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In the process of ripening grapes in it come glycine methionine, leucine, isoleucine, and cyclic amino acids - tyrosine and phenylalanine. Denaturation causes a disturbance of the secondary, tertiary and quaternary structures of proteins and alters its biological and physicochemical properties. Denatured proteins lose their ability to react with other substances, and dissolved in water. The phenomenon of protein denaturation is of great importance in the food industry, particularly in the wine industry. When heated wine proteins coagulate, and the wine acquires resistance to protein clouding. Proteins are precipitated lead acetate, copper hydroxide, ammonium sulfate, sodium tungstate, and tannin. The structure of a protein molecule determines the biological properties of the protein - its enzymatic activity.
Proteins are divided into two groups: proteins, or simple proteins, and proteid - complex proteins. The structure of proteins contain only amino acid residues. Proteid compounds are complex proteins with other substances, non-protein nature. Typically, non-protein component called the prosthetic group, and depending on its chemical composition are following proteid: glycoproteins, lipoproteins, nucleoproteins (a protein associated with nucleic acid that plays an important role in the life of the organism, in particular in the phenomena of heredity).
It should be assumed that the proteid include enzymes and grapes, which are important in biochemistry and technology of wine.
Proteins of grapes and wine are mainly represented by proteid, most of which have enzymatic activity. These include the proteid glycoproteins in carbohydrate fraction which include glucose, fructose, xylose, galactose.
In proteins of grapes in the greatest number found aspartic and glutamic acid and tryptophan, in the least - arginine, histidine, and methionine. Proteins grapes are quite diverse and include several factions.
When the grape processing contents of protein substances varies depending on the technology. Mark obtained by pressing, contains more proteins than the extract by gravity.
Heat treatment of grape juice and wine is a slight decrease in protein nitrogen. |
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