PECTIC SUBSTANCES AND TEXTURE OF FRENCH FRIED POTATOES

French fries made from low specific gravity potatoes are poor in texture and soggy in appearance. High specific gravity potatoes, on the other hand, produce mealy, firm and good-textured french fries. A comparison of raw potatoes of high and low specific gravity for protopectin, the degree of esterification, water-soluble pectins and divalent cations revealed no significant differences. Low specific gravity potatoes, however, were found to contain significantly higher levels of free calcium and lower degree of esterification of water-soluble pectins. Similar comparisons of french fries made from these potatoes showed that low specific gravity fries had a higher degree of protopectin de-esterification, greater breakdown of protopectin and higher levels of free calcium. It was concluded that protopectin of low specific gravity potatoes possesses fewer and/or weaker cross linkages, is poorly polymerized, and a substantial percentage of it breaks down on frying. This weakens the cell wall and results in a french fry of poor texture. © 1969 Springer.