A novel film based on gluten, pectin, and polyphenols and its potential application in high-fat food.

BACKGROUND: A novel film based on some natural ingredients (wheat gluten, pectin, and polyphenols) was used to improve the quality and storage stability of high-fat food due to their good sustainable, mechanical, and edible properties. RESULTS: With the addition of polyphenols from Cedrus deodara (in the form of pine-needle extract (PNE)), the physicochemical properties (thickness, moisture content, and color), mechanical properties (tensile strength and elongation), barrier properties (water vapor, oil, and oxygen permeability, transmittance), and thermal stability of the composite film were improved. According to the analysis of infrared spectroscopy and molecular docking, the main compounds of PNE interacted with wheat gluten by hydrogen bonds and hydrophobic forces to form a compact and stable structure. In addition, the composite film showed a remarkable antioxidant capability to scavenge free radicals, and the film matrix could effectively protect the antioxidant activity of PNE. Furthermore, using cured meat as a model, the composite film exhibited a fine packaging performance in high-fat food during storage, which could obviously inhibit the excessive oxidation of fat and protein of cured meat and was beneficial in forming its special flavor. CONCLUSION: Our results suggest that the composite film possessed good properties and had potential for packing of high-fat foods, which could improve the quality and safety of food during processing and storage. © 2023 Society of Chemical Industry.

Gliadin interacted with tea polyphenols: potential application and action mechanism.

The effect of tea polyphenols (TPs) on noodles quality was investigated, and the interaction mechanism between catechins and gliadins was explored. With TPs addition, noodles showed the significant changes in physicochemical and sensory properties. The water absorption, tensile strength and elasticity increased by 1.35%, 4.98%, 28.51% with 0.5% of TPs, and then decreased with the increasing of TPs. According to the determinations of surface hydrophobicity, spatial structure, thermal properties, amidogen and sulfhydryl content, the structure and properties of gliadin were affected by catechins. Esterified catechins tended to disrupt gliadin structures and non-esterified catechins polymerised gliadin molecules. Furthermore, molecular docking results indicated that catechins interacted with gliadin mainly by hydrogen bonds and hydrophobic action. The reactivity of catechins with gliadin was in the sequence as: epigallocatechin gallate > epicatechin gallate > epigallocatechin > epicatechin, which was based on the account of gallate and B-ring hydroxyl number discrepancy. All results suggested that catechins affected greatly on gliadin, and TPs were potentially used to improve the quality of flour products.

Interaction and action mechanism of starch with different phenolic compounds.

The interaction and action mechanism of starch with different phenolic compounds were investigated. By using scanning electron microscope, nuclear magnetic resonance, Fourier transform infra-red spectroscopy and thermogravimetric analysis, phenolic compounds exhibited the significant effects on the morphology, intensity of hydrogen bond, crystalline structure and thermal stability of starch, respectively. Furthermore, according to the analysis of molecular dynamics simulation by using short-chain glucose (SGS) as model, phenolic compounds could change the spatial configuration of starch, and had the obvious effects on the formation of hydrogen bonds (including intra- and intermolecular hydrogen bonds) and the strength of binding free energy. Meanwhile, epigallocatechin gallate possessed the strongest capacity to change the spatial configuration of starch with the consistent hydrogen bond occupancy and the lowest binding free energy. All present results suggested that phenolic compounds might be potentially utilised for improving the quality of starch in food industry.

Recognition-Enhanced Metastably Shielded Aptamer for Digital Quantification of Small Molecules.

Aptamers are recognized as competitive affinity reagents; their application, however, often suffers from their relatively low target binding affinity, especially for small molecules. We herein introduce the concept of a recognition-enhanced metastably shielded aptamer probe (RMSApt) and explore its performance for digital quantification of low-affinity small molecules. The RMSApt design employs the idea of constructing an allosteric aptamer probe conferring a minor energy gap in the recognition switch process to facilitate target binding and probe response, in turn significantly improving the recognition efficiency for low-affinity targets. The probe design strategy boosts the application of aptamers for precisely quantifying targets with a dissociation constant Kd ranging from 10-4 to 10-9 M, which would cover most of the small-molecule species that exist binding aptamers. Thus, RMSApt would facilitate the translation of aptamers for medical diagnosis, food safety, and environmental screening.

Establishing a novel ternary complex of soybean protein isolated-tannic acid-magnesium ion and its properties.

A ternary complex composed of soybean protein isolated (SPI), tannic acid (TA) and magnesium ion (M) was established to enhance the capability of protein carriers for TA delivery. SPI was firstly covalently bind with TA (TA-SPI) and then M was employed to form the ternary complex (M-TA-SPI). Their structures, gel and digestion properties were further investigated. TA was observed to covalently bind with SPI. TA-SPI and M-TA-SPI complexes showed different molecule size and spatial structures after binding with M and TA. The increasing of TA amount changed the intramolecular interactions, microstructure and texture properties of M-TA-SPI gels. Compared with TA-SPI, M retarded the gastric digestion of M-TA-SPI and caused higher TA release amount in intestinal tract. In this study, M-TA-SPI was determined to be a good carrier to protect and release TA in gastrointestinal digestion. This kind of complex may have potential applications for loading polyphenols in nutraceuticals.

Establishing a novel covalent complex of wheat gluten with tea polyphenols: Structure, digestion, and action mechanism.

Plant-based proteins represent a more sustainable alternative, the approaches to modify and enhance their functionality and application are focused on. Covalent interaction could significantly modify the structure and function properties of protein. This study investigated the effects of covalent interaction between wheat gluten and tea polyphenols on the structure, aggregation, stability, and digestive properties of their covalent complex, as well as the possible action mechanism. The results showed that tea polyphenols could interact with gluten via covalent bonds (CN and/or CS), while tea polyphenols also acted as a bridge connecting gluten molecules, thus making covalent complex to show the larger particle sizes. This covalent interaction significantly changed the secondary structure, tertiary structure, and surface hydrophobicity of gluten. Moreover, covalent complex exhibited the high polyphenols bioaccessibility during in vitro digestion. The peptide bonds of covalent complex were mainly broken in gastric digestion, while the covalent bonds between tea polyphenols and gluten were completely destroyed in intestinal digestion. In addition, their digestates exhibited excellent antioxidant capability. All results suggest that wheat gluten have potential to prepare functional carrier for transporting active compounds and protecting them during digestion.

Creating and characteristics of a novel biomacromolecules complex of pea protein isolated-tannic acid-magnesium ion.

Pea protein isolate (PPI) was used as a carrier matrix to load tannic acid (TA) due to its multiple cavity structures and reaction sites, after that, magnesium ion (M) was further added to form more stable carrier structures. PPI was covalently bound with TA to form TA-PPI complexes in alkaline conditions, then M induced the aggregation of TA-PPI to produce M-TA-PPI complexes. TA mainly interacted with free amino groups and sulfhydryl groups of PPI, thereby decreasing their content in complexes. TA further decreased the α-helix content and increased the ß-sheet and ß-turn content in TA-PPI complexes correspondingly, nevertheless the M would decline these changes in M-TA-PPI complexes. As a result of binding, TA and M jointly increased the average molecular size of complexes. The higher TA addition amount (10-20 mg/g PPI) was conducive to the stronger intramolecular interactions (more hydrophobic interactions and disulfide bonds), gel structure (higher hardness value) and storage modulus in M-TA-PPI gels. Compared with TA-PPI complexes, M-TA-PPI complexes showed higher stability in gastric digestion and higher TA releasement and antioxidant capacity of its digesta in intestinal digestion. This kind of metal-phenolics-protein complexes may have potentials to be a stable and efficient carrier for loading gastric sensitive polyphenols.

Gel properties of Nicandra physalodes (Linn.) gaertn. seeds polysaccharides with tea polyphenols and its application.

The novel gelling polysaccharides (NPGP) were extracted and characterized from Nicandra physalodes (Linn.) Gaertn. seeds, while properties and potential application of NPGP gels with tea polyphenols were further explored. NPGP was composed of GalA, Glc, Rha, Gal, Xyl, Ara, and Man at a molar ratio of 71.87:17.13:3.10:2.55:2.19:1.64:1.52, with molecular weight of 6.32 × 104 Da and low methoxylation degree of 45.21%. The gelling properties of NPGP gel induced by tea polyphenols showed that tea polyphenols significantly improved the structural and rheological properties of NPGP gel, due to the formation of dense network by hydrogen bonds and the increase of crystalline degree of NPGP. NPGP gels with tea polyphenols could significantly ameliorated the texture, water-holding capacity, aggregation, leading force, and moisture distribution of surimi during freeze-thaw cycles. All results suggest that NPGP gels with tea polyphenols has fine properties and show potential to be applied as natural additives in food industry.

Potential of polyphenols from Ligustrum robustum (Rxob.) Blume on enhancing the quality of starchy food during frying.

The increasing concerns about health have led to a growing demand for high-quality fried foods. The potential uses of Ligustrum robustum (Rxob.) Blume, a traditional tea in China, as natural additives to enhance the quality of starchy food during frying was studied. Results indicated that L. robustum polyphenols extract (LREs) could improve the quality of fried starchy food, according to the tests of color, moisture content, oil content, texture property, and volatile flavor. The in vitro digestion results demonstrated that LRE reduced the final glucose content from 11.35 ± 0.17 to 10.80 ± 0.70 mmol/L and increased the phenolic content of fried starch foods from 1.23 ± 0.04 to 3.76 ± 0.14 mg/g. The appearance and polarizing microscopy results showed that LRE promoted large starch bulges on the surface of fried starchy foods. Meanwhile, X-ray diffraction results showed that LRE increased the intensity of characteristic diffraction peak of fried starch with a range of 21.8%-28%, and Fourier transform infrared results showed that LRE reduced the damage to short-range order structure of starch caused by the frying process. In addition, LRE increased the aggregation of starch granules according to the SEM observation and decreased the enthalpy of starch gelatinization based on the differential scanning calorimetry results. The present results suggest that LREs have the potential to be utilized as a natural additive for regulating the quality of fried starchy food in food industries. PRACTICAL APPLICATION: The enhancement of L. robustum polyphenols on the quality of starchy food during frying was found, and its mechanisms were also explored. This work indicated that L. robustum might be used as a novel economic natural additive for producing high-quality fried foods.

Elucidating effects of Epiphyllum oxypetalum (DC.) Haw polysaccharide on the physicochemical and digestive properties of tapioca starch.

Effects of Epiphyllum oxypetalum (DC.) Haw polysaccharide (EP) on physicochemical/digestive properties of tapioca starch (TS) were investigated, and its effects on final quality of TS-based foods were further determined. Results showed EP significantly decreased gelatinization enthalpy (3.92 to 2.11 J/g) and increased breakdown (302 to 382 cp), thereby inducing the gelatinization of TS. Meanwhile, EP decreased setback viscosity (324 to 258 cp), suggesting the retrogradation of TS paste was inhibited. Rheological determination results suggested EP had an impact on the viscoelasticity of TS paste. Moreover, particle size distribution showed EP increased size of TS by cross-linking. Additionally, the suitable addition of EP ameliorated the microstructure and decreased the crystal diffraction peak area of TS gel. Infrared spectroscopy results revealed EP modified the above properties of TS by hydrogen bonds and non-covalent forces. Furthermore, EP inhibited the in vitro digestion of TS paste. Using taro balls as TS-based food model, appropriate addition of EP (0.10 %) improved texture properties, frozen storage stability and color of samples. The present results can not only facilitate the understanding of the modification mechanism of EP on the properties of TS, but also induce the burgeoning of starchy products and the possible application of EP in foods.

Elucidating the influence and mechanism of different phenols on the properties, food quality and function of maize starch.

This study discusses interaction differences between three phenols (protocatechuic acid, naringin and tannic acid) and starch helix, investigates influences of phenols at different doses on properties of maize starch, and further determines their effects on quality and function of maize-starchy foods. Simulated results indicate variations of phenolic structure (phenolic hydroxyl group amount, glycoside structure and steric hindrance) and dose induce phenols form different complexes with starch helix. Formation of different starch-phenols complexes alters gelatinization (1.65-5.63 J/g), pasting form, water binding capacity (8.83-12.69 g/g) and particle size distribution of starch. Meanwhile, differences in starch-phenols complexes are reflected in fingerprint area (R1045/1022: 0.920 to 1.047), crystallinity (8.3% to 17.0%), rheology and gel structure of starch. Additionally, phenols change texture and color of cold maize cake, giving them different antioxidant capacity and lower digestibility. Findings are beneficial for understanding interaction between starch and different phenols and their potential application.

Core-shell structured alginate-based hydrogel beads modified by starch and protocatechuic acid: Preparation, characterization, phenolic slow release and stable antioxidant potential.

A novel core-shell structured alginate-based hydrogel bead modified by co-gelatinizing with starch and protocatechuic acid (PA), was designed to modulate physical properties of beads, release behavior and antioxidant stability of encapsulated bioactives. Core was fabricated by ionotropic gelation, and its formulation (ratio of sodium alginate/starch) was determined by particle size/starch distribution, texture and bioactive encapsulation capacity of core. Then, coating core with shell-forming solution co-gelatinized with different doses of PA, and subsequently cross-linked with Ca2+ to obtain core-shell structured beads. Surface microstructure, mechanical characteristics, and swelling ratio of beads were affected by concentrations of PA. Besides, core-shell structure containing PA could enhance delivery and sustained release of encapsulated phenolic bioactives during in vitro digestion, and improve their antioxidant potential stability. Furthermore, interaction between PA and polysaccharide components was elucidated by FTIR and TGA. The present information was beneficial for the advancement of functional food materials and bioactive delivery systems.

Non-covalent binding of chlorogenic acid to myofibrillar protein improved its bio-functionality properties and metabolic fate.

As natural antioxidants added to meat products, polyphenols can interact with proteins, and the acid-base environment influenced the extent of non-covalent and covalent interactions between them. This study compared the bio-functional characteristics and metabolic outcomes of the myofibrillar protein-chlorogenic acid (MP-CGA) complexes binding in different environments (pH 6.0 and 8.5). The results showed that CGA bound with MP significantly enhanced its antioxidant activity and inhibitory effect on metabolism enzymes. CGA bound deeply into the MP structure hydrophobic cavity at pH 6.0, which reduced its degradation by digestive enzymes, thus increasing its bio-accessibility from 59.5% to 71.6%. The digestion products of the two complexes exhibited significant differences, with the non-covalent MP-CGA complexes formed at pH 6.0 showing significantly higher concentrations of rhetsinine and piplartine, two well-known compounds to modulate diabetes. This study demonstrated that non-covalent binding between protein and polyphenol in the acidic environment held greater promising prospects for improving health.

A polysaccharide from Epiphyllum oxypetalum (DC.) Haw. and its immunomodulatory activity.

A polysaccharide (EOP) from Epiphyllum oxypetalum (DC.) Haw. was isolated and identified, and its immunomodulatory activity was evaluated both in vitro and in vivo. By using multispectral analysis, EOP was determined to be composed of rhamnose, arabinose, galactose, and galacturonic acid at a molar ratio of 26.65:11.48:53.79:6.04, and its molecular weight was 5.77 × 106 Da. In addition, backbone structure of EOP was determined to consist of (1 â†’ 4)-linked ß-Galp, (1 â†’ 2)-linked ß-Rhap, (1 â†’ 3,4)-linked ß-Galp, (1 â†’ 2,4)-linked ß-Rhap and (1 â†’ 4) -linked α-GalpA, terminating with t-ß-Arap and t-ß-Galp. The in vitro immunomodulatory activity assay on RAW 264.7 cell showed that EOP increased the proliferation of macrophages, enhanced its phagocytic capability, and promoted the production of cytokines including nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Furthermore, the in vivo evaluation on zebrafish showed that EOP could reduce the residual content of fluorescent microspheres in zebrafish, which indicated that EOP had the capability to enhance the macrophage phagocytosis. All results suggested that EOP showed a complex structure and exhibited significant immunomodulatory activity both in vitro and in vivo that had the potential to be utilized valuably in food and medicine industries.

Insight into property, function, and digestion of potato starch modified by phenolic compounds with varying structures.

Influences of structural characteristics of phenolic compounds on the properties of potato starch were investigated, and their effects on the quality, function, and digestion of potato starch noodles were further determined. All testing phenolic compounds (including protocatechuic acid [PA], naringin [NA], and tannic acid [TA]) exhibited the significant capability to modify the thermal properties, rheological properties, and enzymatic hydrolysis of potato starch. The high amount of hydroxyl groups, the presence of glycoside structure, appropriate molecular size, and steric hindrance were beneficial to enhance their effects on potato starch. In addition, by changing the microstructure of starch hydrocolloids, PA, NA, and TA could affect the color, texture properties, and cooking properties of potato starch noodles. Meanwhile, PA and TA could endow potato starch noodles with remarkable antioxidant activity. Furthermore, the in vitro digestion of potato starch noodles was obviously inhibited by phenolic compounds, especially for TA. All present results suggested that structural characteristics of phenolic compounds affected their interaction affinity and combination degree with potato starch molecules, so as to modify the properties of starch and affect the quality, function, and digestion of starchy foods, which showed the valuable applications in food and chemical industries. PRACTICAL APPLICATION: The property, function, and digestion characteristics of potato starch show the significant effects on the quality of potato starch products in food industry. In present study, the thermal properties, rheological properties, and enzymatic hydrolysis of potato starch were modified by different phenolic compounds (including protocatechuic acid, naringin, and tannic acid) in varying degrees, whereas the quality, antioxidant activity, and digestion characteristic of potato starch noodles were modified by phenolic compounds with different structures. All results showed the potential application and interaction regularities of phenolic compounds as natural additives for potato starch processing in food industry.

Potato Starch-Based Film Incorporated with Tea Polyphenols and Its Application in Fruit Packaging.

Effects of tea polyphenols (TP) on the physical properties, barrier properties and functionality of potato starch-based film were determined, while the interaction mechanism between TP and starch in film and the application of this film in fruit packaging were further evaluated. TP exhibited different effects on the physical properties of potato starch-based film, including thickness (0.083 to 0.087 mm), moisture content (9.27% to 9.68%), color (ΔE value: 5.41 to 10.55), light transmittance (51% to 62%), tensile properties and thermal properties, and improved its barrier properties, including water vapor permeability (9.68 to 11.84 × 10-11 g m-1 s-1 Pa-1),oxygen permeability (1.25 to 2.78 × 10-16 g m-1 s-1 Pa-1) and antioxidant activity. According to the determination of wide-angle X-ray diffraction, Fourier transform infrared and scanning electron microscope, TP could interact with starch chains via hydrogen bonds to form non-crystal complexes, thus affecting the cross-linking among starch chains and further changing the microstructure of film. Furthermore, film incorporated with TP could improve the storage quality (including weight and texture) of blueberries, and inhibit the enzymatic browning of fresh-cut bananas during storage. All present results suggested that tea polyphenols had potential to enhance the properties and function of potato starch-based film, and the film exhibited the application prospect in fruit packaging and preservation.

Chemical composition and antimicrobial activity of the essential oil of kumquat (Fortunella crassifolia Swingle) peel.

The aim of this study was to determine the main constituents of the essential oil isolated from Fortunella crassifolia Swingle peel by hydro-distillation, and to test the efficacy of the essential oil on antimicrobial activity. Twenty-five components, representing 92.36% of the total oil, were identified by GC-MS analysis. The essential oil showed potent antimicrobial activity against both Gram-negative (E. coli and S. typhimurium) and Gram-positive (S. aureus, B. cereus, B. subtilis, L. bulgaricus, and B. laterosporus) bacteria, together with a remarkable antifungal activity against C. albicans. In a food model of beef extract, the essential oil was observed to possess an effective capacity to control the total counts of viable bacteria. Furthermore, the essential oil showed strongly detrimental effects on the growth and morphological structure of the tested bacteria. It was suggested that the essential oil from Fortunella crassifolia Swingle peel might be used as a natural food preservative against bacteria or fungus in the food industry.

Wheat Starch Modified with Ligustrum robustum (Rxob.) Blume Extract and Its Action Mechanism.

We investigated the modification of wheat starch with Ligustrum robustum (Rxob.) Blume extract (LRE) and determined the action mechanism. Based on differential scanning calorimetry, LRE decreased the gelatinization enthalpy of wheat starch from 19.14 to 7.15 J/g and changed gelatinization temperatures (including the variation in gelatinization onset temperature, peak temperature and conclusion temperature in different degrees). Moreover, LRE affected the pasting viscosity curve of wheat starch, and changed its rheological parameters (including the decrease in storage modulus and loss modulus, as well as the increase in loss tangent). Based on the analysis of scanning electron microscopy and wide-angle X-ray diffraction, LRE increased the hole size and the roughness of the gel microstructure, and decreased the crystallinity of wheat starch. Meanwhile, the evaluation results of the texture analyzer and the colorimeter showed that LRE could change the quality properties (including decrease hardness, fracturability and L* values, as well as increase a* and b* values) of wheat starch biscuits after hot air baking (170 °C). Furthermore, with molecular dynamics simulation analysis, phenolic compounds of LRE combined with starch molecules via H-bonds and affected the formation of molecular bonds (including intra- and intermolecular hydrogen bonds), so as to change the spatial conformation and properties of wheat starch during gelatinization and retrogradation. The present results suggest that LRE can modify the physicochemical properties of wheat starch and further improve its processing properties, indicating its potential in the design and development of starch foods (such as steamed buns, bread, biscuits, etc.).

Effects of casein on the stability, antioxidant activity, and bioavailability of lotus anthocyanins.

Effects of casein on the stability, antioxidant activity, and bioavailability of lotus anthocyanins were investigated. Casein could inhibit the unsatisfactory pH-induced color change of lotus anthocyanins, and improved their photo, oxidation, and thermal stabilities. During the simulated digestion, the anthocyanin retention increased from 65.39 to 76.14 mg C3G/L with the protection of casein, while the DPPH and ABTS scavenging activities of lotus anthocyanins with casein increased to 62.33% and 46.58%, respectively. However, casein with lower concentration showed a better protective effect on lotus anthocyanins due to its self-aggregation tendency at high dose. The zebrafish model further verified that casein could enhance the bioavailability of lotus anthocyanins. Furthermore, molecular docking revealed that casein could interact with anthocyanin by hydrogen bond and hydrophobic interaction, which led to the stronger stability and bioavailability of lotus anthocyanins. The results conveyed that casein could be used as a wall material to protect anthocyanins. PRACTICAL APPLICATIONS: Anthocyanins are natural colorants with multiple biological activities, but the poor stability during processing and digestion limits their application in food industry. In the present research, casein exhibited conspicuous ability to enhance the stability of lotus anthocyanins toward detrimental conditions. Additionally, casein could preserve anthocyanins from degradation during digestion and thus improve the bioavailability. These findings indicated that casein could serve as a potential carrier for encapsulating and delivering anthocyanins. The better stability and bioavailability would promote the application of anthocyanins in food products and human health.

Inhibition of Biofilm Formation and Virulence Factors of Cariogenic Oral Pathogen Streptococcus mutans by Shikimic Acid.

Streptococcus mutans is known as an important oral pathogen causing dental caries, a widespread oral infectious disease. S. mutans synthesize exopolysaccharide (EPS) using glucosyltransferases (Gtfs), resulting in biofilm formation on the tooth surface. Bacterial cells in the biofilms become strongly resistant to a harsh environment, such as antibiotics and host defense mechanisms, making biofilm-based infections difficult to eliminate. Discovering novel antibiofilm agents, especially from natural products, helps to develop effective strategies against this kind of diseases. The present study investigated the inhibitory effect of shikimic acid (SA), one abundant compound derived from Illicium verum extract, on the biofilm formation of S. mutans. We found SA can reduce the EPS synthesized by this oral pathogen and modulate the transcription of biofilm formation related genes, leading to fewer bacterial cells in its biofilm. SA also interacted with cell membrane and membrane proteins, causing damage to bacterial cells. Ex vivo testing of biofilm formation on bovine teeth showed SA strongly decreased the number of S. mutans cells and the number of EPS accumulated on dental enamel surfaces. Moreover, SA exhibits almost no toxicity to human oral cells evaluated by in vitro biocompatibility assay. In conclusion, shikimic acid exhibits remarkable antibiofilm activity against S. mutans and has the potential to be further developed as a novel anticaries agent. IMPORTANCE Natural products are an important and cost-effective source for screening antimicrobial agents. Here, we identified one compound, shikimic acid, from Illicium verum extract, exhibiting antimicrobial activity against S. mutans proliferation. It also inhibits biofilm formation of this bacteria through decreasing Gtf expression and EPS synthesis. Furthermore, this compound exhibits no significant cytotoxicity at its MIC against S. mutans, providing evidence for its clinical application.