| Popis: |
Almost all currently used technologies for the food production are related to the melanoidinformation reaction, which has a significant effect on appearance, taste, nutritional value and consumer properties of the foodstuffs. To assess the effect of heat treatment of food products on their nutritional value, food model systems protein hydrolyzate - glucose, hydrolyzate protein - xylose, hydrolyzate protein - fructose (1:5) have been investigated. The influence of the presence of reducing sugars, the temperature and the duration of heating on the content of amino acids and the extinction of solutions of model food systems have been studied. Linear dependences of the decrease in the total amino acid content in model food systems on the duration of the melanoidin formation reaction have been found. The loss of the total amino acid content when heating to 120 °C for 120 min was 23.9%; at the same time the content of essential amino acids reduced by 15.5-24.6%. The addition of xylose intensified the process of destruction of amino acids in the model system by 12.7%, at the same time glucose provoked the destruction of amino acids by only 2.3%. It has been established that amino acids threonine, isoleucine and histidine were unstable to destruction, regardless of the type of added sugar. When white wheat bread was heated, the loss of its nutritional value was established by reducing the content of such essential acids as threonine (by 26.5%), methionine (by 21.2%), lysine (by 13.3%) and valine (by 12,1%). It was noted that at the same temperature with increasing time of the melanoidin formation reaction, the content of amino acids in the system decreased with simultaneous intensification of the staining of the solutions. Extinction of model food systems varied according to the following equations: hydrolyzate-glucose - y = 0.0022x, hydrolyzate-xylose - y = 0.0028x, hydrolyzate-fructose - y = 0.0032x. |
