Structural consequences of the interaction of puroindolines with gluten proteins.

The effect of puroindolines (PINs) on structural characteristics of wheat proteins was investigated in Triticum turgidum ssp. durum (cv. Svevo) and Triticum aestivum (cv. Alpowa) and in their respective derivatives in which PIN genes were expressed (Soft Svevo) or the distal end of the short arm of chromosome 5D was deleted and PINs were not expressed (Hard Alpowa). The presence of PINs decreased the amount of cold-SDS extractable proteins and the accessibility of protein thiols to specific reagents, but resulted in facilitated solvation of gluten proteins, as detected by tryptophan fluorescence measurements carried out on minimally mixed flour/water mixtures. We propose that PINs and gluten proteins are interacting in the grain or flour prior to mixing. Hydrophobic interactions between PINs and some of the gluten proteins modify the pattern of interactions among gluten proteins, thus providing an additional mechanistic rationale for the effects of PINs on kernel hardness.

Glycaemic response of proso millet-based (Panicum miliaceum) products.

The glycaemic response of millet foods and the effect of processing are not known. Therefore, decorticated proso millet was used to produce four types of common food products (biscuits, couscous, porridge and an extruded snack). Postprandial blood glucose response of these products (all containing 50 g of total starch) was compared to the same foods produced with refined corn, in a crossover human study with 12 healthy male participants (age 26.3 ± 3.8 yr; BMI 23.3 ± 2.8 kg/m2). Capillary blood samples were collected and glycaemic response was determined; differences were assessed using repeat measures ANOVA. Overall, the mean (±SEM) incremental area under the blood glucose response curve (mmol min/l) of the proso millet products was different from the corn products, but individual products (couscous = 66.7 ± 11.6, biscuit = 82.6 ± 13.7, extrudate = 198.7 ± 20.9, porridge = 40.1 ± 5.8) were not significantly lower (couscous = 43.5 ± 5.8, biscuit = 102.0 ± 10.3, extrudate = 198.7 ± 20.9, porridge = 52.2 ± 8.1) (p > .05). Glycaemic response of the products was not dependent on the grain type, but rather product matrix.

Extrusion of Rice, Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin.

The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion.

On the molecular structure of the amylopectin fraction isolated from "high-amylose" ae maize starches.

The amylopectin fractions from starch of a series of amylose-extender (ae) maize samples (HYLON(®) V, VII and VIII starches) were isolated and analysed for their molecular composition and structure. The fractions from all samples contained both a high and a low molecular weight fraction (HMF and LMF), of which LMF increased with the amylose content of the starch and appeared to have substantially more of long chains than HMF. A normal amylose-containing maize starch (NMS), which served as a reference sample, contained very little LMF, which suggested that LMF was the inherent result of the effect of the loss of starch branching enzyme IIb activity in the ae mutants. Clusters were isolated from the amylopectin fractions using Bacillus amyloliquefaciens α-amylase, which effectively hydrolyses long internal chain segments between clusters. During the hydrolysis process, clearly more of small dextrins were released from the ae starches in comparison to NMS. It appeared that some of these small dextrins did not precipitate in methanol together with the majority of the clusters. Nevertheless, isolated clusters from the HYLON starch samples were smaller than in NMS and the clusters possessed a lower density of branches with longer chains. The composition of small, branched building blocks was also clearly different: HYLON starch samples possessed much more of single-branched blocks and less multiple-branched blocks than NMS.

Assessment of Important Sensory Attributes of Millet Based Snacks and Biscuits.

There is an increasing push by consumers for new food products that can provide health benefits. To develop these products, sometimes it is necessary to look to alternative crops, 1 of which is millet. For millet to be successfully adopted by consumers, it is necessary to identify and develop product types that are acceptable to North Americans. Biscuits and extruded snacks were produced using varying amounts of refined proso millet flour (0%, 25%, 75%, and 100%). Sensory analysis was conducted on 8 products (4 types of biscuits and 4 types of extruded snack) in 2 separate tests (1 for biscuits and 1 for snacks). Preferred Attribute Elicitation (PAE), a relatively new sensory method, was used to determine attributes affecting liking of the products. Results indicated that as the amount of millet in the biscuits and extruded snacks increased, the liking of the flavor, texture and overall liking decreased. Millet contributed to a bitter taste and bitter aftertaste, and resulted in gritty and dry food products. Further work is required to refine the products tested as well as to identify further products that can be added to the diet in order to take advantage of the health benefits that millet provides.

Small differences in amylopectin fine structure may explain large functional differences of starch.

Four amylose-free waxy rice starches were found to give rise to gels with clearly different morphology after storage for seven days at 4°C. The thermal and rheological properties of these gels were also different. This was remarkable in light of the subtle differences in the molecular structure of the amylopectin in the samples. Addition of iodine to the amylopectin samples suggested that not only external chains, but also the internal chains of amylopectin, could form helical inclusion complexes. It is suggested that these internal helical segments participate in the retrogradation of amylopectin, thereby stabilising the gels through double helical structures with external chains of adjacent molecules. Albeit few in number, such interactions appear to have important influences on starch functional properties.

Impact of local hydrothermal treatment during bread baking on soluble amylose, firmness, amylopectin retrogradation and water mobility during bread staling.

The impact of hydrothermal processing undergone by bread dough during baking on the degree of starch granule disruption, on leaching of soluble amylose, on water mobility, on firmness and on amylopectin retrogradation during staling has been investigated. Two heating rates during baking have been considered (4.67 and 6.31 °C/min) corresponding respectively to baking temperature of 220 and 240 °C. An increase in firmness and in the amount of retrogradated amylopectin accompanied by a decrease in freezable water has been observed during staling. Although a lower heating rate yielded in larger amount of retrogradated amylopectin retrogradation, it resulted in a lower firmness. Additionally, the amount of soluble amylose and the relaxation times of water measured by Nuclear Magnetic Resonance NMR (T20, T21 and T22) decreased during staling. It was demonstrated that the amount of soluble amylose was higher for bread crumb baked at lower heating rate, indicating that an increasing amount of amylose is leached outside the starch granules. This was corresponding to a greater amount of retrograded amylopectin during staling. Moreover, it was found that the degree of gelatinization differs locally in a same bread slice between the top, the centre and the bottom locations in the crumb. This was attributed to the differences in kinetics of heating, the availability of water during baking and the degree of starch granule disruption during baking. Based on first order kinetic model, it was found that staling kinetics were faster for samples baked at higher heating rate.

Structural characterization of proteins in wheat flour doughs enriched with intermediate wheatgrass (Thinopyrum intermedium) flour.

The high protein and fiber content of intermediate wheatgrass (IWG) - together with its interesting agronomic traits and environment-related benefits - make this perennial crop attractive also for human consumption. Structural characteristics of the proteins in IWG/hard wheat flour (HWF) doughs (at IWG:HWF ratios of 0:100, 50:50, 75:25 and 100:0) - including aggregate formation, thiols availability, and secondary structure changes during dough mixing - were investigated. Proteins in IWG-doughs had higher solubility and thiol content - as function of IWG content - suggesting that protein network was mostly based on non-covalent interactions. While 50% IWG-enrichment gave an increase in random structures, enrichment at ⩾75% resulted in a decrease in ß-sheets with an increase in random structures, indicating a decrease in structural order. The observed differences in protein molecular configuration and interactions in HWF compared to IWG doughs necessitate further investigation to establish their impact on the quality of IWG-enriched bread.

Whole Soy Flour Incorporated into a Muffin and Consumed at 2 Doses of Soy Protein Does Not Lower LDL Cholesterol in a Randomized, Double-Blind Controlled Trial of Hypercholesterolemic Adults.

BACKGROUND: Soy protein may reduce coronary heart disease (CHD) risk by lowering LDL cholesterol, but few studies have assessed whether whole soy flour displays a similar effect. OBJECTIVE: The aim of this study was to assess the dose effect of whole soy flour incorporated into muffins on plasma LDL cholesterol in hypercholesterolemic adults. METHODS: Adults aged 30-70 y (n = 243) with elevated LDL cholesterol (≥3.0 and ≤5.0 mmol/L) were stratified by LDL cholesterol and randomly assigned to consume 2 soy muffins containing 25 g soy protein [high-dose soy (HDS)], 1 soy and 1 wheat muffin containing 12.5 g soy protein and 12.5 g whey protein [low-dose soy (LDS)], or 2 wheat muffins containing 25 g whey protein (control) daily for 6 wk while consuming a self-selected diet. Fasting blood samples were collected at weeks 0, 3, and 6 for analysis of plasma lipids [total, LDL, and HDL cholesterol and triglycerides (TGs)], glucose, insulin, C-reactive protein (CRP), and isoflavones. Blood pressures also were measured. Dietary intake was assessed at weeks 0 and 4 with the use of 3 d food records. Treatment effects were assessed with the use of intention-to-treat analysis with multiple imputation and LDL cholesterol as the primary outcome. RESULTS: In total, 213 (87.6%) participants completed the trial. Participants were primarily Caucasian (83%) and mostly female (63%), with a mean ± SD body mass index (in kg/m2) of 28.0 ± 4.6 and systolic and diastolic blood pressures of 122 ± 16 and 77 ± 11 mm Hg, respectively. Despite a dose-dependent increase in plasma isoflavones (P < 0.001), neither HDS nor LDS had a significant effect on LDL cholesterol compared with control (mean ± SEM changes: control, -0.04 ± 0.05 mmol/L; HDS, 0.01 ± 0.05 mmol/L; and LDS, -0.04 ± 0.06 mmol/L). There were no significant treatment effects on total or HDL cholesterol, TGs, CRP, homeostatic model assessment of insulin resistance, blood pressure, or the Framingham 10-y CHD risk score. CONCLUSION: Consuming 12.5 or 25 g protein from defatted soy flour incorporated into muffins does not reduce LDL cholesterol or other CHD risk factors in hypercholesterolemic adults. This trial was registered at clinicaltrials.gov as NCT01547585.

Thermal properties of barley starch and its relation to starch characteristics.

Amylopectin fine structure and starch gelatinization and retrogradation were studied in 10 different barley cultivars/breeding lines. Clusters and building blocks were isolated from the amylopectin by α-amylase from Bacillus amyloliquefaciens and their structure was characterized. Gelatinization was studied at a starch:water ratio of 1:3, and retrogradation was studied on gelatinized starch at starch:water ratio of 1:2, by differential scanning calorimetry. Three barley cultivars/breeding lines possessed the amo1 mutation, and they all had a lower molar proportion of chains of DP ≥38 and more of large building blocks. The amo1 mutation also resulted in a higher gelatinization temperature and a broader temperature interval during gelatinization. Overall, small clusters with a dense structure resulted in a higher gelatinization temperature while retrogradation was promoted by short chains in the amylopectin and many large building blocks.

Branching patterns in leaf starches from Arabidopsis mutants deficient in diverse starch synthases.

This is the first report on the cluster structure of transitory starch from Arabidopsis leaves. In addition to wild type, the molecular structures of leaf starch from mutants deficient in starch synthases (SS) including single enzyme mutants ss1-, ss2-, or ss3-, and also double mutants ss1-ss2- and ss1-ss3- were characterized. The mutations resulted in increased amylose content. Clusters from whole starch were isolated by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens. The clusters were then further hydrolyzed with concentrated α-amylase of B. amyloliquefaciens to produce building blocks (α-limit dextrins). Structures of the clusters and their building blocks were characterized by chromatography of samples before and after debranching treatment. While the mutations increased the size of clusters, the reasons were different as reflected by the composition of their unit chains and building blocks. In general, all mutants contained more of a-chains that preferentially increased the number of small building blocks with only two chains. The clusters of the double mutant ss1-ss3- were very large and possessed also more of large building blocks with four or more chains. The results from transitory starch are compared with those from agriculturally important crops in the context that to what extent the Arabidopsis can be a true biotechnological reflection for starch modifications through genetic means.

Structure of Arabidopsis leaf starch is markedly altered following nocturnal degradation.

Little is known about the thermal properties and internal molecular structure of transitory starch. In this study, granule morphology, thermal properties, and the cluster structure of Arabidopsis leaf starch at beginning and end of the light period were explored. The structural properties of building blocks and clusters were evaluated by using diverse chromatographic techniques. On the granular level, starch from end of day had larger granule size, thinner crystalline lamellae thickness, lower free surface energy of crystals, and lower tendency to retrograde than that from end of night. On the molecular level, the starch had lower amylose content, larger cluster size, and higher number of blocks per cluster at the end of day than at end of night. It is concluded that the core of the granules contains a more permanent molecular and less-ordered physical structure different from the transitory layers laid down around the core at daytime.

Evolution of amylopectin structure in developing wheat endosperm starch.

In this study, starches extracted from wheat grains harvested at 7, 14, 28, and 35 days after anthesis (DAA) were used as a means of examining the molecular structure of amylopectin (AP) from developing wheat grain. Scanning electron microscopy of wheat grain cross-sections revealed the presence of endosperm at 7 DAA and contained lenticular-shaped developing large (A-type) granules. From 14 DAA onward, spherical-shaped small (B-type) granules coexisted with large granules in the endosperm. During granule development, the fine structure of AP varied with maturity in both large and small granules. Towards the end of the pre-physiological maturity stage (28 DAA), AP in small and large granules had shortest external chain length (ECL), longest internal chain length (ICL) and lowest amount of A-chains. At physiological maturity (35 DAA), these changes in ECL, ICL and amount of A-chains were reversed when compared to 28 DAA. In both large and small granules, the external AP structure was apparently more organized at physiological maturity than at pre-physiological maturity.

Structure of clusters and building blocks in amylopectin from developing wheat endosperm.

Changes in internal structure of amylopectin (AP) during wheat endosperm development were studied by isolating clusters and building blocks of AP from both large A-type and small B-type starch granules at different maturity stages up to harvest time at 49 days after anthesis (DAA). Clusters isolated from B-type granules had a degree of branching (DB) of 16.5-16.8% and were more tightly branched than those isolated from A-type granules (DB 15.7-16.2%). The degree of polymerization (DP) of the clusters increased in both types of granules during the pre-physiological maturity stage up to 28 DAA. Clusters at maturity were smaller with less branches and building blocks than at the end of the pre-maturity stage. It is suggested that this was due to a continuous trimming of the cluster structure after the active period of starch synthesis. Differences were evident between A- and B-type granules with regards to glucan trimming and the type of new chains produced.

Distribution of branches in whole starches from maize mutants deficient in starch synthase III.

An earlier study explored the possibility of analyzing the distribution of branches directly in native, whole starch without isolating the amylopectin component. The aim of this study was to explore if this approach can be extended to include starch mutants. Whole starches from du1 maize mutants deficient in starch synthase III (SSIII) with amylose content of ∼30-40% were characterized and compared with the wild type of the common genetic background W64A. Clusters were produced from whole starch by hydrolysis with α-amylase of Bacillus amyloliquefaciens. Their compositions of building blocks and chains were analyzed further by complete α-amylolysis and by debranching, respectively, whereafter the products were subjected to gel permeation and anion exchange chromatography. The size and structure of the clusters were compared with those of their isolated amylopectin component. Whereas the whole starch of the wild type sample had a branched structure similar to that of its amylopectin component, the results showed that the du1 mutation resulted in more singly branched building blocks in the whole starch compared to the isolated amylopectin. This suggested that amylose and/or intermediate materials in whole du1 starches likely contributed to the composition of branches. This study explored an alternative procedure to characterize the composition of branches in the whole starch without fractionating the components.

Monoacylglycerol gel offers improved lipid profiles in high and low moisture baked products but does not influence postprandial lipid and glucose responses.

Structured emulsions, including monoacylglycerol (MAG) gels, are of interest as alternatives to shortenings rich in saturated and trans fatty acids (SFA and TFA). However, an understanding of their physical and nutritional functionality in baked products is limited. The objective of this randomized crossover study was to compare the postprandial lipid and glucose responses to two different baked product matrices produced with a MAG gel. Differences between study treatments are discussed in the context of underlying ingredient interactions impacting, primarily, starch digestibility. Healthy males (n = 18, 19-40 years, BMI ≤27 kg m(-2), waist circumference ≤102 cm, fasting plasma glucose <5.6 mmoL L(-1), insulin <180 pmol L(-1) and TAG <1.7 mmol L(-1)) attended six study visits, each separated by at least one week, and consumed one of six study treatments with subsequent blood sampling for 6 h for determination of triacylglycerol (TAG), glucose, insulin and free fatty acids (FFA). The study treatments consisted of sugar-free cakes and cookies (high and low moisture products, respectively) produced using either the canola oil-based structured MAG gel or the compositionally-equivalent MAG gel ingredients. Although MAG gel structure per se did not impact postprandial response, all cookies had higher TAG responses compared with cakes, even when matched for fat content. Sugar cookies containing 40 g of the MAG gel or an industry standard stearic-rich shortening were also compared, with no differences observed in postprandial response.

Hydrothermal treatment and iodine binding provide insights into the organization of glucan chains within the semi-crystalline lamellae of corn starch granules.

The importance of glucan chains that pass through both the amorphous and crystalline lamellae (tie chains) in the organization of corn starch granules was studied using heat-moisture treatment (HMT), annealing (ANN), and iodine binding. Molecular structural analysis showed that hylon starches (HV, HVII, and HVIII) contained higher proportion of intermediate glucan chains (HVIII > HVII > HV) than normal corn (CN) starch. Wide angle X-ray scattering revealed that on HMT, the extent of polymorphic transition in hylon starches decreased with increasing proportion of intermediate and long chains. Iodine treated hylon starches exhibited increased order in the V-type polymorphism as evidenced by the intense peak at 20° 2θ and the strong reflection intensity at 7.5° 2θ and the extent of the change depended on the type of hylon starch. DSC results showed that the gelatinization enthalpy of CN and waxy corn starch (CW) remained unchanged after ANN. However, hylon starches showed a significant increase in enthalpy with more distinct endotherms after ANN. It can be concluded that tie chains influence the organization of crystalline lamellae in amylose extender mutant starches.

The impact of milling and thermal processing on phenolic compounds in cereal grains.

Consumption of wholegrain foods has been recommended for healthy diets. The beneficial health properties of wholegrain products have been associated with the presence of higher amounts of dietary fiber and antioxidants and lower calories as compared to their respective refined ones. Phenolic compounds are mainly attributed to antioxidant properties of wholegrain foods. This review article provides a single comprehensive source that describes effects of milling and thermal processing on phenolic compounds and antioxidant properties in cereals. In general, milling and pearling processes affect the distribution of phenolic, compounds and thus antioxidant properties vary among the milling fractions. Thermal processes such as baking and extrusion could cause negative or positive effects on phenolic compounds and antioxidant properties of the end product subject to grain type and processing conditions. Thus factors that enhance health benefits of wholegrain cereal products have been discussed.

Influence of amylopectin structure and degree of phosphorylation on the molecular composition of potato starch lintners.

Morphology, molecular structure, and thermal properties of potato starch granules with low to high phosphate content were studied as an effect of mild acid hydrolysis (lintnerization) to 80% solubilization at two temperatures (25 and 45°C). Light microscopy showed that the lintners contained apparently intact granules, which disintegrated into fragments upon dehydration. Transmission electron microscopy of rehydrated lintners revealed lacy networks of smaller subunits. The molecular composition of the lintners suggested that they largely consisted of remnants of crystalline lamellae. When lintnerization was performed at 45°C, the lintners contained more of branched dextrins compared to 25°C in both low and intermediate phosphate-containing samples. High-phosphate-containing starch was, however, unaffected by temperature and this was probably due to an altered amylopectin structure rather than the phosphate content. After lintnerization, the melting endotherms were broad with decreased onset and increased peak melting temperatures. The relative crystallinity was lower in lintners prepared at 45°C. A hypothesis that combines the kinetics of lintnerization with the molecular and thermal characteristics of the lintners is presented.

Composition of clusters and building blocks in amylopectins from maize mutants deficient in starch synthase III.

Branches in amylopectin are distributed along the backbone. Units of the branches are building blocks (smaller) and clusters (larger) based on the distance between branches. In this study, composition of clusters and building blocks of amylopectins from dull1 maize mutants deficient in starch synthase III (SSIII) with a common genetic background (W64A) were characterized and compared with the wild type. Clusters were produced from amylopectins by partial hydrolysis using α-amylase of Bacillus amyloliquefaciens and were subsequently treated with phosphorylase a and ß-amylase to produce φ,ß-limit dextrins. Clusters were further extensively hydrolyzed with the α-amylase to produce building blocks. Structures of clusters and building blocks were analyzed by diverse chromatographic techniques. The results showed that the dull1 mutation resulted in larger clusters with more singly branched building blocks. The average cluster contained ~5.4 blocks in dull1 mutants and ~4.2 blocks in the wild type. The results are compared with previous results from SSIII-deficient amo1 barley and suggest fundamental differences in the cluster structures.