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Tech. Q. Master Brew. Assoc. Am., 1990, 27(2), 56. English, sp
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Isomerized hop pellets - recent improvements and results of brewery trials.

Grant, H.L. and Wilson, R.J.H.

Abstract
An improved method for isomerising magnesium oxide stabilised hop pellets is described, in which the pellets are carefully heated to just below 50 degrees C, and maintained at that temperature for several days, in the nearly total absence of oxygen. HPLC analysis has shown that although such pellets when untreated contain little or no iso alpha acid, after this treatment around 96% of the alpha acid content has been isomerised, while very little (under 20%) of the volatile hop compounds content has been lost. Brewing trials yielded utilisation rates of up to 68% for the treated pellets (compared with a maximum for regular pellets of 44%). Taste tests indicated that beer flavour was unaffected, while significant cost savings were achieved. It is suggested that pellets made by this process from "aroma" hop varieties would be particularly useful for late addition in the brewing of beers intended to have a pronounced hoppy flavour.
Keywords : efficiency hop pellet hopping hoppy flavour isomerisation quality temperature time