Baking,Ageing, Diabetes: A Short History of the Maillard Reaction

The reaction of reducing carbohydrates with amino compounds described in 1912 by Louis‐Camille Maillard is responsible for the aroma, taste, and appearance of thermally processed food. The discovery that non‐enzymatic conversions also occur in organisms led to intensive investigation of the pathophysiological significance of the Maillard reaction in diabetes and ageing processes. Dietary Maillard products are discussed as “glycotoxins” and thus as a nutritional risk, but also increasingly with regard to positive effects in the human body. In this Review we give an overview of the most important discoveries in Maillard research since it was first described and show that the complex reaction, even after over one hundred years, has lost none of its interdisciplinary actuality.     

Iterated reaction graphs: simulating complex Maillard reaction pathways

This study investigates a new method of simulating a complex chemical system including feedback loops and parallel reactions. The practical purpose of this approach is to model the actual reactions that take place in the Maillard process, a set of food browning reactions, in sufficient detail to be able to predict the volatile composition of the Maillard products. The developed framework, called iterated reaction graphs, consists of two main elements: a soup of molecules and a reaction base of Maillard reactions. An iterative process loops through the reaction base, taking reactants from and feeding products back to the soup. This produces a reaction graph, with molecules as nodes and reactions as arcs. The iterated reaction graph is updated and validated by comparing output with the main products found by classical gas-chromatographic/mass spectrometric analysis. To ensure a realistic output and convergence to desired volatiles only, the approach contains a number of novel elements: rate kinetics are treated as reaction probabilities; only a subset of the true chemistry is modeled; and the reactions are blocked into groups.     

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.     

Maillard反应的高分子产物的研究进展

Maillard反应产物由于其天然性和独特的香味,使其在食品和烟草领域的应用倍受关注.目前,对Maillard反应产物中的小分子化合物的研究已经比较透彻,但是高分子产物的结构及形成机理尚不清楚.虽然Maillard高分子产物及其复杂,但人们通过膜透析、凝胶柱层析等分离方法,对其提纯分级后,再运用凝胶渗透色谱、元素分析、放射性同位素标记、紫外-可见光谱、红外光谱、核磁共振(NMR)、热裂解等分析手段对其进行表征,对Maillard高分子产物的结构和形成机理有了一定的了解.本文对Maillard反应的高分子产物的分离提纯方法、分析表征方法和分子结构的假设模型三方面的研究进展进行了综述.     

New Aspects of the Maillard Reaction in Foods and in the Human Body

The reactions that occur during the cooking, baking, and preservation of foods of all kinds are of great importance for the production of aroma, taste, and color. However, more recently it has been shown that these reactions may be accompanied by a reduction in nutritive value and the formation of toxic compounds. For these reasons, the very complex reactions between reducing sugars and the free amino groups of amino acids or proteins, known as non-enzymatic browning or the Maillard reaction, have again caught the interest of chemists. The Maillard reaction came to be seen in a new light as it was realized that it actually occurred in the human body. As a general rule, the longer the half-life of a protein, the larger the amount of its Maillard products found, i.e., important factors are the ‘age’ or persistence of the protein in the body and the glucose concentration, particularly in diabetics. Many of the symptoms developed by diabetics resemble those of premature aging, which leads to the possibility that glucose, because of its reactivity towards proteins, is fundamentally involved in the normally slow progress of aging.     

CE: a useful analytical tool for the characterization of Maillard reaction products in foods

The Maillard reaction (MR) is a complex series of nonenzymatic reactions between reducing compounds and amines, amino acids, peptides, or proteins that play an important role in the formation of flavors and colors in foods during processing and storage. Also, the antioxidant properties of some Maillard reaction products (MRP) was an additional benefit reported. On the other hand, these reactions decrease the nutritional quality of foods and may result in the formation of toxic MRP. Although, research to assess the risks and benefits associated with the consumption of MRP in the diet is still awaiting for new analytical methodologies to be developed. Structural characterization of MRP has been very challenging due to the chemical diversity of these compounds which present a wide range of polarities and molecular weights, making analyses difficult. CE is a technique that has gained popularity for the separation of complex mixtures that have otherwise proved difficult to analyze. Thus, the purpose of this overview is to give the reader an appreciation of some of the CE analytical developments on the analysis of MRP in model systems and foods, and to address the potential of CE on the characterization of this complex group of compounds.     

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.     

缩醛/缩酮的合成研究进展

民以食为天。然而,鲜有中文文献专业、系统地介绍与食物相关的化学反应,这无疑导致化学课程的教学脱离现实生活,阻碍了大众透过现象看到食物背后的本质。因此,本文重点介绍了为食物带来独特美味及色泽的非酶褐变反应,主要包括焦糖反应、美拉德反应、维生素C的氧化反应等;并从化学的角度探讨食物中与医学相关的分子转变现象,如食盐中碘在体内的转化,反式脂肪酸对健康的影响,酒精的代谢过程等。使化学课程的教学密切联系现实生活,为化学与食品科学、医学等学科之间架起桥梁。     

Structure and physiochemical characteristics of whey protein isolate conjugated with xylose through Maillard reaction at different degrees

The purpose of this study is to prepare Maillard reaction products (MRPs) with both good emulsification and antioxidant activity, and the relationship between the Maillard reaction degree and structural changes of whey protein isolate (WPI) conjugated with xylose through wet-heating was explored. Browning intensity didn’t change while the free amino groups reduced significantly at the initial stage of Maillard reaction (MR). Amino acid analysis indicated that the lysine and arginine reduced significantly. The antioxidant property of the MRPs was significantly improved. The best emulsifying properties could be obtained in the middle degree of MR. The sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis illustrated that WPI and xylose formed high molecular weight conjugates. The circular dichroism spectra suggested that α-helix and random coil were increased while the β-sheet and β-turns were decreased after the MR. All of the MRPs exhibited a marked red shift in the maximum fluorescence intensity, indicating that the hydrophilicity of MRPs was enhanced.     

Separation of amino acids, peptides and corresponding Amadori compounds on a silica column at elevated temperature

Maillard reaction of glucose with amino acids and peptides has become a very important experimental model in the food flavor and pharmaceutical industries for better understanding the mechanism of food flavor generation and drug stability. Because of the amino acid and sugar functional groups present in their structures, most of the reaction components formed during the initial stages of Maillard reaction as well as the substrates are relatively polar. These compounds are poorly retained on a conventional reversed phase column. While polar stationary phases like HILIC column do provide better retention for these polar components, method selectivity could still be a challenge due to the structural similarity between these analytes. In this report, parameters such as pH, mobile phase composition and temperature were investigated using different brands of bare silica columns in order to separate glycine (G), diglycine (DG), triglycine (TG), and the corresponding Amadori compounds of glucose-glycine (GG), glucose-diglycine (GDG) and glucose-triglycine (GTG). An excellent separation for glycine, glycine peptides and their Amadori compounds was obtained on a bare silica column at an elevated temperature.     

Key Aspects of Amadori Rearrangement Products as Future Food Additives

Flavor is one of the most important factors in attracting consumers and maximizing food quality, and the Maillard reaction (MR) is highly-involved in flavor formation. However, Maillard reaction products have a big drawback in their relatively low stability in thermal treatment and storage. Amadori rearrangement products (ARPs), MR intermediates, can alternatively act as potential flavor additives for their better stability and fresh flavor formation ability. This review aims to elucidate key aspects of ARPs’ future application as flavorings. The development of current analytical technologies enables the precise characterization of ARPs, while advanced preparation methods such as synthesis, separation and drying processes can increase the yield of ARPs to up to 95%. The stability of ARPs is influenced by their chemical nature, pH value, temperature, water activity and food matrix. ARPs are associated with umami and kokumi taste enhancing effects, and the flavor formation is related to amino acids/peptides of the ARPs. Peptide-ARPs can generate peptide-specific flavors, such as: 1,6-dimethy-2(1H)-pyrazinone, 1,5-dimethy-2(1H)-pyrazinone, and 1,5,6-trimethy-2(1H)-pyrazinone. However, further research on systematic stability and toxicology are needed.     

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.     

Kinetics of Maillard reaction in a chicken meat model system using a multiresponses modeling approach

This research aimed to study the Maillard reaction pathway in chicken meat. Owing to the complexity of real chicken meat, which is composed of many different types of amino acids and reducing sugars, the experiment was initiated with a glucose/lysine model system with the same concentration ratio of reactants as found in chicken meat. By considering glucose as the rate-limiting substrate, a kinetic model of the glucose/lysine model system was developed. Methylglyoxal (MG) was found to be the principal important α-dicarbonyl compound intermediates that further reacted to form melanoidins. Pyridine was a major volatile compound in this model system. The optimized kinetic model was then further validated in a chicken extract, for which the Maillard reaction mechanism has not been elucidated. However, the kinetic model of the glucose/lysine system could not explain the Maillard reaction in the chicken extract, presumably because both types of intermediates and reaction pathway depend on the reactants. Thus, a kinetic model of the Maillard reaction in the chicken extract was developed based on the main types of detected intermediates. Overall, MG was the central intermediate and acted as a substrate for the formation of furfural, volatile compounds, melanoidins, and unknown carbonyl compound(s) (C_n). Pyrazines and aldehydes were the major volatile compounds in the chicken extract.     

Accurate mass measurements by Fourier transform mass spectrometry in the study of advanced glycation end products/peptides

The Maillard reaction occurring between sugars and amino groups is important in living systems. When amino groups belonging to protein chains are involved, the Maillard reaction has been invoked as responsible for protein cross-linking and the production of 'toxic' compounds. The reaction leads to the production of a heterogeneous group of substances, usually called advanced glycation end products (AGEs). Classical analytical approaches, such as spectroscopic (ultraviolet, fluorescence) and mass spectrometric (matrix-assisted laser desorption/ionization, liquid chromatography/electrospray ionization mass spectrometry) methods, have shown that the digestion mixture is highly complex. However, there are clear differences between the digestion mixtures of glycated and unglycated human serum albumin (HSA). In the former case, possible glycated peptides belonging to the AGE peptide class may be identified. Tandem mass spectrometric experiments on selected species seemed to be promising as regards structural information, but it was thought of interest to undertake the present investigation, based on liquid chromatography/electrospray ionization Fourier transform mass spectrometry, in order to obtain definitive results on their elemental composition. Using this approach, about 20 glycated peptides were detected and their possible structures were postulated by examining the known sequence of HSA.     

Covalently cross-linked proteins & polysaccharides: Formation,characterisation and potential applications

This review presents recent research conducted on the development of various protein-polysaccharide conjugates, their functional properties and industrial applications. These conjugates are formed by the glycosylation of food proteins with carbohydrates via the Maillard reaction and are capable of improving the functional properties of proteins. The Maillard reaction facilitates covalent bonding between a reducing group of a carbohydrate and an amino group of a protein under controlled conditions of temperature, time, pH, and relative humidity. There is a great deal of interest in modifying the functional properties of proteins and in the use of novel conjugates for various industrial applications. This review discusses various methods and their implications for preparing and characterising these conjugates. Furthermore, the physicochemical properties of conjugates such as solubility, thermal stability, emulsifying activity, emulsion stabilising properties, gelling and foaming properties are also analysed. A novel processing technology, a spinning disc reactor, could be an alternative process for the production of protein–polysaccharide conjugates, with desirable functionality in different food systems.     

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.     

Detection of hazelnut in foods using ELISA: challenges related to the detectability in processed foodstuffs

Hazelnuts are widely used nowadays, and can pose a serious threat to allergic consumers due to cross-contamination that may occur during processing. This might lead to the presence of hidden hazelnut in foods. Therefore, reliable tests are needed to detect hazelnut, especially in processed foods. A hazelnut-specific indirect competitive ELISA based on polyclonal chicken antibodies was developed. The polyclonal antibodies were raised against modified hazelnut proteins in order to improve the detectability of hazelnut proteins in processed foods. The assay showed a detection limit of 1.36 microg hazelnut protein/mL of 5 mM urea in phosphate-buffered saline buffer (pH 7.4). Limited cross-reactivity with walnut and pecan nut was observed; no cross-reactivity was observed with other food ingredients. Blank cookies spiked before analysis showed recoveries of 73-107%. However, cookies spiked before baking showed that the detectability was severely decreased. Addition of lactose to the cookies, which led to more severe modification through the Maillard reaction, led to an increase in the detectability. These results indicate that using antibodies developed toward allergens modified through food processing-simulating reactions is a better approach for detection.     

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.     

Separation and partial characterization of Maillard reaction products by capillary zone electrophoresis

Capillary zone electrophoresis proved useful for separating small amounts of both charged and uncharged solutes that are otherwise difficult to analyse. A typical complex mixture that had previously resisted all analytical approaches, including reversed-phase separations, is the products arising from the reaction of free amino acids with aldehydic sugars (Maillard reaction products). By using capillary zone electrophoresis [untreated capillary 50 cm x 75 microns I.D., 18 kV, 0.02 mol/l phosphate buffer (pH 7.5)], a number of products resulting from the reaction of glucose or ribose with glycine, alanine and isoleucine were separated and partially characterized. They were separated (1) without derivatization (and profiles of compounds absorbing at 220 nm were obtained), (2) as phenylthiocarbamyl derivatives in a search for reactive amino groups and (3) after derivatzation with 2,4-dinitrophenylhydrazine in a search for a method for compounds with a free aldehydic group. Phenylthiocarbamyl derivatives were separated in 0.005 mol/l borate buffer (pH 9.6) at 20 kV and 25 microA. Separation of 2,4-dinitrophenylhydrazones was effected by electrokinetic micellar chromatography in the same apparatus using a 50 cm x 75 microns I.D. capillary at 10 kV in 0.01 mol/l Na2HPO4-0.006 mol/l tetraborate, 0.050 mol/l with respect to sodium dodecyl sulphate. The results are compared with those given by high-performance liquid and thin-layer chromatography.     

The absorption and metabolism of modified amino acids in processed foods

The chemical reactions involved in the modifications of amino acids in processed food proteins are described. They concern the Maillard reaction, reaction with polyphenols and tannins, formation of lysinoalanine during alkaline and heat treatments, formation of isopeptides, oxidation reaction of the sulfur amino acids, and isomerization of the L-amino acids into their D-form. Information on the digestion, absorption, and urinary excretion of the reaction products obtained by using conventional nutritional tests is given. The studies that have been made on the metabolism of these molecules by using a radioisotopic approach to follow their kinetics in the organism after ingestion are also reviewed. This approach provides unique data on the quantitation of the metabolic pathways and on the kinetics of the metabolic processes involved.