Determination of the nitrate content of wort, beer and other beverages as well as that of malt and hops.
This method is suitable for wort, beer and other beverages as well as for malt and hops.
Essentially, the nitrate content of beer originates with the nitrate derived from the brewing liquor and the hops (whole hops, hop powder). Nitrate is reduced to nitrite by yeast has not been found to occur at any stage in the brewing process.
Nitrate is reduced with reduced nicotinamide adenine dinucleotide phosphate (NADPH) to nitrite in the presence of the enzyme nitrate reductase (NR) [1].
Nitrate + NADPH + H+ \(^{\underrightarrow{NR}}\) nitrite + NADP+ + H2O
The quantity of NADPH consumed in this reaction is proportional to the amount of nitrate in the sample. NADPH is measured and the determination is performed at 334, 340 oder 365 nm, due to its absorption at these wavelengths.