There are many kinds of bread ranging from sour to sweet. Sourdough is considered old fashioned in our day, but in the time of the Exodus, that was the only type of yeasted bread known. The baker would set aside a lump of dough to be used in the next batch of bread. I have made a sourdough starter and it definitely smells sour.
Hebrew Terms Reflect Sour and Sweet
The Hebrew term for leavening is chametz which has the connotation of sour. On the other hand the Hebrew work for unleavened bread, matstsah has the meaning of sweet. There would be no sourdough taste in unleavened bread.
Jesus Changes our Life from Sour to Sweet
2 Corinthians 5: 17 This means that anyone who belongs to Christ has become a new person. The old life is gone; a new life has begun! 18 And all of this is a gift from God, who brought us back to himself through Christ. And God has given us this task of reconciling people to him. 19 For God was in Christ, reconciling the world to himself, no longer counting people’s sins against them. And he gave us this wonderful message of reconciliation. 20 So we are Christ’s ambassadors; God is making his appeal through us. We speak for Christ when we plead, “Come back to God!” 21 For God made Christ, who never sinned, to be the offering for our sin, so that we could be made right with God through Christ.
When we begin our new life in Christ, our lives move from being sour to being sweet.
Romans 8: 5 Those who are dominated by the sinful nature think about sinful things, but those who are controlled by the Holy Spirit think about things that please the Spirit. 6 So letting your sinful nature control your mind leads to death. But letting the Spirit control your mind leads to life and peace. 7 For the sinful nature is always hostile to God. It never did obey God’s laws, and it never will. 8 That’s why those who are still under the control of their sinful nature can never please God.
To hear how our lives can move from sour to sweet, listen here:
 Keven Howard & Marvin Rosenthal, The Feasts of the Lord, Thomas Nelson Publishers, Nashville, TN., 1997, p. 66.