Conjugate

Engineering

Nanoparticle

Chromatography

Ultrafiltration (renal)

Differential scanning calorimetry

Biochemistry

Chemical engineering

Polysaccharide

Stereochemistry

Thermodynamics

Physics

Organic chemistry

Mathematics

Circular dichroism

Enzyme

Mathematical analysis

Macromolecule

Zeta potential

Molecular mass

Chemistry

Size-exclusion chromatography

Food Hydrocolloids

Tea polysaccharide conjugates (TPCs) are macromolecular polymers comprising polypeptides covalently bound to polysaccharides with a wide range of molecular weights that are found in tea leaves. We previously found that TPCs had emulsifying properties, but the difference in the emulsification stabilities between the high- and low-molecular-weight TPCs was unknown. In this study, the total polysaccharide conjugates (gTPC-T) with average molecular weight of 258,900 Da were extracted from low-grade green tea, from which two separate fractions with average molecular weights of 989,600 Da (22.43%) and 47,780 Da (77.57%), which were referred to as gTPC-1 and gTPC-2, respectively, were separated using an ultrafiltration membrane. The polypeptide chains of the three TPCs (gTPC-T, gTPC-1, and gTPC-2) contained 17 out of the 20 canonical amino acids. In addition, gTPC-1 had the highest acidic monosaccharide content. Circular dichroism (CD) an analysis showed that the secondary structures of the protein moieties of the three TPCs were dominated by α-helices. The nano-differential scanning calorimetry (Nano-DSC) results showed that the transition midpoints (Tm) of the three samples were 86.69, 59.53, and 68.59 °C, respectively. The zeta potential of gTPC-T at weakly acidic or neutral pH (4.0–7.0) was the highest, followed by gTPC-1 and then gTPC-2. Of all three gTPCs, gTPC-1 had the smallest interfacial tension, the highest interfacial pressure, and the best interfacial activity. In addition, gTPC-T slightly better-stabilized the MCT oil-in-water emulsions than gTPC-1, while the emulsification stability of gTPC-2 was the worst. This trend was likely attributed to the synergistic effect between gTPC-1 and gTPC-2.

Purification, characterization, and emulsification stability of high- and low-molecular-weight fractions of polysaccharide conjugates extracted from green tea