Extraction Methods and Functional Properties of Protein from <i>Arthospira platensis</i> for Bioavailability of Algal Proteins

Protein is one of the main nutrients that will be in short supply in the future. Alternative protein sources and production methods are required to fulfil the demand of protein requirements. Proteins from microalgae represent potential raw materials for the generation of protein based food ingredients. Arthospira platensis harbors high protein concentrations and one of the most important factors influencing successful extraction of protein is accessibility of the protein molecules. Process optimization and statistical analysis is necessary to maximize protein extraction. This study attempts to evaluate and compare various methods for their reliability in extracting microalgal proteins. Five different extraction methods namely alkali, enzymatic, thermal, microwave assisted and ultrasonic extraction were performed to obtain protein from A. platensis. Functional properties of the protein isolates were determined at various pH levels. Highest protein yield of 84% was obtained in ultrasound extraction. The lowest solubility of protein was found at pH 5.0 (0.27%) and highest solubility of protein was obtained at pH 9.0 (74.90%). Water holding capacity of protein isolates of S. platensis was in the range of 0.902 – 1.341 g_water/g_protein. The foaming capacity ranged from 19.37 to 41.28%, with the lowest and maximum values obtained at pH 5.0 and 3.0, respectively. Maximum value of foam stability at pH 5.0 was 31.24% and this subsequently decreased when the pH increased. The results revealed that both microwave assisted and ultrasound extraction methods were found suitable to make bioavailability of algal proteins from Arthospira platensis.