Elizabeth Donner

Composition, Molecular Structure, Properties, and In Vitro Digestibility of Starches from Newly Released Canadian Pulse Cultivars

ABSTRACT Pulse starches were isolated from different cultivars of pea, lentil, and chickpea grown in Canada under identical environmental conditions. The in vitro digestibility and physicochemical properties were investigated and the correlations between the physicochemical properties and starch digestibility were determined. Pulse starch granules were irregularly shaped, ranging from oval to round. The amylose content was 34.9–39.0%. The amount of short A chains (DP 6-12) of chickpea starch was much higher than the other pulse starches, but the proportions of B1 and B2 chains (DP 13-24 and DP 25-36, respectively) were lower. The X-ray pattern of all starches was of the C type. The relative crystallinity of lentil (26.2–28.3%) was higher than that of pea (24.4–25.5%) and chickpea starches (23.0–24.8%). The swelling factor (SF) in the temperature range 60–90°C followed the order of lentil ≈ chickpea > pea. The extent of amylose leaching (AML) at 60°C followed the order of pea ≈ chickpea > lentil. However, ...

Investigation of digestibility in vitro and physicochemical properties of A-and B-type starch from soft and hard wheat flour

ABSTRACT In this study, the functional properties of A- and B-type wheat starch granules from two commercial wheat flours were investigated for digestibility in vitro, chemical composition (e.g., amylose, protein, and ash content), gelatinization, retrogradation, and pasting properties. The branch chain length and chain length distribution of these A- and B-type wheat starch granules were also determined using high-performance anion exchange chromatography (HPAEC). Wheat starches with different granular sizes not only had different degrees of enzymatic hydrolysis and thermal and pasting properties, but also different molecular characteristics. Different amylose content, protein content, and branch chain length of amylopectin in A- and B-type wheat starch granules could also be the major factors besides granular size for different digestibility and other functional properties of starch. The data indicate that different wheat cultivars with different proportion of A- and B-type granular starch could result ...

Allelic variants of the amylose extender mutation of maize demonstrate phenotypic variation in starch structure resulting from modified protein–protein interactions

amylose extender (ae−) starches characteristically have modified starch granule morphology resulting from amylopectin with reduced branch frequency and longer glucan chains in clusters, caused by the loss of activity of the major starch branching enzyme (SBE), which in maize endosperm is SBEIIb. A recent study with ae− maize lacking the SBEIIb protein (termed ae1.1 herein) showed that novel protein–protein interactions between enzymes of starch biosynthesis in the amyloplast could explain the starch phenotype of the ae1.1 mutant. The present study examined an allelic variant of the ae− mutation, ae1.2, which expresses a catalytically inactive form of SBEIIb. The catalytically inactive SBEIIb in ae1.2 lacks a 28 amino acid peptide (Val272–Pro299) and is unable to bind to amylopectin. Analysis of starch from ae1.2 revealed altered granule morphology and physicochemical characteristics distinct from those of the ae1.1 mutant as well as the wild-type, including altered apparent amylose content and gelatinization properties. Starch from ae1.2 had fewer intermediate length glucan chains (degree of polymerization 16–20) than ae1.1. Biochemical analysis of ae1.2 showed that there were differences in the organization and assembly of protein complexes of starch biosynthetic enzymes in comparison with ae1.1 (and wild-type) amyloplasts, which were also reflected in the composition of starch granule-bound proteins. The formation of stromal protein complexes in the wild-type and ae1.2 was strongly enhanced by ATP, and broken by phosphatase treatment, indicating a role for protein phosphorylation in their assembly. Labelling experiments with [γ-32P]ATP showed that the inactive form of SBEIIb in ae1.2 was phosphorylated, both in the monomeric form and in association with starch synthase isoforms. Although the inactive SBEIIb was unable to bind starch directly, it was strongly associated with the starch granule, reinforcing the conclusion that its presence in the granules is a result of physical association with other enzymes of starch synthesis. In addition, an Mn2+-based affinity ligand, specific for phosphoproteins, was used to show that the granule-bound forms of SBEIIb in the wild-type and ae1.2 were phosphorylated, as was the granule-bound form of SBEI found in ae1.2 starch. The data strongly support the hypothesis that the complement of heteromeric complexes of proteins involved in amylopectin synthesis contributes to the fine structure and architecture of the starch granule.

Starch chain interactions within the amorphous and crystalline domains of pulse starches during heat-moisture treatment at different temperatures and their impact on physicochemical properties

Pulse (faba bean [FB], black bean [BB] and pinto bean [PB]) starches were heat-moisture treated (HMT) at 80, 100 and 120°C for 12h at a moisture content of ∼23%. Structural changes on HMT were monitored by microscopy, HPAEC-PAD, ATR-FTIR, WAXS, DSC and susceptibility towards acid and enzyme hydrolysis. Amylopectin chain length distribution remained unchanged in all starches on HMT. In all starches, HMT increased crystallinity and gelatinisation temperatures. The gelatinization enthalpy remained unchanged in some starches, whereas it decreased slightly in other starches on HMT. Slowly digestible starch content decreased at all temperatures of HMT, whereas resistant starch content increased at HMT80 and HMT100 (HMT80>HMT100), but decreased at HMT120. Birefringence, B-type crystallites and acid hydrolysis decreased on HMT. The extent of the above changes varied amongst starch sources and genotypes. HMT altered the X-ray pattern from A+B→A. The results of this study showed that structural reorganisation of starch chains during HMT temperature was influenced by starch chain flexibility, starch chain interactions and crystalline stability of the native granules.

Composition, structure, morphology and physicochemical properties of lablab bean, navy bean, rice bean, tepary bean and velvet bean starches

The composition, morphology, structure and physicochemical properties of starches from lablab bean, navy bean, rice bean, tepary bean and velvet bean were examined. Starch yield (on a whole seed basis), total lipid, apparent amylose (AM) and starch damage were in the range 20.6-29.9%, 0.48-0.62%, 22.1-32.1% and 0.004-0.011%, respectively. Difference in amylopectin chain length distribution amongst the starches was marginal. The starches differed significantly with respect to granule morphology, molecular order, molecular orientation, double helical content, gelatinization parameters, swelling factor, AM leaching, thermal stability and enzyme hydrolysis. The results showed that interplay amongst differences in molecular order, double helical content, relative crystallinity, AM content, granule morphology and the extent of interaction between and amongst starch chains within the amorphous and crystalline domains, influenced thermal, rheological and digestibility properties.

Advanced Analytical Techniques to Evaluate the Quality of Potato and Potato Starch

Publisher Summary The potato is an important vegetable and can be consumed in different forms, either fresh as table stock or processed into various products. The quality of potato tubers for table and processing use depends on genetic and environmental factors, and storage temperature, duration, and subsequent conditioning. Starch is the major carbohydrate in potato and is an agriculturally important commodity with many food and nonfood uses. It is the basic source of energy for a majority of the worlds population. Since starch is the major component of the dry matter of potato, its molecular organization and interactions with nonstarch polysaccharides and sugars are important factors influencing sensory attributes and shelf life of potato products, such as mashed potatoes, French fries, and potato chips. Starch plays a major part in supplying the metabolic energy that enables the body to perform its different functions. Starch is classified into rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS), according to the rate of glucose release and its absorption in the gastrointestinal tract.

Physicochemical properties and in vitro starch digestibility of potato starch/protein blends

This study aimed to investigate effects of starch-protein interactions on physicochemical properties and in vitro starch digestibility of composite potato starch/protein blends (0, 5, 10, or 15% protein) during processing (cooking, cooling and reheating). The effect on recrystallization and short-range ordering in starch was studied by light microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy. The results show that protein in the blend proportionally restricted starch granule swelling during cooking and facilitated amylopectin recrystallization during cold-storage. The facilitating effect of protein diminished with increasing blend ratio. Resistant starch content in the processed blends was positively correlated to intensity ratio of 1053/1035cm(-1) in FTIR spectra arising from slow retrogradation of amylopectin (r(2)>0.88, P≤0.05), whose formation was favored by the presence of protein in the blends and further enhanced by cooling of cooked blends. As a conclusion, starch-protein interaction reduced starch digestibility of the processed blends.

Preparation and characterization of soy protein films with a durable water resistance-adjustable and antimicrobial surface

A water resistant surface was first obtained by immobilizing hydrophobic copolymers, poly (styrene-co-glycidyl methacrylate) (PSG), with functional groups on soy protein isolate (SPI) films. XPS and AFM results showed that PSG copolymers were immobilized on the film by chemical bonding, and formed a rough surface with some bumps because of the segregation of two different phases on PSG copolymers. Water resistance of the modified films could be adjusted dramatically by further immobilizing different amounts of guanidine-based antimicrobial polymers, poly (hexamethylene guanidine hydrochloride) (PHMG) on the resulting hydrophobic surface. The introduction of hydrophilic PHMG on the resulting surface generated many micropores, which potentially increased the water uptake of the modified films. Furthermore, the modified SPI films showed higher thermostability compared to native SPI film and broad-spectrum antimicrobial activity by contact killing, attributed to the presence of PHMG on the surface. The modified SPI film with a multi-functional surface showed potential for applications in the packaging and medical fields.

Resistant Starches in Foods

As an emerging functional food ingredient, resistant starch has been shown to have equivalent and/or superior impacts on human health similar to conventional fiber. Resistant starch has been introduced to human nutrition and the food industry in recent years as an increasingly important functional food ingredient. Unlike some carbohydrates and digestible starches, resistant starch resists enzymatic hydrolysis in the upper gastrointestinal tract, resulting in little or no direct glucose absorption. In addition, there is increased microbial fermentation production of short-chain fatty acids (SCFAs) in the large intestine, a typical phenomenon of fiber consumption.

Effect of roasted pea flour/starch and encapsulated pea starch incorporation on the in vitro starch digestibility of pea breads

Oven or microwave roasting and alginate encapsulation of pea flour and starch to produce novel pea ingredients for enrichment of slowly digestible starch (SDS) and resistant starch (RS) content in pea bread were investigated. Pea flour treated either by oven roasting (160°C, 30min) or by microwave roasting (1.1kW, 6min) effectively retained its low starch digestibility similar to its native form (∼25% SDS; ∼60% RS). When oven roasting was applied to pea starch, SDS content increased triply compared to the fully boiled counterpart. Alginate encapsulation effectively controlled carbohydrate release to simulated gastric, intestinal and colonic fluids, and thus largely enriched the SDS and RS fractions in starch. Pea bread containing up to 37.5% of encapsulated roasted MPS pea starch not only provided high SDS and RS fractions (23.9% SDS and 30.2% RS) compared to a white bread control (0.2% SDS and 2.5% RS), but also provided an acceptable palatability.