Ascorbic acid content of most fruits is generally low during early stages of fruit development,since the fruit is at the process of cell division and cell elongation.as the fruit advances toward the stage  of physiological maturity, ascorbic acid content start to increase, due to the increase in the concentration of the sugar galactose. it is known that galactose is the starting point for the synthesis of ascorbic acid. as the fruit enters the ripening  phase, there is a slight decrease in ascorbic acid content. this is the case in most fruits. however, in some fruits, such as water melons,the increase in ascorbic acid continues to the fully mature fruit. there is agood deal of work on gene expression and ascorbic acid synthesis in many fruits.

to reduce deterioration to organelles  and get rid off ROS.  This is a build in mechanism enhanced genetically when excessive amounts of sugars available at the ripening stage

Rippening is senescence and it usualy accompained by highest production of oxidnts,and thus required Vit c as antioxidants to escavene produced oxidants 

Ascorbic acid content of fruits is never constant but varies with some factors which include climatic/environmental conditions, maturity state and position on the tree, handling and storage, ripening stage, specie and variety of the fruits as well as temperature

Hi Dhia,

You said that: "this question is in the area of storage technology of horticultural crops."

During storage, instead of increase of vitamin C, it should decrease. See this link. It states "Vitamin C (also known as ascorbic acid) is highly unstable and has short shelf-life. While unripe fruits have high concentrations of vitamin C, this diminishes as the fruit ripens. As ripe fruits age, the vitamin C continues to disappear."

https://www.education.com/science-fair/article/vitamin-c-ripe-orange/

And, this matches my experience, while unripe (greener) fruits are sourer, ripe fruits are usually not sour, but sweeter (of course, this includes some carbohydrate/sugars change in the fruits)..

Dear Yuan-Yeu Yau Esq

His question was at fruit ripening stage (maturity) thats means before harvesting. No Doubt in storage where low temperature contiuous decrease occurs owing to degredations . Thanks 

Thanks Caser Ghaafar Abdel for your response.

There are two kinds of ripening strategies: (1) Naturally ripening on the trees, (2) harvest them while they are still green and ripening on the shelf. Actually, there are many people who are asking what are the change/difference of the nutrients between (1) and (2). For example, the link below:[https://www.reddit.com/r/askscience/comments/1nnfpz/is_there_a_nutritional_difference_between_fruit/]

So, when he said 'ripening stage', it could refer to either one. But, the Sub-title of his question and his project are something to do with 'storage technology'; that is why I gave the answer above. Just to provide another possible answer to his question.

Thanks Dr. Yuan for kind interpretation... for horticultural harvest, maturity and ripening 

Thanks Caser Ghaafar Abdel. I also read that higher vitamin C during the maturation of fruits on the trees can increase the duration of storage (or shelf time). [I could not find the paper again.] This leads me to think that manipulate the vitamin C synthesis pathway by genetic transformation might be a way to improve later storage efficiency.

The amount of vit.c increase at ripening stage of fruits because during this period the anabolic processes are very intense, these metabolic reactions requiring increased energy intake, this energy is produced in the electron transporting chain where free radicals appear in increased quantity and the synthesis of vitamin C, which acts as coenzyme and captures these free radicals.Therefore, the more free radicals the higher the amount of vitamin C is necessary.

Iuliana

Sure Dear Prof Yuan Since Vit C is a non enzymatic small antioxidant and shelf lief usually depend upon respiration where oxidants are generated Thanks indeed

We devised a method to assay physiological changes in ripening tomatoes. Analysis of the same fruit in two different stages of maturity served to compensate for individual variability. Each fruit was cut in half; one half was analyzed in the green state, the other half was analyzed after ripening. Faster ripening tomatoes contained significantly more ascorbic acid when ripe than did slower ripening ones. In addition, the results indicate that ascorbic acid increases in the ripening of detached

Dear Dr. Taain

the vitamin C contents of many fruits such as sour orange, cashew, apple, mango, pine apple, orange and guava is higher when they are slightly immature, and declines as they hits peak ripeness. For a few, such as water melon, the vitamin C contents does the opposite, it rises with increased ripeness.