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Am. J. Enol. Vitic. 52:4:400-401 (2001)
Copyright © 2001 by the American Society for Enology and Viticulture.
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Comparison of Two Procedures for Assay of Free Amino Nitrogen

Carl E. Shively 1 and Thomas Henick-Kling 1

1 Department of Food Science and Technology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456-0462

Email: cs102{at}cornell.edu

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.

Note:
Acknowledgment: The authors thank Dr. John Barnard, Cornell University, for assistance in statistical analysis.

Key words: Yeast assimilable nitrogen, free amino nitrogen, formol titration, NOPA method






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Copyright © 2001 by the American Society for Enology and Viticulture.