It is the same reason why unleavened bread was used. Bread was a symbol of Christ, and leaven was a symbol of sin or corruption (as it is a bacteria). Jesus never saw corruption. In the same way, fermented wine is wine(the fruit of the vine, aka grape juice) after it has been fermented or corrupted. The blood of Jesus cannot be symbolized with corrupted wine.
In the Bible, both fermented and unfermented wine (grape juice) is referred to as wine. You must look at the context to figure out whether it's talking about fermented or unfermented wine.
EXAMPLES of fermented wine:
Woe to him who gives drink to his neighbors,
pouring it from the wineskin till they are drunk,
so that he can gaze on their naked bodies!
Look not thou upon the wine when it is red, when it giveth his colour
in the cup, when it moveth itself aright.
At the last it biteth like a serpent, and stingeth like an adder.
EXAMPLES of unfermented wine:
The sceptre shall not depart from Judah, nor a lawgiver from between
his feet, until Shiloh come; and unto him shall the gathering of the
Binding his foal unto the vine, and his ass's colt unto the choice
vine; he washed his garments in wine, and his clothes in the blood of
Definitely unfermented as the wine is being squeezed from the grapes.
And gladness is taken away, and joy out of the plentiful field; and in
the vineyards there shall be no singing, neither shall there be
shouting: the treaders shall tread out no wine in their presses; I
have made their vintage shouting to cease.
Same here. Unfermented as the wine is pressed from the fruit of the vine(grapes).
EXAMPLES WITHIN THE CONTEXT OF THE LAST SUPPER
Seeing as the Bible refers to wine as both fermented and unfermented, which was used at the last Supper?
Then he took a cup, and when he had given thanks, he gave it to them,
saying, “Drink from it, all of you. This is my blood of the
covenant, which is poured out for many for the forgiveness of sins.
I tell you, I will not drink from this fruit of the vine from now on
until that day when I drink it new with you in my Father’s kingdom.”
Both "fruit of the vine" and "new" are descriptions of unfermented wine, and are not descriptions of fermented wine.
And he took the cup, and when he had given thanks, he gave it to them:
and they all drank of it. And he said unto them, This is my blood of
the new testament, which is shed for many. Verily I say unto you, I
will drink no more of the fruit of the vine, until that day that I
drink it new in the kingdom of God.
Once again in Mark, Jesus makes the same mention of the fruit of the vine, and new. Luke mentions the same. There is more Biblical proof that this is unfermented, new wine (plain grape juice) than fermented. If anyone feels any different, I challenge you to show me Biblical proof that fermented wine was used in the last supper. You will find there is no Biblical support for this kind of thinking, only traditions of men.
Just ask yourself this. Why would God denounce the use of fermented wine in one part of the Bible, but allow His own Son to drink this? Isn't this inconsistent?
For more information on this, here are some great articles:
- Why I Don't Drink Alcohol
- Christian & Alcohol
- Why are SDAs opposed to drinking wine?