Purification and characterization of kashk protein powder by precipitation and solvent extraction techniques

Kashk is a fermented dairy product that is high in protein; however, it contains elevated levels of salt and lactose, which limit its use in nutritional supplements. This manuscript presents a comprehensive study on the purification and characterization of kashk protein concentrate (KPC). We optimized the precipitation of KPC by varying the concentration of zinc (15–30 mM), ethanol (1–3% v/v), and pH levels (4–7). Characterization techniques and sensory evaluations were employed to assess the quality and acceptability of the dried protein produced using two different drying methods. Under the optimized conditions (pH = 5.19, 1.44% ethanol, and 15 mM zinc), we achieved a protein recovery of 82.40%, a protein solubility of 70.32%, and 0% salt content. Lactose content was measured at 0.19 g/100 g, with the highest levels of minerals and amino acids attributed to phosphorus and glutamic acid, respectively. β-casein displayed the highest molecular mobility on the electrophoresis gel of the K-casein protein concentrate (KPC). FTIR analysis indicated that the precipitation of KPC did not impact the denaturation or unfolding of the protein structure. The spray-dried sample exhibited higher color parameters, moisture content (2.4%), ash content (4.18%), and solubility (72.89%). However, the sensory acceptability of the freeze-dried KPC was greater. Overall, this study provides valuable insights into the purification of KPC, highlighting its potential as a functional ingredient in dietary supplements. • Kashk is a fermented dairy product and a good source of protein. • Kashk protein concentrate (KPC) was precipitated without heat treatment. • Optimized conditions of precipitation were 15 mM zinc, pH = 5.19, and 1.48% ethanol. • 82% protein recovery, 0% salt and 0.19% lactose was obtained at optimized condition. • The highest values of mineral and amino acid belonged to phosphorus and glutamic acid, respectively.