Optimization of the technology for the decoloration of yak milk casein "Qula"

In the process of casein producing from the raw material "Qula", adding alkali, heating, and the impurity of the material will hastenMaillard reaction, and make color become yellow or brown, which will lower thequality of casein.L₂₅(5⁶) orthogonal experiment were used in the study, with Na₂SO₃, Na₂S₂O₄, NaHSO₃ as bleaching agents. Then the data gotten were analyzed to choose the best treatment. Results show that the best dosage formulation is rongalite Ⅰ 0.15 g, sodium sulfite 0.4 g, sodium bisulfite 0.375 g and rongalite Ⅱ 0.2 g in the raw casein("Qula") per 8 g. Meanwhile, infrared spectrum analysis was used to raw casein material, casein "Qula" and fresh milk casein. Results show that there are not differences between casein "Qula" and freshmilk casein in the flavor and useful ingredients.