Changes of pectic substances concentration in potatoes and French fries and the effect of these substances on the texture of the final product.

The texture of fried potato products depends on the building elements present in the cell walls, which play the structure-forming function, as well as on physical and biochemical changes of those elements which take place in the potato tissue, when it is exposed to blanching or frying. For the research the tubers of four potato varieties (Ekra, Orlik, Sumak, and Bryza) were used, which served as material for the production of French fries. In the samples of potato tubers before and after peeling, as well as in French fries blanched in the solutions of 0.4% CaCl2 and 0.4% MgCl2 salts the contents of pectic substances and their effect on the texture of the final product were determined. The process of peeling potato tubers contributed to the decrease of the content of the pectic substances. On the average 20% of the content of water-soluble pectins and about 5% of protopectins was decreased. Water blanching and frying contributed to a further decrease of the pectic substances in French fries in relation to their content in the raw material. However, potato strips blanching in the solutions of calcium and magnesium salts prevents further loss of those substances in the final product. The presence of calcium and magnesium ions in the solution of the blanching salts caused their partial binding by the pectin substances present in the potato tissue, which resulted in the improvement of the texture of French fries, especially obtained from early potato varieties.