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The Influence of Cooked vs. Raw Maize on the Growth of Rats Receiving a 9% Casein Ration¹

Division of Nutrition, Departments of Biochemistry and Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee

Data have been presented confirming reports in the literature that limed maize permits more rapid growth of rats than does raw maize when added to a 9% casein, niacin-free diet. The finding that boiled maize was equivalent in this respect indicates that heat treatment alone increases the supplemental value of maize.

Amino acid analyses of raw maize, limed maize, and boiled maize failed to reveal striking differences in composition. In addition, those amino acids deemed most likely to increase the niacin requirement by producing an amino acid imbalance (lysine and threonine) did not alter growth when added to the cooked maize diets. From these data it is concluded that the cooked maize effect cannot be explained on the basis of an improved amino acid balance.

Chromatographic evidence was obtained for the presence of a "bound" form of niacin in raw maize. This "bound" form can be extracted with acidic 80% methanol and is quite stable in this solvent. The "bound" niacin is also readily extracted by distilled water at room temperature but is relatively unstable under such conditions, yielding free niacin on standing. Both limed and boiled maize were found by paper chromatography to contain only free niacin whereas raw maize contained either 100% "bound" niacin, in the case of acidic methanol extraction, or 30 to 60% "bound" niacin by water extraction. The lability of the "bound" form in aqueous solution suggests that the niacin present in maize occurs largely as the "bound" form as maintained by Kodicek et al. ('56). The conversion of this to free niacin by cooking in either limed water or water alone would appear to explain the superiority of these products in the diet of the rat.

The apparent unavailability of the "bound" form of niacin to the rat and pig (Kodicek et al., '56) suggests that this form may also be unavailable to the human. If so, this finding may explain, in part, the low incidence of pellagra in tortillaconsuming populations. However, the lability of the bound form in aqueous solution would tend to militate against this possibility.

Manuscript received 2 February 1957.

This article has been cited by other articles:

				S. H. Katz, M. L. Hediger, and L. A. Valleroy Traditional Maize Processing Techniques in the New World Science, May 17, 1974; 184(4138): 765 - 773. [PDF]