Extraction, fractionation and functional properties of proteins from the microalgae Chlorella vulgaris

• Extraction of protein from Chlorella vulgaris by pH shifting and ultrafiltration.
• 98% of proteins can be released from cell using high pressure (2 × 2.7 kbar) and pH 12.
• pH 7 reduces yield (71%) but enhances emulsifying capacity (2600 mL oil/g protein).
• Chlorella vulgaris proteins are competitive with commercial emulsifying ingredients.

This paper deals with the extraction and emulsifying properties of proteins from Chlorella vulgaris. Solubilisation of proteins has been achieved using high pressure cell disrupter under pH = 7 or pH = 12. The higher solubilisation yield (52 ± 3% w/w) was obtained using a combination of alkaline conditions and mechanical treatments (2.7 kbar). After solubilisation, proteins were recovered by two procedures: precipitation in acid media and concentration/fractionation by tangential ultrafiltration. Proteins were analysed for their molecular weights, isoelectric points and amino acids compositions and their emulsifying properties were quantified and compared to those of commercial ingredients. In spite of lower yield, better emulsifying capacity was obtained when protein solubilisation takes place at pH = 7 and when using proteins from permeate of tangential ultrafiltration. In all cases, emulsifying capacity (1780 ± 20 and 3090 ± 50 mL oil/g protein) and stability (72 ± 1% and 79 ± 1%) of microalgae proteins remained comparable or higher than the commercial ingredients such as sodium caseinate.