Protein-sugar reaction

Sugars are reactive molecules. Their reaction with amines, R—NH2, is of particular importance to us. Proteins possess a number of amino groups, one at the N-terminus of the protein and one for each lysine residue in the protein. There is a lot of sugar floating around in the human body. So it should not surprise us that there is nonspecific reaction of these sugars with proteins. These reactions are generally slow but they do occur sufficiently fast to be important. 

The Maillard reaction commonly occurs in food products and during food processing. A typical or pure Maillard reaction is simply the reaction of a sugar and an amino acid. Strictly speaking, the sugar must be a reducing carbohydrate and the amino acid can be either free or bound, as a peptide or protein. The reaction generates not only volatile compounds, which provide odor, but also odorless nonvolatile compounds, some of which are colored. 

Microwave food products are rarely as simple as the water and oil systems discussed above and caution must be exercised in predicting the reaction of individual flavor components in complex food systems containing salt, proteins, sugars, starches, and other food ingredients. Liquid products quickly dissipate the microwave energy and result in a more uniform product. Solid food products, multiphase systems, or frozen products develop hot spots during heating which further complicate flavor delivery in these systems. Performance of the flavor in the microwave is dependent not only on the physical/chemical properties of individual flavor components, but more importantly, on the Interaction of these components with complex food systems. 

Fig. 1. Formation of hemoglobin Al. . The configuration of the reacting glucose is mainly in the ring form (F5). The adduct illustrated here is with the terminal P-valine of adult hemoglobin. The same reaction occurs with reacting valine and lysine (and possibly arginine and alanine) residues in peptides and proteins. Similar reactions occur with a variety of sugars. (See Table 1.) Modified from Bunn (B39).

Figure 7.11 Effect of adding crystalline sweet potato 0-amylase (87 fig protein/ml reaction mixture) on the filtration rate (ml/h) and on the reducing sugar content (measured as maltose) in the filtrate at 50°C, 15 psi, in a stirred cell system. Enzyme added ( ) no enzyme added (o).13...

Molecules such as proteins, sugars, and DNA are constructed by Nature in complex environments via simultaneous and/or cascade reactions. This chemoselectivity is today recognized by chemists as the Holy Grail for synthesis towards traly monodisperse macromolecules. The foundation of such accomplishments is based on an initial definition of orthogonal systems, established in 1977 by Barany and Merrifield, who noted that ... 

The flavour components in butter and butterfat are complex and include y- and d-lactones (Boldingh and Taylor, 1962), methyl ketones (Forss, 1972 Langeer and Day, 1964), aldehydes (Badings 1970), short-chain fatty acids (Forss, 1972 Langeer and Day, 1964), sulphides (Patton etal., 1956 Day etal., 1957 Badings etal., 1975), alcohols (Forss, 1972 Langeer and Day, 1964), proteins, sugars and secondary reaction products (Teranishi et al., 1981). 

Chapter 7 highlights analytical mass spectrometry with use of Alkali metal ion reaction (association) in the condensed-phase. Methodology for cationization MS is emphasized in this chapter, which also describes role of M+ adduct of biologically important nucleosides, peptide or protein, sugars, as well as synthetic polymers. The approach and procedure for the structural characterization of biologically important substances from CID, BIRD, BCD, ISD and PSD MS/MS data, are described in detail, being reviewed by hundreds of current topics. 

Free amino- and guanidino-groups. As a model system of protein-sugar Maillard reaction, a powdered sample containing ovomucoid and glucose was incubated at 50 C and 65% relative humidity for various periods from 2 to 20 days. The incubated samples were dissolved in 50 mM Tris-HCl buffer, pH 8.0 and used for chemical and biochemical analyses. 

Maillard reaction) or in the relative absence of sugars (lean meat protein). The reaction leads to a fall in protein digestibility and in the availability of most amino acids, in addition to that of lysine. Destruction of amino acids can also occur. 

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

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