Headspace volatiles profiles of different spring varieties and a wild relative of wheat flour.

Volatile profiling was conducted on four wheat varieties Triticum aestivum cv. Chinese Spring (CS), Highbury (High), Paragon (Para), Pavon76 (Pav76), and one wild relative Triticum timopheevii (P95). Headspace solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to explore differences in flavor formation mechanisms in different flours before and after starch gelatinization. Solvent retention capacity (SRC) analysis revealed subtle differences in water absorption, gluten strength, and starch characteristics across wheat flour types. Rapid Visco Analysis (RVA) of whole wheat flour demonstrated significant variations in pasting properties among wheat varieties, with P95 exhibiting higher viscosities compared to CS and High potentially influenced by starch gelatinization, protein-starch interactions, and lipid content. Aroma contributions of P95 clustered positively in PCA plots, contrasting with the four main varieties, indicative of species-level differentiation. Furthermore, the study highlighted the roles of viscosity, protein structure, lipid content, and fatty acid composition in modulating the release and perception of volatile aroma compounds during heating. This study sheds light on how the distinct characteristics of wheat flour influence aroma profiles, revealing species-level differences and the pivotal role of physiochemical properties in shaping flavor development mechanisms.

Effects of different moisture contents on the structural and functional properties of cellulose with cell wall components in different citrus fibres.

This research used a multi-method approach to analyse the influence of different moisture levels (low, medium and high) on the structural and functional properties of cellulose with cell wall materials such as pectin, lignin, and hemicellulose present in citrus fibres. The influence of the drying and purification processes and the source of the citrus fibres on these interactions were also considered. A fluidized bed dryer results in a higher aggregation of cellulose fibres, which limits their interactions with water, pectin, lignin, and hemicellulose. Citrus fibre suspension produce by a alcohol washing in combination with a centrifugal drying process showed higher storage modulus (G'), loss modulus (G'') and water retention capacity. The compositions of the citrus fibres and the type of hydrogen bonding (analysed by FTIR) play a key role in generating stable rheological and thermal properties as well as controlling the moisture sorption behaviour of the citrus fibres.

Development of a separated-dough method and flour/starch replacement in gluten free crackers by cellulose and fibrillated cellulose.

Two strategies were combined and applied in this study to achieve a desired structure and texture of gluten free crackers and to reduce the calorie content. The first strategy is increasing structural heterogeneity of crackers and doughs and a separated-dough method was developed. A butter dough and a water dough were prepared separately and mixed together and the influence of mixing time was investigated. In the second strategy, which is the incorporation of a structuring material, powdered cellulose and fibrillated cellulose were incorporated in formulation to replace flour and pregelatinised starch with enhanced health benefits of low calorie and high fibre. Powdered cellulose played the role of the skeleton of the gluten free crackers. A laminar structure was observed in crackers when powdered cellulose was initially added to the butter dough. The crackers exhibit high thickness, hardness and fracturability and sharp sound emission which are typically observed in wheat crackers. Pregelatinised starch can be replaced by fibrillated cellulose at a lower addition level.

Effects of psyllium seed husk powder, methylcellulose, pregelatinised starch, and cold water swelling starch on the production of gluten free crackers.

The production of gluten free crackers is challenging because the formation of a gluten network is required. This study investigated the effects of psyllium seed husk powder (PSY), methylcellulose (MC), pregelatinised starch (PGS), and cold water swelling starch (CWSS) on gluten free crackers made of rice flour. The evaluations of pasting properties, dough rheological properties, textural properties, acoustic emissions, and structures were included in this study. Gluten free cracker doughs were more solid-like compared to wheat doughs based on their frequency dependence shown in the mechanical spectra. However, PGS significantly increased the fluid-like property and shapeability. The addition of MC at a high level significantly modified the pasting profile and a secondary swelling and breakdown might occur. As for the crackers, PSY and PGS crackers had comparable textural properties and sound release to wheat crackers, while CWSS crackers were slightly weaker. However, MC did not improve the textural properties compared to rice crackers because the interaction between the MC molecules was limited at the low water addition level, which limited its functionality in cracker making.

Compositional, thermal and water sorption properties of wheat flour: comparing wild-relatives v/s elite wheat varieties used in current plant breeding.

Plant breeders are focused on creating new varieties of wheat with enhanced yield potential without affecting the quality of wheat for food. In this study, four cultivated varieties of wheat, Triticium asetivum and two wild relatives of wheat; Triticum timopheevii and Triticum urartu were studied. The impact of starch and protein content on structural, thermal and water sorption properties of four main wheat cultivars in comparison to the wild relatives has been studied. Wild relatives of wheat required higher temperatures to initiate starch gelatinisation and amylose/lipid complex formation as compared to the four main wheat cultivars. The carbohydrate region in FTIR indicates structural differences (ordered and unordered starch) in the different varieties of wheat flour. The differentiation between wild relatives and main varieties is at the species level. Both wild relatives showed a noticeable difference in moisture sorption behaviour as compared with the 4 main cultivars, especially in terms of monolayer (M0) and the strength of water binding to the primary sites (C) values.

A comprehensive investigation of gluten free bread dough rheology, proving and baking performance and bread qualities by response surface design and principal component analysis.

Contribution of methylcellulose (MC), psyllium seed husk powder (PSY), and water addition level to gluten free bread quality and correlations between dough rheological properties and bread qualities were investigated by response surface design and principal component analysis. The generalised Maxwell model was applied to estimate the relaxation frequency of gluten free doughs. The addition of PSY has a complex influence on pasting viscosity at high temperature and an additional peak was observed. MC significantly influenced dough extensibility and work of adhesion, which are good predictors of bread volume and textural properties. Other rheological responses are less significantly correlated to specific volume, but they are sensitive to formulation variations, reflect dough structures and stability, related to proving behaviours, and correlated to loaf concavity. An inappropriate combination of water and hydrocolloids might lead to problems such as low stability of doughs, overexpansion, and weak crumb structure at high water addition levels, or, in contrast, high rigidity of dough, a trap of excessive air during mixing, and restrained gas cell expansion with high hydrocolloid addition and low water addition.

Effect of moisture content on thermal and water absorption properties of microfibrillar cellulose with polymeric additives.

The aim of this study was 1) to investigate the influence of polymeric additives such as carboxyl methyl cellulose (CMC) and locust bean gum (LBG) added before and after homogenisation on the moisture uptake of microfibrillar cellulose (MFC) in the dry and semi-wet state; and 2) to further understand the thermally induced structural transitions of low moisture MFC in the presence of the polymeric additives. A higher moisture content in the highly dense MFC network maintains the fibrillated network structure, which is lost during the drying process resulting in MFC aggregates. The addition of polymeric additives results in the regaining of the structure upon redispersion of the dry material with CMC being more effective than LBG). Results also indicated that CMC has a high level of compatibility with MFC, whereas LBG appears to have limited distribution in the MFC dense microfibrillar network and probably exists as a separate phase when added after homogenisation, however co-processing of LBG and cellulose significantly changed this behaviour. The presence of low-temperature transitions in MFC/additives/water mixtures indicates the involvement of these semi-flexible polymeric additives in the formation of liquid crystals when added to MFC in low moisture environments (2% and 20% w/w). An insight is offered into the theory of surface interactions between MFC and polymeric additives, which prevents the agglomeration of microfibrils present in the highly fibrillated suspension upon drying.

Interactions between microfibrillar cellulose and carboxymethyl cellulose in an aqueous suspension.

New microstructures with interesting, unique and stable textures, particularly relevant to food systems were created by redispersing Microfibrillar cellulose (MFC). This paper reports the interactions between microfibrillar cellulose and carboxymethyl cellulose (CMC) in redispersed aqueous suspensions, by using rheological measurements on variable ratios of MFC/CMC and correlating these with apparent water mobility as determined by time domain NMR. MFC is a network of cellulose fibrils produced by subjecting pure cellulose pulp to high-pressure mechanical homogenisation. A charged polymer such as CMC reduces the aggregation of microfibrillar/fibre bundles upon drying. Small amplitude oscillatory rheological analysis showed viscoelastic gel-like behaviour of suspensions which was independent of the CMC content in the MFC suspension. A viscous synergistic effect was observed when CMC was added to MFC before drying, leading to improved redispersibility of the suspension. Novel measurements using NMR relaxation suggested that the aggregated microfibrillar/fibre bundles normally dominate the relaxation times (T2). The dense microfibrillar network plays an important role in generating stable rheological properties and controlling the mobility of the polymer and hence the apparent mobility of the water in the suspensions.

A comparison of the sensory and rheological properties of different cellulosic fibres for food.

The impact of different cellulosic microstructures formed by highly entangled fibre networks was studied for food applications as dietary fibre. This paper reports the impact of the microstructure on the rheological and sensory behaviour of the aqueous suspensions of particulate and fibrillated forms of softwood cellulosic fibres, and was compared with citrus fibres. An aqueous suspension of cellulosic fibres shows stable viscoelastic gel-like behaviour as a function of frequency. The particulate form of cellulosic fibres showed the lowest shear viscosity as compared with the entangled network system at comparable concentrations. To provide further insight into the relationship between the structure of cellulosic fibre and taste (salt) perception, an aqueous suspension with matched shear viscosities were studied. A hypothesis to explain why softwood cellulosic fibre (CTE) with an entangled network structure prolongs the taste perception is presented.

Polysaccharide structures and interactions in a lithium chloride/urea/water solvent.

The molten salt hydrate, lithium chloride (LiCl)/urea/water has previously been shown to swell cellulose, but there has so far been no work done to explore its effect on other polysaccharides. In this paper we have investigated the solvent effects of LiCl/urea/water on four natural polysaccharides. Fenugreek gum and xyloglucan, which are both highly branched, were found to increase in viscosity in LiCl/urea/water relative to water, possibly due to the breakage of all intra-molecular associations whereas the viscosity of konjac glucomannan which is predominantly unbranched did not change. Locust bean gum (LBG) had a lower viscosity in LiCl/urea/water compared to water due to the disruption of aggregates. Confocal microscopy showed that fenugreek gum and LBG are able to bind to cellulose in water, however, the conformational change of fenugreek gum in these solvent conditions inhibited it from binding to cellulose in LiCl/urea/water whereas conformational change allowed xyloglucan to bind to cellulose in LiCl/urea/water whilst it was unable to bind in water. Konjac glucomannan did not bind to cellulose in either solvent system. These results provide new insights into the impact of polysaccharide fine structure on conformational change in different solvent environments.

Effect of a small amount of sodium carbonate on konjac glucomannan-induced changes in wheat starch gel.

Wheat starch gels were produced with konjac glucomannan (KGM) and low concentrations of Na2CO3 (0.1-0.2 wt% of starch) using a rapid viscosity analyzer (RVA). The gelling properties of wheat starch in varying ratios of KGM and Na2CO3 were characterized by differential scanning calorimetry (DSC), rheometry and confocal laser scanning microscopy (CLSM). A small amount of Na2CO3 resulted in gels with increased elasticity whereas structural ordering during retrogradation was insignificantly affected. Comparison of CLSM images of composite gels revealed that Na2CO3 at 0.2 wt% of starch allowed the formation of fiber-like extensions around scattered swollen granules by KGM and amylose interaction, making swollen granules disperse within the micro phase, which was not typical in CLSM images of gels in the absence of Na2CO3. Dynamic storage modulus and dynamic power law exponent were substantially higher than those observed for the same concentration of KGM in the presence of Na2CO3, supporting the hypothesis that Na2CO3 could promote strong interchain associations between KGM and starch components.

Effect of a small amount of sodium carbonate on konjac glucomannan-induced changes in thermal behavior of wheat starch.

The effects of konjac glucomannan (KGM) on thermal behavior of wheat starch have been studied in the presence of low concentrations of Na2CO3 (0.1-0.2 wt% of starch). Confocal laser scanning microscopy (CLSM) allows the visualization of the starch gelatinization process and granule remnants in starch pastes. Heating the starch dispersion in KGM-Na2CO3 solution significantly delays granule swelling and inhibits amylose leaching, whereas Na2CO3 alone, at the same concentration, has little effect. Na2CO3 assists KGM in producing the extremely high viscosity of starch paste, attributing to a less remarkable breakdown of viscosity in subsequent heating, and protecting starch granules against crystallite melting. The distinct partially networked film around the surface of starch granules is evident in the CLSM images. We propose that Na2CO3 could trigger the formation of complexes between KGM and starch polymers, which exerts a protective effect on granular structure and modifying gelatinization characteristics of the mixtures.

Konjac glucomannan-induced changes in thiol/disulphide exchange and gluten conformation upon dough mixing.

Effects of konjac glucomannan (KGM) on the changes in gluten upon dough mixing were investigated in this study. Wheat flour was blended with KGM and processed into dough. Farinographic analysis showed that KGM caused a significant increase in water absorption and dough development time to reach maximum consistency. Comparison of electrophoretic protein profile from control dough and KGM-dough revealed that protein fractions were similar in molecular size distribution, but the lability of glutenin aggregates slightly differed. Addition of KGM to gluten induced negative effects on exchange between sulfhydryl groups and disulphide bonds. Fourier transform-Raman spectroscopy indicated that secondary structure of gluten proteins was differentially modified related with water absorption of flours before dough formation. This study reveals that when KGM is added to the dough, conformational behaviours of gluten proteins are changed and the hydroxyl groups of KGM might be involved in the interaction by forming strong intermolecular hydrogen bonding system.

Self-association of novel mixed 3-mono-O-alkyl cellulose: Effect of the hydrophobic moieties ratio.

Heat-induced self-association of regioselectively functionalized 3-O-alkyl celluloses bearing both ethyl- and propyl groups dissolved in water was studied by means of differential scanning calorimetry and oscillatory shear rheology. The measured degrees of substitution were close to 1 but the ratio of ethyl (DSEt) to propyl groups (DSPr) was varied. The aggregation process is intimately coupled with phase separation as shown by the appearance of clouding in the same temperature range. Phase separation is arrested by the incipient gelation; whereby "stronger" gels are produced with high amounts of the propyl substituent than "weaker" phase separating samples as the amount of ethyl groups increases and the amount of propyl groups decreases. The correlation between rheology and thermal analysis clearly demonstrates that aggregation leads to formation of a gel network. It was found that as the ethyl moiety is replaced by propyl group the enthalpies of the thermal transitions increase strongly together with an increase of the elastic modulus (G') and the network is also more coherent with a steady decrease in tanδ (G″/G'). Reversibility was observed on cooling with a marked hysteresis for samples containing high levels of propyl groups. Hysteresis on cooling was explained in term of additional consolidation of the structure occurring at temperature much higher than the aggregation temperature, possibly involving backbone-backbone interactions. Quantitative analysis of the DSC data, based on the two-state thermodynamic model described by Armstrong et al. (1995) enabled evaluation of the van't Hoff enthalpy and the aggregation number. On the basis of those thermodynamic parameters, an "intermolecularly bridged clusters" model is proposed for the heat-induced transition of 3-O-ethyl-propyl cellulose ethers. The van't Hoff enthalpy/calorimetric enthalpy ratio ΔHvH/ΔHcal further indicates on the cooperativity of the process. The number of clusters and indeed the number of molecular chains comprising a cluster are both dependent upon the ratio of the two hydrophobic moieties. An increase in the aggregation number (n) (more aggregates coming together) occurs as ethyl is replaced by propyl, consistent with the observation of a "stronger" gel. The effect of the two different moieties on the physico-chemical properties of 3-O-ethyl-propyl cellulose ethers has been explained in term of different size/hydrophobicity of the two moieties and their distribution.

Preventing gastric sieving by blending a solid/water meal enhances satiation in healthy humans.

Separation of solids and liquids within the stomach allows faster gastric emptying of liquids compared with solids, a phenomenon known as sieving. We tested the hypothesis that blending a solid and water meal would abolish sieving, preventing the early rapid decrease in gastric volume and thereby enhancing satiety. We carried out 2 separate studies. Study 1 was a 2-way, crossover, satiety study of 22 healthy volunteers who consumed roasted chicken and vegetables with a glass of water (1008 kJ) or the same blended to a soup. They completed satiety visual analogue scales at intervals for 3 h. Study 2 was a 2-way, crossover, mechanistic study of 18 volunteers who consumed the same meals and underwent an MRI to assess gastric emptying, gallbladder contraction, and small bowel water content (SBWC) at intervals for 3 h. In Study 1, the soup meal was associated with reduced hunger (P = 0.02). In Study 2, the volume of the gastric contents after the soup meal decreased more slowly than after the solid/liquid meal (P = 0.0003). The soup meal caused greater gallbladder contraction (P < 0.04). SBWC showed a biphasic response with an initial "gastric" phase during which SBWC was greater when the solid/liquid meal was consumed (P < 0.001) and a later "small bowel" phase when SBWC was greater when the soup meal was consumed (P < 0.01). Blending the solid/liquid meal to a soup delayed gastric emptying and increased the hormonal response to feeding, which may contribute to enhanced postprandial satiety.

Mixed 3-mono-O-alkyl cellulose: synthesis, structure characterization and thermal properties.

The 3-mono-O-alkyl cellulose samples bearing two different ether moieties, namely methyl/ethyl, methyl/n-propyl, and ethyl/n-propyl were synthesized applying protecting group technique. The NMR spectra of the peracetylated products revealed the regioselectivity of the alkylation as well as the degree of substitution of both alkyl moieties. The number average degree of polymerization (DPn) monitored by size exclusion chromatography decreases from DPn 117 (Avicel PH-101, starting material) to DPn 34 (sample 4f) due to the multi-step synthesis. It could be demonstrated that the lower critical solution temperature (LCST) is influenced by the degree of substitution of both alkyl groups. For example, LCST values between 33 and 58 °C were measured for aqueous solutions of 3-mono-O-ethyl/n-propyl cellulose. On the contrary, the thermal behavior of a physical mixture of 3-mono-O-ethyl- and 3-mono-O-n-propyl cellulose, e.g., was controlled by the derivative with the lowest LCST.

Solvent effects on starch dissolution and gelatinization.

The disruption of starch granular structure during dissolution in varying concentrations of N-methyl morpholine N-oxide (NMMO) has been studied using three maize starches with varying ratios of amylose and amylopectin. Behavior in NMMO has been characterized by differential scanning calorimetry (DSC), microscopy, rapid viscosity analysis (RVA), and rheometry. Exothermic transitions were observed for the three starches in both 78 and 70% NMMO; the transition changed to an endotherm at 60 and 50% NMMO. Consistent with DSC, hot stage microscopy showed that starch granules dissolved at NMMO concentrations of 78 and 70%, whereas in 60 and 50% NMMO, gelatinization behavior similar to that found for starch in water was observed. Mechanical spectroscopy revealed the dominant viscous behavior (G″ > G') of starch at NMMO concentrations of 70 and 78% and more elastic behavior (G' > G″) at lower concentrations. Starch solutions in 78% NMMO obey the Cox-Merz rule, suggesting that the solutions are homogeneous on a molecular level.

Fast characterization of industrial soy protein isolates by direct analysis with matrix-assisted laser desorption ionization time-of-flight mass spectrometry.

Industrial soy protein isolates (SPIs) due to differences in their processing conditions may differ both in composition and in degree of hydrolysis. As a result, they display different performance in food production and final food properties like consistency and taste. To address this issue, a fast, cheap, and simple method for screening and characterization is required. In this article, the successful analysis of soy protein isolates, a complex mixture of proteins with glycinin and beta-conglycinin as major components, by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) is demonstrated. The preparation implements a fast extraction of the proteins from the raw SPI either under neutral or reducing conditions. The extracts are analyzed subsequently by MALDI-TOF-MS without further purification. Results of the two conditions are compared. Finally, different SPIs from different suppliers are analyzed and compared concerning their consistency. The method could be applied to other plant proteins and mixtures thereof. Since the composition and intactness of different subunits play important roles in functional properties of soy proteins, rapid methods for fingerprinting of different industrial soy protein sources will be valuable tools for successful product formulation.

Complete genomes of two clinical Staphylococcus aureus strains: evidence for the rapid evolution of virulence and drug resistance.

Staphylococcus aureus is an important nosocomial and community-acquired pathogen. Its genetic plasticity has facilitated the evolution of many virulent and drug-resistant strains, presenting a major and constantly changing clinical challenge. We sequenced the approximately 2.8-Mbp genomes of two disease-causing S. aureus strains isolated from distinct clinical settings: a recent hospital-acquired representative of the epidemic methicillin-resistant S. aureus EMRSA-16 clone (MRSA252), a clinically important and globally prevalent lineage; and a representative of an invasive community-acquired methicillin-susceptible S. aureus clone (MSSA476). A comparative-genomics approach was used to explore the mechanisms of evolution of clinically important S. aureus genomes and to identify regions affecting virulence and drug resistance. The genome sequences of MRSA252 and MSSA476 have a well conserved core region but differ markedly in their accessory genetic elements. MRSA252 is the most genetically diverse S. aureus strain sequenced to date: approximately 6% of the genome is novel compared with other published genomes, and it contains several unique genetic elements. MSSA476 is methicillin-susceptible, but it contains a novel Staphylococcal chromosomal cassette (SCC) mec-like element (designated SCC(476)), which is integrated at the same site on the chromosome as SCCmec elements in MRSA strains but encodes a putative fusidic acid resistance protein. The crucial role that accessory elements play in the rapid evolution of S. aureus is clearly illustrated by comparing the MSSA476 genome with that of an extremely closely related MRSA community-acquired strain; the differential distribution of large mobile elements carrying virulence and drug-resistance determinants may be responsible for the clinically important phenotypic differences in these strains.

Elucidation of pectin methylester distributions by capillary electrophoresis.

Evidence is presented that the electrophoretic mobility of the polysaccharide pectin in typical capillary electrophoresis (CE) experiments is determined largely by its chain-averaged charge density, irrespective of how that charge is distributed. This was found to be the case for both high and low calcium sensitive sister fractions separated from a mother sample on the grounds of calcium affinity and for blocky methylester distributions generated by a processive demethylating enzyme. The blockiness of the generated intramolecular methylester distribution was substantiated experimentally, also by CE, by observing the oligomeric digest fragments produced by incubation with endo-polygalacturonase II from Aspergillus niger. The conclusion that the CE migration time is largely invariant to the intramolecular methylester distribution supports the idea that the CE peak shapes can be used to give a useful indication of the intermolecular methylester distribution.