Molecular characterization of primary and secondary lactoseric proteins of whey coming from different cheesesIntroduction

Abstract. There are 2 types of whey coming from dairy products: the first one called primary (PW), which is obtained from the first curd cheese making, and the secondary (SW), that is the residual product after obtaining ricotta cheese. The objective was to obtain and molecularly characterize proteins from primary and secondary whey derived from dairy products (fresh, panela and Oaxaca cheeses). In order to improve production yields of ricotta, various samples of PW were acidified with citric acid and submitted to different temperature conditions and cooking times. The proteins of PW and SW from dairy products were obtained by precipitation with methanol-chloroform, quantified by the Bradford method and analyzed by SDS-PAGE. At 0.5% of lactic acid, temperature of 95°C and cooking time of 30 min, the highest contents of protein (4.920%) were obtained from PW. Quantification in PW and SW was 645.24 μg/mL and 510.34 μg/mL respectively for fresh cheese (FC), the content was similar to the panela cheese (PC). For Oaxaca cheese (OC), the contents were higher, being 993.72μg/mL for PW and 334.45μg/mL for SW. The electrophoretic profile showed a similar protein pattern between FC, PC and OC in PW (10, 75, 88, 150 kDa). For SW, similar bands between FC and PC were obtained, however for OC, lower molecular weight proteins were observed (15, 17 and 29 kDa). In conclusion, the whey from dairy products has different contents of protein and its molecular structure can be different depending on the type of product, heat treatment and whey acidification.