Editing Low oxygen brewing
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* Recirculate the mash | * Recirculate the mash | ||
* Do not sparge | * Do not sparge | ||
when wort is in contact with conventional atmospheric conditions, it is critical to minimize agitation.<ref name=bammul>Bamforth CW, Muller RE, Walker MD. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-51-0079 Oxygen and oxygen radicals in malting and brewing: a review.] ''J Am Soc Brew Chem.'' 1993;51(3):79–88.</ref> The fewest practical number of transfers of wort should be undertaken. When necessary, transfers should be as gentle as possible, with agitator not employed when they are uncovered and with liquid flows directed in such a fashion as to minimize turbulence (e.g., close to vessel walls, bottom entry). Single-vessel systems employing temperature ramping are clearly more advantageous in this regard than are multivessel decoction vessels and systems using cereal cookers. Pumps should riot be leaky and should be large enough to enable large-volume delivery at low speed and with minimum cavitation. Opportunity for oxygen uptake through seals, valves, etc., should be eliminated by regular maintenance. Transfer from vessels should be carefully controlled to ensure that when vessels are approaching emptiness pumping will not suck air into the system. Clearly vessel and piping geometry should be carefully considered to minimize any opportunity for gas uptake. Brewing liquor may contain substantial dissolved oxygen, and the use of deaerated liquor could be considered, not only for mashing-in but also for lautering. Milling, too, can introduce substantial quantities of air. Dry milling under a nitrogen headspace is practical. Further considerations in wet milling, apart from the use of deaerated liquor, include minimizing agitation and introducing gentle transfers. With regard to the kettle, there is clearly substantial scope for oxygen uptake in a turbulent boil if manhole covers are left open. | when wort is in contact with conventional atmospheric conditions, it is critical to minimize agitation.<ref name=bammul>Bamforth CW, Muller RE, Walker MD. [https://www.tandfonline.com/doi/abs/10.1094/ASBCJ-51-0079 Oxygen and oxygen radicals in malting and brewing: a review.] ''J Am Soc Brew Chem.'' 1993;51(3):79–88.</ref> The fewest practical number of transfers of wort should be undertaken. When necessary, transfers should be as gentle as possible, with agitator not employed when they are uncovered and with liquid flows directed in such a fashion as to minimize turbulence (e.g., close to vessel walls, bottom entry). Single-vessel systems employing temperature ramping are clearly more advantageous in this regard than are multivessel decoction vessels and systems using cereal cookers. Pumps should riot be leaky and should be large enough to enable large-volume delivery at low speed and with minimum cavitation. Opportunity for oxygen uptake through seals, valves, etc., should be eliminated by regular maintenance. Transfer from vessels should be carefully controlled to ensure that when vessels are approaching emptiness pumping will not suck air into the system. Clearly vessel and piping geometry should be carefully considered to minimize any opportunity for gas uptake. Brewing liquor may contain substantial dissolved oxygen, and the use of deaerated liquor could be considered, not only for mashing-in but also for lautering. Milling, too, can introduce substantial quantities of air. Dry milling under a nitrogen headspace is practical. Further considerations in wet milling, apart from the use of deaerated liquor, include minimizing agitation and introducing gentle transfers. With regard to the kettle, there is clearly substantial scope for oxygen uptake in a turbulent boil if manhole covers are left open. |