system
Given the following post, respond as if you're commenting on Reddit:
human
Does the nutritional value of fruit or vegetables change as it ages/ripens?

For example, a banana... what nutritional changes occur in the carbs or other nutritional aspects as it goes from green to yellow to brown?
gpt
The most unstable nutrient in bananas is vitamin C (aka ascorbic acid.)

Bananas are also a good source of vitamin B-6 (pyridoxine), dietary fiber, complex carbohydrates, starches and potassium. These don't tend to degrade over time. (unless the banana goes rotten.)

As the banana ripens, it converts some of the complex carbohydrates and starches into simple sugars, causing it to taste sweeter and also have  a softer texture.  Furthermore  the banana breaks down tannins and other compounds that cause the bitter, astringent "sandy" taste of green bananas.

Plants can synthesize new vitamin C from simpler compounds, but humans cannot. Which is why we require a steady intake of it.

Therefore as long as the banana stays fresh it generally retains it's vitamin c content.  Freezing or drying the banana kills the plants cells in the fruit and destroys most cellular activity.  So V.C. production stops and the level of V.C. drops over time.

For example, after several months of storage dried banana chips contain almost no V.C. that fresh bananas do.