Jennifer M. Ames

A Perspective on the Maillard Reaction and the Analysis of Protein Glycation by Mass Spectrometry: Probing the Pathogenesis of Chronic Disease

The Maillard reaction, starting from the glycation of protein and progressing to the formation of advanced glycation end-products (AGEs), is implicated in the development of complications of diabetes mellitus, as well as in the pathogenesis of cardiovascular, renal, and neurodegenerative diseases. In this perspective review, we provide an overview on the relevance of the Maillard reaction in the pathogenesis of chronic disease and discuss traditional approaches and recent developments in the analysis of glycated proteins by mass spectrometry. We propose that proteomics approaches, particularly bottom-up proteomics, will play a significant role in analyses of clinical samples leading to the identification of new markers of disease development and progression.

Applications of the Maillard reaction in the food industry

This paper summarises some recent work concerned with the development of colour and flavour via the Maillard reaction in both aqueous and restricted moisture model systems. High performance liquid chromatography (HPLC) and capillary electrophoresis (CE), both with diode array detection, are discussed for their ability to separate reaction products. The use of the diode array data to classify reaction products is presented. The coloured reaction products identified from aqueous sugar-amino acid systems are summarised, and their contribution to the colour of total model systems is considered. The effects of temperature/ time, pH and high pressure on the development of colour and flavour in Maillard model systems are presented. Colour measurement data and quantitative descriptive analysis (QDA) data are given for a starch-glucose-lysine model system extruded at different feed pH values. The use of a laboratory reaction cell to mimic most of the conditions encountered in the extruder is discussed. Its use to obtain information for the successful prediction of colour development in the extruder is presented.

The Maillard reaction in foods and medicine

Reaction mechanisms food technology kinetics and analytical aspects flavour chemistry toxicology and antioxidants health and disease.

The Maillard Reaction

The Maillard reaction is a type of non-enzymic browning which involves the reaction of carbonyl compounds, especially reducing sugars, with cornpounds which possess a free amino group, such as amino acids, amines and proteins. In most foods, the e-amino groups of the lysine residues of proteins are the most important source of free amino groups, and the ease with which they take part in the reaction explains why the Maillard reaction is the most important route to nutritional damage of food proteins. 1,2 The Maillard reaction in fact comprises a complex network of intertwining reactions and takes place during food processing, especially when heat treatment is involved, and also on storage. Apart from resulting in nutritional damage, the Maillard reaction is also primarily responsible for the development of aroma and colour, which may be desirable or undesirable, in heated foods. It also results in the formation of potentially toxic compounds and in the development of components with antioxidant properties.3 In addition, it occurs in vivo. The Maillard reaction and its ramifications are so important that four symposia have been devoted to it over the last 12 years.4–7

Control of the Maillard reaction in food systems

Abstract The Maillard reaction is of primary importance to the food manufacturer, since it is frequently responsible for the aromas and colours that develop during heating or storage of food products. Our ability to control the reaction is still very limited, although recent studies have indicated how it may be manipulated, particularly with regard to aroma development. The introduction of new processing and cooking techniques, such as microwave heaving, presents a constant challenge to the manufacturer to find ways of manipulating the reaction. The chemistry of the reaction and the factors affecting it are reviewed.

Development of a capillary electrophoresis method for the simultaneous analysis of artificial sweeteners, preservatives and colours in soft drinks

A rapid capillary electrophoresis method was developed simultaneously to determine artificial sweeteners, preservatives and colours used as additives in carbonated soft drinks. Resolution between all additives occurring together in soft drinks was successfully achieved within a 15-min run-time by employing the micellar electrokinetic chromatography mode with a 20 mM carbonate buffer at pH 9.5 as the aqueous phase and 62 mM sodium dodecyl sulfate as the micellar phase. By using a diode-array detector to monitor the UV-visible range (190-600 nm), the identity of sample components, suggested by migration time, could be confirmed by spectral matching relative to standards.

The effect of a model melanoidin mixture on faecal bacterial populations in vitro

The Maillard reaction produces coloured, macromolecular materials (melanoidins) in a variety of foods, on heating. Significant quantities may enter the human gut on a daily basis, but there is little information on their metabolism in the human colon. As the large bowel contains a diverse population of bacteria involved in normal bowel function, it is possible that melanoidins are metabolized therein. Depending on the bacteria involved, there may be disease or health implications. The aim of the present study was to use in vitro models to determine the digestibility of melanoidins and the effect of melanoidins on colonic bacteria in the gastrointestinal tract. Melanoidins were prepared and the effects of simulated upper-gut secretions on their stability determined in a model system. The effects of faecal bacteria were also determined, in batch culture, with a combination of phenotypic and genotypic (probes) criteria being used to identify the microbial diversity involved. Simulation of peptic and pancreatic digestion showed that the melanoidins did not produce detectable amounts of low-molecular-mass degradation products. However, melanoidins affected the growth of gut bacteria during mixed culture growth. The effect was to cause a non-specific increase in the anaerobic bacteria enumerated. This in vitro study indicates that melanoidins can affect the growth of human large-bowel bacteria and serves to demonstrate possible effects that may occur in vivo. Given the large and varied number of food items that contain Maillard reaction products, this may have relevance for lower-gut health.

Formation of Volatile Compounds During Bacillus subtilis Fermentation of Soya Beans

The formation of volatile compounds during the Bacillus subtilis fermentation of cooked, roasted soya bean cotyledons was investigated. The materials examined were: dry roasted cotyledons; autoclaved, roasted cotyledons; and autoclaved, roasted cotyledons fermented for 18 h and 36 h at 35°C. Growth of B subtilis led to the formation of many volatile compounds. The volatile compounds formed in the largest amounts during fermentation were 3-hydroxy-2-butanone (acetoin), 2,5-dimethylpyrazine and trimethylpyrazine. Compounds present at concentrations exceeding their odour threshold values included nonanal, decanal, 1-octen-3-ol, butanedione, 3-hydroxy-2-butanone, 3-octanone, 2,5-dimethylpyrazine, 3,6-dimethyl-2-ethylpyrazine, 2-pentylfuran, dimethyl sulfide, benzaldehyde and 2-methoxyphenol. Compounds found in 18 h fermented cotyledons which were absent, or present in much lower concentrations, in roasted or autoclaved cotyledons included several aliphatic ketones, acetic acid, two aliphatic esters, several pyrazines, 2-pentylfuran, dimethyl sulphide, 2-methoxyphenol and trimethyloxazole. The total mass of volatile compounds present after 36 h incubation was less than half that present after 18 h. This was mainly due to the disappearance of 3-hydroxy-2-butanone, 2,5-dimethylpyrazine and 2,6-dimethylpyrazine. The biogenesis of the volatile compounds is discussed.

Determination ofNɛ-(Carboxymethyl)lysine in Foods and Related Systems

The sensitive and specific determination of advanced glycation end products (AGEs) is of considerable interest because these compounds have been associated with pro‐oxidative and proinflammatory effects in vivo. AGEs form when carbonyl compounds, such as glucose and its oxidation products, glyoxal and methylglyoxal, react with the ɛ‐amino group of lysine and the guanidino group of arginine to give structures including Nɛ‐(carboxymethyl)lysine (CML), Nɛ‐(carboxyethyl)lysine, and hydroimidazolones. CML is frequently used as a marker for AGEs in general. It exists in both the free or peptide‐bound forms. Analysis of CML involves its extraction from the food (including protein hydrolysis to release any peptide‐bound adduct) and determination by immunochemical or instrumental means. Various factors must be considered at each step of the analysis. Extraction, hydrolysis, and sample clean‐up are all less straight forward for food samples, compared to plasma and tissue. The immunochemical and instrumental methods all have their advantages and disadvantages, and no perfect method exists. Currently, different procedures are being used in different laboratories, and there is an urgent need to compare, improve, and validate methods.

The development and application of capillary electrophoresis methods for food analysis

Capillary electrophoresis (CE) offers the analyst a number of key advantages for the analysis of the components of foods. CE offers better resolution than, say, high‐performance liquid chromatography (HPLC), and is more adept at the simultaneous separation of a number of components of different chemistries within a single matrix. In addition, CE requires less rigorous sample cleanup procedures than HPLC, while offering the same degree of automation. However, despite these advantages, CE remains under‐utilized by food analysts. Therefore, this review consolidates and discusses the currently reported applications of CE that are relevant to the analysis of foods. Some discussion is also devoted to the development of these reported methods and to the advantages/disadvantages compared with the more usual methods for each particular analysis. It is the aim of this review to give practicing food analysts an overview of the current scope of CE.