Physicochemical properties and in vitro digestibility of pulse starches and derivatized type 3 resistant starch
Date
2020-01-23
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
The objective of this thesis was to isolate and characterize pea, lentil and faba bean
starches from air-classified flours and to develop a novel type 3 resistant starch (RS3) from the
isolated pulse starches. In the pulse processing industry in Canada, the majority of pulse starches
are generated in the form of starch-rich flours from air classification. The first study aimed to
isolate starches of a high purity from the most common starch-rich pulse flours (i.e., pea, lentil
and faba bean) and to determine and compare the molecular structure, functional properties and
in vitro digestibility of the isolated pulse starches with those of four important commercial
starches (i.e., Roquette pea, normal maize, waxy maize and tapioca). The isolated pulse starches
showed amylose contents and amylopectin branch-chain-length (BCL) distributions similar to
that of Roquette pea starch. Consequently, the granular morphologies, crystalline structure,
thermal properties, pasting properties, gelling ability and in vitro digestibility of the isolated
pulse starches were comparable to those of Roquette pea starch but were distinctively different
from those of commercial maize and tapioca starches.
Because the isolated pea, lentil and faba bean starches exhibited similar amylose contents
and comparable amylopectin BLC distributions, the isolated pea starch was selected as the
representative pulse starch to develop a novel RS3 product through acid thinning, debranching
and recrystallization in the second study, with commercial normal maize starch being included
for comparison. Starting from the respective native starches, the modification method yielded
68.1% of RS3 from pea and 59.6% from normal maize. In vitro starch digestibility assay
revealed that pea RS3 (in both uncooked and cooked states) was less digestible to amylolytic
enzymes than normal maize RS3. The results obtained could be ascribed to the formation of
thermally more stable double-helical crystallites in the former, which consisted of a larger
proportion of intermediate chains and a smaller proportion of short chains when compared with
normal maize RS3. This study indicated that the developed modification method was effective to
increase the enzymatic resistance of pulse starch, which could be employed to prepare lowglycemic
food ingredients and expand new markets for the underutilized co-product.
Description
Keywords
starch-rich pulse flours, starch isolation, pea starch, type 3 resistant starch, in vitro digestibility
Citation
Degree
Master of Science (M.Sc.)
Department
Food and Bioproduct Sciences
Program
Food Science