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Pullulanase (P) and ultrasonication (U) were simultaneously applied to debranch pea starch to enhance slowly digestible starch (SDS) and resistant starch (RS) fractions in the debranched pea starch (DPS). A synergistic debranching effect was found under conditions of pullulanase (40 npun/g) and ultrasonication (100% amplitude in pulse mode, 1 min on followed by 9 min off), which produced 73.5% linear glucans, 18% SDS and 26% RS in the resulting DPS-PU after 6 h of debranching. Even when autoclaving the DPS-PU at 118 °C for 30 min, following cooldown, 11% SDS and 25% RS were retained in the DPS-PU, compared with 0% SDS and 12% RS in autoclaved native pea starch. The SDS fraction in autoclaved DPS-PU further increased to 16% while the RS content remained constant during 14 days of cold storage. In summary, DPS-PU is high in linear glucans, low in starch digestibility and has a thermally stable RS fraction., (Copyright © 2018. Published by Elsevier Ltd.)

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., (Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.)

Consumption of pulses is associated with many health benefits by mechanisms that are not fully understood. This study sought to identify the starch component(s) in cooked lentils responsible for lowering postprandial glycemic response (PPGR). Rapidly digestible (RDS), slowly digestible (SDS) and resistant starch (RS) content of 20 varieties of cooked lentil were determined by in vitro methods and 8 varieties, representing a linear range of SDS, were chosen for a human trial with 10 participants to determine PPGR and glycemic index (GI). Among the 20 lentil varieties, RS accounted for 35% of the variation of in vitro area under the starch hydrolysis curve (SHAUC) (r = -0.587; p < 0.01), but RDS (r = 0.401; p = 0.080) and SDS (r = -0.022; p = 0.927) were not significantly related to SHAUC. Multiple linear regression of in vitro data resulted in an equation [SHAUCest = 30.9RDS - 63.6RS + 9680] that accounted for 70% of the variance in SHAUC, with SDS excluded due to collinearity. In the human trial all 8 lentils had low GI values (10 to 23). Neither GI nor area under the glucose response curve (AUC) was significantly related to RDS, SDS or RS (minimum p = 0.24). However, SHAUC and SHAUCest, respectively, were related to both GI (r = 0.704, p = 0.051; r = 0.773, p = 0.024) and AUC (r = 0.765, p = 0.027; r = 0.822, p = 0.012). These results confirm that lentils have low GI values, which is not reliably predicted by their RDS, SDS and RS contents when considered individually. However, in vitro SHAUC and a combination of RDS and RS may be predictive of the PPGR of lentils.

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., (Copyright © 2016. Published by Elsevier Ltd.)

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-(32)P]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 Mn(2+)-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.

Summary: The aim of this study was to develop a novel and entirely potato‐based staple bread. Bread‐making performance of individual potato components (starch, protein and fibre) were independently evaluated and optimised by their ternary mixture. Flours from yellow and purple potatoes were then incorporated up to 25% of full formula weight to maximise the utilisation of resources. Fresh tuber was further added up to 50% for the full benefits from potatoes. The excessive oven‐rising after the crust hardened was manipulated by delicately balancing the strong swelling power of potato starch, which effectively resolved the cracks on the crust. The resultant potato breads showed a typical bread appearance, loaf size, low porosity but high cell density crumb structure and unique favourable sensory qualities, especially those with 2% potato fibre or 30% fresh tuber. Potato breads staled quickly during storage, but reheating could reverse the bread staleness to a nearly freshly baked state. [ABSTRACT FROM AUTHOR]

Summary: Physicochemical and nutritional properties of flour and isolated starch from eight Canadian lentil cultivars were assessed to identify unique samples and key factors affecting starch digestion. The results showed that nearly half of apparent amylose in lentil flours was underestimated because it was complexed and embedded within the flour matrix, which led to slower starch digestion of cooked flour. Cooked red lentil flours showed significantly higher resistant starch content (11.0%) than flours from green lentils (6.8%) (P < 0.05). Among green lentils, Asterix and Greenland were unique for their high slowly digestible starch content after cooking, possibly owing to their high phenolic content and α‐glucosidase inhibitory activity. Long‐ and short‐range ordering in starch was more indicative of low starch digestion for raw or cooked lentil flour rather than for isolated starch. The results suggest the flour matrix protects the starch ordered structure from enzyme hydrolysis. [ABSTRACT FROM AUTHOR]

The present work examines the ability to reactively modify a pea starch by phosphorylation in a twin-screw extruder without the loss of its granular form, in order to produce a product for functional food uses. This reaction was studied by varying formulation variables of moisture content as well as reactant and sodium sulfate concentration at 95°C and 150 rpm. The modified starch was characterized for its phosphorus content, in vitro digestibility by the Englyst method, thermal gelatinization properties, and pasting behavior. Phosphorus contents of intact starch granules as high as 0.3% were found (close to the 0.4% limit for foods), produced continuously under extrusion conditions corresponding to a residence time of approximately one minute. Higher moisture content and low sodium sulfate concentration favored higher phosphorus content but increased the chances of amylose leaching and agglomerating of the exiting granules. In all cases, the pea starch experienced some change in its gelatinization transition consistent with simultaneous heat-moisture treatment occurring along with the reaction inside the extruder. The current configuration of the process was not found suitable to major increases in resistant starch content though minor improvements in slowly digestible starch content were reported. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, three potato varieties were treated with chlorpropham (CIPC, 35ppm), γ-irradiated (0.1kGy) and stored for up to 5months at 8°C, and the physicochemical properties and in vitro starch digestibility of native and cooked starches were investigated. Sprouting was found to be satisfactorily suppressed by γ-irradiation and CIPC treatment. However, irradiation increased total free glucose content in two potato varieties, and decreased the thermal transition and pasting temperature of starch. The crystallinity of starch in irradiated potatoes decreased significantly (p ⩽0.05) which may explain its decreased resistant starch content. Sprout inhibiting treatments and storage had no effect on in vitro starch digestibility in cooked starches, but cooling cooked starch significantly (p ⩽0.05) increased its resistant starch content. [Copyright &y& Elsevier]

Abstract: This study investigated synergistic impact of amylose and phosphorus on the rheological, thermal, structural and nutritional properties of native potato starch, dry starch gel and freshly cooked gel. The results indicated that starch with a high amylose level and higher phosphorus content showed enhanced retrogradation extent, associated with a well-formed and rigid gel structure and more ordered structure, compared to starch with a lower phosphorus content. Phosphorus content in starch was positively correlated to resistant starch content in native starch (p <0.001) and to the slowly digestible starch content in the starch gel (p <0.05). Amylose content alone appeared not to be a good indicator of the starch digestibility. Phosphorus content played a dominant role in some physicochemical properties of starch when the amylose content was above a threshold level. The temperature ramp test appeared to be a sensitive method to detect the re-crystallisation of starch molecules during the early stages of retrogradation. [Copyright &y& Elsevier]

Abstract: Amylose, the amount of which varies significantly depending on the source, is one of the key components of starch. The proportion of the essentially linear amylose and the highly branched amylopectin greatly influences the physico-chemical properties of starch. In this study, potentiometric titration using an auto-titrator and colorimetric methods were compared for determining amylose contents of a variety of starch samples. Potentiometric titration results for starches from a variety of botanical sources were within the reported literature ranges while the colorimetric method seemed to overestimate amylose content. [Copyright &y& Elsevier]

Abstract: Starch was extracted from irradiated and stored potato tubers and the properties were compared to CIPC (chlorpropham) treated tubers. The granule properties and dynamic viscoelasticity in temperature ramp and frequency sweep modes were studied while heating the samples. Starch structural characteristics were investigated by high performance anion exchange chromatography (HPAEC) and Fourier transform infrared spectroscopy (FTIR). Gamma-irradiation of potato tubers at a dosage of 0.1kGy induced some degradation of starch molecules, resulting in earlier swelling of starch granules, and greater extents of amylose and total carbohydrate leaching. The early swelling phenomenon was also enhanced with tuber storage time. The retrogradation rate and extent for a concentrated starch gel also increased with tuber storage time whereas γ-irradiation delayed the gel retrogradation. Sprout inhibiting methods could be selected based on the specific processing and texture requirements of the end products. [Copyright &y& Elsevier]

Organic acids (5% lactic acid and 5% acetic acid, w/v) and biosolvents (5% ethyl lactate, 5% and 10% d‐limonene, w/v) are used as extraction agents during starch isolation from pea flour. NaOH at 0.4% w/v served as a control. The results show few differences in starch granular morphology, apparent amylose content, and most thermal parameters, and negligible differences in starch crystalline structure. However, noticeable differences are observed in protein and starch damage content, and pasting viscosities among starch isolated by different extraction agents. The starch extracted by 5% ethyl lactate has the highest protein residue (1.1%) compared to others (≤0.4%), while the starch extracted by 5% acetic acid shows the lowest pasting viscosities. d‐Limonene at 5% seems to be a promising biosolvent to isolate pea starch for its low residual protein, and no solvent residue, yet the highest pasting viscosities in starch. Fourier transform infrared spectroscopy (FTIR) detects bands of residual protein in all samples, and also unique bands at 1564, 1575, and 1720 cm−1 related to acid residue in starches extracted by the two organic acids. Chemometric analysis of FTIR spectra differentiates starches extracted by biosolvents from those extracted by alkali and acidic agents. [ABSTRACT FROM AUTHOR]

The present work examines the ability to reactively modify pea starch by lipid complexing in a twin‐screw extruder in order to produce a functional food product. The study considers the influence of moisture content, lipid type (myristic acid, palmitic acid) and content, in tests with differing screw designs to reduce enzymatic digestion. The modified starch was characterized for its physicochemical properties (bound lipid content, pasting properties, and Englyst digestion profiles). With near complete conversion at all tested lipid concentrations, differences found in enzyme resistance and pasting properties for the extruded samples were attributed to differences in the mixing environment. The lipid complexed pea starches under optimized conditions achieved a significant but moderate increase in either resistant starch (from 7.8% to 20%) or slowly digestible starch (from 12% to 23%) content compared to their native counterparts; however, the sought nutritional fractions (slowly digestible and resistant) could only be improved simultaneously with palmitic acid. The highest resistant fraction produced in the study corresponded to the higher shear environment tested and for complexes prepared at the highest lipid content. [ABSTRACT FROM AUTHOR]