Where does the water in a ripe piece of fruit come from?

Factual Questions
1

I bought a nectarines last week and they were a little under ripe. I had one–which was edible–but very crunchy, unsweet, and dry. I left the others on the table for a week and when I bit into one today, it was ripe and brimming with juices. Where did the juice come from?

2

I’m guessing that when starch converts to sugar, H[sub]2[/sub]O is released.

3

It’s the exact opposite, to the best of my knowledge. I don’t know the answer to the OP’s question, unfortunately.

4

Hydrolysis does indeed add a molecule of H2O to starch to generate simpler sugars. However, the degradation of starch by amylase (the same enzyme that breaks down starch in your saliva) increases juciness via osmosis by reducing the floury quality of the fruit. Here is a simple, but effective link (hey it’s late)

http://plantphys.info/plants_human/fruitgrowripe.html

I also assume that you are talking about fruit like bananas that ripen. Some fruits like cherries, oranges, etc… do not really ripen so much as ‘mature.’ This has to be done on the tree for it to really work.

I got asked this question 2 years ago when I first started teaching plant science (I’m a developmental genetcist so this isn’t my area) and it took me far too long to figure it out. Hope this helps -

5

Polysaccharides such as starch and pectin can bind up quite a lot of water by non-covalent interactions. As these large, poorly soluble polysaccharides are broken down to sugars, some of the water is used up for the hydrolysis, but the rest of the bound water is more mobile as the sugar moieties are dissolved in the juice.

6

Awesome answer.