Catechin modulates the copigmentation and encapsulation of anthocyanins in polyelectrolyte complexes (PECs) for natural colorant stabilization.

Our objective was to develop a robust system for anthocyanin-based color intensification, with high-encapsulation capacity and improved stability of the encapsulated natural colorant. Catechin was used to modulate the copigmentation and encapsulation of anthocyanins in counter-ionic polyelectrolyte complexes (PECs) composed of chondroitin sulfate and chitosan. Results showed that catechin copigmentation significantly intensified red color of formulations both with and without encapsulation in PECs and improved the anthocyanin encapsulation efficiency by forming additional dense network through hydrogen bonding. A series of stability assays revealed that anthocyanin stabilizing effect of system depended on the formulated pH and adding order of catechin. The strongest retaining capacity of anthocyanin was observed when catechin was copigmented with anthocyanin directly in PECs at pH 3.3, while the coated layer of catechin covered on PECs would be more effective at pH 4.0 and 5.0. Furthermore, we demonstrated that this delivery system works for anthocyanins from different sources.

Polyelectrolyte microcapsules built on CaCO3 scaffolds for the integration, encapsulation, and controlled release of copigmented anthocyanins.

The all-polysaccharide based polyelectrolyte microcapsules combining copigmentation for anthocyanin encapsulation and stabilization were fabricated. Copigmented complexes of chondroitin sulfate and anthocyanin were preloaded in CaCO3 scaffold, and then microcapsules were created by coating the sacrificial CaCO3 using layer-by-layer technique. It was observed that the preloading of copigmented complex affected the precipitation reaction of CaCO3 and the subsequent entrapment of anthocyanin. With addition of anthocyanin from 0.125 to 0.75 mg, copigmentation can significantly increase the encapsulation efficiency of anthocyanin in CaCO3, whereas such effect was not obvious at higher loadings. The leakage of anthocyanin during CaCO3 core dissolution and storage was also inhibited by two polysaccharide layers coupled with copigmentation, which may be related to the formation of interconnecting networks. Additionally, a higher anthocyanin antioxidant activity was provided by carbohydrate matrix. These findings may allow for the encapsulation of large amounts of water-soluble components; particularly natural colorant by copigmented complex-polyelectrolyte structures.

Anthocyanin stabilization by chitosan-chondroitin sulfate polyelectrolyte complexation integrating catechin co-pigmentation.

The thermochemical instability of anthocyanins (ATC) presents a challenge to their utilization as natural colorants in many food systems. This is addressed herein with the development of polysaccharide based carriers formed by combined encapsulation and copigmentation approaches which utilize polyelectrolyte complexation between chitosan and chondroitin sulfate (CS). At pH 3, a 1.5mg/mL and 1:1wt ratio mix of both polysaccharides produced hydrophilic and positively charged polyelectrolyte complexes (PECs) with which a maximum ATC encapsulation efficiency of 88% could be achieved using a 1:6 elderberry extract as the ATC source. ATC coupled with EGCG co-pigmentation achieved the highest encapsulation efficiencies. Storage studies showed the combination of polysaccharide encapsulation and EGCG copigmentation improved ATC stability against elevated temperature and ascorbic acid. Copigmented PECs were shown to retain ATC color at a rate more than 3-fold greater than of non-encapsulated ATC, and, furthermore, were shown to improve and preserve ATC anti-oxidant activity and stability during storage.

Impact of lignins isolated from pretreated lignocelluloses on enzymatic cellulose saccharification.

Lignins were enzymatically isolated from corn stover and wheat straw samples and subjected to hydrothermal or wet oxidation pretreatments for enzyme adsorption experimentations. Lignin contents of the isolates ranged from 26 to 71 % (w/w); cellulose ranged from 3 to 22 % (w/w); xylan from 0.7 to 6 % (w/w) and ash was from 5.8 to 30 % (w/w). ATR-IR analyses indicated significant and similar levels of calcium in all lignin isolates. Commercial cellulase adsorption studies showed that the presence of these lignins had no significant impact on the total amount of adsorbed enzyme in cellulose and cellulose-lignin systems. Consequently, the presence of the lignins had minimal effect, if any, on enzymatic cellulose conversion. Furthermore, this result, coupled with significant calcium levels in the isolated lignins, supports previous work suggesting lignin-calcium complexes reduce enzyme-lignin interactions.