Evaluation of mineral composition and antioxidant properties of kefir obtained from different milk and kefir culture

In this study, three different kefir cultures were fermented using five different milk samples provided from the markets. In the fermented kefir samples, pH, dry matter, ash amount, carbon dioxide (CO2) amount, titratable acidity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging capacity, reducing power, metal chelating capacity, the total phenolic content (TPC), copper(II) ion reductive antioxidant capacity (CUPRAC) and mineral matter contents were investigated. Kefir samples were found to be similar in terms of pH, dry matter, titratable acidity and ash (p>0.05). It was determined that kefir obtained from kefir culture 3 had 18.8±0.3% of DPPH free radical scavenging capacity and kefir obtained from milk 1 had 24.9±0.4% of DPPH free radical scavenging capacity and higher than other samples (p<0.05). The reduction power of kefir samples were compared with the reduction power of synthetic antioxidants and the reduction power of kefir samples were found to be lower. The metal chelating capacities were compared with EDTA. The total phenolic contents were calculated as the gallic acid equivalent and the CUPRAC values as the caffeic acid equivalent. The amounts of TPC of kefir samples were found range from 28.4 to 50.7 mg GAE kg-1 according to milk brand. When compared in the point of mineral contents, magnesium (Mg), zinc (Zn) and sodium (Na) concentrations of the kefir sample obtained from kefir culture 1 was found to be higher than the kefir samples obtained from other kefir cultures (p<0.05). There was no statistical difference between calcium (Ca) and potassium (K) concentrations in kefir samples (p>0.05). The data obtained from the experimental studies it was determined that kefir cultures and milk brands had an important effect on kefir samples antioxidant properties and mineral contents. Key Words: CUPRAC, DPPH Free Radical Scavenging Capacity, Reducing Power, Kefir, Metal Chelating Capacity, Mineral, Total Phenolic Content