The batch adsorption of the epigallocatechin gallate onto apple pomace

Interactions between cell wall polysaccharides and polyphenols: Effect of molecular internal structure

Cell wall polysaccharides (CPSs) and polyphenols are major constituents of the dietary fiber complex in plant-based foods. Their digestion (by gut microbiota) and bioefficacy depend not only on their structure and quantity, but also on their intermolecular interactions. The composition and structure of these compounds vary with their dietary source (i.e., fruit or vegetable of origin) and can be further modified by food processing. Various components and structures of CPSs and polyphenols have been observed to demonstrate common and characteristic behaviors during interactions. However, at a fundamental level, the mechanisms that ultimately drive these interactions are still not fully understood. This review summarizes the current state of knowledge on the internal factors that influence CPS-polyphenol interactions, describes the different ways in which these interactions can be mediated by molecular composition or structure, and introduces the main methods for the analysis of these interactions, as well as the mechanisms involved. Furthermore, a comprehensive overview is provided of recent key findings in the area of CPS-polyphenol interactions. It is becoming clear that these interactions are shaped by a multitude of factors, the most important of which are the physicochemical properties of the partners: their morphology (surface area and porosity/pore shape), chemical composition (sugar ratio, solubility, and non-sugar components), and molecular architecture (molecular weight, degree of esterification, functional groups, and conformation). An improved understanding of the molecular mechanisms that drive interactions between CPSs and polyphenols may allow us to better establish a bridge between food processing and the bioavailability of colonic fermentation products from CPSs and antioxidant polyphenols, which could ultimately lead to the development of new guidelines for the design of healthier and more nutritious foods.

Development of broccoli by-products as carriers for delivering EGCG

Novel delivery systems for epigallocatechin gallate (EGCG) were developed using broccoli by-products and their fractions as carriers. Puree and pomace from broccoli by-products had higher adsorption capacities for EGCG than juice at 25 °C (43.20 mg g^-1, 39.47 mg g^-1 and 25.22 mg g^-1 dry weight for pomace, puree and juice respectively). Chemical sorption is the rate-controlling step for EGCG-broccoli interactions. Langmuir and Freundlich models well described the adsorption of EGCG onto puree and pomace. FTIR results indicated that EGCG-puree had stronger interaction than EGCG-pomace. When the same level of EGCG (∼26 mg) was added to different matrices, more EGCG (∼20%) was recovered from the in vitro digestion system of EGCG-loaded puree than from the EGCG-loaded pomace (14%) and neat EGCG (9%). The antioxidant capacity of the whole digesta was positively correlated with the EGCG levels. Broccoli by-products are promising carriers for delivering and stabilizing EGCG through gastrointestinal digestion.

The application of pomelo peel as a carrier for adsorption of epigallocatechin-3-gallate

BACKGROUND

Pomelo (Citrus grandis) is the largest citrus fruit, the peel of which is a well-known agricultural wastes. Disposal of pomelo peel after consumption is a serious environment problem. As a natural, versatile bio-absorbent, pomelo peel has shown excellent adsorption capacity for several pollutants, attributed to its micro-pores; however, there is no relevant report on its adsorption capacity for natural products or food ingredients. The ability of pomelo peel to adsorb epigallocatechin-3-gallate (EGCG) was examined in this study. The physicochemical characterizations of pomelo peel were determined by Fourier transform infrared spectroscopy, scanning electron microscopy and high-performance liquid chromatography. The adsorption process of EGCG onto pomelo peel from aqueous solution was carried out at a range of concentrations (50-800 mg L^-1 ) and temperatures (25, 40 and 55 °C).

RESULTS

The main components of pomelo peel are composed of dietary fiber, which provide sufficient adsorption sites during the adsorption process. The adsorption of EGCG onto pomelo peel showed excellent fitness with a pseudo-second-order model. Both Langmuir and Freundlich models were able to describe the isothermal adsorption of EGCG onto pomelo peel. The results of thermodynamic analysis suggested that adsorption is spontaneous and endothermic in nature, and that the process is likely to be dominated by a physisorption mechanism.

CONCLUSION

The results of this study indicate that pomelo peel has potential adsorption capacity for EGCG, which can be used as an effective, low-cost carrier for delivery of natural products in functional food and dietary supplement applications. © 2018 Society of Chemical Industry.

The effective and selective separation of (-)-epigallocatechin gallate by molecularly imprinted chitosan beads

The (-)-epigallocatechin gallate (EGCG) imprinted chitosan beads (EICBs) were fabricated for the effective and selective separation of EGCG. The EGCG molecules interacted with the amino groups of chitosan in the imprinting process, resulting in a highly porous structure of EICBs and more adsorption sites. Consequently, EICBs exhibited better adsorption performance than non-imprinted chitosan beads. The maximum adsorption capacity of EGCG onto EICBs reached 135.50 mg/g at 313 K. The imprinting factor of EICBs was 4.22, indicating that EICBs possess good recognition ability and selectivity for EGCG. After five cycles of reuse, only a slight decrease (7.77%) in the adsorption capacity was observed, demonstrating the satisfactory reusability of EICBs. Furthermore, the adsorption of EGCG onto EICBs is deduced to be the monolayer adsorption on an energetically homogeneous surface; the hydrogen bonding between EGCG and EICBs is the main driving force for the adsorption. Our studies suggest that EICBs have a great potential for the effective and selective separation of EGCG.

Binding of tea catechins to rice bran protein isolate: Interaction and protective effect during in vitro digestion

Rice bran protein isolate (RBPI) was prepared from defatted rice bran and used to deliver tea catechins. RBPI had the high adsorption selectivity for tea catechins over caffeine. The adsorption characteristics of tea catechins onto RBPI were determined over a range of time (0-300min), concentration (0.25-3.5gL^-1) and temperatures (5°C, 20°C and 35°C). The adsorption kinetic data of EGCg and total catechins (TC) onto RBPI showed excellent fitness with the pseudo-second-order model, indicating that chemisorption is the dominating process. Langmuir and Freundlich models adequately described the isothermal adsorption of tea catechins onto RBPI, and the maximum adsorption of EGCg and TC were achieved at 5°C. SDS-PAGE profiles indicated that globulin and albumin were the major soluble proteins in RBPI to bind tea catechins. Fourier transforms infrared spectroscopy analysis showed that the protein secondary structures of RBPI were altered upon interaction with catechins, with a great increase in random coil and β-antiparallel, a minor increase in α-helix and a reduction in large loop and turn. Binding tea catechins to RBPI respectively increased the recovery% of EGCg and TC from 10.5% and 17.7% to 29.5% and 31.6% after in vitro intestinal digestion. Thus, RBPI is a promising food matrix for delivering tea catechins to gastrointestinal tract.

Protection of epigallocatechin gallate against degradation during in vitro digestion using apple pomace as a carrier

Apple pomace, a byproduct of the apple juice processing industry, may be used as a matrix for carrying phytochemicals. High-pressure processing (600 MPa for 5 min) or heat treatment (121 °C for 5 min) of wet apple pomace can increase the shelf life of the pomace but may influence the carrier properties of the wet pomace for phytochemicals. We examined the effects of these processing treatments on the adsorption capacity of apple pomace for epigallocatechin gallate (EGCG) and the stability of EGCG in simulated gastrointestinal fluids in vitro. Both processing treatments reduced the adsorption capacity but protected EGCG against degradation in the simulated gastrointestinal fluids. The extent of EGCG degradation in simulated gastrointestinal fluids in vitro in the presence of apple pomace was not influenced by gastric and intestinal enzymes, suggesting that pH had the overriding influence on EGCG degradation. This study showed the potential of apple pomace as a carrier for EGCG in functional food applications.