Vakaleris-Price and Hull Methods for Determining Soluble Tyrosine and Tryptophan in Blue Cheese

Abstract

To establish a suitable method for measuring the degree of proteolysis in blue cheese (as a measure of ripening), the Hull procedure and the Vakalaris-Price method were compared. In recovery experiments using three different spectrophotometers and known amounts of tyrosine and tryptophan, discrepancies between the three spectrophotometers in their absorbance readings at 290nm were wide. To eliminate discrepancies that could have been caused by differing sensitivities of instruments, we used a wavelength of 285nm instead of 290nm.Seven loaves of domestic blue cheese were examined. High tyrosine contents were obtained in five of seven blue cheese samples with the Vakalaris-Price method as compared with Hull procedure. Extracts from blue cheese contained interfering compounds that absorbed at the ultraviolet-wavelength used with the Vakalaris-Price procedure.