Michael J. Selig

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.

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.

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.

Transglutaminase-treated conjugation of sodium caseinate and corn fiber gum hydrolysate: Interfacial and dilatational properties

This study compliments previous work where peroxidase was successfully used to crosslink corn fiber gum (CFG) with bovine serum albumin and improve CFGs emulsifying properties. Herein, an alternative type of enzyme, transglutaminase, was used to prepare conjugates of CFG and sodium caseinate. Additionally, the CFG was partially hydrolyzed by sulfuric acid and its crosslinking pattern with caseinate was evaluated. The interfacial crosslinking degree between caseinate and CFG increased after hydrolysis according to high performance size exclusion chromatography. The equilibrium interfacial tension of CFG hydrolysate-caseinate conjugate was lower than that of CFG-caseinate conjugate as the rearrangement rate of the CFG hydrolysate-caseinate conjugate was higher. The dilatational modulus of CFG hydrolysate decreased from that of CFG.

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.