Construction and characterization of antioxidative ferulic acid-grafted carboxylic curdlan conjugates and their contributions on ß-carotene storage stability.

Grafting copolymerization of phenolic acids onto polysaccharides is an important strategy to improve their biological activities. In this study, ferulic acid (FA)-grafted carboxylic curdlan conjugates, namely, Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA, were synthesized by free radical-induced grafting. Results showed that FA was covalently grafted onto carboxylic curdlans via ester bonds. The grafting ratios of Cur-8-g-FA, Cur-24-g-FA, and Cur-48-g-FA were 223.03 ± 12.63, 115.63 ± 5.96, and 152.30 ± 4.57 mg FA/g, respectively, which were related with the carboxylate contents, molecular weights, and chain conformations of carboxylic curdlans. Compared with carboxylic curdlans, the FA-grafted carboxylic curdlan conjugates had lower thermal stability, molecular weight, and rheological property and looser surface morphology but had more prominent antioxidant benefits in vitro, which were proportional to their grafting ratios. Moreover, good storage stability against chemical degradation was exhibited by the ß-carotene in Pickering emulsions stabilized by Cur-8-g-FA with a high grafting ratio and molecular weight.

Preparation, characterization, rheological and antioxidant properties of ferulic acid-grafted curdlan conjugates.

In this study, water-soluble curdlan products (Cur and Cur-D) were prepared by an alkali-neutralization treatment process, after which ferulic acid (FA)-grafted Cur conjugates (Cur-g-FA and Cur-D-g-FA) were fabricated in the presence and absence of salt by adopting an approach involving free-radicals generated by the ascorbic acid/hydrogen peroxide redox pair under an inert atmosphere. Results showed that FA was successfully grafted onto the C-6 and C-4 positions of the Cur chains through covalent linkages and that the presence of salt exerted minor influences on the grafting ratios and structural characterizations of the products. Cur-g-FA and Cur-D-g-FA showed decreased crystallinity, thermal stability, and rheological properties, as well as a distinct surface morphology, when compared with those of native Cur. However, Cur-g-FA and Cur-D-g-FA also exhibited remarkably enhanced free-radical scavenging ability and antioxidant capacity in vitro. These results indicate that FA-grafted Cur conjugates have great potential application in the field of functional foods.

Quaternized curdlan/pectin polyelectrolyte complexes as biocompatible nanovehicles for curcumin.

In this study, a positively charged quaternized curdlan (Qcurd) was used to fabricate polyelectrolyte complex nanoparticles (PEC NPs) with a negatively charged pectin via electrostatic complexation. Results showed that the Qcurd/pectin PEC NPs prepared with 0.5 mg/mL Qcurd and pectin solutions, 1:2 pectin/Qcurd mass ratio, and pH 4.0 in the absence of NaCl were characterized by a spherical morphology in nanoscale, an average particle size of 68 nm, and good dispersibility in aqueous solutions. Curcumin was encapsulated in the Qcurd/pectin PEC NPs through hydrogen bonding with an encapsulation efficiency of ∼82%, a loading content of 13%, and a pH-dependent controlled release. Curcumin-loaded PEC NPs exhibited a significantly enhanced water solubility, excellent free radical scavenging ability and antioxidant capacity in vitro as compared with those of free curcumin.

Effect of different drying methods on the product quality and bioactive polysaccharides of bitter gourd (Momordica charantia L.) slices.

In this study, three drying methods, namely, hot-air drying, freeze drying (FD), and infrared radiation drying (ID), were applied to dry bitter gourd (Momordica charantia L.) slices. Results showed that the drying methods had significant influences on appearance, color, rehydration ratio, and microstructure of dried bitter gourd. FD provided high-quality dried bitter gourd products due to the uniform honeycomb network and less collapsed structure. Three water-soluble bitter gourd polysaccharides (BPS-H, BPS-F, and BPS-I) were obtained from the bitter gourd dried using the three drying methods. The three polysaccharides exhibited similar preliminary structural characteristics with different monosaccharide compositions and molecular weights. BPS-I obtained from ID-dried bitter gourd had higher sugar and uronic acid contents than BPS-H and BPS-F. BPS-I exhibited stronger antioxidant activities and bile acid-binding capacity in vitro than BPS-H and BPS-F. Moreover, BPS-F and BPS-I showed significant α-amylase inhibitory activities in vitro.