The World's Most Popular Assay? A Review of the Ninhydrin- Based Free Amino Nitrogen Reaction (FAN Assay) Emphasizing the Development of Newer Methods and Conditions for Testing Alcoholic Beverages

摘要

This review covers what is, arguably, the world's most widely used food industry-related assay, the ninhydrin reaction, for the determination of the free amino nitrogen content of biological materials, including beverages and foods. This assay, for application to beer and wine samples, was adapted for use in a multi-well format and demonstrated the potential to scale down and run more multi-well tests in brewing quality control testing laboratories. Scaling down brewery laboratory tests reduces demands for expensive reagents, limits waste, and makes for simpler, less expensive disposal, while also giving a faster turnaround of results for many assays. In redefining the ninhydrin free amino nitrogen assay for use with modern instruments, we rediscovered the most efficient reagents and optimal conditions for application of this test in the contemporary brewing laboratory. Six critical parameters for ninhydrin reactions (buffer composition, incubation time, temperature, pH, assay volume, and reducing agent) have been reassessed with a new microwell assay combining all of them, now providing high precision and sensitivity. Finally, new reduced volume and microwell-based FAN assay formats should prove useful to many brewing, enology, distilling, and food laboratories for the routine determination of free or total useable nitrogen, and for further refinement and optimization of this important assay.