[Spectrophotometric method for determination of protein in food with Hantzsch reaction]

A new spectrophotometric method for the determination of protein in food was developed. The method is based on the reaction of ammonia in Kjeldahl digest with acetylacetone for maldehyde reagent in pH4.8 acetate medium to yield a yellow compound 3,5-diacetyl-2,6-dimethyl-1,4-dihydropyridine. Beer's law is obeyed in the concentration range of 0-10.0 mg/L at 400 nm. The molar absorptivity in terms of nitrogen was 1.7 x 10(-3). The recoverites of the added standard samples were 99.6%-101.2%, and relative standard deviation was below 3.7%.