Characterization of Protein Concentrate from Spirulina Platensis Microalgae Using Microwave and Alkaline-Acid Extraction Methods

Siti Narsito  Wulan; Septian Dwi  Nurrachman; Raden Satrio Mukti  Wibowo Jayadiningrat; Harijono   Harijono

doi:10.18502/jnfs.v10i4.20010

Siti Narsito Wulan Department of Food Science and Biotechnology, Faculty of Agricultural Technology, Brawijaya University, 65145 Malang, East Java, Indonesia.
Septian Dwi Nurrachman Department of Food Science and Biotechnology, Faculty of Agricultural Technology, Brawijaya University, 65145 Malang, East Java, Indonesia.
Raden Satrio Mukti Wibowo Jayadiningrat Department of Food Science and Biotechnology, Faculty of Agricultural Technology, Brawijaya University, 65145 Malang, East Java, Indonesia.
Harijono Harijono Department of Food Science and Biotechnology, Faculty of Agricultural Technology, Brawijaya University, 65145 Malang, East Java, Indonesia.

DOI: https://doi.org/10.18502/jnfs.v10i4.20010

Keywords: Proteins; Spirulina; Extraction and processing industry; Microwaves; Alkalies; Acids.

Abstract

Background: Spirulina platensis is a microalgae type of Cyanobacteria in the form of filaments that resemble spirals (helix) ranging in size from 3-30 µm. Spirulina platensis is rich in nutritional sources, one of which is protein. However, the utilization of protein is limited by the rigidity of the cell wall of spirulina. The study aimed to compare protein extraction using various methods. Methods: Extraction process was carried out to obtain Spirulina platensis protein concentrate. Three methods were evaluated: physical extraction using a conventional microwave, alkali-acid extraction, and a combination of the two, namely, microwave and alkali-acid extraction. The protein extracts were dried and analyzed for its yield, protein content as well as its functional properties. Results: The spirulina powder contained 53.00±1.13% protein (dry basis). The alkaline-acid extraction produced protein concentrate with the highest protein content (67.04±3.85% dry basis), slightly higher than the combined methods (65.54±1.92% dry basis) and significantly higher than the microwave extraction (55.44±5.29% dry basis). However, the alkaline-acid extraction produced the lowest yield of protein concentrate powder (13.90±0.28%) as compared to the other methods. The protein concentrate had a moisture content ranging from 7.68-10.81%, water holding capacity (WHC) ranging from 0.95-1.64 g H₂O/g protein and foaming capacity (FC) ranging from 102-168%. Conclusions: Alkaline-acid extraction produced dried protein concentrate of spirulina with the highest protein content, the highest WHC and the lowest FC. The extraction methods/techniques not only affect the protein yield and content, but also its functionality.