BIOCHEMICAL AND NUTRITIONAL ASSESSMENT OF TUBERS FROM 16 CULTIVARS OF SWEET-POTATO (IPOMOEA-BATATAS L)

Proximate composition, starch content, total sugar content, mineral profile, trypsin inhibitor activity, and total oxalate content of tubers from 16 cultivars of sweetpotato (Ipomoea batatas L.) were determined. Sweetpotato cultivars differed (P < 0.05) with regard to all of these parameters. The amino acid composition of eight selected cultivars also showed differences among cultivars in the proportions of most amino acids. The mean in vitro digestibility of sweetpotato protein was 75.8%, which indicates that sweetpotato protein is well utilized. The apparent metabolizable energy values for poultry of sweetpotato tuber meals prepared from different cultivars ranged from 14.34 to 14.76 MJ/kg of dry weight (mean, 14.54 MJ/kg), highlighting the potential usefulness of sweetpotato tubers as an energy source in tropical regions. Trypsin inhibitor activity in the tubers was not related to the in vitro protein digestibility or apparent metabolizable energy values, suggesting that the presence of trypsin inhibitor does not influence the nutritive value of sweetpotato tubers, at least in the cultivars evaluated in this study.