My grandparents in Toronto bought 10 kg of Ontario coronation grapes from Loblaws on Sep 1 2019, as they have been doing the past 10 years. They don't know why, but the grapes taste too sour and acidic this year, and they couldn't eat any more after tasting a few. So they placed them in a freezer to sweeten them.
Today they thawed 20 grapes but these still taste inordinately sour and acidic! So:
For maximal sweetness, how long ought they freeze them?
How does the duration of freezing affect the sweetening? To wit, what are the 1st and 2nd derivatives of freezing w.r.t. sweetening? Did I formulate my question correctly with calculus?