Chen Tan

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.

Polyelectrolyte microcapsules built on CaCO 3 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 0.75u202fmg, 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.

Polyelectrolyte Complex Inclusive Biohybrid Microgels for Tailoring Delivery of Copigmented Anthocyanins

This study fabricated a novel biohybrid microgel containing polysaccharide-based polyelectrolyte complexes (PECs) for anthocyanins. Herein, anthocyanins were encapsulated into PECs composed of chondroitin sulfate and chitosan, followed by incorporation into alginate microgels using emulsification/internal gelation method. We demonstrated that PECs incorporation strongly affected the properties of microgels, dependent on the polysaccharide concentration and pH in which they were fabricated. The dense internal network surrounded by an alginate shell was clearly visualized in cross-sectioned PECs-microgels. Stability studies carried out under varying ionic strength and pH conditions demonstrated the stimuli-responsiveness of the PECs-microgels. Additionally, the presence of PECs conferred microgels with high rigidity during freeze-drying and excellent reconstitution capacity upon rehydration. These observations were attributed to the modulation of electrostatic and hydrogen-bonding cross-linking between PECs and the alginate gel matrix and suggest the PECs inclusive microgels hold promise as delivery vehicles for the controlled release of hydrophilic bioactive compounds.

Synergistic Bathochromic and Hyperchromic Shifts of Anthocyanin Spectra Observed Following Complexation with Iron Salts and Chondroitin Sulfate

Grape anthocyanins are not traditionally used on complexation studies, as the main compounds lack a catechol group. In this study, concomitant metal complexation (Fe2+ and/or Fe3+) and co-pigmentation with chondroitin sulfate (CHS) were shown to synergistically affect the color spectra of grape anthocyanins at varying pHs. In general, the addition of iron salts resulted in small reductions in maximum absorbance at pH 3 and a bathochromic shift at pH 4 and 5. On the other hand, CHS resulted in hypochromic shifts at pH 3 and 4. When combined, these compounds broadened the peak at higher wavelengths associated with blue color, and resulted in significantly higher (pu2009<u20090.05) area under the curve at these wavelengths even at pH 3. Interestingly, this synergistic effect seemed to work only at low pH. All observed effects were achieved using low concentrations of metals and CHS. The results should interest those aiming to achieve anthocyanin color modulation through metal complexation at modest loadings.

Combination of internal structuring and external coating in an oleogel-based delivery system for fish oil stabilization

In this study, we created oleogel-based formulations featuring varying degrees of beeswax for internal structure and whey protein isolate (WPI) as external coating to improve the oxidative stability of fish oil. Oleogel was characterized by rheological analysis to access gelation behavior, and morphology was visualized using electron microscopy. It was found that the WPI-coated oleogel displayed strong physical stability during storage. The oxidative assay demonstrated that WPI-coated oleogel had the best protection against fish oil oxidation under both thermal treatment and ultraviolet-C radiation. The oxidation of fish oil was inhibited by 2-3 fold, compared to its unencapsulated form. This stability was attributed to the modulation of beeswax and WPI on the micropolarity and microviscosity of the formulation, as evidenced by pyrene fluorescence measurement. Our approach combining internal structuring and external coating may contribute to the development of oleogel system for efficient delivery of lipophilic bioactive components.

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.

Anthocyanidins and Anthocyanins

Anthocyanins are an abundant class of natural water-soluble red-purple flavonoid pigments found in a broad range of plant tissues, from flowers to berries to certain root vegetables. Centered around a core flavylium structure, these unique biomolecules exist with a broad diversity of substituted chemical structures. This molecular diversity affects the numerous functional properties, color presentation, stability, and human health benefits anthocyanins have to offer. Beyond function as a pigment, the health benefits of anthocyanins have been of growing interest to researchers as well as consumers. Most notable for their high antioxidant capacity, these biomolecules have additionally been shown to have antidiabetic, cardioprotective, and neuroprotective effects, amongst others. The diverse and growing potential of anthocyanins will continue to elevate their already attractive stature in food and nutritional industries aiming to mitigate the usage of synthetic colorants and functional ingredients in products.