Protein-based Coatings Research Articles

Recent advances in protein-based coatings for food packaging: a review

Recent advances in protein-based coatings for food packaging: a review

Role of Driving Force on Engineering Layer-by-Layer Protein/Polyphenol Coating with Flexible Structures and Properties

Protein-based coatings are of immense interest due to their rich biological functions. Layer-by-layer (LbL) assembly, as a powerful means of transferring protein functions to the material surface, has received widespread attention. However, the assembly mechanism of protein-based LbL coatings is still far from being explained, not only because of protein structure and function diversity but also characterization limitations. Herein, we monitored in situ the LbL assembly process of tannic acid (TA) and lysozyme (Lyz), a classic pair of polyphenol and protein, by combining quartz crystal microbalance with dissipation monitoring (QCM-D) and spectroscopic ellipsometry (SE). The water content, morphology, mechanical properties, antioxidant activity, and the driving force of TA-Lyz coating engineered under different pH values were analyzed in detail by various techniques. The water content, a key factor in TA-Lyz coatings, increased with increasing assembled pH values, which resulted in a porous morphology, inhomogeneous mechanical distribution, faster assembly growth, and better antioxidant activity in both acellular and cellular levels. In addition, high water content is unfavorable to both entropy and enthalpy changes, and the thermodynamic driving force of TA and Lyz assembly mainly comes from the enthalpy change brought by the noncovalent interaction between TA and Lyz. These results provide new insights into engineering the structure, function, and assembly mechanisms of protein-based coatings.

Interface Reversible Electric Field Regulated by Amphoteric Charged Protein-Based Coating Toward High-Rate and Robust Zn Anode

HighlightsAlternating positively and negatively charged surface controlled by pH expedites andhomogenizes Zn2+ flux, endowing the Zn- silk fibroin (SF) anode with low polarizationvoltage and stable stripping/plating.Experimental analyses with theoretical calculations suggest that SF coating facilitates thedesolvation of [Zn(H2O)6]2+ and provides nucleation sites for uniform deposition.Symmetric battery of Zn–SF anodes delivers high-rate performance (up to 20 mA cm−2)and excellent stability (1500 h at 1 mA cm−2; 500 h at 10 mA cm−2) with cumulativecapacity of 2.5 Ah cm−2.

Active Casein Coatings and Films for Perishable Foods: Structural Properties and Shelf-Life Extension

There is an urgent need to increase the food supplies to fulfil the demands of future generations as the population of the world is expected to grow beyond 10 billion by 2050. An essential component for ensuring global food security is to reduce food losses during the post-harvest stage. Active edible coatings and films are a promising sustainable preservation technology for shelf-life extension of food products by hindering decay kinetics of minimally processed fruits and vegetables (F&V), by restricting the mass transfer of moisture, aroma, or gases and carrying an active compound, such as an antioxidant or antimicrobial. Active protein-based coatings and films have the potential to extend the shelf-life of food products by decreasing their respiration rates, as they exhibit an excellent gas barrier and good mechanical properties as compared to other biopolymeric packaging. Among protein-based biopolymers, casein and its derivatives as packaging films have been extensively studied due to their low cost, complete biodegradability, and availability. Currently, there is no review study focusing on caseinate-based active coating and film, thus, this review aims to give insights on the composition, rheology, structure, and properties of caseinate-based formulations by critically discussing the results presented in the literature. A methodological approach was followed to obtain relevant literature to discuss the influence of additives on the shelf-life of F&V. Furthermore, changes in secondary structure of casein were observed after incorporation of bioactive compounds (i.e., phenolic acids). Likewise, there is a need to explore chemical interactions among bioactive compounds and biopolymer material by using in silico and laboratory trials as food additives have shown to influence the physicochemical properties of film and shelf-life of food products.

Antimicrobial Peptide-Loaded Pectolite Nanorods for Enhancing Wound-Healing and Biocidal Activity of Titanium.

Titanium is widely utilized for manufacturing medical implants due to its inherent mechanical strength and biocompatibility. Recent studies have focused on developing coatings to impart unique properties to Ti implants, such as antimicrobial behavior, enhanced cell adhesion, and osteointegration. Ca- and Si-based ceramic (CS) coatings can enhance bone integration through the release of Ca and Si ions. However, high degradation rates of CS ceramics create a basic environment that reduces cell viability. Polymeric or protein-based coatings may be employed to modulate CS degradation. However, it is challenging to ensure coating stability over extended periods of time without compromising biocompatibility. In this study, we employed a fluorous-cured collagen shell as a drug-loadable scaffold around CS nanorod coatings on Ti implants. Fluorous-cured collagen coatings have enhanced mechanical and enzymatic stability and are able to regulate the release of Ca and Si ions. Furthermore, the collagen scaffold was loaded with antimicrobial peptides to impart antimicrobial activity while promoting cell adhesion. These multifunctional collagen coatings simultaneously regulate the degradation of CS ceramics and enhance antimicrobial activity, while maintaining biocompatibility.

Comparing Protein Adsorption onto Alumina and Silica Nanomaterial Surfaces: Clues for Vaccine Adjuvant Development

Protein adsorption onto nanomaterial surfaces is important for various nanobiotechnology applications such as biosensors and drug delivery. Within this scope, there is growing interest to develop alumina- and silica-based nanomaterial vaccine adjuvants and an outstanding need to compare protein adsorption onto alumina- and silica-based nanomaterial surfaces. Herein, using alumina- and silica-coated arrays of silver nanodisks with plasmonic properties, we conducted localized surface plasmon resonance (LSPR) experiments to evaluate real-time adsorption of bovine serum albumin (BSA) protein onto alumina and silica surfaces. BSA monomers and oligomers were prepared in different water-ethanol mixtures and both adsorbing species consistently showed quicker adsorption kinetics and more extensive adsorption-related spreading on alumina surfaces as compared to on silica surfaces. We rationalized these experimental observations in terms of the electrostatic forces governing protein-surface interactions on the two nanomaterial surfaces and the results support that more rigidly attached BSA protein-based coatings can be formed on alumina-based nanomaterial surfaces. Collectively, the findings in this study provide fundamental insight into protein-surface interactions at nanomaterial interfaces and can help to guide the development of protein-based coatings for medical and biotechnology applications such as vaccines.

Unraveling How Ethanol-Induced Conformational Changes Affect BSA Protein Adsorption onto Silica Surfaces.

Protein adsorption at solid-liquid interfaces is highly relevant to a wide range of applications such as biosensors, drug delivery, and pharmaceuticals. Understanding how protein conformation in bulk solution impacts adsorption behavior is fundamentally important and could also lead to the development of improved protein-based coatings. To date, relevant studies have been conducted in aqueous solutions, while it remains largely unknown how organic solvents and more specifically solvent-induced conformational changes might influence protein adsorption. Herein, using the quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) techniques, we systematically investigated the real-time adsorption behavior of bovine serum albumin (BSA) protein onto silica surfaces in different water-ethanol mixtures ranging from 0 to 60% (v/v) ethanol. The results showed that there was greater protein adsorption at higher ethanol fractions in the 10-30% range, while more complex adsorption profiles were observed in the 40-60% range. The combination of QCM-D and LSPR measurements led us to further identify specific cases in water-ethanol mixtures where washing steps caused densification of the adsorbed protein layer as opposed to typical desorption of weakly adsorbed molecules in aqueous conditions. We discuss mechanistic factors that drive these overall adsorption trends by taking into account how ethanol fraction affects BSA conformation in bulk solution. Together, our findings demonstrate that BSA proteins can adsorb onto silica surfaces across a wide range of water-ethanol mixture conditions, while specific adsorption profiles depended on the ethanol fraction in a manner closely linked to solution-phase conformational properties.

Understanding how natural sequence variation in serum albumin proteins affects conformational stability and protein adsorption

Serum albumins are evolutionary conserved proteins that are found in many animal species, and purified forms are widely used in biotechnology applications, such as components within surface passivation coatings and drug delivery systems. As such, there has long been interest in studying how serum albumins adsorb onto solid supports, although existing studies are limited to one or two species. Herein, we comprehensively investigated three serum albumins of bovine (BSA), human (HSA), and rat (RSA) origin, and discovered striking differences in their conformational stabilities and adsorption properties. Together with bioinformatics analysis, dynamic light scattering (DLS) and circular dichroism (CD) spectroscopy measurements revealed that the proteins form different types of macromolecular assemblies in solution. BSA and HSA existed as individual monomers while RSA formed multimers, and each protein exhibited sequence-dependent variations in conformational stability as well. Quartz crystal microbalance-dissipation (QCM-D) and localized surface plasmon resonance (LSPR) experiments further showed that BSA and HSA proteins adsorb to form well-packed adlayers, and the extent of protein uptake and spreading depended on their unique conformational stabilities. Conversely, RSA adsorption resulted in sparse adlayers and appreciably less spreading of the adsorbed multimers, as confirmed by attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy experiments. Together, our findings demonstrate that significant differences in conformational stability and adsorption behavior exist even between evolutionary conserved serum albumins with high sequence and structural similarity and illustrate how rational engineering of protein structures and stabilities, guided by insights from nature, might be useful to design protein-based coatings for various biointerfacial science applications.

Hybrid coating of alginate microbeads based on protein-biopolymer multilayers for encapsulation of probiotics.

A hybrid coating based on multilayers of proteins and biopolymers was developed to enhance the protection performance of alginate microbeads against acidic conditions for delivery of probiotics (Lactobacillus rhamnosus GG). Zeta potential measurements and quartz crystal microbalance with dissipation confirmed layer-by-layer deposition of protein-polymer layers. The stability of protein-based coatings during simulated gastric fluid (SGF) treatment was monitored by microscopy. Protein-coated microbeads were partially dismantled, whereas polymer-coated microbeads were intact after a sequential treatment in simulated gastric and intestinal fluids. This suggests that hybrid formulation offers an advantage over the coatings based on biopolymer multilayers in terms of better release of bacteria. Uncoated alginate microbeads completely dissolved and could not protect bacteria after SGF treatment whereas microbeads with hybrid coating showed increased physical stability and a modest decrease of culturability of 3.8 log units. Therefore, this work provides a concept for future protein-based hybrid coatings for bacterial delivery systems.

Novel Mussel-Inspired Universal Surface Functionalization Strategy: Protein-Based Coating with Residue-Specific Post-Translational Modification in Vivo.

Surface functionalization can effectively endow materials with desirable properties, promoting the performance between the material and environment, with extensive applications. However, a universal and straightforward surface functionalization method with biocompatibility is scarce. In this study, with synthetic biology strategy, recombinant mussel plaque protein with a zwitterionic peptide inspired by molecular chaperone was engineered through post-translational modification, in which 3,4-dihydroxyphenylalanine was residue-specifically obtained efficiently from tyrosine with tyrosinase coexpressed in vivo. The rational designed chimeric protein coating in this work could successfully anchor to various substrates and exhibit excellent antifouling performance in resisting protein adsorption, cell attachment, and bacterial adhesion with eminent biocompatibility.

Temperature-Induced Denaturation of BSA Protein Molecules for Improved Surface Passivation Coatings.

Bovine serum albumin (BSA) is the most widely used protein for surface passivation applications, although it has relatively weak, nonsticky interactions with hydrophilic surfaces such as silica-based materials. Herein, we report a simple and versatile method to increase the stickiness of BSA protein molecules adsorbing onto silica surfaces, resulting in up to a 10-fold improvement in blocking efficiency against serum biofouling. Circular dichroism spectroscopy, dynamic light scattering, and nanoparticle tracking analysis showed that temperature-induced denaturation of BSA proteins in bulk solution resulted in irreversible unfolding and protein oligomerization, thereby converting weakly adhesive protein monomers into a more adhesive oligomeric form. The heat-treated, denatured BSA oligomers remained stable after cooling. Room-temperature quartz crystal microbalance-dissipation and localized surface plasmon resonance experiments revealed that denatured BSA oligomers adsorbed more quickly and in larger mass quantities onto silica surfaces than native BSA monomers. We also determined that the larger surface contact area of denatured BSA oligomers is an important factor contributing to their more adhesive character. Importantly, denatured BSA oligomers were a superior passivating agent to inhibit biofouling on silica surfaces and also improved Western blot application performance. Taken together, the findings demonstrate how temperature-induced denaturation of BSA protein molecules can lead to improved protein-based coatings for surface passivation applications.

Edible coating on litchi (Litchi chinensisSonn.) for improvement of fruit quality and shelf life: a review

Litchi (Litchi chinensis Sonn.) is one of the most important fruit crops of Sapindaceae family. As far as export of agricultural products is concerned, by virtue of its delicious taste, excellent flavour, attractive appearance and high nutritional value, it has gained popularity in many parts of the world. Litchi peels changes so quickly to brown colour within 1-2 days of harvesting. Post-harvest browning in litchi fruit is mainly associated with degradation of anthocyanin due to aerobic oxidation. However, to stay in global market, which is turning more and more competitive day by day, it is of paramount importance to maintain high standard in the qualities of fruits produced and providing longer shelf life. Many polyamines and SO2 fumigation reduces browning but leaves undesirable residue in fruit that are health hazardous and even neurotoxicity of chemicals has been reported. Keeping the seriousness in the problem and to avoid glut in the market, the present review explores the advances in technology to manage pericarp browning and to maintain overall fruit quality. Edible coating is widely applicable in fresh fruit, vegetable or their fresh-cut materials which are quite safe, environment friendly and economically acceptable. Many types of edible coatings such as polysaccharide-based coatings, cellulose and its derivatives, protein-based coatings are available to overcome losses of economic value, reduces the respiration rate as well as the physiological loss of fruit weight.

Simulation and Experimental Validation of the Denaturation of a Whey Protein-Based Coating During Convection and/or Infrared Drying on a Plastic Film and Influence on its Oxygen Barrier Properties

ABSTRACTThe in-process denaturation of native whey protein-based coatings, film temperature, residual humidity, and protein degree of denaturation was simulated with combined existing models. The simulation was validated experimentally through determining the degree of denaturation of the protein in the coating. Whey protein-based formulations were applied, and denaturation was induced via infrared heating during the drying process. The oxygen transmission rate was measured and correlated with the degree of denaturation. The observed influence of the denaturation degree allowed the identification of a critical denaturation degree improving oxygen barrier. The developed simulation appears as an efficient tool for optimizing the processing and properties of protein-based materials.

Evaluation of Egg White Protein-Based Coatings to Improve the Protection of Frozen Atlantic Salmon (Salmo salar)

ABSTRACTThe effects of different egg white protein coatings on Atlantic salmon quality preservation after 4 months of frozen storage were evaluated. These coatings increased the yield of the fillets and protected them from lipid oxidation, providing better protection than glazing. Egg white protein coatings were better options than glazing to preserve salmon color during frozen storage. The best results were obtained with the application of coatings before freezing. No clear effects of the type and concentration of plasticizer in most quality parameters were found. Egg white protein + glycerol 2:1 applied before freezing was the best coating for frozen Atlantic salmon protection.

State of the Art in the Development and Properties of Protein-Based Films and Coatings and Their Applicability to Cellulose Based Products: An Extensive Review

There is increasing research towards the substitution of petrochemicals by sustainable components. Biopolymers such as proteins, polysaccharides, and lipids derive from a variety of crop sources and most promisingly from waste streams generated during their processing by the agro food industry. Among those, proteins of different types such as whey, casein, gelatin, wheat gluten, soy protein or zein present a potential beyond the food and feed industry for the application in packaging. The general protein hydrophilicity promotes a good compatibility to polar surfaces, such as paper, and a good barrier to apolar gases, such as oxygen and carbon dioxide. The present review deals with the development of protein-based coatings and films. It includes relevant discussion for application in paper or board products, as well as an outlook on its future industrial potential. Proteins with suitable functionalities as food packaging materials are described as well as the different technologies for processing the coatings and the current state of the art about the coating formulations for selectively modulating barrier, mechanical, surface and end of life properties. Some insights onto regulations about packaging use, end of life and perspectives of such natural coating for decreasing the environmental impact of packages are given.

Valorization of industrial by-products: development of active coatings to reduce food losses

An active coating based on soy protein, obtained as by-product from soy oil production, was used to extend the shelf-life of beef patties. On the one hand, the use of industrial by-products contributes to valorize by-products by preparing value added products. On the other hand, the extension of food shelf-life contributes to the reduction of food looses and could allow the use of lower amounts of packaging, reducing plastic waste. With this regard, some physicochemical and textural parameters of beef patties were analyzed in this study. The incorporation of the soy protein-based coating delayed food oxidation, prevented moisture loss and improved textural parameters of beef patties. Since the appearance and texture of food are very relevant aspects when purchasing food products, the improvement of these quality attributes showed in this study highlights the potential of using active coatings, such as the soy protein-based coatings analyzed in this work. In particular, their use would bring social benefits such as shelf-life extension and thus, reduction of food losses, but also the possibility of reducing the amount of packaging used to preserve food and the environmental and economical benefits associated with this reduction of packaging.

Quality and Shelf Life of Cold and Frozen Rainbow Trout (Oncorhynchus mykiss) Fillets: Effects of Fish Protein-Based Biodegradable Coatings

The Klunzinger’s ponyfish (Equulites klunzingeri) protein powder extracted with acid or alkali aided process as a biodegradable coating material for rainbow trout (Oncorhynchus mykiss) fillets during cold (+2°C) and frozen storage (–18°C) were investigated. The coating with alkaline treated protein (AlPC) and acid treated protein (AcPC) extended the shelf life of fillets from 11 to 14 days in cold storage and improved the quality parameters in three months frozen storage period. According to total viable count and total psychrophile count results, bacteria grew more quickly in uncoated fillets than coated fillets. The protein-based coating did prevent spoilage of the rainbow trout fillets as reflected by a decrease in pH, total volatile base-nitrogen and free fatty acids during cold and frozen storage period. Therefore, this study demonstrated that fish protein-based coating had a positive effect on maintaining the rainbow trout fillets quality, and edible coatings from discard fish can offer a promising alternative for preserving fish fillets.

Whey protein-based coatings on frozen Atlantic salmon (Salmo salar): Influence of the plasticiser and the moment of coating on quality preservation

The effects of different whey protein concentrate coating formulations (with or without glycerol or sorbitol in two proportions) on frozen Atlantic salmon quality parameters were evaluated. The influence of the moment of coating application (before or after freezing) was also studied. The coating application after freezing increased the thaw yield, decreased the drip loss, and modified colour parameters of frozen and thawed fillets, in comparison with application before freezing. The moment of coating also influenced the colour of cooked fish fillets. The type of plasticiser affects the colour of thawed and cooked samples, but not the colour of frozen samples. The protein coatings delayed lipid oxidation of salmon fillets, providing better protection against it than water glazing, and this effect was more pronounced when glycerol instead of sorbitol was used in the coating formulation.WPC+glycerol (1:1) coating was the best for frozen Atlantic salmon protection. The sensory properties of salmon fillets were not modified by the use of this coating.

EFFECT OF EDIBLE COATING AND MODIFIED ATMOSPHERE PACKAGING ON ENZYMATIC BROWNING OF FRESH-CUT PERSIMMONS 'ROJO BRILLANTE'

Persimmon fruit 'Rojo brillante' can be marketed as a fresh-cut commodity after removal of the astringency by application of high levels of CO 2 . However, the commercial success of the product is limited mainly due to enzymatic browning. Therefore, the usefulness of an edible coating with antioxidant activity and modified atmosphere packaging (MA) has been investigated in this work. Persimmon pieces were dipped in a coating composed by soy protein isolate, citric acid and calcium chloride, or in water as a control. Fruit samples were then packed in trays with air or two gas mixtures (MA-A: 15% CO 2 + 5% O 2 + 80% N 2 ; MA-B: 50% O 2 + 50% N 2 ), sealed with polypropylene films and stored at 5°C for 10 days. In samples packed with air, a control treatment was also performed by macro perforating the polypropylene film to ensure no gas modification in the package. Changes in atmosphere composition, color (CIE L * a * b * ), visual quality, and texture were evaluated. Coated samples had lower a * values than uncoated samples. Enzymatic browning was further reduced, as indicated by high L * values, when samples were stored under MA-A. However, MA-B damaged the tissue of the fruit, resulting in decreasing L * and increasing a * values. These results correlated with the visual evaluation. Coated samples under MA-A were evaluated as above the limit of commercialization during all the storage time by the judges. Fruit texture was not influenced by the application of either MA or coating. During storage, the gas composition of the samples stored under ambient atmosphere with non-perforated film and in samples stored under MA-B showed a sharp increase and decrease on CO 2 and O 2 , respectively. While in the other treatments (macro-perforated films and MA-A) gases were only slightly modified during storage. The results indicate that even when soy protein-based coatings showed a good effectiveness by itself, the combined use of MA-A with the soy protein-based coatings presents a synergic effect reducing browning of fresh-cut persimmon.

A Solution for Biocompatibility Problems

Here, we describe the biocompatibility of solution-processable organic semiconducting polymers. Low-operating voltage organic thin-film transistor (OTFT) devices have been fabricated, which can be used as sensors in electrolytes. The devices are based on regioregular poly(3hexylthiophene) (P3HT), being both a reasonably conductive and optically active polymer. To overcome biocompatibility problems, protein-based coatings and oxygen-plasma treatments have been adopted to enable growth of adherent living cells on those modified surfaces. With the demonstration of biocompatible semiconducting polymeric layers, a hurdle for the realizations of low-cost and mass-produced sensors in life science has been overcome. This opens new possibilities and applications of biological sensing with organic electronic devices.