Reliable measurements of the size distributions of starch molecules in solution: Current dilemmas and recommendations

Characterization of structure-function properties relevant to copper-activated pyrite depression by different starches

Starches can adsorb on and depress copper-activated pyrite desirably during flotation, an important process in ore mineral extraction. In order to develop structure/function relationships, adsorption on and depression properties of copper-activated pyrite at pH 9 by normal wheat starch (NWS) and high-amylose wheat starch (HAW), dextrin, and a range of oxidized normal wheat starches (peroxide and hypochlorite treated) were investigated. Adsorption isotherms and bench flotation performance were compared with kinematic viscosity, molar mass distribution, surface coverage, and substituted functional groups assay. The differences in molar mass distribution and substituted functional groups among oxidized starches had little influence on the depression of copper-activated pyrite. However, the introduction of -C=O and -COOH substituents, combined with depolymerization, improved solubility and dispersibility, reduced aggregated structures, and strengthened surface binding of oxidized polymers, compared with NWS and HAW. At high concentrations, HAW, NWS, and dextrin were adsorbed onto the pyrite surface more than oxidized starches. However, at the low concentrations of depressant used in flotation, oxidized starches were more effective at selectively masking copper sites. This study suggests that a stable chelation between Cu(I) and starch ligands is necessary for depression of copper-activated pyrite at pH 9, which can be achieved with oxidized wheat starch.

Size selectivity in adsorption of polydisperse starches on activated carbon

The influence of molecular weight, polydispersity, and degree of branching of four potato starches (Paselli MD10, Eliane MD6, Eliane MD2, and highly branched starch) on the adsorption rates on activated carbon (Norit CA1) was investigated. Changes in starch concentration and size distribution over time were analysed by Total Starch Assay and Size Exclusion Chromatography. Average molecular weight and degree of branching of a starch scaled negatively with average adsorption rate. Within a size-distribution, adsorption rates scaled negatively with increasing molecule size, resulting in an increased average molecular weight in solution of between 25 % and 213 % and a decreased polydispersity of between 13 % and 38 %. Simulation with dummy distributions estimated the ratio of adsorption rates for 20th percentile and 80th percentile molecules within a distribution to range between a factor 4 and 8 for the different starches. Competitive adsorption decreased the adsorption rate of molecules above the average size within a sample distribution.

Effect of modification by maltogenic amylase and branching enzyme on the structural and physicochemical properties of sweet potato starch

Sweet potato starch (SPSt) was treated sequentially with the combination of maltogenic amylase (MA) and branching enzyme (BE) (MA → BE) or BE and MA (BE→MA) to modify its structural and physicochemical properties. Following the MA → BE and BE→MA modifications, the degree of branching was increased from 12.02 % to 44.06 %; whereas, the average chain length decreased from 18.02 to 12.32. Fourier-transform infrared spectroscopy and digestive performance analysis indicated that the modifications reduced hydrogen bonds and increased resistant starch in SPSt. Rheological analysis revealed that the storage and loss moduli of the modified samples were lower than those of the control samples, except for starch treated with MA alone. X-ray diffraction measurements suggested that the re-crystallisation peak intensities of the enzyme-modified starches were lower than those of the untreated sample. The retrogradation resistance ability of the analysed samples followed the order: BE→MA-starches > MA → BE-starches > untreated starch. The relationship between the crystallisation rate constant and short branched chains (DP_6-9) was well described by linear regression. This study provides a theoretical foundation for retarding the retrogradation of starch, which can improve food quality and extend the shelf-life of enzymatically modified starchy foods.

Polymer-Solvent Interactions in Modified Starches Pastes-Electrokinetic, Dynamic Light Scattering, Rheological and Low Field Nuclear Magnetic Resonance Approach

Starch paste is a very complex dispersion that cannot be clearly classified as a solution, colloid or suspension and many factors affects its properties. As these ambiguities constitute a barrier to technological development, the aim of this study was to investigate the interaction of starch macromolecules with water by analysing the results of rheological properties, low field nuclear magnetic resonance (LF NMR), dynamic light scattering (DLS) and ζ potential analyses. Starch pastes with a concentration of 1%, prepared with distilled water and buffered to pH values of 2.5, 7.0 and 9.5 were analysed. It was proved that the pH buffering substantially decreased the values of consistency index but the pH value itself was not significant. LF NMR studies indicated that the dissolution of starch in water resulted in a reduction in spin-lattice as well as spin-spin relaxation times. Moreover, changes in relaxation times followed the patterns observed in rheological studies. Electrokinetic and DLS analyses showed that potential values are primarily influenced by the properties of the starches themselves and, to a lesser extent, by the environmental conditions. The conducted research also showed complementarity and, to some extent, substitutability of the applied research methods as well as exclusion chromatography (a method not used in this work).

An allelic series of starch-branching enzyme mutants in pea (Pisum sativum L.) reveals complex relationships with seed starch phenotypes

A set of mutant pea lines carrying induced mutations within the major seed-expressed starch-branching enzyme gene has been characterised at the molecular, chemical and agronomic levels. Eight of the induced mutations, three of which predicted a premature stop codon, were compared with the naturally occurring starch-branching enzyme mutation within the same genetic background. Starch, amylose and sugar measurements, coupled with analysis by ultra-high performance liquid chromatography-size exclusion chromatography of starches, identified a range of phenotypes which were grouped according to the nature of the mutation. Homology modelling of proteins supported the differences in phenotypes observed. Differences in field performance were evident for selected mutants, particularly in seed yield and mean seed weight traits for early compared with late spring sowings. The data show the potential of an allelic series of mutants at this locus for nutritional studies. CHEMICAL COMPOUNDS: starch, amylose, amylopectin, raffinose, stachyose, verbascose.

The Effect of Chemical Modification on the Rheological Properties and Structure of Food Grade Modified Starches

Starch in its pure form can be used as a functional component of numerous food products; however, much better results both in terms of technological and economical aspects are obtained with the use of modified starches. The aim of the work was to establish how chemical modification affects the molecular structure of potato starch and, as a consequence, its rheological properties as well as texture forming ability. Commercial food-grade potato starch preparations oxidized starch, acetylated starch, distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate were the investigated material. The experimental methods included: viscographic analysis of pasting properties, flow rheometry, texture profile analysis, size exclusion chromatography with triple detection. The obtained data were further analyzed employing principal component and hierarchical cluster analysis. It was found that chemical modification leads to substantial changes in the molecular and functional properties of starch products. Oxidation process leads to depolymerization, which causes a substantial decrease in viscosity. Acetylation results mostly in stabilization of rheological properties during thermal processing. Crosslinking of starch leads to an improvement in thickening capabilities, while the type of crosslinking agent used for modification has a secondary effect. Sterilization of all types of modified potato starch pastes leads only to minor changes in their texture and rheological properties.

Physicochemical impact of cellulose nanocrystal on oxidation of starch and starch based composite films

A cellulose nanocrystal based oxidation system is developed for oxidizing starch in the presence of NaClO, and provides an alternative and green method to improve the oxidizing degree of oxidized starch. The underlying mechanism for the oxidation was studied with confocal laser scanning microscopy. It was found that cellulose nanocrystal would penetrate into the starch microparticles and contribute to oxidation. The function of cellulose nanocrystal on the physicochemical properties of oxidized starch was investigated. With the incorporation of the oxidized starch into starch/polyvinyl alcohol/glyceryl composite films, the mechanical property and transparency of the films improved substantially. The highest oxidation level of starch was attained at 0.5 wt% cellulose nanocrystal dosage and the carboxylate content was 1.10%, the composite film showed the maximum transparency of 0.66 and highest contact angle of 102.0°. Meanwhile, the best film was obtained with oxidized starch containing 1.0 wt% cellulose nanocrystal. Compared to native starch and TEMPO-oxidated starch, the cellulose nanocrystal-based oxidized starch improved the hydrophobicity of film more substanially. In conclusion, cellulose nanocrystal acts as prooxidant and reforcing agent in this starch-based composite film, which makes them promising materials in the preparation of novel composite materials.

Monovalent Salt and pH-Induced Gelation of Oxidised Cellulose Nanofibrils and Starch Networks: Combining Rheology and Small-Angle X-ray Scattering

Water quality parameters such as salt content and various pH environments can alter the stability of gels as well as their rheological properties. Here, we investigated the effect of various concentrations of NaCl and different pH environments on the rheological properties of TEMPO-oxidised cellulose nanofibril (OCNF) and starch-based hydrogels. Addition of NaCl caused an increased stiffness of the OCNF:starch (1:1 wt%) blend gels, where salt played an important role in reducing the repulsive OCNF fibrillar interactions. The rheological properties of these hydrogels were unchanged at pH 5.0 to 9.0. However, at lower pH (4.0), the stiffness and viscosity of the OCNF and OCNF:starch gels appeared to increase due to proton-induced fibrillar interactions. In contrast, at higher pH (11.5), syneresis was observed due to the formation of denser and aggregated gel networks. Interactions as well as aggregation behaviour of these hydrogels were explored via ζ-potential measurements. Furthermore, the nanostructure of the OCNF gels was probed using small-angle X-ray scattering (SAXS), where the SAXS patterns showed an increase of slope in the low-q region with increasing salt concentration arising from aggregation due to the screening of the surface charge of the fibrils.

Insights into the structure and conformation of potato resistant starch (type 2) using asymmetrical flow field-flow fractionation coupled with multiple detectors

Insight into the structure and conformation characteristics of starch that influence its enzyme susceptibility is import for its potential application. In this study, the capacity of asymmetrical flow field-flow fractionation (AF4) coupled online with multi-angle light scatting (MALS) and differential refractive index (dRI) detectors (AF4-MALS-dRI) for monitoring of change in structure and conformation of potato starch during enzymatic hydrolysis was evaluated. The dissolution behavior of potato resistant starch (type 2) (PRS) was investigated. The effect of incubation time and amyloglucosidase concentration on the structure and conformation of potato starch was studied. The apparent density and the ratio of R_g (radius of gyration) to R_h (hydrodynamic radius) obtained from AF4-MALS-dRI were proven to be important parameters as they offer an insight into conformation of PRS at molecular level. Results suggested that gelatinization process made potato amylose molecules have a loose and random coil conformation which could contribute to an acceleration of enzymatic hydrolysis of potato starch. Furthermore, an intermediate with an elongated branched conformation was found between amylose and amylopectin populations, which may play a role in digestion property of potato starch. The results demonstrated that AF4-MALS-dRI is a powerful tool for better understanding of conformation of PRS.

Genetic and Environmental Variation in Starch Content, Starch Granule Distribution and Starch Polymer Molecular Characteristics of French Bread Wheat

This study investigates genetic and environmental variation in starch content and characteristics of 14 French bread cultivars. Understanding the impact of these factors on wheat quality is important for processors and especially bakers to maintain and meet the requirements of industrial specifications. Different traits were evaluated: starch content, distribution of starch granules, percentage of amylose and amylopectin and their molecular characteristics (weight-average molar mass, number-average molar mass, polydispersity and gyration radius). Genetic, environment and their interaction had significant effects on all parameters. The relative magnitude of variance attributed to growth conditions, for most traits, was substantially higher (21% to 95%) than that attributed to either genotype (2% to 73%) or G × E interaction (2% to 17%). The largest environmental contribution (95%) to total variance was found for starch dispersity. The highest genetic influence was found for the percentage of A-type starch granules. G × E interaction had relatively little influence (≈7%) on total phenotypic variance. All molecular characteristics were much more influenced by environment than the respective percentages of amylose and amylopectin were. This huge difference in variance between factors obviously revealed the importance of the effect of growing conditions on characteristics of cultivars.

The importance of glycogen molecular structure for blood glucose control

Type 2 diabetes incidence continues to increase rapidly. This disease is characterized by a breakdown in blood glucose homeostasis. The impairment of glycemic control is linked to the structure of glycogen, a highly branched glucose polymer. Liver glycogen, a major controller of blood sugar, comprises small β particles which can link together to form larger α particles. These degrade to glucose more slowly than β particles, enabling a controlled release of blood glucose. The α particles in diabetic mice are however easily broken down into β particles, which degrade more quickly. Because this may lead to higher blood glucose, understanding this diabetes-associated breakdown of α-particle molecular structure may help in the development of diabetes therapeutics. We review the extraction of liver glycogen, its molecular structure, and how this structure is affected by diabetes and then use this knowledge to make postulates to guide the development of strategies to help mitigate type 2 diabetes.

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Diabetes involves uncontrolled blood glucose levels

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Liver glycogen acts as a blood glucose buffer

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Diabetes can lead to molecularly fragile liver glycogen particles

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Molecularly fragile liver glycogen may exacerbate poor blood glucose control

Investigation of the Adsorption Behavior of Jet-Cooked Cationic Starches on Pulp Fibers

The optimization of the thermal treatment of cationic starch in the paper industry offers the opportunity to reduce the energy consumption of this process. Four different industrially relevant cationic starches, varying in source, cationization method and degree of substitution were treated by a steam-jet cooking procedure, comparable to industrially employed starch cooking processes. The influence of the starch properties and cooking parameters on the adsorption behavior of the starches on cellulosic pulp was investigated. The adsorbed amount was affected by the cooking temperature and the type of starch. For some starch grades, a cooking temperature of 115 °C can be employed to achieve sufficient starch retention on the pulp fibers. The energy consumption could further be reduced by cooking at higher starch concentrations without loss of adsorption efficiency.

Molecular Dispersion of Starch as a Crucial Parameter during Size-Exclusion Chromatography

Starch, α-polyglucan consisting of a large number of anhydroglucose units joined by α-1,4- and α-1,6-glycosidic bonds, seems to be characterized by a simple structure when compared to other natural polymers. Nevertheless, starches of various botanical origins have different physicochemical properties that are related to the differences in molecular and supramolecular structure of this polymer. In terms of the functional value of starch, the behavior of its macromolecules in solution is the most important result of its structural features. Extremely high molecular mass is the fundamental structural property of starch. Water, considered simply as a solvent for solubilization, does not provide molecular dispersion of starch without its degradation. The objectives of this study are to characterize the suitability of a new aqueous media (urea/NaOH) for enhancing the dispersion of native corn and potato starches and its effect on the consequent size-exclusion chromatography (SEC) analysis. The results were referred to other aqueous base solvents used for dispersing starch (NaOH and KOH). The samples were separated using SEC with triple detection and phosphate buffer (pH 8.0) with urea as the eluent. The characteristics of tested normal and waxy starches were compared. The results revealed that urea/NaOH did not degrade starch during the dispersion process. The recovery of starches, however, was not higher than 42%. These results prove that while the urea/NaOH solvent allows to obtain cold-water-soluble starch, the degree of disintegration of the intramolecular interactions of amylopectin chains is still insufficient.

Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest

The objective of this study was to determine if the pre-harvest glyphosate application time affects the chemistry of wheat starch. Glyphosate was sprayed at the ripe stage (recommended) and the soft dough stage (early application) of hard red spring wheat. Wheat kernel samples were collected before application and every 3 days until harvest, after which different starch characteristics were analyzed. The results indicate that glyphosate timing does not impact the spatial distribution or morphology of starch granules, as well as the percentage or molecular weight of amylose and amylopectin. However, thermal characteristics of wheat starch, especially when glyphosate was applied at the soft dough stage, showed significant differences. A decrease in the average amylopectin chain length and differences in the proportion of short-, medium-, and long-chain amylopectin was also observed. Overall, this study shows that the pre-harvest application of glyphosate can affect wheat starch chemistry, especially if applied earlier than recommended. PRACTICAL APPLICATIONS: Glyphosate is the most commonly used herbicide in the world, and it is sometimes used pre-harvest during wheat cultivation. The recommended time of application is 7 days prior to harvest when the crops are in the ripe stage of physiological maturity. However, some crops may not be at this stage during application due to non-uniform maturation in the field. The goal of this work was to determine the effect of glyphosate application time (recommended/ripe stage vs. early/soft dough stage) on wheat starch chemistry. The results show that the starch chain length characteristics and thermal behavior are impacted, especially if applied early. Thus, this study shows the importance of timely application to avoid effects on starch chemical properties, which in return could impact starch functionality in food systems. This information is critical in the field of agriculture and to our knowledge this study is one of the first in this area.

Cationic starches in paper-based applications-A review on analytical methods

This review focuses on cationic starches with a low degree of substitution (<0.06) which are mainly used for production of paper-based products. After a brief introduction on starch in general, cationization pathways and importance of cationic starches in paper production, this review emphasizes on the analytical challenges from different perspectives. These include the different length scales of starches when in solution: the macromolecular level, their assembly into nm aggregates and finally hydrocolloids with hundreds of nanometers of diameter. We give an overview on the current state of the art on the analysis of such challenging samples and aim at providing a guideline for obtaining and presenting reliable analytical data.

Preharvest Glyphosate Application during Wheat Cultivation: Effects on Wheat Starch Physicochemical Properties

Due to nonuniform maturation, some plants may not be at the recommended stage of maturity when preharvest glyphosate is applied. The objective of this study was to determine how preharvest glyphosate timing affects wheat starch physicochemical properties. Two wheat cultivars were grown in three locations, and glyphosate was applied at the soft dough stage (early application) and the ripe stage (commercial standard). Upon harvest, starch chemical characteristics were studied. The proportion of B-type starch granules was lower in treated samples, although the starch molecular weight was not affected. Rapidly digestible starch content was highest when glyphosate was applied at the ripe stage, and lowest in the control, and vice versa for slowly digestible starch. Additionally, flour pasting viscosity was significantly higher in samples treated at the soft dough stage. Overall, the effects on wheat starch physicochemical characteristics were more pronounced when glyphosate was applied at the soft dough stage of maturity.

Competition between Granule Bound Starch Synthase and Starch Branching Enzyme in Starch Biosynthesis

BACKGROUND

Starch branching enzymes (SBE) and granule-bound starch synthase (GBSS) are two important enzymes for starch biosynthesis. SBE mainly contributes to the formation of side branches, and GBSS mainly contributes for the synthesis of amylose molecules. However, there are still gaps in the understanding of possible interactions between SBE and GBSS.

RESULTS

Nineteen natural rice varieties with amylose contents up to 28% were used. The molecular structure, in the form of the chain-length distribution (CLDs, the distribution of the number of monomer units in each branch) was measured after enzymatic debranching, using fluorophore-assisted carbohydrate electrophoresis for amylopectin and size- exclusion chromatography for amylose. The resulting distributions were fitted to two mathematical models based on the underlying biosynthetic processes, which express the CLDs in terms of parameters reflecting relevant enzyme activities.

CONCLUSIONS

Finding statistically valid correlations between the values of these parameters showed that GBSSI and SBEI compete for substrates during rice starch biosynthesis, and synthesis of amylose short chains involves several enzymes including GBSSI, SBE and SSS (soluble starch synthase). Since the amylose CLD is important for a number of functional properties such as digestion rate, this knowledge is potentially useful for developing varieties with improved functional properties.

Purification, characterization and anti-fatigue activity of polysaccharide fractions from okra (Abelmoschus esculentus (L.) Moench)

The aim of this study was to investigate the anti-fatigue activity of polysaccharide fractions from Abelmoschus esculentus (L.) Moench (AE) in mice. After crude polysaccharide (CAEP) was extracted from AE and purified by DEAE cellulose-52 column, two polysaccharide fractions (AEP-1 and AEP-2) were obtained. The structural analysis suggested that AEP-1 and AEP-2 were a RG-I polysaccharide and an AG-II polysaccharide, respectively. According to the results of the weight-loaded swimming test, compared with the negative control group, the CAEP, AEP-1 and AEP-2 treatment groups could prolong the swimming time, decrease serum urea nitrogen (SUN) and blood lactic acid (BLA), and increase hepatic glycogen (HG) and muscle glycogen (MG), which indicated that okra polysaccharides have an effective anti-fatigue activity. Furthermore, our study exhibited the anti-fatigue mechanism of okra polysaccharide was correlated with retarding the accumulation of creatine kinase (CK) and lactate dehydrogenase (LDH) in serum, and enhancing succinate dehydrogenase (SDH), adenosine triphosphate (ATP) and adenosine triphosphatase (ATPase) levels. In addition, the anti-fatigue activity of AEP-1 was stronger than that of AEP-2, and significantly better than that of CAEP. Therefore, AEP-1 and AEP-2 may be the main active anti-fatigue functional substances of AE.

Ultra-high performance liquid chromatography-size exclusion chromatography (UPLC-SEC) as an efficient tool for the rapid and highly informative characterisation of biopolymers

Starch has a complex molecular structure, with properties dependent on the relative chain lengths and branching structure of its constituent molecules, which varies due to polymorphisms in starch biosynthetic genes, as well as environmental factors. Here we present the application of ultra-high performance size exclusion chromatography to the separation of starch chains from plant seeds. Several methods, have been used to analyse chain length distributions in starch, all with limitations in terms of analysis time, sample preparation and molecular weight range. Here we demonstrate that chain length distributions can be obtained with dramatically reduced analysis time using ultra-high performance size exclusion chromatography. The method may also show improvements in resolution of some fine structural features. Understanding links between starch fine structure and biosynthetic genes will allow bioengineering of starches with tailored properties. This technique may have application to the size separation and resolution of a range of biopolymers of value to the food, drink and pharmaceutical industries.

Critical and speculative review of the roles of multi-protein complexes in starch biosynthesis in cereals

Starch accounts for the majority of edible carbohydrate resources generated through photosynthesis. Amylopectin is the major component of starch and is one of highest-molecular-weight biopolymers. Rapid and systematic synthesis of frequently branched hydro-insoluble amylopectin and efficient accumulation into amyloplasts of cereal endosperm is crucial. The functions of multiple starch biosynthetic enzymes, including elongation, branching, and debranching enzymes, must be temporally and spatially coordinated. Accordingly, direct evidence of protein-protein interactions of starch biosynthetic enzymes were first discovered in developing wheat endosperm in 2004, and they have since been shown in the developing seeds of other cereals. This review article describes structural characteristics of starches as well as similarities and differences in protein complex formation among different plant species and among mutant plants that are deficient in specific starch biosynthetic enzymes. In addition, evidence for protein complexes that are involved in the initiation stages of starch biosynthesis is summarized. Finally, we discuss the significance of protein complexes and describe new methods that may elucidate the mechanisms and roles of starch biosynthetic enzyme complexes.

Production of starch nanoparticles by dissolution and non-solvent precipitation for use in food-grade Pickering emulsions

The aim of this study was to investigate non-solvent precipitation of starch to produce nanoparticles that could be used in Pickering emulsions. The material used was waxy maize, modified with octenyl succinic anhydride. Different methods of non-solvent precipitation were investigated, and a method based on direct mixing of an 8% starch solution and ethanol (ratio 1:1) was found to produce the smallest particles. The particle size was measured using AFM and AF4, and was found to be in the range 100-200nm. However, both larger particles and aggregates of nanoparticles were observed. The emulsion produced using the precipitated starch particles had a droplet size that between 0.5 and 45μm, compared to emulsions produced from waxy maize granules, in which had a size of 10-100μm. The drop in size contributed to increased stability against creaming. The amount of starch used for emulsion stabilization could also be substantially reduced.

Impact of bread making on fructan chain integrity and effect of fructan enriched breads on breath hydrogen, satiety, energy intake, PYY and ghrelin

Recently, there has been considerable interest in the satiety inducing properties of inulin type fructans (ITF) as a tool for weight management. As a staple food, breads provide an excellent vehicle for ITF supplementation however the integrity of the ITF chains and properties upon bread making need to be assessed. Breads enriched with 12% fructooligosaccharides (FOS) and 12% inulin were baked and the degree of polymerisation of fructans extracted from the breads were compared to those of pure compounds. An acute feeding study with a single blind cross-over design was conducted with 11 participants to investigate the effect of ITF enriched breads on breath hydrogen, self-reported satiety levels, active ghrelin, total PYY and energy intake. Size exclusion chromatography indicated that little or no depolymerisation of inulin occurred during bread making, however, there was evidence of modest FOS depolymerisation. Additionally, ITF enriched breads resulted in increased concentrations of exhaled hydrogen although statistical significance was reached only for the inulin enriched bread (p = 0.001). There were no significant differences between bread types in reported satiety (p = 0.129), plasma active ghrelin (p = 0.684), plasma PYY (p = 0.793) and energy intake (p = 0.240). These preliminary results indicate that inulin enriched bread may be a suitable staple food to increase ITF intake. Longer intervention trials are required to assess the impact of inulin enriched breads on energy intake and body weight.