Characteristics of native and enzymatically hydrolyzed common wheat (Triticum aestivum) and dicoccum wheat (Triticum dicoccum) starches

Abstract

The compositional, structural, and enzymatic digestibility of starches isolated from common wheat and dicoccum wheat were determined to find out the possible reason for hypoglycemic nature of dicoccum wheat. The gelatinization temperature range (65±3 °C) as well as the elution profile of both the starches on Sepharose CL-2B gel were comparable, but the peak (PV, 233 RVU) and set back viscosity (SB, 140 RVU) of dicoccum wheat starch were higher than common wheat starch (PV, 211 RVU; SB, 113 RVU) as recorded in rapid visco-analyser (RVA). The degree of crystallinity (DOC: 29%) and the thermal energy (TE: 142.35 J) of dicoccum wheat starch were considerably higher than the DOC (23%) and TE (67.82 J) of the common wheat starch. The starches were digested with alpha-amylase (human salivary), beta-amylase (barley malt), pullulanase (Klebsiella pneumoniae), and amyloglucosidase (Aspergillus niger), and the solubilized fraction was separated from the undigested fraction (residue) by centrifugation. Characterization of the sugars in the solubilized fraction from alpha-amylase were glucose, maltose, and oligosaccharides of 3–7 DP, maltose from beta-amylase, maltotriose from pullulanase and glucose from amyloglucosidase. However, the molecular weight (Mw) of the residues from the enzymatic digestion of dicoccum wheat starch was slightly higher than that of the common wheat starch. The microscopic examination of residues also exhibited a few bigger chunks in case of dicoccum wheat starch and a large number of smaller sized pieces in the case of common wheat starch. Since, starch is the major component of wheat, these parameters may help to explain subtle differences in the digestibility that exist between common wheat and dicoccum wheat.