Thermal, spectroscopic, SEM and rheological datasets of native and quaternized guar gum.
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ABSTRACT:
SUBMITTER: Tyagi R
PROVIDER: S-EPMC7205758 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Three guar gum derivatives with hydrophobic unsaturated long-chains were successfully synthesized, including oleic guar gum (OGG), linoleic guar gum (LGG) and erucic guar gum (EGG). The guar gum derivatives were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Moreover, comparative studies on the rheological behaviours of guar gum (GG) and three guar gum derivatives were performed. Regardless of their hydrophobic side groups, all sample solutions showed the properties of non-Newtonian shear-thinning fluids, and their complex viscosities (η*) increased significantly with increasing concentration. In contrast to GG, OGG or EGG, LGG exhibited the strongest shear-thinning property when the concentration is 1 wt%. It was found that the frequency-dependent viscous (G'') and elastic modulus (G') curves of GG and its derivatives aqueous solutions cross at a specific frequency. This crossover frequency decreases with increasing sample concentration, indicating that the viscoelasticity is highly dependent on polymer concentration. In addition, when the molar substitution (MS) of the repeating sugar units in the guar gum derivatives is less than 0.08, the LGG solution showed more obvious solid-like rheological properties than the OGG and EGG solutions at the same concentration.
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Project description:Improving the gel texture and stability of rice starch (RS) by natural hydrocolloids is important for the development of gluten-free starch-based products. In this paper, the effects of guar gum and locust bean gum on the pasting, rheological properties, and freeze-thaw stability of rice starch were investigated by using a rapid visco analyzer, rheometer, and texture analyzer. Both gums can modify the pasting properties, revealed by an increment in the peak, trough, and final viscosities, and prevent the short-term retrogradation tendency of RS. Dynamic viscoelasticity measurements also indicated that the starch-gum system exhibits superior viscoelastic properties compared with starch alone, as revealed by its higher storage modulus (G'). Compared with the control, the hysteresis loop area of the guar gum-containing system and locust bean gum-containing system was reduced by 37.7% and 24.2%, respectively, indicating that the addition of gums could enhance shear resistance and structure recovery properties. The thermodynamic properties indicated that both gums retard short-term retrogradation as well as long-term retrogradation of the RS gels. Interestingly, the textural properties and freeze-thaw stability of the RS gel were significantly improved by the addition of galactomannans (p < 0.05), and guar gum was more effective than locust bean gum, which may be due to the different mannose to galactose ratio. The results provide alternatives for gluten-free recipes with improved texture properties and freeze-thaw stability.
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Project description:Guar gum consists mainly of galactomannan, and constitutes the endosperm of guar seeds that acts as a reserve polysaccharide for germination. Due to its molecular structure and physical properties, this biopolymer has been considered as one of the most important and widely used gums in industry. However, for many of these applications this (hemi-)cellulosic structure needs to be modified or (partially) depolymerized in order to customize and improve its physicochemical properties. In this study, transcriptome was employed to decipher the complete enzymatic arsenal for guar gum depolymerization by Aspergillus niger.
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Project description:Mineral precipitation via microbial activity is a well-known process with applications in various fields. This relevance of microbially induced calcite precipitation (MICP) has pushed researchers to explore various naturally occurring MICP capable bacterial strains. The present study was performed to explore the efficiency of microbially induced calcite precipitation (MICP) via locally isolated bacterial strains and role of guar gum, which is a naturally occurring polymer, on the MICP process. The strains were isolated from local soil and screened for urease activity Further, the urease positive strain was subjected to urea and calcium chloride based medium to investigate the efficacy of isolated strain for microbial induced precipitation. Among screened isolates, the soil bacterium that showed urease positive behaviour and precipitated calcium carbonate was subjected to 16S rRNA gene sequencing. This strain was identified as Bacillus velezensis. Guar gum-a natural polymer, was used as a sole carbon source to enhance the MICP process. It was observed that the isolated strain was able to breakdown the guar gum into simple sugars resulting in two-fold increase in calcium carbonate precipitate. Major bio-chemical activities of isolated strain pertaining to MICP such as ammonium ion concentration, pH profiling, and total reducing sugar with time were explored under four different concentrations of guar gum (0.25%, 0.5%, 0.75% and 1% w/v). Maximum ammonium ion concentration (17.5 ?g/ml) and increased pH was observed with 1% guar gum supplementation, which confirms augmented MICP activity of the bacterial strain. Microstructural analysis of microbial precipitation was performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, which confirmed the presence of calcium carbonate in different phases. Further, XRD and SEM based studies corroborated that guar gum supplemented media showed significant increase in stable calcite phase as compared to media without guar gum supplementation. Significant diverse group of nitrogenous compounds were observed in guar gum supplemented medium when subjected to Gas Chromatography-Mass spectrometry (GC-MS) profiling.
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Project description:Guar gum is an important raw material in the food, textile and oil industries, but the biosynthesis of guar gum remains unclear. To illuminate the genes involved in guar gum biosynthesis, guar beans from 30 and 40 days after flowering (DAF) were used for RNA sequencing in this study. A total of 2,535 and 2,724 preferentially expressed genes were found in 30 and 40 DAF endosperm, and 3,720 and 2,530 preferentially expressed genes were found in 30 and 40 DAF embryos, respectively. Of these, mannan synthase genes, α-galactosyltransferase genes and cellulose synthase genes were preferentially expressed in the endosperm from 30 and 40 DAF. The high expression level of these glycometabolism genes in endosperm is consistent with the expectation that the main component of guar gum is galactomannan. We believe that genes related to guar gum biosynthesis found in this study will be useful for both new variety development via genetic engineering and synthetic biology research on guar gum biosynthesis in the future.
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Project description:The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of guar gum (E 412) as a food additive. In the EU, guar gum was evaluated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1970, 1974 and 1975, who allocated an acceptable daily intake (ADI) 'not specified'. Guar gum has been also evaluated by the Scientific Committee for Food (SCF) in 1977 who endorsed the ADI 'not specified' allocated by JECFA. Following the conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010, the Panel considered that adequate exposure and toxicity data were available. Guar gum is practically undigested, not absorbed intact, but significantly fermented by enteric bacteria in humans. No adverse effects were reported in subchronic and carcinogenicity studies at the highest dose tested; no concern with respect to the genotoxicity. Oral intake of guar gum was well tolerated in adults. The Panel concluded that there is no need for a numerical ADI for guar gum (E 412), and there is no safety concern for the general population at the refined exposure assessment of guar gum (E 412) as a food additive. The Panel considered that for uses of guar gum in foods intended for infants and young children the occurrence of abdominal discomfort should be monitored and if this effect is observed doses should be identified as a basis for further risk assessment. The Panel considered that no adequate specific studies addressing the safety of use of guar gum (E 412) in food categories 13.1.5.1 and 13.1.5.2 were available. Therefore, the Panel concluded that the available data do not allow an adequate assessment of the safety of guar gum (E 412) in infants and young children consuming these foods for special medical purposes.
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Project description:The objective of this study was to develop biodegradable active film to improve the shelf-life of minimally processed fresh-produce. Guar gum (GG) based films with improved properties were fabricated by employing tween-80 (0.88%) as emulsifier, nanoclay (13.9%) as reinforcement, beeswax (1.21%) for hydrophobicity, glycerol (3.07%) as plasticizer, and grape pomace extract (5%) as active ingredient (%w/w of GG). Active films had a tensile strength of 122 MPa and water vapor transmission rate of 69 gm-2d-1. Films demonstrated significant antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Salmonella Typhimurium. The 2 kGy irradiated minimally processed pomegranate arils packed in film demonstrated a shelf-life of 12 days as compared to 4 days for unirradiated samples. The observed improvement in shelf-life was due to a radiation-induced release of antimicrobial volatiles from active films as confirmed by headspace analysis using GC-MS. Suitability of active films for food irradiation applications is thus demonstrated.
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