Comparative Protein Quantification in Ultra Heat Treated Milk Using Kjeldahl Versus Dye Binding Methods

Abstract

The goal of this study was to compare a Dye Binding Method with the standard Kjeldahl method in the context of protein determination in Ultra-Heat Treated (UHT) milk. Protein contents were determined in (25) samples of milk collected immediately post- ultra-heath treatment of milk and (25) samples collected after six-month storage at room temperature in Kjeldahl and Amido black methods. Samples digested using concentrated sulfuric acid at high temperatures and assayed using Automated Kjeldahl (Foss, Kjeltec™ 8200). Whereas, undigested samples were mixed with Amido Black a and density of color was measured against Amido black dilution series at wavelength of 620 nm. First stage: the average concentration of protein was (2.9256±0.01193 g/100 mL) versus (2.9396±0.01338 g/100 mL) using Kjeldahl versus Amido Black A respectively, with an average difference of (0,014). The concentrations ranged between (2.890-2.940 g/100 mL) and (2.910-2.960 g/100 mL) with a Coefficient of variation is (0.41%) and (0.46%) for Kjeldahl and Amido Black, respectively. (P) Value >0.0001. Therefore, there are no variances significantly different between two methods. Second stage: First stage: the average concentration of protein was (2.9224±0.03961 g/100 mL) versus (2.932±0.007071 g/100 mL) using Kjeldahl versus Amido Black A, respectively, with an average difference of (0.0096). The concentrations ranged between (2.770-3.000 g/100 mL) and (2.920- 2.940 g/100 mL) with a Coefficient of variation is (1.36%) and (0.24) for Kjeldahl and Amido Black respectively. (P) Value<0.0001. Therefore, there are variances significantly different between two methods.