Answer: If the hulls of the seeds turned brown during drying, they may have been dried at too high a temperature. If the hulls were brown while still on the flowerhead, it may be a sign of fungal disease or insect infestation. There are 3 seed weevils that attack sunflower seeds while the plant is growing. The worm-like larvae of these weevils eat the seed inside the hull. Sometimes they only nibble at the seed and sometimes they consume it entirely. What's left, then, is an empty hull with no seed inside.
Without knowing whether the brown color is a result of fungal or insect problems, or from poor drying conditions, it's difficult to say whether the seeds are safe to eat. Since the seeds are not a normal color, I think I'd use them to feed the birds over the winter rather than eat them myself.
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