Comparison of Enzymatic and ISE Methods for Ammonia Measurements in Untreated Red and White Juices and Wines

Abstract

The use of a standard, commercial enzymatic assay for determination of ammonia in juices and wines, with a focus on red juices and wines, has been investigated. Ammonia standards were prepared in model wine solutions, white juice and wine, and red juice and wine that ranged from 0 to 300 mg/L of added ammonia. Ammonia concentration in all standards was then determined by enzymatic assay and by ion-selective electrode for comparison. Repeatability and linearity of the enzymatic assay were excellent for both red juice and wine with only a simple filtration step as a pretreatment. Replicate measurements had a coefficient of variation of less than 2%, and the correlation coefficients (R) for both juice and wine were greater than 0.99. These results were similar to those found for the ion-selective electrode measurements.