Prediction of starch hydrolysis in native starches studied in vitro

Starches from different botanical origin (sago, rice, wheat, corn, sweet potato, arrowroot, and potato as well as sweet potato meal, cassava pulp, and tapioca) with varying total starch (TS) and amylose content were assessed for hydrolysis in vitro by gastric enzymes and their starch fractions were characterized as rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). The relationship between starch hydrolysis (SH) and organic matter digestibility, as well as total variability among TS, amylose content, RDS, SDS, and RS fractions of these test starches were also studied. SH varied significantly ranging from 9.8% in potato starch to 85.5% in sago starch with organic matter digestibility (OMD) of 22.36 and 95.04%, respectively. Significantly positive relationships were also recorded between SH and OMD, SDS, RDS and a significantly negative relationship with RS. Prediction equations were proposed to estimate SH from OMD and TS, and the correlation between estimates and determined SH values was high (r=0.89, p<0.0001), alluding to the possibility of estimating SH in starches using OMD and starch content values, hence enabling fast screening and predictability of starch fermentation kinetics for various aspects of nutrition studies.