Hydrolysis of Tropical Tuber Starches by Bacterial and Pancreatic α‐Amylases

Abstract

AbstractAction of porcine pancreatic and Bacillus subtilis α‐amylases on native tuber starches of yam (Dioscorea alata), sweet potato (Ipomea batatas) and tannia (Xanthosoma sagittifolium) was studied in comparison with the well known potato and cassava starches. Large differences in enzymes susceptibilities were observed when studied on 24h. Yam starch was 3.5% hydrolysed with 2,8 μkat amylase/g starch, three times less than potato and tannia starches while sweet potato starch was 53% hydrolysed, two times less than cassava starch. Except yam, level of hydrolysis was higher with porcine pancreatic amylase than with the Bacillus subtilis amylase while initial hydrolysis rate was lesser.Microscopic observations and image analysis pointed out that the polyhedric shaped granules of tannia, sweet potato and cassava starches were much more damaged than the spherical ones. Pitting occured preferentially on the edges of the granules and the enzymes penetrated into the starch granule by pores and canals of corrosion. Conversely to other starches, hydrolysis of yam starches evidenced greater differences between action of Bacillus subtilis and pancreatic α‐amylases. The enzymes acted by pitting some parts of the granules surface, the number of pores and their size being related to enzyme source.