Beer stone
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The most common surface deposit on stainless steel brewing equipment is beer stone, or calcium oxylate. Beer stone usually appears as a dull brownish to brownish-white film on the metal’s surface. It is most likely to occur in stainless steel brew kettles, hop jacks, counterflow heat exchangers, and primary fermentors. Prolonged contact with hot wort will result in the greatest amount of beer stone buildup. It is necessary to remove the beer stone before it affects the flavor, or, worse, becomes a sanitization problem. The reason this calcium-based buildup occurs is that stainless steel is not wetted by hot wort; a thin layer of air remains between the steel and the hot wort, allowing precipitate to literally bake onto the stainless surface.[1]
Oxalate is present in barley malt and reacts with calcium to form beerstone. Calcium oxalate can precipitate at any point in the brewing process, but it is a particular problem if it precipitates in the bottle because the crystals act as gas nucleation sites and cause foaming and gushing. Therefore it is recommended that the water have sufficient calcium during the mash and boil to ensure early precipitation.[2]
Calcium oxalate, Ca(COO)2, is deposited as beer stone during fermentations, and an adequate level of calcium ions ensures that the deposition is nearly complete. Crystals of calcium oxalate formed later in packaged beer provide nuclei for the breakout of carbon dioxide and so can cause gushing and haze.[3]
Calcium oxalate normally separates from beer during fermentation and storage and is the major constituent (50–65%) of the beer stone which forms on the inner surface of fermentation and storage tanks. [4]
References[edit]
- ↑ https://www.probrewer.com/library/used-tanks/the-care-and-feeding-of-stainless-steel/
- ↑ water ch3
- ↑ Briggs DE, Boulton CA, Brookes PA, Stevens R. Brewing Science and Practice. Woodhead Publishing Limited and CRC Press LLC; 2004.
- ↑ Montanari L, Mayer H, Marconi O, Fantozzi P. Chapter 34: Minerals in beer. In: Preedy VR, ed. Beer in Health and Disease Prevention. Academic Press; 2009:359–365.