A Rapid Spectrophotometric Method for Measuring Cheese Ripening

Abstract

A rapid, direct method for estimating the degree of proteolysis in ripening cheese was studied by me asuring absorption of UV light by a clear, sodium citrate-hydrochloric acid extract of cheese at pH 4.4 [plus or minus] 0.05; these measurements were closely correlated with the per cent of soluble nitrogen in the cheese extract. Measurements of the optical density of the cheese from 40 lots of varying ages revealed peaks of all absorption spectra between 274 and 275 m[mu]. The coefficient of correlation between optical density of the cheese extract and percentage of soluble nitrogen measured in the cheese abstract by Kjeldahl was 0.958. Concentrations of soluble tyrosine and soluble tryptophan were measured spectrophotometrically at optical densities of 270 and 290 m[mu]. Equations were developed by Vierordt''s method of analysis of 2 component systems for this pair of wave lengths. Relationships between these compounds and percentage of soluble nitrogen in the cheese were linear and highly significant; the coefficient of correlation between soluble tyrosine and percentage of soluble N was 0.956, while that between soluble tryptophan and percentage of soluble nitrogen was 0.886. Flavor intensity estimated in the 40 lots of cheese showed a linear relationship to soluble tyrosine.