Do the Elements of Communion Matter?

On the wine vs. grape juice issue, I wrote a brief Q&A on that subject that you can find here: Protestant Transubstantiation (History of). Also, Keith Mathison wrote a four-part series on that subject entitled Protestant Transubstantiation that is available in the Theology section of IIIM Magazine Online. The church at which I am a member offers both wine and grape juice, so that each may follow his/her conscience on the matter.

Unleavened bread is undoubtedly what Jesus used at the Last Supper, in keeping with Old Testament regulations (Exod. 12:14-15), and per the name of the feast in the New Testament ("Unleavened Bread," Matt. 26:17; Mark 14:1,12; Luke 22:1,7). While no text of the institution of the Lord's Supper specifically records the use of unleavened bread, I would think this ought to be inferred from the Old Testament and from the name of the feast. I would not say that using leavened bread somehow invalidates the sacrament, but I would think that the symbolism and tradition would be stronger when unleavened bread is used (per the same arguments Keith uses regarding wine in his articles).

We should, however, be very clear that "leaven" is not the same thing as "yeast." If I know my breads, this morning at my church we used something like King's Hawaiian Sweet Bread. This is a very light and fluffy bread, clearly made with yeast. But it is also unleavened. In ancient days, yeast was rare. "Leaven" was the normal means people used to obtain yeast. Specifically, "leaven" was a remnant of dough that was allowed to rot or ferment. As it rotted/fermented, yeast (a fungus) from the air would land on and breed in the dough. This remnant of dough was then added to the next day's batch of dough. After the next day's batch of dough was mixed but before the dough was baked, a remnant would be taken from it to serve as leaven for the following day. And so onà This process continued throughout the year until the time of Passover arrived, at which point all leaven was purged from the house and the bread was baked from an entirely new batch of dough. Thus, unleavened bread is not bread without yeast, but rather a fresh batch of dough (cf. 1 Cor. 5:7 where the contrast is between "old leaven" and a "new lump"). Yeast is clean and healthy; leaven is a potential source of disease and infection. Most breads in Western culture these days, so far as I am aware, are unleavened; most are also made with yeast. (I must confess that I am fairly ignorant regarding culinary practices in the rest of the world.)