Soluble antioxidant compounds regenerate the antioxidants bound to insoluble parts of foods

Liberated bioactive bound phenolics during in vitro gastrointestinal digestion and colonic fermentation boost the prebiotic effects of triticale insoluble dietary fiber

Phenolics in bound form extensively exist in cereal dietary fiber, especially insoluble fiber, while their release profile in gastrointestinal tract and contribution to the potential positive effects of dietary fiber in modulating gut microbiota still needs to be disclosed. In this work, the composition of bound phenolics (BPs) in triticale insoluble dietary fiber (TIDF) was studied, and in vitro gastrointestinal digestion as well as colonic fermentation were performed to investigate BPs liberation and their role in regulating intestinal flora of TIDF. It turned out that most BPs were unaccessible in digestion but partly released continuously during fermentation. 16 s rRNA sequencing demonstrated that TIDF possessed prebiotic effects by promoting anti-inflammatory while inhibiting proinflammatory bacteria alongside boosting SCFAs production and antioxidative BPs contributed a lot to these effects. Results indicated that TIDF held capabilities to regulate intestinal flora and BPs were important functional components to the health benefits of cereal dietary fiber.

The power of the QUENCHER method in measuring total antioxidant capacity of foods: Importance of interactions between different forms of antioxidants

Antioxidants play a crucial role in maintaining human health by counteracting oxidative stress and regulating redox balance within the body. The mixture of various antioxidant compounds in different forms (i.e., free, bound, insoluble) in food creates a redox active environment both in the human body and in the food system. Acting as both electron donors and acceptors while interacting with each other can either result in antagonism through pro-oxidative effects, or synergism through regeneration of one antioxidant by another. During the antioxidant capacity measurement, besides the individual antioxidant effects of the antioxidant components, these effects that occur because of their interaction with each other should be also considered. Classical antioxidant capacity measurement methods mostly concentrate on the fractions of foods that can be extracted with either water, alcohol, lipid, or acid/alkaline solutions. Antioxidants that cannot be extracted with any solvent are mostly ignored in these methods. On the other hand, the QUENCHER method, which allows direct measurement of antioxidant capacity foods without extraction, offers a rational solution to the limitations of traditional extraction-based methods. This approach considers the antioxidant capacity and interactions of all antioxidant forms that can be found in a food matrix, at the same time. This review provides detailed insights into the advantages of QUENCHER as a holistic approach for the accurate measurement of the antioxidant capacity of foods.

Study of the acetylation-induced changes in the physicochemical and functional characteristics of insoluble dietary fiber from wheat bran

BACKGROUND

Wheat bran is rich in dietary fiber (DF), particularly insoluble dietary fiber (IDF). Although the benefits for human health following the consumption of these DFs have been documented, the lower water retention capacity (WRC) and other properties still limit the applications of DF. Therefore, the current research investigated the impact of acetylation on the changes in the corresponding physicochemical and functional properties of DF.

RESULTS

The current results indicated the acetylated group restricted the alignment of the molecular chains, which led to an increased amorphous phase in the fiber structure, followed by an enhanced thermal sensitivity and a reduced crystallinity as evidenced by X-ray diffraction (XRD). Moreover, the acetylation of the IDFs enhanced the cholesterol absorption capacity, but the corresponding antioxidant capacity and cation exchange capacity were reduced, which might be due to the partial loss of the phenolic compounds onto the polysaccharides during the modification. Interestingly, a lower degree of substitution (DS) of the IDF achieved from water-acetic anhydride modification led to a higher WRC and water swelling capacity (WSC). In contrast, a higher DS from acetic anhydride modification demonstrated a greatly improved in vitro hypoglycemic performance of the IDF, including α-amylase inhibitory activity and glucose dialysis retardation index (GDRI), compared to the other samples.

CONCLUSION

This study highlights a new approach to modify the functionality of IDFs via acetylation and the design of a novel IDF with hypoglycemic activity. © 2023 Society of Chemical Industry.

A comprehensive review of matcha: production, food application, potential health benefits, and gastrointestinal fate of main phenolics

Matcha, a powder processed from tea leaves, has a unique green tea flavor and appealing color, in addition to many other sought after functional properties for a wide range of formulated food applications (e.g., dairy products, bakery products, and beverage). The properties of matcha are influenced by cultivation method and processing post-harvest. The transition from drinking tea infusion to eating whole leaves provides a healthy option for the delivery of functional component and tea phenolics in various food matrix. The aim of this review is to describe the physico-chemical properties of matcha, the specific requirements for tea cultivation and industrial processing. The quality of matcha mainly depends on the quality of fresh tea leaves, which is affected by preharvest factors including tea cultivar, shading treatment, and fertilization. Shading is the key measure to increase greenness, reduce bitterness and astringency, and enhance umami taste of matcha. The potential health benefits of matcha and the gastrointestinal fate of main phenolics in matcha are covered. The chemical compositions and bioactivities of fiber-bound phenolics in matcha and other plant materials are discussed. The fiber-bound phenolics are considered promising components which endow matcha with boosted bioavailability of phenolics and health benefits through modulating gut microbiota.

Polyphenol-Dietary Fiber Conjugates from Fruits and Vegetables: Nature and Biological Fate in a Food and Nutrition Perspective

In the past few years, numerous studies have investigated the correlation between polyphenol intake and the prevention of several chronic diseases. Research regarding the global biological fate and bioactivity has been directed to extractable polyphenols that can be found in aqueous-organic extracts, obtained from plant-derived foods. Nevertheless, significant amounts of non-extractable polyphenols, closely associated with the plant cell wall matrix (namely with dietary fibers), are also delivered during digestion, although they are ignored in biological, nutritional, and epidemiological studies. These conjugates have gained the spotlight because they may exert their bioactivities for much longer than extractable polyphenols. Additionally, from a technological food perspective, polyphenols combined with dietary fibers have become increasingly interesting as they could be useful for the food industry to enhance technological functionalities. Non-extractable polyphenols include low molecular weight compounds such as phenolic acids and high molecular weight polymeric compounds such as proanthocyanidins and hydrolysable tannins. Studies concerning these conjugates are scarce, and usually refer to the compositional analysis of individual components rather than to the whole fraction. In this context, the knowledge and exploitation of non-extractable polyphenol-dietary fiber conjugates will be the focus of this review, aiming to access their potential nutritional and biological effect, together with their functional properties.

DAF-16 is involved in colonic metabolites of ferulic acid-promoted longevity and stress resistance of Caenorhabditis elegans

BACKGROUND

Ferulic acid (FA) is a dietary polyphenol widely found in plant tissues. It has long been considered to have health-promoting qualities. However, the biological properties of dietary polyphenols depend largely on their absorption during digestion, and the effects of their intestinal metabolites on human health have attracted the interest of researchers. This study evaluated the effects of three main colonic metabolites of FA - 3-(3,4-dihydroxyphenyl)propionic acid (3,4diOHPPA), 3-(3-hydroxyphenyl)propionic acid (3OHPPA) and 3-phenylpropionic acid (3PPA) - on longevity and stress resistance in Caenorhabditis elegans.

RESULTS

Our results showed that 3,4diOHPPA, 3OHPPA and 3PPA extended the lifespan under normal conditions in C. elegans whereas FA did not. High doses of 3,4diOHPPA (0.5 mmol L^-1 ), 3OHPPA (2.5 mmol L^-1 ) and 3PPA (2.5 mmol L^-1 ) prolonged the mean lifespan by 11.2%, 13.0% and 10.6%, respectively. Moreover, 3,4diOHPPA, 3OHPPA and 3PPA treatments promoted stress tolerance against heat, UV irradiation and paraquat. Furthermore, three metabolites ameliorated physical functions, including reactive oxygen species and malondialdehyde levels, motility and pharyngeal pumping rate. The anti-aging activities mediated by 3,4diOHPPA, 3OHPPA and 3PPA depend on the HSF-1 and JNK-1 linked insulin/IGF-1 signaling pathway, which converge onto DAF-16.

CONCLUSION

The current findings suggest that colonic metabolites of FA have the potential for use as anti-aging bioactivate compounds. © 2022 Society of Chemical Industry.

Optimization of reaction conditions for the design of cereal-based dietary fibers with high antioxidant capacity

BACKGROUND

Bound antioxidants are distinguished by their strong potential to defend the body against oxidative stress. Cereal bran fractions contain antioxidant compounds bound to dietary fiber, but this only occurs to a limited extent. Increasing the quantity of bound antioxidant compounds using soluble phenolic compounds is thought to be a possible method for designing cereal-based dietary fibers with high antioxidant potential. Certain cereal bran samples (wheat, oat, rye, and rice) were reacted with different concentrations of beverages (green tea infusion, black tea infusion, espresso, and red wine), rich in various soluble phenolic compounds. The interactive effects of parameters (time, temperature, and pH) and the optimum conditions for the reaction were determined using response surface methodology.

RESULTS

Green tea infusion (30 g·L^-1 ) was found to be the most effective beverage. The pH rather than the time and temperature had significant (O p < 0.0001) effects on the reaction. Neutral or slightly alkaline conditions (pH 7.0-7.9) and mild temperatures (at about 50 °C) were found to be optimum to increase the antioxidant capacity of cereal bran samples. The total antioxidant capacity of oat bran treated with green tea infusion under optimum conditions (53.3 °C, pH 7.4, 60.0 min) reached 226.42 ± 0.88 mmol Trolox equivalent·kg^-1 . The free amino groups in cereal bran were also found to decrease (32-95%) after treatment.

CONCLUSION

It is possible to design functional cereal-based dietary fibers, rich in bound antioxidant compounds through treatment with green tea infusion under optimum conditions. © 2022 Society of Chemical Industry.

A New Approach for Quantifying Purpurogallin in Brewed Beverages Using LC-MS in Combination with Solid Phase Extraction

Purpurogallin (PPG) is a phenolic compound known for its high antioxidant properties in plant-based food materials. However, there is no easy and reliable method for direct determination of PPG in brewed beverages owing to its hydrophobicity, which makes it hard to separate from the background hydrophobic components. Therefore, a method employing solid-phase extraction (SPE) and liquid chromatography-mass spectrometry (LC-MS) was developed for detection and quantification of PPG in brewed beverages, and PPG content was quantified in commercial coffee, cocoa, and tea samples. The limits of detection and quantification were 71.8 and 155.6 ng/g dry weight (dw), respectively. The recovery with SPE was 26.6%. When combined with acetonitrile extraction (ANE), the recovery was 6.8%, higher than 2.6% with water extraction (WTE). Test tube extractions were better than moka pot brewing (MPB) for PPG quantification. Total PPG content of ground coffees prepared by ANE, WTE, and MPB ranged between 635 and 770, 455 and 630, and 85 and 135 ng/g dw, respectively. PPG was detected in two English breakfast tea samples (335−360 ng/g dw) using WTE, but not in cocoa samples. ANE showed higher (p < 0.05) PPG levels, but WTE (r = 0.55, p < 0.01) correlated better with MPB than ANE (r = 0.43, p < 0.01). The result indicated that WTE is the best method to determine PPG in brewed beverages. This work demonstrated that PPG was significant in brewed coffee, and our pioneer study in developing the method for beverage sample preparation and LC-MS analysis has made possible industrial applications and provided new perspectives for future research.

Phytochemical profile, bioactivity and prebiotic potential of bound polyphenols released from Rosa Roxburghii fruit pomace dietary fiber during in vitro digestion and fermentation

The aim of this study was to elucidate liberation and phytochemical profile of bound polyphenols existed in dietary fiber (RPDF) isolated from Rosa roxburghii fruit pomace during in vitro simulated...

The Effects of Bioactive Compounds from Blueberry and Blackcurrant Powder on Oat Bran Pastes: Enhancing In Vitro Antioxidant Activity and Reducing Reactive Oxygen Species in Lipopolysaccharide-Stimulated Raw264.7 Macrophages

In this study, blueberry and blackcurrant powder were chosen as the phenolic-rich enrichments for oat bran. A Rapid Visco Analyser was used to form blueberry and blackcurrant enriched oat pastes. An in vitro digestion process evaluated the changes of phenolic compounds and the in vitro antioxidant potential of extracts of pastes. The anthocyanidin profiles in the extracts were characterised by the pH differential method. The results showed that blueberry and blackcurrant powder significantly increased the content of phenolic compounds and the in vitro antioxidant capacity of pastes, while the total flavonoid content decreased after digestion compared to the undigested samples. Strong correlations between these bioactive compounds and antioxidant values were observed. Lipopolysaccharide-stimulated RAW264.7 macrophages were used to investigate the intracellular antioxidant activity of the extracts from the digested oat bran paste with 25% enrichment of blueberry or blackcurrant powder. The results indicated that the extracts of digested pastes prevented the macrophages from experiencing lipopolysaccharide (LPS)-stimulated intracellular reactive oxygen species accumulation, mainly by the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signalling pathway. These findings suggest that the bioactive ingredients from blueberry and blackcurrant powder enhanced the in vitro and intracellular antioxidant capacity of oat bran pastes, and these enriched pastes have the potential to be utilised in the development of the functional foods.

Interactions between free and bound antioxidants under different conditions in food systems

This review aimed to give comprehensive information about the interactions between free and bound antioxidants naturally found in different food matrices. In this context, firstly, the free and bound antioxidant terms are defined; their place in the daily diet, the path they follow in the body and their characteristics are explained. Factors affecting the interactions have been revealed as a result of the compilation of studies conducted until today, related to bound and free antioxidant interactions. Accordingly, it was observed that many factors such as reaction environment, concentration, pH, chemical structure, source and antioxidant/prooxidant nature of the compounds were effective on interactions. It has been emphasized that the interactions between free and bound antioxidants have a dynamic balance that can easily change under the influence of various factors, which in turn needs the interactions to be handled specifically for each case.

Insoluble dietary fibre scavenges reactive carbonyl species under simulated physiological conditions: The key role of fibre-bound polyphenols

Polyphenols bound to insoluble fibre may scavenge reactive carbonyl species by surface chemical reactions. In the present study, this hypothesis was tested by investigating the ability of bound-polyphenol rich insoluble dietary fibre (BP-IDF) isolated from blackberry pomace, red cabbage, and wheat bran in scavenging carbonyl compounds. Three BP-IDF showed high scavenging efficacy for glyoxal, methylglyoxal, acrolein and malondialdehyde. Upon in vitro digestion, trapping capacity was retained by the insoluble fraction suggesting that carbonyl trapping activity and physiological relevance needs to be extended to undigestible materials. The removal of bound polyphenols from the polysaccharide backbones through alkaline and acidic treatment reduced by up to 90% of trapping capacity of BP-IDF. Moreover, methylglyoxal-polyphenol adducts were detected bound to blackberry pomace BP-IDF after hydrolysis. These findings demonstrated that polyphenols bound to IDF scavenged reactive carbonyl species and highlighted the physiological relevance of BP-IDF in limiting carbonyl stress along all the gastrointestinal tract.

Physiological relevance of food antioxidants

Dietary antioxidants are associated with prevention of oxidative stress related chronic diseases including certain types of cancer, cardiovascular diseases, diabetes, and neurodegenerative diseases. In recent years, there has been a growing interest in extending the knowledge on their physiological effects in human body. There are numbers of epidemiological, clinical, meta-analysis, and in vitro studies to explain formation mechanisms of each chronic diseases as well as the potential effects of dietary antioxidants on these diseases and gut health. Comprehensive studies for food antioxidants' journey from dietary intake to target tissues/organs deserve a serious consideration to have a clear understanding on the physiological effects of dietary antioxidants. Therefore, absorption and metabolism of dietary antioxidants, and the factors affecting their absorption, such as solubility of antioxidants, food matrix, and interaction between antioxidants have been evaluated in several research articles. This chapter provides an overview about potential health effects of dietary antioxidants considering with their absorption and metabolism in human body.

Phytochemical Profile, Bioactivity, and Prebiotic Potential of Bound Phenolics Released from Rice Bran Dietary Fiber during in Vitro Gastrointestinal Digestion and Colonic Fermentation

Whole-grain dietary fiber is rich in bound-form phenolics, and the biological activity of this special structural feature has attracted increasing attention. In this study, rice bran dietary fiber (RBDF) was subjected to in vitro gastrointestinal digestion and colonic fermentation to investigate the liberation of bound phenolics and their potential activities. Bound phenolics were released at a higher ratio during colonic fermentation (27.57%) than gastrointestinal digestion (2.68%). Nine phenolic compounds were detected from the fermentation supernatants. The released phenolics showed radical scavenging activity (DPPH and ABTS assays) and α-glucosidase inhibitory activity (IC₅₀ = 19.11 μg GAE/mL). Compared with phenolics-removed RBDF (PR-RBDF), RBDF had a significantly stronger prebiotic effect on the microbes associated with diabetes (Lactobacillus spp., Akkermansia muciniphila, and Faecalibacterium prausnitzii). These findings indicate that bound phenolics may act as important functional components that could contribute to the health benefits of whole-grain dietary fiber.

Behaviour of Trolox with macromolecule-bound antioxidants in aqueous medium: Inhibition of auto-regeneration mechanism

This work aimed at investigating the behaviour of Trolox, vitamin E analogue, in presence of macromolecule-bound antioxidants in aqueous radical medium. Three main groups of macromolecule-bound antioxidants were assayed: dietary fiber (DF), protein and lipid-bound antioxidants, represented by whole wheat, soybean and olive oil products, respectively. Experimental studies were carried out in aqueous ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical medium. Trolox and macromolecule-bound antioxidants were added to radical separately and together in different concentrations. Antioxidant capacities were determined using QUENCHER procedure. pH of radical media was altered for DF and protein-bound antioxidant studies to examine its effect. Chemometric tools were used for experimental design and multivariate data analysis. Results revealed antagonistic interactions for Trolox with all macromolecule-bound antioxidants. The reason behind this antagonism was investigated through oxidation reactions of Trolox via mass spectrometry analysis. Consequently, a proof was obtained for inhibitory effect of bound-antioxidants on auto-regeneration reactions of Trolox.

Dietary Advanced Glycosylation End-Products (dAGEs) and Melanoidins Formed through the Maillard Reaction: Physiological Consequences of their Intake

The main purpose of this review is to clarify whether the consumption of food rich in melanoidins and dietary advanced glycosylation end-products (dAGEs) is harmful or beneficial for human health. There are conflicting results on their harmful effects in the literature, partly due to a methodological issue in how dAGEs are determined in food. Melanoidins have positive functions particularly within the gastrointestinal tract, whereas the intake of dAGEs has controversial physiological consequences. Most of the in vivo intervention trials were done comparing boiled versus roasted diet (low and high dAGE, respectively). However, these studies can be biased by different lipid oxidation and by different calorie density of foods in the two conditions. The attraction that humans have to cooked foods is linked to the benefits they have had during mankind's evolution. The goal for food technologists is to design low-energy-dense products that can satisfy humans' attraction to rewarding cooked foods.

Regeneration of tert-butylhydroquinone by tea polyphenols

To study the antioxidant capacity (AC) regeneration of tert-butylhydroquinone (TBHQ) by tea polyphenols (TPs), a separable system has been designed for its evaluation. The AC values of three natural food matrices (liquorice, oat, and ginger) and TBHQ regenerated by TPs were all higher than their controls, and similar to the initial values (p<0.05). The average regeneration efficiency (RE) value was 1.49 for these three natural food matrices, and 0.82 for TBHQ. Electron paramagnetic resonance spectroscopy analysis has revealed the synergistic effect of TBHQ and TPs, which arose from the regeneration of TBHQ by TPs. The RE value of TBHQ regeneration by TPs embedded in a gelatine membrane was 0.51. The results demonstrated that TPs showed a capacity for regenerating TBHQ, indicating a potential application in regenerative packaging, whereby one antioxidant would be added to the food matrix, with another one as the regenerator incorporated into the packaging material.

Electrochemical reverse engineering: A systems-level tool to probe the redox-based molecular communication of biology

The intestine is the site of digestion and forms a critical interface between the host and the outside world. This interface is composed of host epithelium and a complex microbiota which is "connected" through an extensive web of chemical and biological interactions that determine the balance between health and disease for the host. This biology and the associated chemical dialogues occur within a context of a steep oxygen gradient that provides the driving force for a variety of reduction and oxidation (redox) reactions. While some redox couples (e.g., catecholics) can spontaneously exchange electrons, many others are kinetically "insulated" (e.g., biothiols) allowing the biology to set and control their redox states far from equilibrium. It is well known that within cells, such non-equilibrated redox couples are poised to transfer electrons to perform reactions essential to immune defense (e.g., transfer from NADH to O₂ for reactive oxygen species, ROS, generation) and protection from such oxidative stresses (e.g., glutathione-based reduction of ROS). More recently, it has been recognized that some of these redox-active species (e.g., H₂O₂) cross membranes and diffuse into the extracellular environment including lumen to transmit redox information that is received by atomically-specific receptors (e.g., cysteine-based sulfur switches) that regulate biological functions. Thus, redox has emerged as an important modality in the chemical signaling that occurs in the intestine and there have been emerging efforts to develop the experimental tools needed to probe this modality. We suggest that electrochemistry provides a unique tool to experimentally probe redox interactions at a systems level. Importantly, electrochemistry offers the potential to enlist the extensive theories established in signal processing in an effort to "reverse engineer" the molecular communication occurring in this complex biological system. Here, we review our efforts to develop this electrochemical tool for in vitro redox-probing.

Adaptation and Validation of QUick, Easy, New, CHEap, and Reproducible (QUENCHER) Antioxidant Capacity Assays in Model Products Obtained from Residual Wine Pomace

Evaluation of the total antioxidant capacity of solid matrices without extraction steps is a very interesting alternative for food researchers and also for food industries. These methodologies have been denominated QUENCHER from QUick, Easy, New, CHEap, and Reproducible assays. To demonstrate and highlight the validity of QUENCHER (Q) methods, values of Q-method validation were showed for the first time, and they were tested with products of well-known different chemical properties. Furthermore, new QUENCHER assays to measure scavenging capacity against superoxide, hydroxyl, and lipid peroxyl radicals were developed. Calibration models showed good linearity (R(2) > 0.995), proportionality and precision (CV < 6.5%), and acceptable detection limits (<20.4 nmol Trolox equiv). The presence of ethanol in the reaction medium gave antioxidant capacity values significantly different from those obtained with water. The dilution of samples with powdered cellulose was discouraged because possible interferences with some of the matrices analyzed may take place.

Synergism between soluble and dietary fiber bound antioxidants

This study investigates the synergism between antioxidants bound to dietary fibers (DF) of grains and soluble antioxidants of highly consumed beverages or their pure antioxidants. The interaction between insoluble fractions of grains containing bound antioxidants and soluble antioxidants was investigated using (i) a liposome-based system by measuring the lag phase before the onset of oxidation and (ii) an ESR-based system by measuring the reduction percentage of Fremy's salt radical. In both procedures, antioxidant capacities of DF-bound and soluble antioxidants were measured as well as their combinations, which were prepared at different ratios. The simple addition effects of DF-bound and soluble antioxidants were compared with measured values. The results revealed a clear synergism for almost all combinations in both liposome- and ESR-based systems. The synergism observed in DF-bound-soluble antioxidant system paints a promising picture considering the role of fiber in human gastrointestinal (GI) tract health.

Rapid and repeatable redox cycling of an insoluble dietary antioxidant: electrochemical analysis

There are many unresolved questions concerning the health benefits of dietary antioxidants due in part to the complexity of the materials and mechanisms of action. We applied a new electrochemical method and report new observations for one of the richest sources of dietary antioxidants. We observed that the insoluble fraction of clove is redox-active and can be rapidly and repeatedly switched between oxidized and reduced states. Also, the radical scavenging antioxidant properties of insoluble clove are largely independent of this reversible redox activity, which is similar to observations made with the natural phenolic melanin. In contrast to melanin, insoluble clove was observed to have little pro-oxidant activity (as measured by H2O2 generation) irrelevant to whether it was poised in an oxidized or reduced state. These results suggest that dietary antioxidants, even when insoluble and nonabsorbed, can undergo important redox interactions in the intestinal tract.

Release of antioxidant capacity from five plant foods during a multistep enzymatic digestion protocol

This study aimed at elucidating the influence of food matrix on the release of antioxidant activity from five plant foods (apple, spinach, walnut, red bean, and whole wheat). To this purpose a protocol based on sequential enzymatic digestion was adopted. The total antioxidant capacity (TAC) of both solubilized and insoluble materials was measured at each step. Results showed that the overall TAC obtained by enzyme treatments was usually higher than that obtained by chemical extraction-based methods. In apple most of the TAC was released upon water washing and after pepsin treatment, whereas in spinach, beans, and whole wheat the TAC released by treatments with bacterial enzymes was prominent. Walnut had the highest TAC value, which was mainly released after pancreatin treatment. Therefore, the enzyme treatment is fundamental to estimate the overall potential TAC of foods having a high amount of polyphenols bound to dietary fiber or entrapped in the food matrix.