Preparation,Bioactivities and Applications in Food Industry of Chitosan-Based Maillard Products: A Review

Chitosan, a biopolymer possessing numerous interesting bioactivities and excellent technological properties, has received great attention from scientists in different fields including the food industry, pharmacy, medicine, and environmental fields. A series of recent studies have reported exciting results about improvement of the properties of chitosan using the Maillard reaction. However, there is a lack of a systemic review about the preparation, bioactivities and applications in food industry of chitosan-based Maillard reaction products (CMRPs). The presence of free amino groups in chitosan allows it to acquire some stronger or new functional properties via the Maillard reaction. The present review aims to focus on the current research status of synthesis, optimization and structural identification of CMRPs. The applications of CMRPs in the food industry are also discussed according to their biological and technological properties such as antioxidant, antimicrobial activities and inducing conformational changes of allergens in food. Some promising directions for future research are proposed in this review, aiming to provide theoretical guidance for the further development of chitosan and its derivatives.     

Milk proteins as vehicles for bioactives

Milk proteins are natural vehicles for bioactives. Many of their structural and physicochemical properties facilitate their functionality in delivery systems. These properties include binding of ions and small molecules, excellent surface and self-assembly properties; superb gelation properties; pH-responsive gel swelling behavior, useful for programmable release; interactions with other macromolecules to form complexes and conjugates with synergistic combinations of properties; various shielding capabilities, essential for protecting sensitive payload; biocompatibility and biodegradability, enabling to control the bioaccessibility of the bioactive, and promote its bioavailability.The review highlights the main achievements reported in the last 3 years: harnessing the casein micelle, a natural nanovehicle of nutrients, for delivering hydrophobic bioactives; discovering unique nanotubes based on enzymatic hydrolysis of α-la; introduction of novel encapsulation techniques based on cold-set gelation for delivering heat-sensitive bioactives including probiotics; developments and use of Maillard reaction based conjugates of milk proteins and polysaccharides for encapsulating bioactives; introduction of β-lg–pectin nanocomplexes for delivery of hydrophobic nutraceuticals in clear acid beverages; development of core-shell nanoparticles made of heat-aggregated β-lg, nanocoated by beet-pectin, for bioactive delivery; synergizing the surface properties of whey proteins with stabilization properties of polysaccharides in advanced W/O/W and O/W/O double emulsions; application of milk proteins for drug targeting, including lactoferrin or bovine serum albumin conjugated nanoparticles for effective in vivo drug delivery across the blood-brain barrier; beta casein nanoparticles for targeting gastric cancer; fatty acid-coated bovine serum albumin nanoparticles for intestinal delivery, and Maillard conjugates of casein and resistant starch for colon targeting.Major future challenges are spot-lighted.     

Recent advances in heterogeneous catalysts for the synthesis of imidazole derivatives

Among the bioactive heterocyclic frameworks, nitrogen containing multisubstituted imidazoles are versatile building blocks of many naturally occurring products. Imidazoles possess wide range of biological properties including anticancer, anti-inflammatory, antimicrobial, and antihypertensive activities with potential applications in other sectors. Multicomponent reactions in combination with heterogeneous catalysts and nanocomposites have contributed significantly to organic synthesis in general and imidazoles, in particular with high functional group tolerance. Owing to their tunable properties, lower operational cost, thermal stability, recyclability, and easily separation from products, heterogeneous catalysts and nanocomposites are integral part of numerous pharmaceutical, agrochemical, and industrial processes. There has been increased focus on the development of green and sustainable catalytic procedures for the building of novel and biologically potent imidazole conjugates. This article emphasizes the recent advances in recyclable catalysts and protocols, and their merits for the synthesis of diverse multisubstituted imidazole conjugates by one-pot reaction approach and the catalyst and reactant interactions.     

Protein–polysaccharide interactions and aggregates in food formulations

The protein–polysaccharide combinations that lead to electrostatic complex and coacervate formation are the object of extensive research using both layer-by-layer and mixed emulsion approaches. The protein–polysaccharide conjugates demonstrated interesting physicochemical properties as stabilizers and emulsifiers, as well as texture modifiers in food products. Furthermore, they are potential optimal nutrient delivery systems. Their complex behavior due to several factors such as pH, ionic strength, concentration, heat, and mechanical treatments is the main reason behind the continuous growth of the research field. The review is reporting some recent advances on the topic, along with an overview of the possible interactions between protein and polysaccharide, from Maillard reaction to enzymatic cross-linking passing through coacervates.     

Synergistic DNA- and Protein-Based Recognition Promote an RNA-Templated Bio-orthogonal Reaction

Biomolecular assemblies composed of proteins and oligonucleotides play a central role in biological processes. While in nature, oligonucleotides and proteins usually assemble via non-covalent interactions, synthetic conjugates have been developed which covalently link both modalities. The resulting peptide-oligonucleotide conjugates have facilitated novel biological applications as well as the design of functional supramolecular systems and materials. However, despite the importance of concerted protein/oligonucleotide recognition in nature, conjugation approaches have barely utilized the synergistic recognition abilities of such complexes. Herein, the structure-based design of peptide-DNA conjugates that bind RNA through Watson-Crick base pairing combined with peptide-mediated major groove recognition is reported. Two distinct conjugate families with tunable binding characteristics have been designed to adjacently bind a particular RNA sequence. In the resulting ternary complex, their peptide elements are located in proximity, a feature that was used to enable an RNA-templated click reaction. The introduced structure-based design approach opens the door to novel functional biomolecular assemblies.     

Emulsion stabilisation using polysaccharide–protein complexes

There is a great deal of interest in the Food Industry in the use of polysaccharides and proteins to stabilise oil-in-water emulsions and there is a particular interest nowadays in the use of polysaccharide–protein complexes. There are three classes of complexes namely; (a) naturally-occurring complexes in which protein residues are covalently attached to the polysaccharide chains as is the case, for example, with gum Arabic; (b) Maillard conjugates, which are formed by interaction of the reducing end of a polysaccharide with an amine group on a protein forming a covalent bond; and (c) electrostatic complexes formed between a polysaccharide and a protein with opposite net charge. This review sets out our current understanding of the nature of these different polysaccharide–protein complexes and their ability to stabilise oil-in-water emulsions.     

Structural and functional alterations in major peanut allergens caused by thermal processing

The majority of foods that we eat are subjected to some type of processing either at home or by the manufacturer. The biochemical reactions that occur in foods as a result of thermal processing can be both beneficial and harmful. Here, we briefly review the effects of thermal processing and some of the effects of the Maillard reaction on the allergenicity of food proteins. Specifically, we focus on the known effects of roasting on the allergenic properties of peanut proteins and the contribution of Maillard reaction products or advanced glycation end products to these observed effects. The most thorough understanding of the effects of thermal processing on allergenicity involves the peanut proteins. Thermal processing alters specific biophysical and immunological properties of peanut proteins, such as structure, function, solubility, digestibility, immunoglobulin E (IgE) binding, and T-cell responses. A better understanding of the effects of thermal processing-induced biochemical and immunological alterations is of utmost importance for proper risk assessment of existing and newly introduced proteins in the food source, as well as development of effective diagnostic tools and therapeutic treatments for food allergy.     

Advances and trends in the design, analysis, and characterization of polymer–protein conjugates for “PEGylaided” bioprocesses

In addition to their use as therapeutics and because of their enhanced properties, PEGylated proteins have potential application in fields such as bioprocessing. However, the use of PEGylated conjugates to improve the performance of bioprocess has not been widely explored. This limited additional industrial use of PEG-protein conjugates can be attributed to the fact that PEGylation reactions, separation of the products, and final characterization of the structure and activity of the resulting species are not trivial tasks. The development of bioprocessing operations based on PEGylated proteins relies heavily in the use of analytical tools that must sometimes be adapted from the strategies used in pharmaceutical conjugate development. For instance, to evaluate conjugate performance in bioprocessing operations, both chromatographic and non-chromatographic steps must be used to separate and quantify the resulting reaction species. Characterization of the conjugates by mass spectrometry, circular dichroism, and specific activity assays, among other adapted techniques, is then required to evaluate the feasibility of using the conjugates in any operation. Correct selection of the technical and analytical methods in each of the steps from design of the PEGylation reaction to its final engineering application will ensure success in implementing a "PEGylaided" process. In this context, the objective of this review is to describe technological and analytical trends in developing successful applications of PEGylated conjugates in bioprocesses and to describe potential fields in which these proteins can be exploited.     

Advances in self-crosslinking of acrylic emulsion: what we know and what we would like to know

This review covers various strategies that enable self-crosslinking of acrylic emulsion, and gives a detailed idea of different one component (1K) crosslinking systems along with their reaction mechanisms, film properties and applications. The review is categorized into four main parts: (i) self-condensation of N-methylol functionality (ii) reaction of keto-hydrazide or acetoacetoxy-diamine functional group (iii) self-condensation of organofunctional silanes (iv) metal complex (salts, chelates) reaction with backbone functional group such as acetoacetoxy group or carboxylic group (v) UV curable functional monomers. These crosslinking reactions are low-temperature curable and offers excellent film properties than the conventional two-pack (2K) cross-linking emulsion system. This crosslinking system has good potential application in water-based coatings. Various examples are portrayed, along with a discussion of their advantages, drawbacks and limitations.     

Simultaneous Ultrasound and Heat Enhance Functional Properties of Glycosylated Lactoferrin

Protein-polysaccharide covalent complexes exhibit better physicochemical and functional properties than single protein or polysaccharide. To promote the formation of the covalent complex from lactoferrin (LF) and beet pectin (BP), we enhanced the Maillard reaction between LF and BP by using an ultrasound-assisted treatment and studied the structure and functional properties of the resulting product. The reaction conditions were optimized by an orthogonal experimental design, and the highest grafting degree of 55.36% was obtained by ultrasonic treatment at 300 W for 20 min and at LF concentration of 20 g/L and BP concentration of 9 g/L. The formation of LF-BP conjugates was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared (FTIR) spectroscopy. Ultrasound-assisted treatment can increase the surface hydrophobicity, browning index, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radicals scavenging activity of LF due to the changes in the spatial configuration and formation of Maillard reaction products. The thermal stability, antioxidant activity and emulsifying property of LF were significantly improved after combining with BP. These findings reveal the potential application of modified proteins by ultrasonic and heat treatment.     

Semisynthetic DNA–Protein Conjugates for Biosensing and Nanofabrication

Conjugation with artificial nucleic acids allows proteins to be modified with a synthetically accessible, robust tag. This attachment is addressable in a highly specific manner by means of molecular recognition events, such as Watson–Crick hybridization. Such DNA–protein conjugates, with their combined properties, have a broad range of applications, such as in high‐performance biomedical diagnostic assays, fundamental research on molecular recognition, and the synthesis of DNA nanostructures. This Review surveys current approaches to generate DNA–protein conjugates as well as recent advances in their applications. For example, DNA–protein conjugates have been assembled into model systems for the investigation of catalytic cascade reactions and light‐harvesting devices. Such hybrid conjugates are also used for the biofunctionalization of planar surfaces for micro‐ and nanoarrays, and for decorating inorganic nanoparticles to enable applications in sensing, materials science, and catalysis.     

Techno-functional properties of edible insect proteins and effects of processing

Insects represent a rich source of protein and a more sustainable alternative to conventional animal sources. Insect proteins are diverse in amino acid composition, structure, and physicochemical and functional properties. Processing treatments cause changes in properties of insect proteins and protein-enriched fractions of varying purity, affecting their techno-functional properties and the possible application range. This review discusses recent findings on the effect of processing techniques on the techno-functionality of insect protein fractions including solubility, foaming, emulsifying, and gelling properties. It is demonstrated that a treatment type and its intensity alter physicochemical and functional properties to different degrees. The review also shows the potential for the production of insect-derived food ingredients with tailored functional properties using the diversity of available processing methods.     

美拉德反应的研究进展

美拉德反应主要指还原糖与氨基酸、蛋白质之间的复杂反应,它与食品加工、疾病生理过程等有重要关系.除该反应对食品品质影响的研究仍在进行外,近来美拉德反应的研究更多地集中在蛋白质交联、类黑素、动力学以及丙烯酰胺等与人类健康关系更密切的方面,本文从这些方面综述了美拉德反应的进展.     

Novel aflatoxin derivatives and protein conjugates

Aflatoxins, a group of structurally related mycotoxins, are well known for their toxic and carcinogenic effects in humans and animals. Aflatoxin derivatives and protein conjugates are needed for diverse analytical applications. This work describes a reliable and fast synthesis of novel aflatoxin derivatives, purification by preparative HPLC and characterisation by ESI-MS and one- and two-dimensional NMR. Novel aflatoxin bovine serum albumin conjugates were prepared and characterised by UV absorption and MALDI-MS. These aflatoxin protein conjugates are potentially interesting as immunogens for the generation of aflatoxin selective antibodies with novel specificities.     

Industrial proteins as a green alternative for ‘petro’ polymers: Potentials and limitations

For the development of technical applications of polymers from renewable resources, various biopolymers are being studied. In this paper, the opportunities for industrial proteins on this market are discussed e.g. for use in (technical) coatings, adhesives, surfactants and plastics. The use of protein modifications for the improvement of functional properties relevant for technical applications is addressed.     

Molecular dynamics studies show solvation structure of type III antifreeze protein is disrupted at low pH

Antifreeze proteins are a class of biological molecules of interest in many research and industrial applications due to their highly specialized function, but there is little information of their stability and properties under varied pH derived from computational studies. To gain novel insights in this area, we conducted molecular dynamics (MD) simulations with the antifreeze protein 1KDF at varied temperatures and pH. Water solvation and H-bond formation around specific residues – ASN14, THR18 and GLN44 – involved in its antifreeze activity were extensively studied. We found that at pH1 there was a disruption in water solvation around the basal and the ice binding surfaces of the molecule. This was induced by a small change in the secondary structure propensities of some titrable residues, particularly GLU35. This change explains the experimentally observed reduction in antifreeze activity previously reported for this protein at pH1. We also found that THR18 showed extremely low H-bond formation, and that the three antifreeze residues all had very low average H-bond lifetimes. Our results confirm long-standing assumptions that these small, compact molecules can maintain their antifreeze activity in a wide range of pH, while demonstrating the mechanism that may reduce antifreeze activity at low pH. This aspect is useful when considering industrial and commercial use of antifreeze proteins subject to extreme pH environments, in particular in food industrial applications.     

脂蛋白合成新进展

生物体内的信号传导蛋白在膜上的定位与其生物功能的发挥依赖于特定脂肪链的修饰,然而传统的基因表达法合成脂蛋白,得到的纯品产率很低.在近10年中,逐渐发展起来一种新的合成方法,即将化学合成脂修饰的多肽与基因表达培养蛋白相结合,可以合成出具有多条脂肪链修饰的蛋白缀合物,并且整个合成过程在非常温和的环境中进行,产品能保持较高的纯度和活性.采用该方法合成的脂蛋白用于体外的实验中,其结果与生物体内的现象非常接近.脂蛋白合成方法的发展对研究细胞中的信号传导过程具有重要的意义,并在药物合成和提高药效方面都有很多应用,这对于研究恶性肿瘤等疾病的发病机理起到了重要的推动作用.同时该脂蛋白合成的成功是采用化学法合成生物大分子解释生物体内的现象一个重大的突破,是化学生物学发展重要的一步.     

Chemoenzymatic Synthesis of Polypeptides for Use as Functional and Structural Materials

Polypeptides inspired by the natural functional and structural proteins present in living systems are promising materials for various fields in terms of their versatile functionality and physical properties. Designing and synthesizing mimetic sequences of specific peptide motifs in proteins are important for exploring the functionality of natural proteins. Chemoenzymatic polymerization, which utilizes aminolysis (i.e., the reverse reaction of hydrolysis catalyzed by proteases), is a useful technique for synthesizing artificial polypeptide materials and has several advantages, including facile synthesis protocols, environmental friendliness, scalability, and atom economy. In this review, recent progress in chemoenzymatic polypeptide synthesis for the production of functional and structural materials for various applications is summarized in conjunction with the current status of technical challenges in the field.     

Application of surface plasmon resonance for the detection of carbohydrates,glycoconjugates, and measurement of the carbohydrate-specific interactions: A comparison with conventional analytical techniques. A critical review

Carbohydrates (glycans) and their conjugates with proteins and lipids contribute significantly to many biological processes. That makes these compounds important targets to be detected, monitored and identified. The identification of the carbohydrate content in their conjugates with proteins and lipids (glycoforms) is often a challenging task. Most of the conventional instrumental analytical techniques are time-consuming and require tedious sample pretreatment and utilising various labeling agents. Surface plasmon resonance (SPR) has been intensively developed during last two decades and has received the increasing attention for different applications, from the real-time monitoring of affinity bindings to biosensors. SPR does not require any labels and is capable of direct measurement of biospecific interaction occurring on the sensing surface. This review provides a critical comparison of modern analytical instrumental techniques with SPR in terms of their analytical capabilities to detect carbohydrates, their conjugates with proteins and lipids and to study the carbohydrate-specific bindings. A few selected examples of the SPR approaches developed during 2004–2011 for the biosensing of glycoforms and for glycan–protein affinity studies are comprehensively discussed.     

Functional properties of nisin–carbohydrate conjugates formed by radiation induced Maillard reaction

Nisin–carbohydrate conjugates were prepared by irradiating nisin either with glucose or dextran. Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino and reducing sugar groups indicating occurrence of the Maillard reaction catalyzed by irradiation. Nisin–carbohydrate conjugates showed a broad spectrum antibacterial activity against Gram negative bacteria (Escherichia coli, Pseudomonas fluorescence) as well as Gram positive bacteria (Staphylococcus aureus, Bacillus cereus). Results of antioxidant assays, including that of DPPH radical-scavenging activity and reducing power, showed that the nisin–dextran conjugates possessed better antioxidant potential than nisin–glucose conjugate. These results suggested that it was possible to enhance the functional properties of nisin by preparing radiation induced conjugates suitable for application in food industry.