Amino acid-fructose mixtures

Figure 6. Mutagenic activity of fructose-amino acid mixtures in Ames strain TA100. (Reproduced with permission from Ref. 58. Copyright 1981, Institute of...

The most efficient method for the clean hydrolysis of sucrose is by the use of invertase, leading to an equimolar mixture of glucose and fructose (invert sugar). The presence of salts increases the rate of thermal degradation of sucrose.337 The reaction is also possible in the presence of such heterogeneous acidic catalysts as zeolites.338 The hydrolysis of the glycosidic bond is the first step of a number of subsequent reactions that can occur on the glucose and fructose residues, such as dehydrations, combinations with amino acids (Maillard reaction), and many other chemicals or fermentation processes.339... 

The purpose of this work was to investigate the occurrence and heat-induced origin of cyclic dipeptides (DKPs) in cocoa and separately, to study the mechanism of DKP formation in simplified reaction systems. Also, the formation of volatiles vas measured in a series of model Maillard reactions of peptides, amino acid mixtures and fructose. 

Figure 9.64 Chromatogram obtained after injection of a yQ-galactosidase incubation mixture onto a 45 mm x 3.6 mm cation-exchange column. Mobile phase pyridine-acetic acid-water (6 60 176, v/v). Flow rate, 0.4 mL/min temperature, 50°C. In front of lactose-lysine some free amino acids elute which are the result of proteolytic activity in the intestinal enzyme preparation. Peaks 1, lactose-lysine 2, /8-alanine (internal standard) 3, fructose-lysine. (From Schreuder and Welling, 1983.)...

Dawes and Edwards (1966) isolated it from the volatiles obtained by heating a mixture of D-fructose and glycine or L-3-phenylalanine. Wang et al. (1969) presented a model reaction in which the product of condensation of pyruvaldehyde with any amino acid degraded by a Strecker reaction can form an aminoketone which by subsequent steps of self-condensation and oxidation formed 2,5-dimethylpyrazine (Wang et al., 1969 Manley et al., 1974). It was found in a heated cysteine/glucose model system (Sheldon et al., 1986). 

A combination of capillary elecfrophoresis and tandem MS is considered as a eomplementary technique to LC/MS, with the potential for higher resolving power in some cases. It was successfully applied to model mixtures of D-fructose-amino acids, but its practical utiUty for determination of fructosamines in food/biosamples needs to be established. 

H-NMR spectroscopy was subsequently investigated as a tool for the identification of Amadori products [65]. Isomeric mixtures of fructose derivatives of amino acid products in solution [66] as well as characterization of glycated proteins [67] were examined by exploiting this method. 

Cocoa pulp is composed of (m/m) 82-87% water, 10-15% mono- and disaccharides, 1-5% pectin, 1-3% citric acid, 0.1-0.4% other non-volatile organic acids (e.g., malic acid, oxalic acid, and succinic acid), 0.5-0.7% proteins, and 8-10% minerals and oligoelements (Lehrian and Patterson 1983 Schwan et al. 1995 Barel 1998). Of the mono- and dissacharides present, about 60% is sucrose and 39% is a mixture of fructose and glucose, which are the pulp invertase hydrolysis products of sucrose. The concentration of sucrose, fructose, and glucose is a function of cultivar and fruit age unripe pods contain a higher proportion of sucrose and ripe pods contain mainly fructose and glucose (Lehrian and Patterson 1983 Thompson et al. 2007, 2013). The amino acids, glutamic acid and... 

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