Sugars reactions with amino acids

During the processing of foods, several chemical reactions affect the structure of some amino acids reactions with reducing sugars and polyphenols, interaction of the side chains of the amino acids, oxidation, etc. In some cases, these chemical modifications do not seem to change the nutritional availability of the amino acids involved, while in other cases, they do. In all cases, the presence of the newly formed molecules induces biochemical and physiological changes. 

The mechanism of the browning process involves the Maillard reaction, which was discovered by Louis-Camille Maillard in 1912. In this process amino acids react with sugars to create brown Or golden brown products. The same reaction is responsible for much of the browning that occurs during the manufacture and storage of foods. It is also the reason that beer is golden brown. 

The mechanism of the browning process involves the Maillard reaction, which was discovered by Louis-Camille Maillard in 1912. In this process amino acids react with sugars to create... 

Maiilard Reaction. In amino acids, the amino group tends to form condensation products with aldehydes. This reaction is regarded as the cause of the browning reaction when an amino acid and a sugar coexist. A characteristic flavor, useful in food preparations, is evolved along with the color in this reaction,... 

Some authors have indicated that the sugar-amino acid reactions of the Maillard type are of minor importance in citrus juices because of the high acidities involved. Studies in our laboratories (42-44) would tend to indicate that, to the contrary, the amino acids and sugars are of more than just minor importance in the darkening of citrus juices. Huffman (42) treated citrus juices with cationic ion-exchange resins to remove amino acids, proteins, and the mineral cations, then restored the cations. 

The formation of jV-glycosylamino acids, as mentioned in the previous Section, takes place under rather clearly defined conditions and will not be discussed further. The present Section will be concerned with the effect, on the Maillard reaction, of (a) external conditions and (b) the presence or absence of substances other than the amino acid and the sugar. 

M. Namiki, T. Hayashi, and S. Kawakishi, Free radicals developed in the amino-carbonyl reaction of sugars with amino acids, Agric. Biol. Chem., 1973, 37, 2935-2936. 

M. Namiki and T. Hayashi, Development of novel free radicals during amino-carbonyl reaction of sugars with amino acids, J. Agric. Food Chem., 1975, 23, 487 -91. 

Akabori amino acid reactions. (1) Formation of aldehydes by oxidative decomposition of a-amino acids when heated with sugars. (2) Reduction of a-amino acids and esters by sodium amalgam and ethanolic hydrochloric acid to the corresponding a-amino aldehydes. (3) Formation of alkamines by... 

Studies have been made of the influence of y-radiation on starch, and it was found that depolymerization takes place, and water-soluble dextrins are formed, but the aim of those studies was not connected with the preparation of syrups for caramelization. "However, nonenzymic browning can be induced by y-radiation. In such cases, the formation of melanoi-dins from sugars and amino acids competes with reaction of both types of reagent with hydroxyl radicals produced from water, the reaction medium. ... 

Hayashi, T. and Namiki, M. Role of sugar fragmentation in an early stage browning of amino-carbonyl reaction of sugar with amino acid, Agric. Biol. Chem., 50, 1965, 1986. 

---