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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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Összefoglalás

Kutatásaink során eltérő őszi búzafajták lisztjéből készült kenyerek sütőipari tulajdonságait vizsgáltuk. A búzalisztet 30%-ban helyettesítettük tritikáléliszttel, adalékanyagként guart és szejtánt alkalmaztunk. Mértük a kenyerek magasságát, sütési és száraz tömegét, elbíráltuk ízét.

Eredményeink alapján megállapítható, hogy az adalékanyagok a kenyérmagasságot és a kenyér száraz tömegét növelték, míg a sütési tömegre nem voltak hatással (98,72–103,23%). A kenyér magasságnál a szejtán hatása kifejezettebb. A száraz kenyértömeg esetében két fajtánál (Mező, Hajdúság) a szejtán, kettőnél (Árkus, Rárós) pedig a guar bizonyult hatásosabbnak.

A kenyerek között ízhatásban lényegi eltérést nem tapasztaltunk, az adalékanyagok használata az ízre nem volt kifejezett hatással. Az eredmények is azt mutatják, hogy az alkalmazott adalék anyagok alkalmasak a lisztkeverékből készült kenyér tetszetős megjelenésének fokozására.

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selected guar gum and xanthan gum. Guar gum is a naturally occurring carbohydrate polymer consisting of straight chain monomer with single membered galactose branches and two units of mannose by β- d (1 → 4) linkages. Guar gum is a galactomannan [ 1

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.D., Pérez, G.T., León, A.E. & Añón, M.C. (2004): Effect of emulsifier and guar gum on micro structural, rheological and baking performance of frozen bread dough. Fd Hydrocolloids, 18, 305–313. Añón M

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Acta Alimentaria
Authors: N. Nedić Tiban, V. Piližota, D. Šubarić, D. Miličević and M. Kopjar

dynamic viscoelastic properties of guar and carrageenan using the Bird-Carreau constitutive model. J. Fd Sci. , 49 , 1569-1572. Predicting steady shear and dynamic viscoelastic properties of guar and carrageenan using the Bird

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Effects of hydrocolloids (arabic gum, guar gum, and xanthan gum) on the physicochemical and rheological properties of whole-barley fortified cracker flour were determined using solvent retention capacity, alveograph, and Mixolab profiles. Results showed that the water absorption of whole-barley fortified cracker flour was reduced by the additional arabic gum. Besides, arabic gum was more effective in reducing the resistance to inflation and improving the extensibility of whole-barley fortified dough. Mixolab parameters indicated that the weakening of gluten proteins and the rate of starch retrogradation in whole-barley fortified cracker dough were reduced by the presence of arabic gum. Guar gum and xanthan gum promoted the rate of protein breakdown, but slowed down the starch gelatinization and retrogradation rate during the Mixolab heating-cooling cycle. In conclusion, involved arabic gum rather than guar gum or xanthan gum is benefit to improve the baking quality of wholebarley fortified saltine crackers.

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Abstract  

Polyamino group-containing resins act both as chelating ion exchangers and weakly basic anion exchangers depending upon the species in contact in the solution. In the present work, ion exchangers based on polyamine incorporated polysaccharides (cellulose and galactomannan or guaran) have been used for removal of radioisotopes of185W as WO 4 2– ,99Mo as MoO 4 2– and125Sb as Sb3+ from their separate aqueous solutions. These chelating anion exchangers have been synthesized by reaction of polysaccharides with epichlorohydrin followed by the respective polyamines as nucleophiles in a strongly alkaline medium. WO 4 2– and MoO 4 2– are adsorbed from their aqueous solutions through anion exchange process by chloride form of cellulose-triethylenetetraamine (cellulose-trien), cellulose-tetraethylenepentaamine (cellulose-tetren), guaran-triethylenetetraamine (guar-trien) and guar-tetraethylenepentaamine (guar-tetren) weakly basic anion exchangers. Guar-tetren chelating polymer has been found to be highly selective for125Sb isotopes presumably due to the presence of chelating cis-hydroxy and tetren groups in the galactomannan matrix.

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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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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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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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