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A: We can science this, I promise! Food darkens in two ways: enzymatically with oxygen and phenols, or from maillard reactions from cooking. Darkening can occur from scorching the wort during wort production, or using malt extract (which is darker from oxidation, or from production of the extract). If the darkening is not from the hot side, then the browning was caused by oxidation. Check out this [https://en.wikipedia.org/wiki/Browning_(food_process) Wikipedia page on food browning] for an overview of enzymatic browning.