Spirulina (Arthrospira platensis) is rich in C-phycocyanin (C-pc), a protein-pigment complex with antioxidant, anti-inflammatory, hepatoprotective and anti-carcinogenic properties. This protein requires an extraction phase due to its intracellular location; preferably a cold extraction as high temperatures can alter its functionality. The extraction techniques currently used, such as a succession of freezing and thawing phases, are time-consuming and energy-consuming. Greek researchers at the Agricultural Products Technology Institute (ITAP) have investigated the possibility of using high-pressure treatments to facilitate the extraction of C-phycocyanin.
High-pressure treatment involves applying pressures of 100 to 600 MPa (equivalent to 1,000 to 6,000 bars) to a food product packaged in flexible packaging, using a mediator liquid to apply the pressure evenly throughout the product. This treatment generates protein modifications that can alter the functionality of enzymes and the integrity of cell membranes.
The researchers cultivated spirulina (Arthrospira platensis) in photobioreactors and harvested it after 14 days. The samples were diluted in various media, including distilled water, and packed in HDPE polyethylene containers. They were then treated at pressures ranging from 100 to 600 MPa for 0, 10 or 20 minutes (20°C). Extraction of C-pc and total soluble proteins was carried out at various points over a 24-hour period by centrifuging the solution and recovering the supernatant.
The results showed that high pressures allow good extraction of C-pc from distilled water. The treatment was particularly effective at pressures of up to 300 MPa (10 min). Microscopic observation (see Figure 1) showed that this level of pressure resulted in cell rupture, allowing the contents of the cytoplasm to be dispersed in the extraction medium.
Above 300 MPa, lower yields have been observed. Indeed, high pressure treatment can cause irreversible changes to the structure of proteins, leading to a drop in their extractability.
The research team then sought to optimise the high-pressure treatment. The optimum condition identified was to treat spirulina diluted in distilled water for 10 minutes at 300 MPa, which would enable 90% of the C-ps and 60% of the total soluble proteins to be extracted in around 1.6 hours.
This study demonstrated the benefits of high pressure treatments for extracting C-ps from spirulina quickly and efficiently, while reducing the energy consumed. In fact, the authors of this study also evaluated the energy required to extract 90% of the C-ps from spirulina using High Pressure treatment, and compared it with a ‘freeze-thaw’ type extraction technique. The result was unequivocal: the energy expenditure for the High Pressure treatment was almost 60 times lower!
Source : Marianna Giannoglou, Varvara Andreou, Ioanna Thanou, Giorgos Markou, George Katsaros, High pressure assisted extraction of proteins from wet biomass of Arthrospira platensis (spirulina) – A kinetic approach, Innovative Food Science & Emerging Technologies, Volume 81, 2022, 103138, ISSN 1466-8564, https://doi.org/10.1016/j.ifset.2022.103138 
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