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Abstract  

Phase transition behaviour of neutral galactomannans, i.e., locust bean gum (LBG), tara gum (Tara-G) and guar gum (GG)-water systems is investigated. In this study, water content {Wc=(gram of water)/(gram of dry sample)} of these systems was varied from 0.2 to 3.6 g g-1. In the DSC heating curves, glass transition (Tg), cold crystallization (Tcc) and melting (Tm) were observed in all three samples. In addition, liquid crystal transition (T*) was observed in GG-water systems at a temperature higher than Tm. Using Tg, Tcc, Tm and T*, phase diagrams of each system were established. From the melting enthalpy of ice in the systems, three types of water, non-freezing water (Wnf), freezing bound water (Wfb) and free water were calculated. The maximum amount of Wnf was observed at Wc=0.7 g g-1, where Tg showed the lowest temperature. The amount of Wnf in LBG and GG is higher than that of Tara-G, whereas the highest amount of Wfb is found in GG. T* was only observed in GG-water systems. It is concluded that frequency of the side chains in the repeating unit of the main chains of these three galactomannan affects the frozen structure of the glassy state in the presence of water.

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Formation and rheological properties of mixed protein-polysaccharide gels (composites) was studied. The composites consisted of whey proteins gelling separately, which were surrounded by polysaccharide gel. The polysaccharide gels were obtained from κ-carrageenan and κ-carrageenan-galactomannan (guar gum and locust bean gum) mixtures. The texture of gels obtained was examined by their compression and bending test. The composite gels obtained from 14% WPI solution and the 1.5% mixture of κ-carrageenan with locust bean gum in a 1:1 ratio exhibited a higher shear stress value at fracture in comparison to WPI gels, but they were less resistant to fracture in the bending test. The texture of gels was highly influenced by pH.

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Structure and properties of bread dough and crumb

Calorimetric, rheological and mechanical investigations on the effects produced by hydrocolloids, pentosans and soluble proteins

Journal of Thermal Analysis and Calorimetry
Authors: A. Schiraldi, L. Piazza, O. Brenna, and E. Vittadini

The effects of hydrocolloids (guar and locust bean gums), soluble pentosans, and whey proteins on staling of bread crumb were investigated by means of DSC, rheometry, and image analyis. One current hypothesis, that these ingredients would behave as “water binders” and, at least the former two, as anti-staling agents, was indeed confirmed, although this action might be indirect. All the samples considered showed an exothermic DSC peak preceding the endotherm of the amylopectin fusion. According to a previous work, this signal was attributed to a water-dependent cross-linking process that would involve next-neighbouring polymer chains.

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Differential scanning calorimetry (DSC) was used to analyze the influence of different hydrocolloids (xanthan, guar, and locust bean gums, carboxymethylcellulose and sodium alginate) on the gelatinization of corn starch in systems with starch concentration ranging between 0.1 and 0.7 g starch/g mixture. The reduction of available water produced a shift in gelatinization temperature, especially of the conclusion temperature. The effect was more marked for ionic hydrocolloids. The influence of hydrocolloids on glass transition temperature (T g) of gelatinized starch suspensions and on the glass transition temperature of the maximally freeze-concentrated solute/unfrozen water matrix (T′ g) was also studied.T′ g onset values ranged between −4.5 and −5.5‡C for corn starch pastes with and without hydrocolloids. Those hydrocolloids that increased the viscosity of the unfrozen matrix inhibited additional ice formation during thawing (devitrification).

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Phase diagrams of aqueous whey protein (WP) and polysaccharide (PS) mixtures, including carboxymethylcellulose (CMC), k-carrageenan (C) and locust bean gum (LG) are presented in this paper at pH from 5.0 to 7.0 with 0.1 to 0.5 M NaCl. Thermodynamic incompatibility of WP-CMC, WP-LG and WP-C systems increased as pH was close to the isoelectric point of WP (pI=5.2). Increasing salt concentration (0.1 to 0.5 M) increased the incompatibility of WP-LG and WP-CMC systems. However, the effect of NaCl on thermodynamic incompatibility of WP-C was the opposite, i.e. increasing salt concentration decreased the thermodynamic incompatibility of the system. The type of the polysaccharides was the critical factor, which affected the compatibility of WP-PS systems. The thermodynamic compatibility of WP-PS systems decreased in the following order: locust gum ≯ carboxymethylcellulose ≯ k-carrageenan.

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Chen, Y., Liao, M.-L., Boger, D.V. & Dunstan, D.E. (2001): Rheological characterisation of κ-carrageenan locust bean gum mixtures. Carbohydr. Polymers , 46 , 117–124. Dunstan D

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from alginate-locust bean gum microcapsules . Carbohyd. polym. , 103 , 587 – 595 . Corcoran , B.M. , Stanton , C. , Fitzgerald , G.F. & Ross

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. Shi , L.E. , Zhang , Z.L. , Song , Y.Q. , Zhou , M.L. , Yu , W.M. & Tang , Z.X. ( 2013 b): Encapsulation of Lactobacillus bulgaricus in carragenan-locust bean gum coated milk microspheres with double layer structure

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were measured at angles 2θ = 4–40° with step of 0.017° and count time of 50 s. Prior to analysis, LN dispersions were transformed into a paste using locust bean gum as thickening agent, i.e., 1 mL of dispersion was mixed with ~1 mg of gum and then

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] similar to locust bean gum consisting of a (1 → 4) linked α- d -mannopyranose backbone with branch points from their six positions linked to α- d -galactose (i.e., 1 → 6-linked-α- d -galactopyranose). There are between 1.5 and 2 mannose residues for every

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