The two loaves of bread waived on Pentecost represent the two groups being harvested:

1. The Dead that are resurrected,
2. The Living that never died and are raptured.

The reason its loaves and not sheafs is because the 'wheat' has been 'processed' through creation, experiencing evil and knowing how to spot it, knowing what it looks like, what it's like to live though, and as Kings and Priests will understand and be the leaders/guiders of the fruit of Israel which will grow during the 1000 year reign and beyond.