Response surface optimization of ultrasound-assisted protein extraction from Spirulina platensis: investigation of the effect of extraction conditions on techno-functional properties of protein concentrates

In the present study, optimum extraction conditions of proteins from Spirulina platensis were determined by using response surface methodology. Box–Behnken design of experiments was performed to investigate the effects of temperature (25, 35, 45 °C), pH (7, 8, 9) and time (60, 90, 120 min) on water absorption capacity (WAC), oil absorption capacity (OAC), emulsifying activity (EA), emulsifying stability (ES), foaming capacity (FC) and foaming stability (FS) of the protein concentrates (PC). WAC of the PC varied with time while OAC changed with temperature and pH. The PC had high values of OAC (10.22 g of oil/g of protein) and WAC (5.12 g of water/g of protein) under extraction conditions of pH of 8 temperature of 45 °C and time of 60 min. On the contrary, there were no significant changes in emulsifying properties of PC under different extraction conditions (p > 0.05), while foaming stability of the PC varied with the interactive effect of temperature and time. The optimum extraction conditions were 43.87 °C for temperature, 7.16 for pH and 60 min for time. Under these conditions, WAC, OAC, FC, FS, EA and ES values were obtained as 4.41 g of water/g, 10.13 g of oil/g, 300%, 83.94%, 42.99% and 92.50%, respectively. The results obtained through this investigation indicated that protein concentrates from Spirulina platensis have higher functional properties than other algae. Therefore, Spirulina platensis proteins can be thought as an inexpensive source of protein for food industry due to its extraordinary functionality.