Proposed Method for the Quantitative Determination of Oxalate in Beer and Wort. Z. I. Alavi and D. B. West, Siebel Products and Services, Enzyme Products Div., Miles Laboratories, Inc., Chicago, IL 60646. J. Am. Soc. Brew. Chem. 41:0024, 1983.

Insoluble calcium oxalate crystals cause haze, sediment, and overfoaming in packaged beer. Brewers prefer to lower the oxalate content of their products so that crystallization does not occur in the consumer package. Numerous methods to determine oxalate in beer have been published, but none has gained wide acceptance. The present method uses double ion-exchange columns and subsequent precipitation of oxalate as calcium oxalate to remove known or suspected interfering compounds. The separated oxalate is dissolved in acid and reacted with indole (2,3-benzopyrrole) to form a pink to red color, conforming with Beer's Law. The color is measured at 525 nm and the concentration calculated from a standard curve. Although the method is time consuming, it gives excellent recoveries from the resin columns and from malt beverages.

Keywords: Calcium oxalate, Cereal adjuncts, Indole, Ion-exchange resins, Malt beverages