I have been taught that the two loaves of the Feast of Weeks represent the fact that the Church of God is made up of Jews and Gentiles. Yeast is a picture of sin; lack of yeast is a picture of holiness. The fact that these loaves are made with yeast, while all other grain offerings are without yeast, indicates that these loaves represent imperfect human beings—both Jews and Gentiles—who will be brought into the Church when it is formed on the future (from the Old Testament perspective) Day of Pentecost.
The fact that the grain offering with the Wave Sheaf lamb is two omers of flour points to the fact that the sacrifice of the Lamb of God will bring two categories of people—both Jews and Gentiles, some from every tribe and nation—into His Kingdom.
Though all this is true, I believe there is a better interpretation of the two loaves of Pentecost.
Leaven or yeast does not always represent “sin” in the Scriptures. After all, Jesus likened the kingdom of heaven to leaven. There is both bad and good yeast.
Yeast is a microscopic fungus consisting of single cells that reproduce by budding, and are capable of converting sugar into alcohol and carbon dioxide. Over 1,500 species of yeast have been identified. Bad or “wild” yeast will ruin bread, making it unfit for human consumption. Wild yeast is a picture of sin, which permeates and contaminates all that it touches. On the other hand, carefully cultivated baker’s yeast, which has been nurtured and protected to prevent the invasion of wild and undesirable yeasts and bacteria, is used to bake wonderful delicious bread. Good yeast is fundamental in raising bread, converting heavy dough into a light, porous, elastic product which, when baked, is appetizing and nutritious. This yeast has been rightly termed the “soul of bread.” 
When the New Testament refers specifically to unleavened bread, it uses the Greek word azumos. The context in all uses of azumos is the Feast of Unleavened Bread (commonly called Passover week).
All other New Testament references to bread use the Greek word artos. This ordinary bread contains yeast. The same word artos used when we pray “Give us this day our daily bread” is used when Jesus said, “I am the bread of life,” and when He referred to Himself as the “bread of God … who comes down from heaven and gives life to the world.” Christ is the artos—the raised, leavened, perfect bread that brings eternal life!
Implications for the Church
For Christ-followers the concept of good leaven is exciting. The leaven which causes their loaf to reach the fullness of perfection is the Holy Spirit of God within them—the Spirit of grace, supplication, love and power. God’s Spirit works like good yeast within us to change us into the image of God in character and true holiness!
 Matt. 13:33; Luke 13:20-21
 A Treatise on Baking, p.51.
 Matt. 26:17; Mark 14:1, 12; Luke 22:1, 7; Acts 12:3; 20:6; 1 Cor. 5:7-8
 John 6:35, 48
 John 6:32-33, 50-51
 2 Tim.1:6-7; Heb.10:29; Eph.6:18