Carotenoid Pigments in Tubers of the Katahdin Variety of Irish Potato

Flesh color in Irish potato varieties ranges from almost pure white to a deep canary yellow. The yellowish tinge of "white-fleshed'' varieties is intensified after dehydration, becoming a definite yellow if the tubers have been harvested in an immature state, as is the case with material grown in the south (1, 2). This residual yellow color, when it occurred, was at one time considered by the Army Quartermaster Corps to be due to a faulty technique in dehydration and as a result such material was graded downward. It was soon recognized, however, that this yellow color was due to the presence of naturally occurring carotenoid pigments. Caldwell, Brunstetter, Culpepper, and Ezell (3) showed that 19 "white-fleshed'' varieties, representing fully-matured material, averaged 0.021 mg. of total carotenoid pigments per 100 gm. fresh weight, while 3 normally yellow-fleshed varieties averaged 0.138 mg. per 100 gm. fresh weight. This means that when the total concentration of carotenoid pigments is about 1 p.p.m. on a dry weight basis, the yellow color of the dried product will be slight. When the total pigment concentration is about 7 p.p.m. dry weight, the dried product will have a marked yellow color. One of the findings of the present paper is that in the case of the Katahdin variety, harvested in an immature state, there was still a pronounced yellow color in the dried product when the concentration of carotenoid pigments was 3 p.p.m. dry weight. This paper reports an intensive study of the carotenoid pigments in three samples of the Katahdin variety, with the purpose of separating and identifying as many of the pigments as possible.