Mashing-in
Mixing of the strike water, water used for mashing in, and milled grist must be done in a such a way as to minimize clumping and oxygen uptake. This was traditionally done by first adding water to the mash vessel, and then introducing the grist from the top of the vessel in a thin stream. This has led to a lot of oxygen absorption, and loss of flour dust to the surrounding air. A premasher, which mixes the grist with mash-in temperature water while it is still in the delivery tube, reduces oxygen uptake and prevents dust from being lost.
Mashing in is typically done between 35 and 45 °C (95 and 113 °F), but, for single-step infusion mashes, mashing in must be done between 62–67 °C (144–153 °F) for amylases to break down the grain's starch into sugars. The weight-to-weight ratio of strike water and grain varies from 1⁄2 for dark beers in single-step infusions to 1⁄4 or even 1⁄5, ratios more suitable for light-colored beers and decoction mashing, where much mash water is boiled off.
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