Kitinoja www.postharvest.org
The Postharvest Education Foundation
Perishable produce such as Bananas, Mangoes, Plantains, Pears, Tomatoes etc have some variation in their degree of sweetness and nutrition when they are allowed to mature and are ripened on the mother plant, compared to when harvested unripe and forced to ripen. Over ripened fruit can deteriorate easily and when the sugar spilled on the neighboring fruits in the package it can attract Ants which can damage and attract mold.
QUESTIONS Submitted by: Samuel Ayuba Hamisu (Nigeria)
1. What causes the variation in sweetness when fruits are allowed to mature and ripened on the mother tree compared to those harvested unripe and forced to ripend using ethylene gas?
2. What are the chemical compositional differences that cause the variation in their degree of sweetness?
LK answers: The main difference is the amount of starches that are stored in the fruit when it is harvested, and how much of those starches have been changed to sugars. A fruit that is harvested before it is fully mature will never ripen properly once it is off the plant (it may soften or turn color, but it will not become sweet or have good flavours or aromas). If the fruit is allowed to become fully mature, then it will have enough starches stored so that when it ripens (either naturally or via stimulation with ethylene gas) it will be good quality. But if a fruit is alllowed to ripen on the plant then it will be able to continue to benefit longer from the mother plant’s photosynthesizing and building up more starch and sugars, and the flavors, aromas and color will be the highest quality when it ripens.
Often in the USA fruits are harvested too early and shipped a long distance to market, and so they never develop good flavor. In Africa and India some fruits are harvested when the market price is high (which is usually early in the harvesting season) but before the fruits are fully mature. Leaving the fruits on the plants to ripen is a good idea, but since fully ripe fruits are too soft to survive the marketing chain, we need to choose when to harvest based upon how far away (in time and in distance) the market is from the farm. So harvesting somewhere in the middle (not to early, not too late) will be the most practical choice.