Comparative analysis of trypsin inhibitor levels in sweet potato cultivars in Sri Lanka

Abstract

Sweet potato [Ipomea batatas (L) Lam.] is a commonly consumed root crop in Sri Lanka. A study was undertaken to estimate the nutritional aspects in terms of trypsin inhibitory activity (TIA) of five different cultivars of sweet potato (SWP1-Wariyapola red, SWP3-Wariyapola white, SWP4-Pallepola, SWP5-Malaysian variety and SWP7-CARI 273) commonly consumed in Sri Lanka. The moisture level ranged between 65.0 ± 3.4 and 74.6 % ± 1.9 and the crude protein content varied between 1.2 ± 0.1 and 3.3 % ± 0.1. The TIA in unheated and heated sweet potato root samples varied between 1.9 ± 0.01 to 15.4 ± 0.4 and 0.156 ± 0.01 to 13.0 ± 0.01, respectively. In all the cultivars studied the TIA was significantly different at p < 0.05 and there was a significant reduction in TIA levels in all the heated samples compared to the raw samples. The highest TIA level was observed in SWP4 and the lowest in SWP1 in both heated and unheated samples. In terms of nutritive quality, SWP 7 cultivar was comparatively superior to the other cultivars studied with regard to the dry matter content, crude protein level and the TIA level per gram of protein. It may be possible to improve the nutritive quality of other cultivars through crop enhancing with high protein levels while lowering the TIA.