Abstract:
This study aimed to make available data on some starch characteristics of
selected sweet potato (SP) cultivars available in Sri Lanka and to see
whether there is a correlation with the high glycaemic indices (>70) of
these tubers. Sweet potato varieties Ama, Wariyapola Red, Wariyapola
White and Dhawala were selected for the study. Both raw and boiled sweet
potato flours were used for the determination of size distribution of
carbohydrate by using SepharoseTM CL-6 B column with KOH and
carbohydrate contents were quantified by phenol-sulphuric assay. Bed
volume was determined using glucose (5mg/ mL). Amylose content of
flour was determined calorimetrically. High molecular weight carbohydrate
(HMWC; Kav< 0.2) contents of studied SP ranged between 7-11% in raw
and 6-10% in boiled flour. Intermediate molecular weight carbohydrate
(IMWC)(0.2<Kav<0.8) contents of both raw and boiled sweet potato
varieties were high and ranged between 86-89% and 89-94%. The low
molecular weight carbohydrate contents (LMWC; Kav> 0.8) constituted
<6% of carbohydrates in both raw and boiled, indicating low free sugar
content. Amylose contents of the raw and cooked samples were less than
30 indicating high amylo pectin contents in SP. The high amylo pectin with
intermediate molecular weight may have contributed to the high glycemic
indices observed in the sweet potato varieties.
