|MadSci Network: Botany|
I am going to answer this question in general terms. Since you have access to a university library and probably an extension service, you can research specifics for tomato and peach.
Fruits undergo several changes during the ripening process. These include the breakdown of chlorophyll to expose other colored pigments which leads to the color changes we recognize as ripening. Some of these (the carotenoids) are precursors to vitamin A synthesis in humans. Another change that takes place is the conversion of starch to sugar, providing sweetness. Cell wall components are broken down and volatile compounds produced to make the fruit softer and flavorful. All these changes are designed to make the fruit more palatable and attractive to animal (including human) dipersers and requires the expenditure of significant energy by the plant. This information is available in most general botany texts.
I found no specific information on the rate of degradation of nutrients in tomato or peach, but in general, the fresher the better. However a couple of points should be mentioned. Low temperature storage slows degradation in most cases. Also, degradation varies with handling and processing methods. For example hot and wet processing both degrades vitamins due to heat and leaches nutrients out of fruits and vegetables. Low temperature drying preserves and concentrates nutrients.
I was able to get some specifics for red and green tomato provided by the Cooperative Extension Service (at the Univ. of Rhode Island). Their source was: Pennington, J.A.T. (1989). Food values of portions commonly used.
GREEN RED Vitamin A (IU) 789 1394 Vitamin C (mg) 29 22 Vitamin B1 (mg) 0.07 0.07Other B vitamins (B2, B12, niacin) were the same for red and green fruit. You may notice that vitamin A increases when ripening occurs (as color develops) while vitamin C decreases, so the stage of maximum nutrient content may depend on the nutrient of interest. I recommend a trip to the library to find the specifics for the fruit and nutrients that interest you.
Try the links in the MadSci Library for more information on Botany.
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