Alain Marcati

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

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 (2.7kbar). 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±50mLoil/g protein) and stability (72±1% and 79±1%) of microalgae proteins remained comparable or higher than the commercial ingredients such as sodium caseinate.

Separation and fractionation of exopolysaccharides from Porphyridium cruentum

In this work the extraction of EPSs from culture media of Porphyridium cruentum, by dialysis, solvent-precipitation with 3 polar alcohols (methanol, ethanol and isopropanol) and membrane separation techniques has been studied. Diafiltration (DF) using a membrane with a 300 kDa molecular weight cut off was the most efficient technique compared to solvent-extraction and dialysis methods. After extraction, EPS fraction was characterized in terms of rheological properties and biochemical content. The product exhibited shear thinning behavior and a critical overlap concentration equal to 0.6 g/L. The monosaccharide composition was investigated after acidic hydrolysis. Xylose, galactose, glucose and glucuronic acid were identified as the main constitutive monomers.

Structural characterization and thermal behavior of a gum extracted from Ferula assa foetida L.

The gum asafoetida, an oleo-gum-resin from root of Ferula assa foetida, was extracted through alcoholic procedure followed by water extraction and then biochemically characterized using colorimetric assays, Fourier infrared spectroscopy, gas chromatography coupled to mass spectrometry, and 1D and 2D nuclear magnetic resonance. The gum was mainly composed of carbohydrates (67.39% w/w) with a monosaccharide distribution of 11.5: 5.9: 2.3: 1 between Gal, Ara, Rha and GlcA (molar ratio) and proteins (arabinogalactan protein). The polysaccharide consisted of a (1→3)-β-d-galactan backbone ramified predominantly from O-6 but also from O-4 and O-4,6. Side chains included terminal-α-l-Araf, terminal-α-l-Rhap, (1→3)-α-l-Araf, (1→5)-α-l-Araf, terminal-β-d-Galp, β-d-GlcA and traces of (1→4)-β-d-GlcA. X-ray diffraction pattern showed a semi crystalline microstructure. Thermal behavior of the gum was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed temperatures below and upper 200°C as dominant regions of weight loss.

Rheological and functional properties of asafoetida gum

The asafoetida gum was extracted and purified from oleo-gum-resin of Ferula assa foetida root and characterized by high pressure anions exchange chromatography after acidic hydrolysis. It was composed of Gal:Ara:Rha:GlcA with the ratio 11.5:5.0:2.1:1.0. This monosaccharide composition was found similar to that of a commercial Arabic gum which exhibited a Gal:Ara:Rha:GlcA ratio of 11.7:5.4:3.2:1.0. As the Arabic gum is currently used for its emulsifying properties, the two gums were evaluated for their functional and rheological behaviors. Surface and interfacial tensions values were lower for asafoetida gum compared to Arabic gum. Critical micelle concentration was achieved at concentrations of 0.5% w/w and 1% w/w for asafoetida and Arabic gums, respectively. Values of emulsion capacity, emulsion stability and foaming properties were considerably higher for asafoetida gum in contrast to emulsion activity index that was lower than that of Arabic gum. As those of Arabic gum, solutions of asafoetida gum (2-30% w/w) exhibited Newtonian flow behavior at shear rates between 1 and 500 s-1. Apparent viscosities of Arabic and asafoetida gums were close and logically decreased by increasing temperature (10-80 °C). Higher viscosities were achieved at higher pH and CaCl2 concentrations.