Konjac glucomannan-based highly antibacterial active films loaded with thyme essential oil through bacterial cellulose nanofibers/Ag nanoparticles stabilized Pickering emulsions.

The aim of this study was to develop novel konjac glucomannan (KGM)-based highly antibacterial active films, where five types of films were prepared and compared. The microstructure results showed that KGM-based films loaded with thyme essential oil (TEO) through bacterial cellulose nanofibers/Ag nanoparticles (BCNs/Ag nanoparticles) stabilized Pickering emulsions (Type V films) displayed the smoothest surface and the most evenly dispersed TEO droplets as compared with the other four types of films. Moreover, Type V films showed the highest contact angle value (86.28°), the best thermal stability and mechanical properties. Furthermore, Type V films presented the highest total phenol content (13.23 mg gallic acid equivalent/g film) and the best antioxidant activity (33.96 %) as well as the best sustained-release property, thus showing the best antibacterial activity, which was probably due to that BCNs/Ag nanoparticles and TEO displayed a synergistic effect to some extent. Consequently, Type V film-forming solutions were used as coatings for tangerines. The results showed that the tangerines treated with Type V coatings displayed excellent fresh-keeping properties. Therefore, the coatings, KGM-based film-forming solutions loaded with TEO through BCNs/Ag nanoparticles stabilized Pickering emulsions, have great potential for the preservation of fruits and vegetables.

Synthesis of bacterial cellulose nanofibers/Ag nanoparticles: Structure, characterization and antibacterial activity.

The aim of this study was to compare the characterization of bacterial cellulose nanofibers/Ag nanoparticles (BCNs/Ag nanoparticles) obtained by three different pretreatment methods of BCNs (no pretreatment, sodium hydroxide activation pretreatment and TEMPO-mediated oxidation pretreatment), which were recoded as N-BCNs/Ag nanoparticles, A-BCNs/Ag nanoparticles and O-BCNs/Ag nanoparticles, respectively. The results of scanning electron microscopy and transmission electron microscopy showed the prepared Ag nanoparticles by three different pretreatment methods were spherical and dispersed on the surface of BCNs, while the Ag nanoparticles in O-BCNs/Ag nanoparticles displayed the smallest diameter with a value of 20.25 nm and showed the most uniform dispersion on the surface of BCNs. The ICP-MS result showed O-BCNs/Ag nanoparticles had the highest content of Ag nanoparticles with a value of 2.98 wt%, followed by A-BCNs/Ag nanoparticles (1.53 wt%) and N-BCNs/Ag nanoparticles (0.84 wt%). The cytotoxicity assessment showed that the prepared BCNs/Ag nanoparticles were relatively safe. Furthermore, the O-BCNs/Ag nanoparticles had the best antioxidant and antibacterial activities as compared with the other two types of BCNs/Ag nanoparticles, where O-BCNs/Ag nanoparticles destroyed the structure of bacterial cell membranes to lead the leakage of intracellular components. This study showed that O-BCNs/Ag nanoparticles as antibacterial agents have great potential in food packaging.

PH sensitive double-layered emulsions stabilized by bacterial cellulose nanofibers/soy protein isolate/chitosan complex enhanced the bioaccessibility of curcumin: In vitro study.

In this work, double-layered emulsions stabilized by bacterial cellulose nanofibers/soy protein isolate/chitosan complex were prepared using layer-by-layer self-assembly technology and used for the delivery of curcumin, and the physical and delivery properties of the prepared double-layered emulsions were investigated. The zeta-(ζ) potential of colloidal particles confirmed that the chitosan was adsorbed on surface of the single-layered emulsion droplets by attractive electrostatic interactions. Meanwhile, the physical properties showed that the double-layered emulsions displayed high pH-sensitivity and showed relatively higher stability under acid environment. Furthermore, the in vitro digestion result showed that the curcumin loaded by double-layered emulsions were more stable during simulated gastric digestion as compared with that loaded by single-layered emulsions. Especially, the bioaccessibility of curcumin delivered by the double-layered emulsions (77.4 ± 3.25%) was significantly higher than that of curcumin delivered by single-layered emulsions (32.8 ± 2.56%). Therefore, it can be concluded that the prepared double-layered emulsions showed a great potential application in the delivery of fat-soluble bioactive compounds.

Low oil Pickering emulsion gels stabilized by bacterial cellulose nanofiber/soybean protein isolate: An excellent fat replacer for ice cream.

Food-grade Pickering emulsion gels with different oil phase fractions stabilized by Bacterial cellulose nanofibers/Soy protein isolate complex colloidal particles were prepared by one-step method. The properties of Pickering emulsion gels with different oil phase fractions (5 %, 10 %, 20 %, 40 %, 60 %, 75 %, v/v) and their applications in ice cream were investigated in the present study. The microstructural results showed that Pickering emulsion gels with the low oil phase fractions (5 %-20 %) were an emulsion droplet-filled gel, where the oil droplets were embedded in the network structure of cross-linked polymer, while Pickering emulsion gels with higher oil phase fractions (40 %-75 %) were an emulsion droplet-aggregated gel, which formed a network structure by flocculated oil droplets. The rheology result showed that the low oil Pickering emulsion gels had the same excellent performance as the high oil Pickering emulsion gels. Furthermore, the low oil Pickering emulsion gels showed good environmental stability under harsh conditions. Consequently, Pickering emulsion gels with 5 % oil phase fraction were used as fat replacers in ice cream and ice cream with different fat replacement rates (30 %, 60 % and 90 %, w/w) was prepared in this work. The results showed the appearance and texture of the ice cream with low oil Pickering emulsion gels as fat replacers was similar to that of the ice cream with no fat replacers, and the melting rate of the ice cream with low oil Pickering emulsion gels as fat replacers showed the lowest value of 21.08 % during the 45 min of melting experiment, as the fat replacer rate in the ice cream reached to 90 %. Therefore, this study demonstrated that low oil Pickering emulsion gels were excellent fat replacers and had great potential application in low calorie food production.

Characterization of bacterial cellulose nanofibers/soy protein isolate complex particles for Pickering emulsion gels: The effect of protein structure changes induced by pH.

In this work, the influence of soy protein isolated at different pH values (1-9) on the self-assembly behaviors of bacterial cellulose nanofibers/soy protein isolate (BCNs/SPI) colloidal particles via anti-solvent precipitation were investigated. The results showed that the formation of BCNs/SPI at pH values of 1-5 was mainly driven by electrostatic interaction, while the formation of those at pH values of 5-9 was driven by weak molecular interactions including hydrogen bonding and steric-hindrance effect. The FTIR demonstrated that the conformation of protein involved a transition from order to disorder at the level of secondary structure as pH values were away from the isoelectric point. The fluorescence spectroscopy and UV-vis adsorption spectroscopy indicated that hydrophobic region of SPI at pH value of 5 displayed more exposed as compared with that at pH values away from the isoelectric point. The changes in structure conformation of SPI induced by pH values led to the changes in properties of the BCNs/SPI colloidal particles including particle size, microstructure, crystallinity, hydrophily, thermal stability, and rheological properties. Furthermore, the structures of BCNs/SPI colloidal particles at different pH values significantly affected the stability of Pickering emulsion gels stabilized by the corresponding complex colloidal particles. This study provided a theoretical basis for the design of food-grade Pickering emulsion gels stabilized by BCNs/SPI complex colloidal particles.

Nanocellulose: An amazing nanomaterial with diverse applications in food science.

Recently, nanocellulose has gained growing interests in food science due to its many advantages including its broad resource of raw materials, renewability, interface stability, high surface area, mechanical strength, prebiotic characteristics, surface chemistry versatility and easy modification. Since then, this review summarized the sources, morphology, and structure characteristics of nanocellulose. Meanwhile, the mechanical, chemical, and combined treatment methods for the preparation of nanocellulose with desired properties were elaborated. Furthermore, the application of nanocellulose in Pickering emulsions, reinforced food packaging, functional food ingredient, food-grade hydrogels, and biosensors were emphasized. Finally, the safety, challenges, and future perspectives of nanocellulose were discussed. This work provided key developments and effective benefits of nanocellulose for future research opportunities in food.

Auto-fluorescence of cellulose paper with spatial solid phrase dispersion-induced fluorescence enhancement behavior for three heavy metal ions detection.

Auto-fluorescence of cellulose paper is often considered as an interfering fluorescence, which directly impedes the cellulose paper as a substrate material. This paper creatively explored the composition and properties of auto-fluorescence, and lignosulfonate was primarily speculated as the main source of auto-fluorescence. Surprisingly, its spatial solid phrase dispersion-induced fluorescence enhancement behavior was found. Then, cellulose paper was modified with Mn-doped ZnS quantum dots, and the prepared ratiometric fluorescent paper chip has good performances on morphology, stability, and fluorescence properties. Besides, the paper chip exhibited different fluorescence responses to three heavy metal ions in water sample. The limit of detection for Cd2+, Hg2+ and Pb2+ reached 1.61 nM, 0.01 nM, and 0.02 nM, respectively. In short, the molecular simulation results theoretically proved that heavy metal ions owned substitution affinity with lignosulfonate. Ultimately, this study was the first attempt to utilize paper-based auto-fluorescence, which could better accelerate the development of paper-based chips.

Digestion of Plant Dietary miRNAs Starts in the Mouth under the Protection of Coingested Food Components and Plant-Derived Exosome-like Nanoparticles.

The regulatory functions of plant miRNAs on mammalian bodies are controversial, mainly because stability of the miRNAs in the digestive tract, as the prerequisite for their cross-kingdom effects, has somehow been overlooked. Hence, as the first stage of food ingestion, stability of plant miRNAs in human saliva has been investigated. The results show that plant miRNAs are of considerable resistance against salivary digestion, as surviving miRNAs more than 20 fM are detected. The stability varies dramatically, which can be explained by the difference in tertiary structure, governing their affinities to RNase. Surprisingly, miRNAs of low initial concentrations can end up with high survival rates after digestion. Plant miRNAs can be loaded into exosome-like nanoparticles (ELNs) and microcapsules formed by food components, both of which protect the miRNAs from being degraded in human saliva. Overall, plant miRNAs can apply certain strategies to maintain constant concentrations, paving the way for their potential cross-kingdom effects.

Recent progress in the preparation, chemical interactions and applications of biocompatible polysaccharide-protein nanogel carriers.

Nanogel carriers are rapidly emerged as a major delivery strategy in the fields of food, biology and medicine for small particle size, excellent solubility, high loading, and controlled release. Natural polysaccharides and proteins are selected for the preparation of biocompatible, biodegradable, low toxic, and less immunogenic nanogels. Different polysaccharides and proteins form complex nanogels through different interaction forces (e.g., electrostatic interaction and hydrophobic interaction). The present review pursues three aims: 1) to introduce several well-known dietary polysaccharides (chitosan, dextran and alginate) and proteins (whey protein and lysozyme); 2) to discuss the types, preparation methods, chemical interactions and properties of various biocompatible complex carriers; 3) to present the application and prospect of polysaccharide-protein complex in bioactive ingredient delivery, nutrient encapsulation and flavor protection. We expect that the integration with nano-intelligent technology will improve the functional ingredient loading, recognition specificity and controlled release capabilities of polysaccharide-protein nanocomposites to generate new intelligent nanogels in the field of food industry in the future.

Load phycocyanin to achieve in vivo imaging of casein-porous starch microgels induced by ultra-high-pressure homogenization.

Traditional bioactive substances are often limited in practical application due to their poor stability and low solubility. Therefore, it is imperative to develop biocompatible high loading microgel carriers. In this study, a novel type of casein-porous starch microgel was prepared under ultra-high-pressure homogenization, by using porous starch with the honeycomb three-dimensional network porous structure. Molecular interaction force analysis and thermodynamic analysis showed that electrostatic interaction played a major role in the formation of microgels. Circular dichroism and Fourier transform infrared spectroscopy showed that homogenization and pH were the main factors, which affected the formation and structural stability of microgels. Compared with casein-glutinous rice starch microgels, the encapsulation efficiency and loading capacity of phycocyanin in casein-porous starch microgels were increased by 77.27% and 135.10%, respectively. Thus, casein-porous starch microgels could not only achieve a sustained release effect, but also effectively transport phycocyanin to the gastrointestinal tract of zebrafish, while achieving good fluorescence imaging in vivo. Ultimately, the prepared casein-porous starch microgels could enrich the nanocarriers material, and contribute to the research of safe and effective fluorescent imaging materials.

Improved characterization of nanofibers from bacterial cellulose and its potential application in fresh-cut apples.

The present research aimed to study the nanofibers from bacterial cellulose (BC) by HCl hydrolysis and explore its new potential application in fresh-cut apples. Bacterial cellulose nanofibers (BCNs) showed low and more homogeneity particle size, as well as higher zeta potential and transparency in comparison with BC, which was confirmed by morphological analysis. Physical properties analysis showed that BCNs was more excellent semi-crystalline polymer with higher thermal stability as compared with BC. Rheological results displayed that BCNs suspensions presented a shear thinning behaviour with higher apparent viscosity, storage (G') and loss (G'') moduli at the same concentration in comparison with BC. Furthermore, BCNs suspensions were more stable than BC suspensions under storage condition of 4 °C. Additionally, 2% (wt%) of BCNs suspensions were coated on fresh-cut apples. Results showed that the samples coated with BCNs suspension displayed more excellent properties of keeping fresh-cut apples as compared with that coated with BC suspensions, including delaying weight loss, improving firmness and soluble solids content, reducing browning index and titratable acidity. Therefore, the low cost and high biocompatibility of BCNs can be used as new coatings for fresh-cut apples and have great potential to coat fresh-cut fruits and vegetables in food industry.

Characterizations of bacterial cellulose nanofibers reinforced edible films based on konjac glucomannan.

This study was aimed at developing edible films of konjac glucomannan (KGM) with different contents of bacterial cellulose nanofibers (BCNs). The effects of different contents of BCNs (0-4% (w/w)) on the properties of KGM-based edible films were investigated in the present work. The rheological properties showed that the film-forming solutions displayed an entanglement system with G'G″ at high frequencies. SEM indicated that BCNs were well dispersed in the BCNs/KGM films. With the increase of BCNs contents, the surface morphology of the films assessed by AFM displayed an increased trend in the surface roughness. Moreover, the films were formed mainly through hydrogen bonds as indicated by FTIR analysis. XRD, DSC and TGA showed that the crystallinity and the thermal stability of films increased with the increase of BCNs. Meanwhile, barrier properties of films were improved by the addition of BCNs. Additionally, with the increase of BCNs, the tensile strength (TS) of the films increased, while the elongation at break (EAB) was increased and then decreased. Therefore, reinforcement of KGM-based films with BCNs leads to enhance barrier and mechanical properties with promising potential as packaging films for food products.

Emulsions stabilized by nanofibers from bacterial cellulose: New potential food-grade Pickering emulsions.

In the present work, we investigated the formation and stability of Pickering emulsions stabilized by nanoparticles generated from bacterial cellulose (BC) by hydrochloric acid hydrolysis. The resulting particles, called nanofibers, presented a ribbonlike shape with diameters of 30-80nm and range in length from 100nm to several micrometers. The obtained nanofibers showed good hydrophilic and lipophilic properties and had significant ability to reduce the surface tension of oil/water droplets from 48.55±0.03 to 34.52±0.05mN/m. The oil-in-water Pickering emulsions with a peanut oil concentration of 15% (v/v) were stabilized by only 0.05% (w/v) nanofibers and displayed a narrow droplet size distribution and high intensity with an average droplet size of 15.00±0.82nm. The morphological studies confirmed the nano-scaled droplets of emulsions. The effects of pH values and temperatures on the creaming ability and physical stability were also evaluated by zeta-potential and droplet sizes. Results showed that emulsions displayed relatively lower creaming ability at pH<7, while displayed optimal physical stability and dispersibility at pH≥7. The temperature (20-100°C) and time-dependent test (0-4weeks) indicated that the Pickering emulsions stabilized by only 0.05% (w/v) nanofibers displayed excellent stability. Due to the sustainability and good bio-compatibility of nanofibers from BC, the developed emulsions stabilized by low concentration of nanofibers can be used as new food-grade Pickering emulsions and have great potential to deliver lipophilic bioactive substances in food industry.

Bacterial Cellulose Relieves Diphenoxylate-Induced Constipation in Rats.

This study was to probe the effects of bacterial cellulose (BC) on diphenoxylate-induced constipation in rats. Administration with BC at 500 mg/kg of body weight in diphenoxylate-induced constipation rats distinctly improved the carmine propulsion rate (83.5 ± 5.2%), shortened the defecating time of the first red feces (249.0 ± 23.3 min), and increased the weight of carmine red feces within 5 h (2.7 ± 1.3 g). The levels of aquaporins (AQP-2, AQP-3, and AQP-4) and inhibitory neurotransmitters (nitric oxide, nitric oxide synthetase, vasoactive intestinal peptide, and arginine vasopressin) in the BC-treated groups reduced by 31.9-40.0% ( p < 0.01) and 21.1-67.7% ( p < 0.01) compared to those in the constipation group, respectively. However, the secretion of excitability neurotransmitters (substance P and motilin) in the BC-treated groups was increased by 20.0-39.9% ( p < 0.01). The activities of ATPases in the colon of constipation rats were significantly weakened by BC administration ( p < 0.01). Histological morphology of the colon showed that BC supplementation could effectively increase the length of villus cells and the thickness of colonic mucosa and muscle ( p < 0.01). Moreover, BC supplementation could protect colonic smooth muscle cells against apoptosis. All of the findings suggest that BC supplementation effectively relieves constipation in rats and BC would be used as a great promising dietary fiber for alleviating constipation.

Enhanced anti-obesity effects of bacterial cellulose combined with konjac glucomannan in high-fat diet-fed C57BL/6J mice.

This study aimed to investigate the effects of supplementation with bacterial cellulose (BC), konjac glucomannan (KGM) and combined BC/KGM fiber on high-fat (HF)-diet-induced obesity in C57BL/6J mice. The results showed that combined supplementation with BC/KGM in HF-fed mice was more efficient in reducing body weight, lowing serum lipid profiles and suppressing insulin resistance than single supplementation with BC or KGM. Moreover, supplementation with combined BC/KGM fiber more efficiently alleviated HF-diet-induced liver injury by decreasing hepatic steatosis in comparison with supplementation with BC or KGM alone. Furthermore, supplementation with combined BC/KGM fiber in HF-fed mice had a more positive effect on obesity-associated hepatic inflammation by reducing levels of TNF-α and IL-6 and suppressing the protein expression of Nrf-2/ARE in comparison with supplementation with BC or KGM alone. Consumption of these dietary fibers, especially mixed BC/KGM, resulted in an improved antioxidant defense system and reduced lipid peroxidation in the liver by increasing the activity of antioxidant enzymes and reducing the formation of MDA in the liver. Moreover, supplementation with these fibers regulated the levels of leptin and adiponectin and inhibited the protein expression of PPARγ by reducing the size of cells in the adipose tissue of HF diet-fed mice. Therefore, fiber supplementation (especially with combined BC/KGM) efficiently inhibited HF-induced obesity in mice by reducing insulin resistance, liver injury and inflammation, enhancing the antioxidant defense system and regulating the secretion of adipocytokines and adipogenesis-associated proteins.

Simultaneous separation and purification of chlorogenic acid, epicatechin, hyperoside and phlorizin from thinned young Qinguan apples by successive use of polyethylene and polyamide resins.

The method for separating and purifying chlorogenic acid (CA), epicatechin (EC), hyperoside (HY) and phlorizin (PH) simutaneously from young Qinguan apples by successive use of X-5 and polyamide resins has been developed in this study. The order of adsorption capacities of X-5 for the four phenolics was PH>HY>EC>CA, and the adsorption equilibriums of the four phenolics onto X-5 resin conformed to Langmuir isotherms preferentially. The adsorption kinetics of EC and CA onto X-5 conformed to the pseudo-first-order model, while that of HY and PH accorded with the pseudo-second-order model. Interestingly, the values of equilibrium adsorption capacities (Qe) calculated in the preferential kinetics models were closer to that of theoretical maximum adsorption capacities (Q0) calculated by Langmuir isotherms. Through dynamic adsorption and desorption using X-5 and polyamide resins with ethanol solution as strippant, CA, EC, HY and PH were obtained with purities of 96.21%, 95.34%, 95.36% and 97.36%, respectively.

Nitrate causes a dose-dependent augmentation of nitric oxide status in healthy women.

Green leafy vegetables, high in dietary nitrate, may contribute to cardiovascular health by augmenting nitric oxide status. The exogenous enterosalivary pathway of nitrate reduction to nitrite appears to be a critical determinant of the effects of nitrate. Our primary objective was to investigate the dose-response of nitrate intake on nitric oxide status and nitrate reduction in the mouth. We also assessed whether antibacterial toothpaste can inhibit nitrate reduction and blunt subsequent increases in circulating nitric oxide. A randomised, controlled, crossover trial with healthy women (n = 16) was conducted. The acute effects of four doses of nitrate (0 mg, 100 mg, 200 mg, 400 mg, as well as 400 mg plus antibacterial toothpaste), administered in random order, were compared. Measurements included biomarkers of plasma nitric oxide status, assessed by measuring S-nitrosothiols + other nitroso species (RXNO) and nitrite, and a biomarker of nitrate reduction in the mouth, assessed by measuring salivary nitrite. Compared to 0 mg, all doses of nitrate resulted in higher plasma RXNO and nitrite, and salivary nitrite (P < 0.05). A linear dose-response to nitrate intake was observed with plasma RXNO and nitrite, and salivary nitrite (P < 0.001). Antibacterial toothpaste did not alter nitrate reduction in the mouth (P > 0.9) or blunt the increase in nitric oxide status (P > 0.9). Thus, our study has demonstrated that increasing nitrate intake results in a dose-related increase in nitrate reduction in the mouth and nitric oxide status, and that use of antibacterial toothpaste does not inhibit nitrate reduction or blunt increases in circulating nitric oxide.