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.

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 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.

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.

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.

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.

Effects of Ligustrum robustum (Rxob.) Blume extract on the quality of peanut and palm oils during storage and frying process.

The potential uses of Ligustrum robustum (Rxob.) Blume extract as a natural antioxidant to protect the quality of different oils during storage and frying process were studied. The results showed that L. robustum extract has been shown to retard the decline in the quality of both oils based on the tests of acid value, peroxide value, p-anisidine value, color, volatile flavor, and fatty acid compositions, and the protective effect of L. robustum extract on the quality of peanut oil was better than that of palm oil. By the component analysis, L. robustum extract was found to have a total phenols content of 140.75 ± 1.52 mg/g, and ligurobustoside C was identified as the main phenolic compound. The thermogravimetric and differential scanning calorimetry results showed that L. robustum extract enhanced the oxidative stability of peanut and palm oils. In addition, Fourier transform infrared results indicated that L. robustum extract had protective effects on the C=C bond and ester bond of oil molecule. Moreover, by using electron spin resonance technique, L. robustum extract showed the ability to inhibit and scavenge alkyl-free radicals in both oils. The present results suggested that L. robustum extract may protect the quality of oils during the storage and frying process by inhibiting the oxidation of unsaturated fatty acids and might be a potential natural antioxidant in the food industry. PRACTICAL APPLICATIONS: The excellent antioxidant ability of Ligustrum robustum (Rxob.) Blume extract on the oxidation of different oils and its low price indicated that it could be used as a new low-cost natural antioxidant in oil processing.

Potential of phenolic compounds in Ligustrum robustum (Rxob.) Blume as antioxidant and lipase inhibitors: Multi-spectroscopic methods and molecular docking.

Ligustrum robustum (Rxob.) Blume is traditionally served as a functional tea in China. In this work, the antioxidant activities of L. robustum (Rxob.) Blume extract (LRE) were evaluated and its inhibitory effect and mechanism on pancreatic lipase were further investigated. With the high contents of phenols (139.70 ± 1.41 mg gallic acid equivalent/g extract) and flavonoids (326.46 ± 7.36 mg rutin equivalent/g extract), LRE showed significant antioxidant activities (p < 0.05) for scavenging free radicals and hydrogen peroxide, inhibiting lipid peroxidation and providing strong reducing power. Meanwhile, LRE displayed remarkable inhibitory activity on pancreatic lipase with a low half-effective inhibitory concentration (IC50 ) of 2.469 ± 0.005 mg/ml which was further determined as non-competitive inhibition. The spectroscopic results showed that LRE inhibited the activity of pancreatic lipase by modifying the tertiary and secondary structures of lipase. Moreover, four phenolic compounds (acteoside, lipedoside A, oleuropein and ligurobustoside C) were identified from LRE by the high performance liquid chromatography-quadrupole- time of flight-mass spectrometry. In addition, according to molecular docking analysis, the four phenols could interact with pancreatic lipase by hydrogen bonds, so as to change the spatial structure of pancreatic lipase and inhibit its catalytic activity. The present results suggest that LRE not only exhibits strong antioxidant capacity but possesses effectively inhibitory activity on pancreatic lipase, which might have the potential to be developed as functional food and nutraceuticals for the prevention of metabolic diseases. PRACTICAL APPLICATION: Ligustrum robustum (Rxob.) Blume extract has been confirmed to possess antioxidant activity and lipase inhibitory activity, which indicates that the L. robustum extract has the potential to prevent oxidative stress and regulate fat metabolism. This work suggests that L. robustum extract can be served as a novel resource to prepare nutraceuticals and functional food in food industries.

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 and mechanism of tea polyphenols on the quality of oil during frying process.

The effects and action mechanism of tea polyphenols (TP) on the quality of rapeseed oil during frying process were investigated. Results showed that compared with control, TP (0.04%, w/w) exhibited the remarkable ability to inhibit the deterioration of acid value, peroxide value, anisidine value, viscosity, and color of frying oil. By using gas chromatography-mass spectrometry, frying oil with TP showed the higher content of unsaturated fatty acids (72.79%) and lower content of trans fatty acids (3.36%) than those of control. Meanwhile, frying oil with TP had a higher total phenolic content than control at the same frying time. In addition, the thermo gravimetric-differential scanning calorimetry results showed that TP could increase the oxidation stability of rapeseed oil. Furthermore, according to the Fourier transform infrared and molecular dynamic simulation results, TP could reduce the breaking degree of = C-H bond, C-O-C bond, and C = C bond in oil molecules, and inhibit the oxidation of oil components by inhibiting the generation of free radicals and eliminating free radicals. All present results suggested that TP showed the potential value to be used for protecting the quality of oil during the frying process in food and chemical industries. PRACTICAL APPLICATIONS: The inhibitory effect of tea polyphenols on the deterioration of quality of rapeseed oil during frying was found and the mechanism had also preliminarily interpretation. This work provided a method for monitoring the quality of fry oil and provided the theoretical basis for the use of tea polyphenols in frying.

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.

A functional polysaccharide film forming by pectin, chitosan, and tea polyphenols.

The formation, properties and functions of a polysaccharide film (CPFT) were investigated. CPFT was created by loading TP into pectin and chitosan matrix by blending method. Comparing with control, the thickness and the water vapor permeability of CPFT were increased with the addition of TP, and the tensile strength of CPFT was reduced by 17% while its elongation at break was increased by 37%. Then, fourier transform infrared (FTIR) spectrum and scanning electron microscope (SEM) results showed that TP had interacted with the film substrates and might made CPFT more complex. Furthermore, CPFT showed the remarkable slow-release, antioxidant and antiseptic activities, which were all concentration-dependent. Moreover, the degeneration of color in fresh beef could be effectively inhibited by CPFT during the 8 days storage. All present results suggested that CPFT showed the potential value to be used as a functional edible polysaccharide film applied in food industries.