Lignin-Rich PHWE Hemicellulose Extracts Responsible for Extended Emulsion Stabilization

Area of Science:

• Food science and technology
• Biomaterials science
• Colloid and surface chemistry

Background:

• Wood hemicelluloses, specifically galactoglucomannans (GGM) and glucuronoxylans (GX), are known for their emulsion-stabilizing properties.
• Phenolic residues coextracted with hemicelluloses via pressurized hot water extraction (PHWE) are hypothesized to enhance emulsion stability.
• The precise role and structure of these phenolic residues in stabilizing oil-in-water emulsions require detailed characterization.

Purpose of the Study:

• To characterize the structure of phenolic residues associated with GGM and GX from wood extracts.
• To elucidate the role of these phenolic residues and purified hemicelluloses in the physical and oxidative stabilization of oil-in-water emulsions.
• To investigate the contribution of lignin-carbohydrate complexes to emulsion stability.

Main Methods:

• Fractionation of PHWE GGM and GX into phenolic-rich (GGM-phe, GX-phe) and purified hemicellulose (GGM-pur, GX-pur) fractions via centrifugation.
• Preparation of rapeseed oil-in-water emulsions using these fractions as stabilizers.
• Assessment of physical stability (droplet-size distribution) and oxidative stability (peroxide values) over a 3-month accelerated storage test.
• Chemical characterization of fractions using NMR spectroscopy and other methods.

Main Results:

• Phenolic-rich fractions significantly contributed to emulsion formation and improved long-term physical stability.
• All tested hemicelluloses inhibited lipid oxidation; GX was the most effective, indicating antioxidant properties of associated phenolic structures.
• Phenolic fractions (GGM-phe, GX-phe) were primarily composed of lignin with a high frequency of native β-O-4 structures and γ-ester type lignin-carbohydrate complexes.

Conclusions:

• Phenolic residues, mainly lignin, play a crucial role in enhancing both the physical and oxidative stability of wood hemicellulose-stabilized emulsions.
• The presence of lignin-carbohydrate complexes, particularly of the γ-ester type, is strongly linked to the excellent stabilizing capabilities of PHWE hemicelluloses.
• These findings highlight the potential of utilizing wood-derived phenolic-hemicellulose complexes as natural emulsifiers and antioxidants in various applications.