TY - JOUR T1 - Comparison of Two Procedures for Assay of Free Amino Nitrogen JF - American Journal of Enology and Viticulture JO - Am J Enol Vitic. SP - 400 LP - 401 DO - 10.5344/ajev.2001.52.4.400 VL - 52 IS - 4 AU - Carl E. Shively AU - Thomas Henick-Kling Y1 - 2001/01/01 UR - http://www.ajevonline.org/content/52/4/400.abstract N2 - Wine yeasts are capable of utilizing nitrogen in two forms: free amino nitrogen and ammonium nitrogen. In this study, a total of 39 must samples were collected from New York State wineries and assayed for free amino nitrogen using formol titration and the o-phthaldialdehyde/N-acetyl-L-cysteine spectrophotometric assay (NOPA) method. These two procedures differ considerably in their chemistry and instrumentation required for analysis. Formol titration requires only a pH meter while the NOPA procedure requires a spectrophotometer with UV capability. Both methods have been used widely in the wine industry and it is important to know whether the two methods give comparable results. Our comparison presented here indicates they do yield similar results.Acknowledgment: The authors thank Dr. John Barnard, Cornell University, for assistance in statistical analysis. ER -