Biochemical Techniques and Instrumentation

Analysis of protein by Spectrophotometer (Lowry's Method)

Nitrogen is the major nutrient in fish and shellfish. Nitrogen occurs in amino acids, purine and pyrimidine bases, vitamins, aminosugars, alkaloids, compound lipid, etc. Protein can be estimated by different methods such as Microkjeldahl method, Biuret method, Bradford method and Lowry’s method. Microkjeldahl method is a widely adopted one to estimate the crude protein content by estimating the nitrogen content in a variety of samples ranging from microbial cells to meat. No method is 100% sensitive.The protein has to be hydrolyzed and the resultant amino acids has to be estimated to get exact quantification of protein. The method developed by Lowry et al. (1951) is sensitive enough to give a moderately constant value of protein and is followed widely. The protein content of enzyme extracts is usually determined by this method.