Carbohydrate Composition and Nutritional Quality for Rats of Sorghum Tô Prepared from Decorticated White and Whole Grain Red Flour

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Abstract
The carbohydrate composition and nutritional quality of acid, neutral and alkali tô, prepared from a decorticated white (DW) flour containing no polyphenols or whole grain red (WGR) flour high in polyphenols, were studied. The diets were characterized with regard to nonstarch polysaccharides, Klason lignin, resistant starch (RS) and amino acid content. The nutritional properties were studied in balance trials with rats. Digestible energy of DW flour was higher than that of WGR flour because of a lower dietary fiber (DF) content and a higher digestibility of DF. Recovery of cellulose in feces of rats fed diets containing DW flour was 45–59% and recovery of noncellulosic polysaccharides (NCP) was 17–31%. In rats fed diets derived from WGR flour, recoveries were 76–83 and 54–67% for cellulose and NCP, respectively. Cooking resulted in formation of appreciable amounts of RS. Twenty-three to fifty-six percent of the RS in DW tô and 59–74% of RS from WGR tô were recovered in feces. Endosperm protein kafirins formed complexes during cooking. The result was a lower true protein digestibility and higher biological value in tô than in flour. Amino acid data revealed that the unavailable kafirins serve as a nitrogen source for the hindgut microflora. A high affinity of dietary polyphenols for proline and glycine residues can be postulated from digestible amino acid data. The net effect was a change in the excretory route of nitrogen from urine to feces.