Complexation of thermally-denatured soybean protein isolate with anthocyanins and its effect on the protein structure and in vitro digestibility

Advances in dietary proteins binding with co-existed anthocyanins in foods: Driving forces, structure-affinity relationship, and functional and nutritional properties

Anthocyanins, which are the labile flavonoid pigments widely distributed in many fruits, vegetables, cereal grains, and flowers, are receiving intensive interest for their potential health benefits. Proteins are important food components from abundant sources and present high binding affinity for small dietary compounds, e.g., anthocyanins. Protein-anthocyanin interactions might occur during food processing, ingestion, digestion, and bioutilization, leading to significant changes in the structure and properties of proteins and anthocyanins. Current knowledge of protein-anthocyanin interactions and their contributions to functions and bioactivities of anthocyanin-containing foods were reviewed. Binding characterization of dietary protein-anthocyanins complexes is outlined. Advances in understanding the structure-affinity relationship of dietary protein-anthocyanin interaction are critically discussed. The associated properties of protein-anthocyanin complexes are considered in an evaluation of functional and nutritional values.

The Effect of Glycosylated Soy Protein Isolate on the Stability of Lutein and Their Interaction Characteristics

Lutein is a natural fat-soluble carotenoid with various physiological functions. However, its poor water solubility and stability restrict its application in functional foods. The present study sought to analyze the stability and interaction mechanism of the complex glycosylated soy protein isolate (SPI) prepared using SPI and inulin-type fructans and lutein. The results showed that glycosylation reduced the fluorescence intensity and surface hydrophobicity of SPI but improved the emulsification process and solubility. Fluorescence intensity and ultraviolet–visible (UV–Vis) absorption spectroscopy results showed that the fluorescence quenching of the glycosylated soybean protein isolate by lutein was static. Through thermodynamic parameter analysis, it was found that lutein and glycosylated SPI were bound spontaneously through hydrophobic interaction, and the binding stoichiometry was 1:1. The X-ray diffraction analysis results showed that lutein existed in the glycosylated soybean protein isolate in an amorphous form. The Fourier transform infrared spectroscopy analysis results revealed that lutein had no effect on the secondary structure of glycosylated soy protein isolate. Meanwhile, the combination of lutein and glycosylated SPI improved the water solubility of lutein and the stability of light and heat.

Milk protein hydrolysates obtained with immobilized alcalase and neutrase on magnetite nanoparticles: Characterization and antigenicity study

Enzymatic hydrolysis is the most commonly used method to reduce the antigenicity of milk protein, but free protease is unstable and difficult to recycle after application. In this study, alcalase and neutrase were selected for immobilization on the modified magnetic Fe₃ O₄ nanoparticles. The reusability of the immobilized enzyme was 68.23% of the total starting activity after 5 recycling batches. The optimal hydrolysis conditions were an enzyme to substrate ratio of 6000 U/g and reaction at 50℃ and pH 8.5 for 3 h. Under these conditions, 22.76% hydrolysis of hydrolysate was achieved, and the antigenicity reduction rates of β-lactoglobulin and casein were 21.34% and 30.89%, respectively. In addition, 82.75% of the hydrolysate had a molecular weight less than 1 kDa, and free amino acids represented 13.65% of the sample. This result showed that the hydrolysis with immobilized enzyme was similar to that with free enzyme and the immobilized enzyme could be applied to produce hypoallergenic hydrolysate. PRACTICAL APPLICATION: Reduces milk protein allergenicity.

The reciprocal interaction between polyphenols and other dietary compounds: Impact on bioavailability, antioxidant capacity and other physico-chemical and nutritional parameters

Polyphenols are plant secondary metabolites, whose biological activity has been widely demonstrated. However, the research in this field is a bit reductive, as very frequently the effect of individual compound is investigated in different experimental models, neglecting more complex, but common, relationships that are established in the diet. This review summarizes the data that highlighted the interaction between polyphenols and other food components, especially macro- (lipids, proteins, carbohydrates and fibers) and micronutrients (minerals, vitamins and organic pigments), paying particular attention on their bioavailability, antioxidant capacity and chemical, physical, organoleptic and nutritional characteristics. The topic of food interaction has yet to be extensively studied because a greater knowledge of the food chemistry behind these interactions and the variables that modify their effects, could offer innovations and improvements in various fields ranging from organoleptic, nutritional to health and economic field.

Effects of "nine steaming nine sun-drying" on proximate composition, protein structure and volatile compounds of black soybeans

Nine steaming nine sun-drying is a traditional processing technology for food or medicinal materials. The dynamic changes of the proximate composition, protein structure and volatile compounds during nine-time steaming and sun-drying of black soybeans (BS) were studied. The proximate composition results showed that the content of protein, carbohydrate and fat of BS decreased after processing, whereas the relative content of amino acids remained basically unchanged. Protein structure was evaluated using Fourier transform infrared spectroscopy (FT-IR), Ultraviolet absorption spectroscopy (UV) and Fluorescence spectroscopy. FT-IR result revealed that the relative contents of β-sheet and β-turn of the secondary structure of black soybean protein isolate (BSPI) decreased but the relative contents of α-helix and random coil increased after steaming and sun-drying. The results of UV and fluorescence spectroscopy confirmed changes in the protein conformation. In addition, SPME-GCMS analysis demonstrated that hydrocarbons, alcohols and aldehydes were the main volatile compounds. The relative contents of 1-octen-3-ol and hexanal, which are the main sources of beany flavor decreased significantly compared with raw BS. Principal component analysis (PCA) results showed that the volatile compounds of nine steamed and nine sun-dried BS could be well distinguished during the process. These findings may therefore provide a scientific basis for the application of nine-time steamed and sun-dried BS in food industry and contribute to the understanding of process-induced chemical transformations in this ancient processing technique.

Chemosensor Strip from Kepok Banana Bracts Extract (Musa paradisiaca L.) for Detection of Tuna Freshness

Anthocyanins as chemosensory compounds for amines have been tested in this study. Because anthocyanins are sensitive to pH changes, while amines have an alkaline nature, they can cause structural changes in anthocyanins, resulting in changes in the color of anthocyanins. The source of anthocyanins was the Kepok banana bracts (Musa paradisiaca L.), which were extracted using a mixture of ethanol:HCl 0.15% (3:2). The types of anthocyanin compounds were characterized using a UV-Vis spectrophotometer. The anthocyanin content obtained varied from 1.26 mg/100 g to 5.08 mg/100 g. The type of anthocyanin in the Kepok banana bracts was found as a cyanidin-3-rutinoside with maximum absorption at 513 nm at pH 1. The color of anthocyanin extract varied with changes in pH; it turned red in acid and faded in neutral solutions. The green color in the alkaline solution changes to brownish-yellow was associated with anthocyanin degradation. The color change at different pH indicates that banana bracts are regarded as a potential chemosensory compound to detect tuna freshness. The chemosensor was applied to a cellulose-based strip and exhibited a color change that corresponded to the increase in pH and was comparable to the results of the pH meter measurement. The structural changes of anthocyanin before and after the tuna freshness test were identified by the FTIR-ATR, indicating a change in the anthocyanin structure. Tuna freshness began to diminish after being stored for 12 and 24 hours at room temperature, marked by a color change of the paper strip to colorless and blackish gray.

Effect of Soybean Protein Isolate-7s on Delphinidin-3-O-Glucoside from Purple Corn Stability and Their Interactional Characterization

Anthocyanins are abundant in purple corn and beneficial to human health. Soybean protein isolate-7s (SPI-7s) could enhance the stability of anthocyanins. The stable system of soybean protein isolate-7s and delphinidin-3-O-glucoside complex (SPI-7s-D3G) was optimized using the Box–Behnken design at pH 2.8 and pH 6.8. Under the condition of pH 2.8, SPI-7s effectively improved the sunlight-thermal stabilities of delphinidin-3-O-glucoside (D3G). The thermal degradation of D3G conformed to the first order kinetics within 100 min, the negative enthalpy value and positive entropy value indicated that interaction was caused by electrostatic interaction, and the negative Gibbs free energy value reflected a spontaneous interaction between SPI-7s and D3G. The interaction of SPI-7s-D3G was evaluated by ultraviolet visible spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy. The results showed that the maximum absorption peak was redshifted with increasing the α-helix content and decreasing the β-sheet contents, and D3G quenched the intrinsic fluorescence of SPI-7s by static quenching. There was one binding site in the SPI-7s and D3G stable system. The secondary structure of SPI-7s had changed and the complex was more stable. The stabilized SPI-7s-D3G will have broad application prospects in functional foods.

Antioxidant Content and Antioxidant Capacity of the Protein-Rich Powdered Beverages Enriched with Flax Seeds Gum

Powdered beverages produced from dried fruit and vegetables are new products whose properties may be tailored by adding efficient nutrients and functional ingredients. The analyses of low-molecular antioxidants and antioxidant properties as well as nutrient content and digestibility were tested in beverages enriched with lentil proteins (AGF) and flaxseed gum (FSG). A replacement of sprouted lentil flour with the AGF deteriorated the phenolic content. As a main source of phenolics and vitamin C, lyophilized parsley leaves and broccoli sprouts were recognized. (There was no clear effect of the FGS.) The highest content of phenolics was determined in the beverages with these additives without the AGS (c.a. 125 μg/g). The AGF significantly improved the ability to quench ABTS radicals and reduce power. The best results were for the beverages without the FSG. (The effect was enhanced by lyophilized fruit and green vegetables.) The lowest chelating power and ability to quench hydroxyl radicals were in the beverages based on the AGF (improvement by the FSG and green vegetables). The tailoring of beverages' recipes significantly increased protein content and did not affect nutrient digestibility. The modifications allow obtaining the beverages exhibiting multidirectional antioxidant properties, being a source of easily bioaccessible starch and proteins.

Effect of Fractionation and Processing Conditions on the Digestibility of Plant Proteins as Food Ingredients

Plant protein concentrates and isolates are used to produce alternatives to meat, dairy and eggs. Fractionation of ingredients and subsequent processing into food products modify the techno-functional and nutritional properties of proteins. The differences in composition and structure of plant proteins, in addition to the wide range of processing steps and conditions, can have ambivalent effects on protein digestibility. The objective of this review is to assess the current knowledge on the effect of processing of plant protein-rich ingredients on their digestibility. We obtained data on various fractionation conditions and processing after fractionation, including enzymatic hydrolysis, alkaline treatment, heating, high pressure, fermentation, complexation, extrusion, gelation, as well as oxidation and interactions with starch or fibre. We provide an overview of the effect of some processing steps for protein-rich ingredients from different crops, such as soybean, yellow pea, and lentil, among others. Some studies explored the effect of processing on the presence of antinutritional factors. A certain degree, and type, of processing can improve protein digestibility, while more extensive processing can be detrimental. We argue that processing, protein bioavailability and the digestibility of plant-based foods must be addressed in combination to truly improve the sustainability of the current food system.

Interaction of lentil protein and onion skin phenolics: Effects on functional properties of proteins and in vitro gastrointestinal digestibility

The effect of protein-phenolic interactions on the functional properties of lentil protein and in vitro gastrointestinal digestibility in different systems (extract solution, protein-phenolic solution, and emulsion) was studied. The presence of phenolic compounds negatively affected the foaming and emulsion properties of lentil protein. During in vitro gastrointestinal digestion, total phenolic content (TPC) and antioxidant capacity of the samples were decreased with the presence of lentil protein at the initial phase, however, they were found to be the highest in emulsions at the intestinal phase. The amount of protocatechuic acid and phenolic acid derivative was increased at the intestinal phase, while that of other phenolic compounds was decreased. Quercetin was not detected at the intestinal phase in all systems, while its glycoside derivatives were determined, which were the highest in emulsions. Anthocyanins were also the highest in extract solution among all systems. Protein-phenolic interactions had a significant effect on functional properties of lentil proteins, and bioaccessibility or antioxidant capacity of phenolic compounds.

Antibacterial, Antioxidation, UV-Blocking, and Biodegradable Soy Protein Isolate Food Packaging Film with Mangosteen Peel Extract and ZnO Nanoparticles

The objective of this study was to prepare a functional biodegradable soy protein isolate (SPI) food packaging film by introducing a natural antimicrobial agent, mangosteen peel extract (MPE, 10 wt% based on SPI), and different concentrations of functional modifiers, ZnO NPs, into the natural polymer SPI by solution casting method. The physical, antioxidant, antibacterial properties and chemical structures were also investigated. The composite film with 5% ZnO NPs had the maximum tensile strength of 8.84 MPa and the lowest water vapor transmission rate of 9.23 g mm/m² h Pa. The composite film also exhibited excellent UV-blocking, antioxidant, and antibacterial properties against Escherichia coli and Staphylococcus aureus. The TGA results showed that the introduction of MPE and ZnO NPs improved the thermal stability of SPI films. The microstructure of the films was analyzed by SEM to determine the smooth surface of the composite films. ATR-FTIR and XPS analyses demonstrated the strong hydrogen bonding of SPI, MPE, and ZnO NPs in the films. The presence of ZnO NPs in the composite films was also proved by EDX and XRD. These results suggest that SPI/MPE/ZnO composite film is promising for food-active packaging to extend the shelf life of food products.

Covalent and non-covalent interactions of cyanidin-3-O-glucoside with milk proteins revealed modifications in protein conformational structures, digestibility, and allergenic characteristics

Currently, there is a need to explore the effects of different types of protein-anthocyanin complexations, as well as the possible changes in the nutrition and allergenicity of the formed complexes. Here, we systematically investigated the covalent and non-covalent interactions between cyanidin-3-O-glucoside (C3G) and two major milk proteins, α-casein (α-CN) and β-lactoglobulin (β-LG). Fluorescence quenching data showed that, under non-covalent conditions, C3G quenched the fluorescence of the two proteins via a static process, with the interaction forces being revealed; for covalent products, decreased fluorescence intensities were observed with red shifts in the λ_max. Multiple spectroscopic analyses implied that C3G-addition induced protein structural unfolding through transitions between the random coil and ordered secondary components. With a two-stage simulated gastrointestinal (GI) digestion model, it was seen that covalent complexes, not their non-covalent counterparts, showed reduced protein digestibility, ascribed to structural changes resulting in the unavailability of enzyme cleaving sites. The GI digests displayed prominent 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation-scavenging abilities (3.8-11.1 mM Trolox equivalents per mL digest), in contrast to the markedly reduced 1,1-diphenyl-2-picrylhydrazyl radical-scavenging capacities. Additionally, covalent protein-C3G complexes, but not their non-covalent counterparts, showed lower IgE-binding levels in comparison to the native control. This study provides new understanding for the development of anthocyanin-milk protein systems as functional ingredients with health-beneficial properties.

Preparation and characterizations of antibacterial–antioxidant film from soy protein isolate incorporated with mangosteen peel extract

The mangosteen peel extract (MPE) was used to obtain soy protein isolate (SPI) films. The results show that MPE exhibited a high content of total phenolics and antioxidant activity. Moreover, the MPE can enhance the antibacterial–antioxidant properties, UV-visible light barrier properties, and water-resistant properties of the SPI films. The presence of MPE resulted in an increase in water vapor permeability and hydrophobicity. The extract addition also reduced the film’s crystallinity along with a decrease in the mechanical property and lowering of the maximum degradation temperature. Attenuated total reflectance Fourier transform infrared spectroscopy revealed that the polyphenols in MPE could interact with SPI through hydrogen bonds and hydrophobic interactions, and the addition of MPE changed the secondary structure of SPI with a decrease in β-sheets and an increase in β-turns and random coils. Scanning electron microscopy showed that all the films exhibited smooth and homogenous morphology on the surface and on some layers through cross-sectional images. Our results suggested that the MPE would be a promising ingredient to make SPI films used as an active packaging material.

Structural and compositional changes of whey protein and blueberry juice fermented using Lactobacillus plantarum or Lactobacillus casei during fermentation

This study aimed to improve the stability of the anthocyanins and phenolic acids of blueberry by forming hydrogen bonds or hydrophobic interactions with whey protein using lactic acid fermentation. The effects of the initial pH on the characteristics of the whey protein and blueberry juice system fermented using Lactobacillus plantarum and Lactobacillus casei were investigated. The color and total phenol and anthocyanin contents of the blueberry juice and whey protein system became stable after fermentation using Lactobacillus plantarum and Lactobacillus casei. Fluorescence measurements and Fourier transform infrared spectroscopy (FTIR) analysis reveal that the characteristics of whey protein and blueberry juice changed significantly after fermentation using Lactobacillus plantarum and Lactobacillus casei indicating the binding of anthocyanins or phenolic hydroxyl groups of blueberry to N-H, C-N and C[double bond, length as m-dash]O groups of whey protein. The α-helix content of whey protein and blueberry fermented using Lactobacillus plantarum alone decreased by 18% and β-sheet content increased by approximately 27% compared to whey protein fermented using Lactobacillus plantarum.

Complexation of rice glutelin fibrils with cyanidin-3-O-glucoside at acidic condition: Thermal stability, binding mechanism and structural characterization

The complexation of rice glutelin fibrils (RGFs) with cyanidin-3-O-glucoside (C3G) at acidic condition was investigated. The RGFs at pH 3.5 had a greatest protective effect on the thermal stability of C3G. The binding of C3G for RGFs was exothermic and driven by hydrophobic and electrostatic interactions. The RGFs exhibited a stronger binding interaction with C3G than rice glutelin (RG), resulting from the exposure of hydrophobic groups and positive charges on the fibrils surface, and thus RGFs exhibited better protective effect on C3G. The interaction with C3G resulted in the rearrangement of polypeptide chain, thereby reducing the β-sheet content. The larger aggregates were observed in RG/RGFs-C3G complexes due to protein-polyphenols aggregation. It was noteworthy that the pre-formed RGFs were restructured into entangled aggregates due to the interaction. This study proposed a novel protein fibril to protect anthocyanins, expanding the application of anthocyanins as stable and functional ingredients in acidic food systems.

Interaction mechanisms and structure-affinity relationships between hyperoside and soybean β-conglycinin and glycinin

Hyperoside (HYP) is an important natural product that is widely distributed in fruits and whole grasses of various plants. It is also used by consumers as a healthy ingredient. This work explored the interaction mechanisms between HYP and two main soy proteins, namely, β-conglycinin (7S) and glycinin (11S), using computational simulation and multi-spectroscopic technology. In this study, the docking and dynamic simulation showed that HYP was stable in the hydrophobic pockets of the proteins. The conformation and microenvironment of 7S/11S also changed after binding to HYP. The binding of HYP to 7S/11S was a state quenching with a good affinity at 4 °C. This result was determined from the binding constant values of (1.995 ± 0.170) × 107 M-1 and (2.951 ± 0.109) × 107 M-1, respectively. The 7S/11S-HYP complex delineated here will provide a novel idea to construct an embedding and delivery system in improving the benefits of HYP for the development of high value-added food products.

Combination of copigmentation and encapsulation strategies for the synergistic stabilization of anthocyanins

Copigmentation and encapsulation are the two most commonly used techniques for anthocyanin stabilization. However, each of these techniques by itself suffers from many challenges associated with the simultaneous achievement of color intensification and high stability of anthocyanins. Integrating copigmentation and encapsulation may overcome the limitation of usage of a single technique. This review summarizes the most recent studies and their challenges aiming at combining copigmentation and encapsulation techniques. The effective approaches for encapsulating copigmented anthocyanins are described, including spray/freeze-drying, emulsification, gelation, polyelectrolyte complexation, and their combinations. Other emerging approaches, such as layer-by-layer deposition and ultrasonication, are also reviewed. The physicochemical principles underlying the combined strategies for the fabrication of various delivery systems are discussed. Particular emphasis is directed toward the synergistic effects of copigmentation and encapsulation, for example, modulating roles of copigments in the processes of gelation and complexation. Finally, some of the major challenges and opportunities for future studies are highlighted. The trend of integrating copigmentation and encapsulation has been just started to develop. The information in this review should facilitate the exploration of the combination of multistrategy and the fabrication of robust delivery systems for copigmented anthocyanins.

Investigation on the interaction of acrylamide with soy protein isolate: Exploring the binding mechanism in vitro

Acrylamide (AA), which is a carcinogen in humans, has been a research focus in terms of food risk assessment. However, few published studies have explored protein strategies to reduce the health risks of AA. The objective of this study was to investigate the binding of AA with soy protein isolate (SPI) and elucidate the binding mechanism. The results showed that AA could bind with nontreated, heat-treated, high-pressure homogenization-treated, and ultrasound-treated SPI in vitro. Fourier-transform infrared spectroscopy suggested that secondary structure of SPI changed significantly after binding with AA in the nontreated and different treated groups. Moreover, fluorescence quenching experiments suggested that the quenching of SPI by AA was static quenching and hydrogen bonds, hydrophobic interactions, and van der Waals forces were involved in this process. PRACTICAL APPLICATION: The study of SPI and AA binding could provide a new perspective for reducing the bioaccessibility of AA in human body by using protein. The results showed that SPI could potentially be used as a novel health strategy to reduce the harm of AA in the human body.

Soybean germination limits the role of cell wall integrity in controlling protein physicochemical changes during cooking and improves protein digestibility

Previous studies showed that in vitro digestibility of proteins in cooked beans is modulated by heat treatment and that the effect may be different whether proteins are heated in intact cotyledon or in a bean flour. In this study, germinated and non-germinated soybean cotyledons and flour were boiled at 100 °C for varying times (30, 90, or 180 min). After grinding, the level of trypsin inhibitors, protein aggregation, surface hydrophobicity, the secondary structure, and in vitro digestibility were studied. The presence of an intact cell wall during cooking increased protein denaturation temperature by about 10% and reduced the denaturation of trypsin inhibitors, and induced distinct changes in protein surface hydrophobicity and secondary structure. These physicochemical properties translated into an increment in protein degree of hydrolysis (DH, 72%) of protein cooked for 30 min as flour compared to proteins cooked in intact soybean tissues (64%). Increase in cooking times (90 and 180 min) resulted in limited improvement in the protein digestibility and changes in protein physicochemical properties for both boiled cotyledons and flour. Soybean germination resulted in distinct changes in protein physicochemical properties and higher protein DH% of raw soybean (61%) compared to non-germinated raw soybean (36%). An increase in protein digestibility of germinated soybean was also observed after boiling for both cotyledon and flour. However, significant differences in DH% were not observed between proteins boiled in intact cotyledon and in a flour. This work provides extra knowledge of the role of cellular integrity on protein properties in plant foods and suggests that germination or grinding before cooking may increase protein digestibility.

Soy Protein: Molecular Structure Revisited and Recent Advances in Processing Technologies

Rising health concerns and increasing obesity levels in human society have led some consumers to cut back on animal protein consumption and switch to plant-based proteins as an alternative. Soy protein is a versatile protein supplement and contains well-balanced amino acids, making it comparable to animal protein. With sufficient processing and modification, the quality of soy protein can be improved above that of animal-derived proteins, if desired. The modern food industry is undergoing a dynamic change, with advanced processing technologies that can produce a multitude of foods and ingredients with functional properties from soy proteins, providing consumers with a wide variety of foods. This review highlights recent progress in soy protein processing technologies. Using the current literature, the processing-induced structural changes in soy protein are also explored. Furthermore, the molecular structure of soy protein, particularly the crystal structures of β-conglycinin and glycinin, is comprehensively revisited.

Influence of high-intensity ultrasound on the IgE binding capacity of Act d 2 allergen, secondary structure, and In-vitro digestibility of kiwifruit proteins

Kiwifruit can trigger allergic reactions that can lead to death, causing public health concerns worldwide. In the present study, we treated kiwifruit samples with high-intensity ultrasound (20 kHz, 400 W, 50% duty cycle) for 0 to 16 min to evaluate its effect on the IgE binding capacity of kiwifruit allergen Act d 2, secondary structure and in-vitro digestibility of kiwifruit proteins. The changes in the protein solubility and microstructures of kiwifruit were also analyzed. The results showed that treatment with powerful ultrasound caused a significant disruption in the microstructure of kiwifruit tissues, leading to the changes in the secondary structures of proteins, including a loss of alpha-helixes and an increase in beta-sheet structures. These structural changes were due to the ultrasound treatment, especially 16 min of treatment, resulted in a 50% reduction in Act d 2 allergen content and significantly improved in-vitro digestibility up to 62% from the initial level of 35%. Furthermore, the solubility of the total proteins present in kiwifruit samples was significantly decreased by 20% after 16-min ultrasound processing. The results of this work showed that high-intensity ultrasound treatment has a potential application in reducing the allergenicity of kiwifruit or related products.

Effects of Anthocyanins in Composite Meals on Cardiometabolic Outcomes-A Systematic Review of Randomized Controlled Feeding Trials

Accumulating epidemiological evidence suggests that anthocyanin intake is associated with reduced risks of cardiometabolic disorders, highlighting the importance of incorporating the phytochemical in our diets. Numerous food-based intervention studies have examined, in controlled meal settings, the role of anthocyanin on cardiometabolic health; but their effects have not been systematically summarized. This study aims to systematically review and summarize the effects of anthocyanin consumption with composite meals on cardiometabolic health from randomized controlled feeding trials. A systematic literature search for relevant human nutritional intervention studies was performed using PubMed, Embase, Cochrane Library, CINAHL Plus with Full Text, and Scopus databases. The Cochrane Risk of Bias tool was used to assess the study quality. Eighteen articles involving 371 participants were included in this review. Consistent improvements from anthocyanin intake were found in glycemic, gastric inhibitory peptide (GIP), interleukin-6 (IL-6), and oxygen radical absorbance capacity (ORAC) responses. Anthocyanin intake did not significantly affect other markers of energy metabolism, vascular functions, oxidative stress and antioxidant status, as well as inflammatory responses. Inconsistencies in successful outcomes between epidemiological studies and included interventions were largely attributed to matrix effects, which may impede the bioaccessibility of anthocyanins and consequently, limiting its health benefits when co-delivered with some foods.

Microencapsulated mulberry anthocyanins promote the in vitro-digestibility of whey proteins in glycated energy-ball models

The effects of mulberry anthocyanins (MAs) on the digestibility of whey proteins (WP) in freshly-prepared and stored energy balls were studied. Results showed that MAs increased digestibility of the energy balls by increasing their hydrolysis-degree, soluble peptides-fractions, and decreasing their particle's size and agglomeration. To understand the mechanism of the promoting and/or inhibiting digestive effects of MAs, secondary structure alterations and binding of WP-MAs-mixtures were therefore measured. Results revealed that MAs could noncovalently/covalently interact with WP and form WP-MAs-adducts. This interaction seemed to be responsible for the alterations in the secondary structure of WP which could promote the digestibility of the energy balls subsequently. MAs also partially unfolded the structure of digested-WP through fluctuating their α-helix and β-sheet. It was concluded that the unfolding in WP-structure induced by MAs-interactions might increase accessibility of the peptide bonds to the digestive enzymes and consequentially facilitate the protein's digestibility in the energy balls.

A review of the interaction between anthocyanins and proteins

Anthocyanins have good physiological functions, but they are unstable. The interaction between anthocyanins and proteins can improve the stability, nutritional and functional properties of the complex. This paper reviews the structural changes of complex of anthocyanins interacting with proteins from different sources. By circular dichroism (CD) spectroscopy, it was found that the contents of α-helix (from 15.90%-42.40% to 17.60%-52.80%) or β-sheet (from 29.00%-50.00% to 29.40%-57.00%) of the anthocyanins-proteins complex increased. Fourier transform infrared spectroscopy showed that the regions of amide I (from 1627.87-1641.41 cm^-1 to 1643.34-1651.02 cm^-1) and amide II (from 1537.00-1540.25 cm^-1 to 1539.00-1543.75 cm^-1) of anthocyanins-proteins complex were shifted. Fluorescence spectroscopy showed that the fluorescence intensity of the complex decreased from 150-5100 to 40-3900 a.u. The thermodynamic analysis showed that there were hydrophobic interactions, electrostatic and hydrogen bonding interactions between anthocyanins and proteins. The kinetic analysis showed that the half-life and activation energy of the complex increased. The stability, antioxidant, digestion, absorption, and emulsification of the complex were improved. This provides a reference for the study and application of anthocyanins and proteins interactions.

Binding affinity, antioxidative capacity and in vitro digestion of complexes of grape seed procyanidins and pork, chicken and fish protein

Studies have reported that procyanidins can interact with proteins, thereby affecting their structure, function, and bioaccessibility. In this paper, we investigated the interaction between grape seeds procyanidins (GSP) and animal source protein (from pig, chicken and fish), and the effects on the protein structure, antioxidant capacity and bioaccessibility of GSP. Fluorescence results showed that the binding constant of GSP-protein complex was 10-10⁴ M^-1, and the main forces were van der Waals force, hydrogen bonds and hydrophobic interactions. The antioxidant capacity of GSP was masked by GSP-protein complexes formed. The circular dichroism indicated that GSP had an effect on the content of α-helix and β-sheet in the secondary structure of pork and chicken proteins, but had little effect on the secondary structure of fish protein. The results showed that the protein can bind to GSP and affect its antioxidant activity and bioaccessibility. This study can provide reference for further study on the digestion and absorption of the complexes and offer health guidance in the preparation of diets.

A Study of Structural Change During In Vitro Digestion of Heated Soy Protein Isolates

Use of soy protein isolate (SPI) as the encapsulating material in emulsions is uncommon due to its low solubility and emulsification potential. The aim of this study was to improve these properties of SPI via heat treatment-induced modifications. We modified SPI under various heating conditions and demonstrated the relationship between structure and in vitro digestibility in simulated gastric fluid by means of Sodium Dodecyl Sulphide-Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Raman spectroscopy. It was found that the degree of hydrolysis (DH) of SPI increased and then decreased upon increasing exposure to heat. Different subunits of conglycinin were digested and degraded by pepsin. Heat treatment improved digestion characteristics that would reduce e the unnecessary loss of protein, offering potential for the efficient delivery of nutrients in nanoemulsions. These results could have significant relevance for research groups that are interested in the biological interactions and activity of functional SPI.

Study on condition of ultrasound-assisted thermo-alkali-modified peanut protein embedding curcumin for nanoparticles

This study investigated the effects of ultrasound-assisted thermo-alkali modification on the molecular structure of peanut protein. Further, the preparation conditions involved in embedding curcumin by the modified pea protein were also studied. It was found that within the pH range of 7 < pH < 11, with an increase in pH, the content of free sulfhydryl group in peanut protein isolate gradually increased from 10.35 ± 0.63 μmol/g (pH = 7) to 18.26 ± 0.93 μmol/g (pH = 10); and the content of disulfide bonds decreased from 44.62 ± 0.48 μmol/g (pH = 7) to 34.26 ± 2.03 μmol/g (pH = 11). In the ultrasonic power range (P < 300 W), with an increase in power, the content of free mercapto group in peanut protein isolate gradually increased from 12.44 ± 0.73 μmol/g to 19.46 ± 0.24 μmol/g (P = 250 W); and the content of disulfide bonds decreased from 42.29 ± 1.24 μmol/g to 33.28 ± 0.64 μmol/g (P = 300 W). Within the temperature range of 70 °C < T < 90 °C, with an increase in temperature, the content of free sulfhydryl group in peanut protein isolate gradually increased from 10.35 ± 0.94 μmol/g (T = 70 °C) to 19.67 ± 0.68 μmol/g (T = 90 °C), and the content of disulfide bonds decreased from 45.02 ± 2.84 μmol/g (T = 70 °C) to 34.26 ± 2.03 μmol/g (T = 90 °C). Response surface test was used to optimize the preparation conditions of nanoparticles from curcumin. The results showed that the optimum parameters of ultrasonic-assisted modification of peanut protein embedding curcumin were pH = 9.8, heating temperature T = 90 °C, ultrasonic power Q = 225 W, and heating time S = 21 min. Under these conditions, the embedding rate of curcumin reached 83.27 + 1.06%, the ABTS⁺ scavenging activity generally decreases with time over the 2 days period measured in PPI solution and PPI nanoparticles (PPN), the ABTS⁺ scavenging activity decreased from 40.8%, 52.2% and 67.3% to 27.1%, 39.0% and 60.5%, respectively. Compared with pure curcumin, the antioxidant activity was increased at presence of PPI.

Interaction of Protein Isolate with Anthocyanin Extracted from Black Soybean and Its Effect on the Anthocyanin Stability

The interactions between black soybean protein isolate (B-SPI) and cyanidin 3-O-glucoside (C3G), anthocyanin extracted from black soybean coat was investigated under neutral conditions. The fluorescence spectra showed that C3G had fluorescence quenching effects on B-SPI. Thermodynamic parameters showed that ∆G < 0, which demonstrated that the binding was a spontaneous reaction. Since ΔH > 0 and ΔS > 0, the interactions between C3G and B-SPI was mainly hydrophobic interactions. Fourier infrared spectroscopy results suggested that the contents of α-helix and β-sheet structure showed an increasing trend, whereas the β-angle content displayed a decreasing trend. The degradation of C3G followed first-order kinetics at 85 °C and 100 °C. After the interactions with B-SPI, the degradation rate constant was decreased and the half-life of C3G was prolonged from 70.25 ± 0.90 min to 175.64 ± 38.04 min at 85 °C, from 62.68 ± 1.1 min to 72.51 ± 2.5 min at 100 °C (p < 0.05). The results indicated that the interactions of B-SPI and C3G improved the thermal stability of C3G under heating conditions.