I would like to make my own wine. However I will not be able to watch over it the entire time to assure it has not been touched by a nuchri.
May I cook the grapes in hot water PRIOR to adding in yeast and any extra sugar I want to put in, and thereby consider the wine to have been mevushal? Or does cooking it at this early stage (prior to any fermentation) not qualify as making it mevushal? Or even if it does qualify as mevushal is the mevushal status then no longer continue if the wine ferments subsequently and becomes a better (alcoholic) wine.
Note: once it was cooked I would have to wait till it cooled down in order to add the yeast or the yeast would get cooked and die.
It is controversial if cooking the grapes will render the wine mevushal regarding yayin nesach. There are a number of kashrus organizations in the states that rely on the lenient opinion.
Iggeros Moshe YD 1:50, 2:52 says that it would be considered mevushal, also see Har Tzvi Y:D 112 cites Amudei Ohr that says the same thing. However Avnei Nezer YD 113:20 is machmir.