One-step spraying of protein-anchored chitosan oligosaccharide antimicrobial coating for food preservation.

The persistent global issues of unsafe food and food waste continue to exist. Microbial contamination stands out as a major cause of losses in perishable foods like vegetables and fruits. Herein, we report a self-assembling coating based on disulfide bond cleavage-induced bovine serum albumin (BSA), where the antimicrobial activity of chitosan oligosaccharide (COS) is stably anchored in the coating by electrostatic interactions during the unfolding-aggregation phase of BSA. The intrinsic antimicrobial activity of COS, combined with the positively charged and hydrophobic regions enriched on the BSA coating, significantly disrupts the integrity of bacterial structures. Furthermore, the BSA@COS coating can easily adhere in situ to the grooves on the surface of strawberries through a simple one-step spraying process, extending the shelf life of strawberries and bananas by nearly three times. This makes it a potential economic alternative to current commercial antimicrobial coatings, offering a solution to the rampant global issue of food waste.

Soy protein particles as stabilizers of heat-stable O/W emulsions with 20% protein content.

In response to the increasing demand for nutritionally rich foods, consumer preference for protein-enriched beverages has grown. However, heat-induced protein aggregation and gelation significantly hinders the production of high-protein drinks. In this study, oil-in-water (O/W) emulsions with exceptional thermal stability were formulated using modified soy protein particles (MSPs). These MSPs effectively resisted gel formation, even at a protein concentration of up to 20% (w/v). In contrast, emulsions prepared with untreated soy proteins (SPs) experienced pronounced gelation under identical conditions. The compact structure of MSPs, in comparison to SPs, imparted resistance to heat-induced denaturation and aggregation. Additionally, the emulsion displayed heightened heat processing insensitivity, due to the enhanced hydrophobicity of MSPs and their rapid adsorption at the oil-water interface, resulting in a denser, more elastic, and resilient interfacial film. These findings provide practical insights for the formulation of protein-rich milk alternatives, meeting the evolving market demands.

Constructing a strongly interacting Pea-Cod binary protein system by introducing metal cations toward enhanced gelling properties.

Developing prospective plant-animal binary protein systems with desirable nutritional and rheological properties stands as a significant and challenging pursuit within the food industry. Our understanding of the effect of adding salt on the aggregation behavior of food proteins is currently based on single model protein systems, however, this knowledge is rather limited following binary protein systems. Herein, various ionic strength settings are used to mitigate the repulsive forces between pea-cod mixed proteins during the thermal process, which further benefits the construction of a strengthened gel network. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) collectively demonstrated that larger heat-induced protein aggregates were formed, which increased in size with higher ionic strength. In the presence of 2.5 mM CaCl2 and 50 mM NaCl, the disulfide bonds significantly increased from 19.3 to 27.53 and 30.5 µM/g, respectively. Notably, similar aggregation behavior could be found when introducing 2.5 mM CaCl2 or 25 mM NaCl, due to the enhanced aggregation tendency by specific binding of Ca2+ to proteins. With relevance to the strengthened cross-links between protein molecules, salt endowed composite gels with preferable gelling properties, evidenced by increased storage modulus. Additionally, the gelling temperature of mixed proteins decreased below 50 °C at elevated ionic strength. Simultaneously, the proportion of network proteins in composite gels increased remarkably from 82.05 % to 93.61 % and 92.31 % upon adding 5.0 mM CaCl2 and 100 mM NaCl, respectively. The findings provide a valuable foundation for designing economically viable and health-oriented plant-animal binary protein systems.

Heat-induced agglomeration of water-soluble cod proteins toward gelled structures.

Cod proteins (CPs) have potential applications in designing desirable gel-based products, and this study aimed to unravel their heat-induced aggregation pattern and further probe the roles in protein gels. SDS-PAGE analysis indicated that high-precipitation-coefficient aggregates (HPCAs) of CPs aggregates were composed of considerable polymers of myosin heavy chains and actin, and their low-precipitation-coefficient aggregates (LPCAs) contained myosin light chains and tropomyosin. Studies from correlation analysis between the structure and aggregation kinetics revealed that the generation of ß-sheet and SS bonds were responsible for their spontaneous thermal aggregation induced by heating temperature and protein concentration, respectively. Additionally, as protein denaturation ratio increased, more and larger HPCAs were formed, which was evidenced driving the network formation of protein gels and resulting in higher storage modulus (G') values. These novel findings may be applicable to other animal proteins for better tailoring the manufacturing of muscle gel-based products.

Synergistic Antimicrobial Hybrid Bio-Surface Formed by Self-Assembled BSA Nanoarchitectures with Chitosan Oligosaccharide.

Innovation in green, convenient, and sustainable antimicrobial packaging materials for food is an inevitable trend to address global food waste challenges caused by microbial contamination. In this study, we developed a biogenic, hydrophobic, and antimicrobial protein network coating for food packaging. Experimental results show that disulfide bond breakage can induce the self-assembly of bovine albumin (BSA) into protein networks driven by hydrophobic interactions, and chitosan oligosaccharide (COS) with antimicrobial activity can be stably bound in this network by electrostatic interactions. The inherent antimicrobial activity of COS and the numerous hydrophobic regions on the surface of the BSA-network give the BSA@COS-network significant in vitro antimicrobial ability. More importantly, the BSA@COS-network coating can prolong the onset of spoilage of strawberries in various packaging materials by nearly 3-fold in storage. This study shows how surface functionalization via protein self-assembly is integrated with the biological functioning of natural antibacterial activity for advanced food packaging applications.

Effect of phytic acid combined with lactic acid on color and texture deterioration of ready-to-eat shrimps during storage.

To retard the deterioration of texture and color of ready-to-eat (RTE) shrimps during storage, phytic acid (PA) and lactic acid (LA) were used to soak the shrimp prior to cooking. The factors affecting texture (water holding capacity, protein oxidation and degradation, and microstructure) and color (Maillard reaction and lipid oxidation) were determined separately. The free radical and copper ion content were also determined in order to investigate the regulation mechanism of phytic acid and lactic acid on the texture and color of RTE shrimps. It was found that the inhibitor-treated RTE shrimps showed better texture and color properties than the control group, and the compound inhibitor (PA + LA) showed a better inhibition effect than single inhibitor. In addition, PA and LA prevented the oxidation of RTE shrimps by scavenging free radicals and chelating copper ions, which in turn enabled the regulation of color and texture deterioration.

Lactoferrin network with MC3T3-E1 cell proliferation, auxiliary mineralization, antibacterial functions: A multifunctional coating for biofunctionalization of implant surfaces.

Developing biocompatible, low-immunoreactive, and antibacterial implants are challenging yet fundamental to osteosynthesis. In this study, mineralization-stimulative and antibacterial networking nanostructures are assembled via amyloid-like aggregation of lactoferrin (LF) triggered by reducing the intramolecular disulfide bonds. Due to the adhesive property of their rich ß-sheet architecture, the LF networks are amenable to the deposition upon the surface of various implant materials, functionalizing the implants with cell-proliferative, mineralization-stimulative, and antibacterial properties. Specifically, the abundant functional groups and amino acids exposed on the surface of LF networks provide abundant functional microdomains for subsequent mineralization of different forms of calcium ions and promote the formation of hydroxyapatite (HAp) crystals in simulated body fluids. We further demonstrate that the LF network inherits the innate antibacterial properties of LF and exerts a synergistic antibacterial ability with surface-enriched positively charged and hydrophobic amino acid residues, disrupting bacterial biofilm formation, enhancing microbial cell wall perturbation, and ultimately leading to microbial death. The results underscore the feasibility of the LF network as a multifunctional coating on bioscaffold surfaces, which may provide insight into its future applications in next-generation artificial bone implants with bacterial/biofilm clearance and bone tissue remodeling capabilities.

High internal phase Pickering emulsions stabilized by a cod protein-chitosan nanocomplex for astaxanthin delivery.

High internal phase Pickering emulsions (HIPPEs) stabilized by a food protein have attracted widespread attention. In this study, a novel cod protein-chitosan nanocomplex was prepared through electrostatic interactions and used as a particle emulsifier to stabilize the oil-water interface. The application of the cod protein-chitosan nanocomplex was demonstrated in the formation of stable HIPPEs with an internal phase as high as 84%. The influence of the system composition on the stability, microstructure and rheology of the HIPPEs was determined. The HIPPEs stabilized by the cod protein-chitosan nanocomplex formed a compact three-dimensional network structure, which gave the emulsion a higher storage modulus, viscoelasticity and good thixotropy. Interestingly, the chemical stability of astaxanthin was significantly improved by the developed HIPPEs. The bioavailability of astaxanthin in the HIPPEs stabilized by the nanocomplexes of 2.0% (w/w) cod protein and 0.1% (w/w) chitosan reached 49%. In summary, these results demonstrated that the food-grade cod protein-chitosan nanocomplex had potential in the development of HIPPEs, which could be used as carriers for hydrophobic bioactive compound delivery.

Reduced Adhesive Force Leading to Enhanced Thermal Stability of Soy Protein Particles by Combined Preheating and Ultrasonic Treatment.

Developing liquid systems with high protein contents is drawing intensive attention; however, this is challenged by heat-induced aggregation and gelation of proteins. Herein, we described a facile but robust approach of combined preheating and ultrasonic treatment (CPUT) to fabricate soy protein particles (SPPs) with enhanced heat stability. Results showed that these heat-stable particles, upon reheating at 1% (w/v), showed antiaggregation property evidenced from no obvious changes of the particle size distributions of suspensions. Besides, no gelation was found in the reheated test for SPPs suspended even at a concentration of 10% (w/v). In contrast, the control formed sol-gel after heating. The rearrangements of soy protein molecules by CPUT led to the formation of SPPs with reduced surface energy, which was primarily responsible for their heat stability. These findings highlighted that the CPUT could prepare thermally stable soy proteins, providing insights into the application of soy proteins in protein-enriched beverages.

Preheat-induced soy protein particles with tunable heat stability.

Recently, there is a growing interest in developing protein-enriched beverages with improved nutritional and functional properties. However, this is challenged by heat-induced aggregation and gelation of edible proteins, which limits their practical applications in high protein systems. In this study, soy protein particles (SPPs) with tunable heat stability were prepared by simply preheating soy proteins suspensions (pH 6.4 and 1% (w/v) concentration) at different temperatures and times. Results showed that heat-stabled SPPs were successfully obtained at high preheating temperatures with prolonged time. The SPPs structures were found to be highly unfolded, denatured, and compact. In addition, these particles exhibited lower viscosities and higher flow behavior index without gelation, whereas those prepared at lower preheating temperatures were found to readily gel after reheating. These results provide useful insights on how heat stable SPPs can be prepared, which extends their further application in protein-enriched beverages and relevant products.

Effects of fluorescent carbon dots from the baked lamb on energy and lipid metabolism.

Food-borne carbon dots (CDs) may cause health risks due to their unique properties. However, previous efforts were mainly focused on the characterization of their physicochemical properties, their effects on cellular metabolism are not entirely revealed. Herein, the features and potential toxicity of CDs from lamb baked for 15, 30, and 45 min were evaluated, their cytotoxicity increased with the extension of baking time. Furthermore, the metabolic responses of PC12 cells after exposure to CDs from lamb baked for 45 min were investigated. The CDs perturbed purine metabolism, causing reactive oxygen species accumulation. Meanwhile, the CDs down-regulated glycolysis and TCA cycle, led to a significant decrease in ATP. Additionally, the CDs induced triglyceride accumulation, mainly through enhanced fatty acid biosynthesis. The adverse effects of CDs from baked lamb involved the perturbation of energy production, purine metabolism, and triglyceride biosynthesis, which provided additional information about the risks of CDs from food items.

The effects of carbon dots produced by the Maillard reaction on the HepG2 cell substance and energy metabolism.

Endogenous nanoparticles produced during food processing have received considerable attention due to their unique physicochemical properties and potential safety risks. However, the bio-impact of endogenous nanoparticles on cell metabolism has not been fully studied. In this work, the effects of carbon dots (CDs) derived from the Maillard reaction of glucose and lysine on the cellular substance and energy metabolism were assessed using HepG2 cells as a model. When the HepG2 cells were incubated with 10.0 mg mL-1 of CDs, the mitochondrial membrane potential decreased significantly and the mitochondrial function was affected. The extracellular acidification rate and oxygen consumption rate were decreased in comparison to normal cells without CDs. The CDs blocked the glycolysis pathway by reducing the activities of key enzymes including phosphofructokinase and pyruvate kinase. The energy supply pathway of HepG2 cells changed from glycolysis to TCA cycle, but the increase of the TCA cycle flux could not meet the requirements for restoring cell proliferation. The increase of the compensatory flux in the TCA cycle may be the result of up-regulation of the metabolism of glucogenic amino acids and ketogenic amino acids, while lipid metabolism did not seem to be affected in this process.

Inducing secondary structural interplays between scallop muscle proteins and soy proteins to form soluble composites.

Developing food protein structures with the freedom to tune their internal molecular arrangements is a fascinating aspect for serving the demands of multifunctional food components. However, a protein's conformation is highly submissive to its amino acid sequences, posing a great limitation on controlling its structural rearrangements. In this study, based on simply co-dissolving scallop muscle proteins (SMPs, water-insoluble) and soya proteins (SPs) at pH 12 prior to neutralization, the unfolding-folding pathways of both proteins were altered. Structural characterizations evidenced the complexation of SMPs and SPs using their secondary structures as the building blocks. Due to hydrophobic coalition between the α-helix (from SMPs) and ß-sheet (from SPs), the co-assembled structures obtained considerable resistance against folding triggered by the hydrophobic effect. In addition, the kinetics by which the SMPs and SPs folded together was tailor-made by the compositional differences of the two proteins, resulting in the formation of well-defined, water-dispersible nanospheres with a tunable size and internal arrangements of the backbones. This study would enrich our choice of manipulated protein structures and enlarge the available protein sources with tailorable functions when applied in specific scenarios.

Correction: Insights into melanoidin conversion into fluorescent nanoparticles in the Maillard reaction.

Correction for 'Insights into melanoidin conversion into fluorescent nanoparticles in the Maillard reaction' by Dongmei Li et al., Food Funct., 2019, 10, 4414-4422.

Correction: Adverse effects of fluorescent carbon dots from canned yellow croaker on cellular respiration and glycolysis.

Correction for 'Adverse effects of fluorescent carbon dots from canned yellow croaker on cellular respiration and glycolysis' by Dongmei Li et al., Food Funct., 2019, 10, 1123-1131.

Insights into melanoidin conversion into fluorescent nanoparticles in the Maillard reaction.

The Maillard reaction is a well known chemical reaction in the food industry, in which melanoidins are generally considered as the final product. However, the exact final products of the Maillard reaction are far from being well understood. The conversion mechanism of melanoidins is of importance for explanation of the whole process of the Maillard reaction. In this paper, the conversion of melanoidins in the Maillard reaction was studied using glucose and lysine as raw materials. Our results showed that fluorescent nanoparticles (FNPs) can be formed after the hydrothermal reaction of melanoidins at 180 °C for 2, 4, 6 and 8 hours, respectively. Unlike melanoidins, the FNPs are highly water-soluble and strongly fluorescent and have a particle size of around 0.7-6.8 nm. X-ray photoelectron spectroscopy and 1H NMR spectroscopy analysis demonstrated that there are many functional structures like carboxyl, hydroxyl, aldehyde, amine and aromatic groups produced on the surface of the FNPs. Total elemental analysis indicated that the oxidization of the FNPs was intensified with the extension of reaction time. The thermogravimetric kinetics of the FNPs were significantly different from those of melanoidins. More heterocyclic and aromatic compounds were found in the pyrolysis products of the FNPs with the extension of reaction time. The results of this paper provided new insights into the conversion of melanoidins for further understanding of the Maillard reaction.

A novel "turn-on" fluorometric and magnetic bi-functional strategy for ascorbic acid sensing and in vivo imaging via carbon dots-MnO2 nanosheet nanoprobe.

Ascorbic acid (AA) is an essential vitamin and plays an irreplaceable role in humans' daily life. Therefore, it is of profound significance to develop effective strategies for AA sensing. Herein, a novel bi-functional sensing strategy was developed by using carbon dots (CDs) and MnO2 nanosheet as the fluorometric/magnetic signal source. When AA was absence, the fluorescence of CDs was quenched by MnO2 nanosheet due to the inner filter effect. Neither the fluorescence nor magnetic signal of the nanoprobe can be detected. In the presence of AA, a redox reaction occurred between MnO2 nanosheet and AA resulting in the generation of magnetic resonance imaging (MRI) response Mn2+ and decomposing of MnO2 nanosheet structure, thus leading to the recovery of CDs fluorescence. The detection limit of the AA was determined to be 2.89 µM with a linear range of 0-80 µM in fluorescence mode, and detection limit of 0.776 µM with a linear range of 0-80 µM in MRI mode when used transverse relaxation rate as signal. Furthermore, the developed fluorometric/magnetic bi-functional nanoprobe showed good biocompatibility, high response rate, high selectivity towards AA and could be used to analyses AA in real samples. Moreover, in vivo imaging of AA in mice was achieved in magnetic mode. The fluorometric/magnetic bi-function sensor for AA detection was introduced, which provided a novel strategy for sensor design based on CDs.

Fluorescent carbon dots in baked lamb: Formation, cytotoxicity and scavenging capability to free radicals.

The formation and properties of nanostructures during food processing have attracted much attention in recent years. Herein, the formation and physicochemical properties of fluorescence carbon dots (CDs) from baked lamb at different baking temperatures (200, 300, and 350 °C) were investigated. The morphology, surface functional groups and fluorescent quantum yield of the CDs were found to be highly dependent on the heating temperature. Biocompatibility of CDs investigation indicated that they were able to disperse onto both the cell membrane and the cytoplasm of HepG2 cells, and alter the cell cycle progression slightly. Moreover, the CDs from baked lamb of 350 °C showed the maximum scavenging capability to free radicals and could protect the cell from oxidative damage in vitro. This contribution represents the first report regarding the properties and formation process of CDs in baked lamb, providing valuable insights into baking temperature influence on physicochemical properties of the CDs.

Adverse effects of fluorescent carbon dots from canned yellow croaker on cellular respiration and glycolysis.

The effect of endogenous carbon nanoparticles from food sources is one of the hot topics in the current food research field. The relationship between the foodborne nanoparticle properties and the cytotoxic mechanism has been insufficiently studied. In this work, carbon dots (CDs) with strong fluorescence were found and purified from canned yellow croaker, and their cytotoxicity was investigated for the first time. The canned yellow croaker CDs are nearly spherical with a particle size distribution in the range of 1.8-5.8 nm. The fluorescence quantum yield of the isolated CDs is 9.7% and the maximum excitation wavelength is 340 nm, with a significant redshift phenomenon in fluorescence spectra. The surface elemental analysis showed that the composition of the canned yellow croaker CDs was C (76.42%), N (6.49%), and O (16.7%), and various functional groups are on the surface. The CDs have good stability in sodium chloride solution and the fluorescence intensity was stable within the pH value of 4 to 10. A strong fluorescence quenching effect was found upon the addition of Cu2+ and Fe3+ to the CD aqueous solution. The CDs can easily enter the interior of the live cells. Moreover, a concentration-dependent behavior of HepG2 cell viability was found when the cells were incubated with the canned yellow croaker CDs. Glycolysis and mitochondrial function analysis of HepG2 cells revealed that both the extracellular acidification rate and oxygen consumption rate significantly decreased in contrast to the normal level prior to the addition of CDs. In addition, the CDs significantly inhibited the glycolytic pathway by reducing the activity of key enzymes hexokinase and pyruvate kinase in the glycolytic pathway.