After‐Cooking Discoloration of Potatoes. Iron Content in Relation to Blackening Tendency of Tissuea

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Abstract
SUMMARY: Data are presented on the iron contents of stem and bud end, whole and deproteinized, extracts of 41 samples of potatoes representing various degrees of discoloration. The stem end generally contained more iron than the bud end. Statistical analysis of all samples treated as one group revealed a highly significant correlation (1% level) between increasing iron content and increasing degree of after‐cooking discoloration. Of the two types of iron studied, “free iron” and “protein iron,” the protein iron gave the higher degree of correlation with blackening.The highly significant correlation between iron values and degree of discoloration was lost in about half the cases when subgroups of the samples were formed according to location grown, crop year, and variety.The data revealed that the percentage of total iron associated with the protein is higher in the stem end of the potato. Also, the stem‐end protein contained considerably more iron than the bud‐end protein. The difference in iron content between stem‐end protein and bud‐end protein showed a highly significant correlation (1% level) with tendency to blacken.
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