Define Plan showing various steps of non-enzymatic browning?

The plan showing the various steps of non-enzymatic browning is presented in figure

Figure: Plan showing various steps of non-enzymatic browning

It is obvious from figure, that browning may occur by compounds entering at any point. In the first reaction, aldoses and ketose react with amines and the reaction is known as Amadori reaction. The product of the reaction can undergo number of fates depending upon the conditions of the reactions as can be seen in figure. It can, in neutral or acidic media, lose water and form a ring compound of the Schiff's base of hydroxymethyl furfural, or furfural and then eliminate the amine to form the free hydroxy methyl furfural or furfural. In the dry state, it can form reductones which have high reduction potential. Or, finally, the product can undergo fission to form small molecules such as acetol (CH₃ COCH₂OH), pyruvaldehyde (CH₃COCHO), diacetyl (CH₃COCOCH₃) and others. In the diagram shown, it is obvious that all of those compounds react with amines to form aldimines or ketimines or polymerize to aldols and similar large molecules, which subsequently react with amines. The final brown pigments are produced that contain nitrogen. The second browning reaction is caramelization. Sugars will show caramelization when heated at relatively high temperatures. This type of reaction is markedly affected by high pH. While the browning of these carbohydrates is not as rapid as in the presence of amino compounds, it is accelerated in the presence of carboxylic acid, salts of these acids, phosphates and metal ions. These accelerators are commonly present in foods. The nitrogen free intermediates formed in carbonyl amino browning reactions are also produced in non amino browning The formation of 1, 2 enolization, furfural and hydroxymethyl furfural by dehydration and sugar fission products has been demonstrated in some of the model systems. It has also been shown that these intermediates will form colored polymers in the absence of amino compounds. Thus this fits well in the above Figure after Amadori rearrangement forming different nitrogen free polymers.