Potentiometric titration studies on xanthan solutions

The potentiometric behavior of xanthan solutions was analyzed as a function of ionic strength, polymer concentration and temperature. For a given value of the polymer dissociation constant, α, pK_a was linearly correlated with C_s^1/3 (salt concentration). At polymer concentrations below 7.5 g liter^-1, pK_a was a function of polymer concentration. However, when the polymer concentration was higher than this value, pK_a was independent of polymer concentration. Potentiometric titration confirmed the significance of the hydrogen bond and the carboxylate group on the secondary structure of xanthan which suggested that the ordered xanthan conformation is stabilized mainly by hydrogen bonds. These can be disrupted by increasing the electrostatic potential of the molecule or by increasing the solution temperature. Neither the ionic strength nor the polymer concentration affected the secondary structure of xanthan at 25°C. However, ionic strength should reduce the repulsive force between charged groups in xanthan; this would explain the salt stabilization of the secondary structure observed at the higher test temperatures (35–70°C).     

Swelling and Rheological Studies of Some Starch Hydrogels

Hydrogels with moderate water retention capacity and salt stability have been prepared from starch, oxidized starch, and amylopectin all crosslinked with epichlorohydrin. The swelling power was measured in water and in various salt solutions of different concentrations. The swelling capacity decreases with increasing both the crosslinker and the polymer concentration. The plateau modulus (G′_p) of the prepared gels was determined from complex dynamic viscosity measurements. G′_p was measured as a function of the epichlorohydrin and polymer concentrations. The loss modulus (G″) for the prepared gels was also measured and was always found to be almost zero. The molecular weight between two entanglement points (mesh width) was estimated from the G′_p values. The ratio between the number of elastically effective entanglement points, calculated from the G′_p values, and that calculated from complete conversion of the cross-linker was also estimated for various gels. It was found that this ratio is very small (0.2–0.7%) for gels prepared with 10 wt-% starch, it increases however to 13% at higher starch concentration of 25 wt-%.     

Study of xanthan gum/waxy corn starch interaction in solution by viscometry

The objective of the study was to investigate the molecular interactions of xanthan gum and waxy corn starch in a ternary system. Solutions of xanthan gum/(waxy corn starch) blends dissolved in a mixed solvent of 90% DMSO/10% H₂O (v/v) were studied by means of viscometry as a function of total polymer concentration and composition. The classical Huggins equation, η_sp/C=[η]+bC, which expresses the specific viscosity (η_sp) of a polymer as a function of the concentration C, was found to be suitable for all blends in the dilute system. The intrinsic viscosity ([η]) and Huggins parameter b of the blends increased with the increase of xanthan fraction in the blends. Meanwhile, the addition of xanthan gum also dramatically lowered the overlap concentration (C*) of the blends. The results indicate that xanthan gum is a good thickener, and xanthan gum and waxy corn starch are attracted to each other in the solution under study.     

Structures and pesticidal activities of derivatives of dinitrophenols. XI. Effects of substitution of dinitrophenols with C3 to C13 alpha-branched alkyl groups and of esterification on the eradication of cucumber mildew

The eradication of cucumber mildew caused by Sphaerotheca fuliginea (Schlecht. ex Fr.) Poll. with 2-(C₄ to C₁₃ α-branched alkyl)-4,6-dinitrophenols and 4-(C₄ to C₁₃ α-branched alkyl)-2,6-dinitrophenols was examined. 2-(C₈ to C₁₃ α-Branched alkyl)-4,6-dinitrophenols were highly active, but O-methylation produced compounds with no activity. 4-(C₇ to C₁₀ and several C₁₁ to C₁₃ α-branched alkyl)-2,6-dinitro-phenols gave a significant degree of eradication. 2-(C₆ to C₁₃ α-Branched alkyl)-4,6-dinitrophenols were significantly more active than their 4-alkyl-2,6-dinitrophenol analogues. Esterification of C₄ to C₇ α-branched alkyl dinitrophenols to methyl- or ethyl- carbonates or crotonates gave compounds with enhanced activity. Generally, the methyl- or ethyl- carbonates or 2-C₈-alkyl-4,6-dinitrophenols were as active as the parent phenols, but the higher alkyl carbonates or crotonates had lower activity. Esterification of 2-(C₉ to C₁₃ α-branched alkyl)-4,6-dinitrophenols to ethyl carbonates and crotonates gave compounds with reduced activity.     

KCI, CaCI2, Na+ Binding, and Salt Taste of Gum Systems

Aqueous nonionic (0.3% w/v) and ionic (0.1% and 0.3% w/v) gum systems containing NaCl, or equal weights of NaCl plus KCl, or NaCl plus CaCl, were examined. At equivalent molar concentrations of added ions, ²³Na NMR transverse relaxation rates (R₂, set^?1) showed an increase in average Na⁺ mobility with the addition of K⁺ or Ca²⁺ to ionic gum systems. Correspondingly, salt taste increased with addition of KCl as determined by Decision Boundary modeling of subject identification data. Viscosity did not affect saltiness. Na⁺ was free to induce salt taste when K⁺ was bound to the gum. Enhancement of salt taste by KCl is due, in part, to competitive binding of Na⁺ and K⁺ in a system.     

Myofibrillar Protein Solubility of Model Beef Batters as Affected by Low Levels of Calcium, Magnesium and Zinc Chloride

Preblended composites of semimembranosus and adductor muscles were stored 12h at 4°C with 2.0% NaCl, 0 or 0.05% CaCl₂, MgCl₂, or ZnCl₂ and 0 or 0.4% sodium tripolyphosphate (STPP). Model systems were formulated to contain 30% fat (high fat; HF) or 10% fat (low fat; LF). Divalent salts lowered extract pH and ZnCl₂ elicited the greatest reduction. At both fat levels, CaCl₂ increased and ZnCl₂ decreased protein solubility, compared to the control (p<0.05). Myosin was not detected in ZnCl₂-treated HF and LF batters without STPP and in the presence of STPP, MgCl₂ and ZnCl₂ increased myosin concentration at both fat levels (p<0.05). Zinc chloride increased actin concentration in HF batters; whereas, MgCl₂ decreased soluble actin in LF batters (p<0.05). Magnesium chloride (0.05%) increased soluble proteins in LF batters containing 0.4% STPP by increasing myosin extractability.     

Structures and pesticidal activities of derivatives of dinitrophenols. IX. Effects of substitution of dinitrophenols with C4 to C13 alpha-branched alkyl groups and of esterification on the eradication of apple mildew

The eradication of apple mildew caused by Podosphaera leucotricha (Ell. and Everh.) Salm. with 2-(C₄ to C₁₃ α-branched alkyl)-4,6-dinitrophenols and 4-(C₄ to C₁₃ α-branched alkyl)-2,6-dinitrophenols was examined. 4-(1-Ethylbutyl)- and most 4-(C₇ to C₁₂ α-branched alkyl)-2,6-dinitrophenols were significantly more active than their 2-alkyl-4,6-dinitrophenol analogues. Compounds containing 4-C₁₃ alkyls did not show significant activity. Activity generally increased as the α-alkyl branch lengthened. Methyl carbonates did not show lower activity than the parent phenols, but esterification of 4-(C₁₂ or C₁₃ α-branched alkyl)-2,6-dinitrophenols to ethyl carbonates or crotonates gave compounds with reduced activity. Methyl-, ethyl- or isopropyl-carbonates and crotonates of 4-(1-ethylhexyl)-2,6-dinitrophenol had much higher activity than the corresponding esters of the 4-(1-methylheptyl) isomer or of 2-(1-ethyl-hexyl)-4,6-dinitrophenol. Compounds containing long ester chains (C₇ or C₈) had less activity than 4-(1-ethylhexyl)-2,6-dinitrophenol. O-Methylation produced compounds with less activity than the parent 4-(1-ethylhexyl)- and 4-(1-propyl-pentyl)-2,6-dinitrophenols.     

UV resistance graft modification of poly(p-phenylene-l,3,4-oxadiazole) fiber with polyhedral oligomeric silsesquioxane

Using the reaction of amino and acyl chloride generated amide bond, poly(p-phenylene-1,3,4-oxadiazole) (p-POD) fiber was pretreated with sulfuric acid solution and was acyl chlorinated with dichloromethane and thionyl chloride. Then octa-ammonium polyhedral oligomeric silsesquioxanes (POSS-NH₂) linked on the fiber surface with the amide bond, which was as UV absorbent to retard UV photoaging. Under the existing experimental conditions, a higher sulfuric acid solution concentration, a higher temperature or a longer time was beneficial for increasing the fixed amount of POSS and prevent the UV accelerated aging of the fiber. The surface morphology, tensile strength, crystallinity, degree of orientation of fibers, and intrinsic viscosity of polymer solution were characterized in detail. This graft process with POSS-NH₂ introduced silicon elements onto the fiber surface. Changes in the surface morphology and chemical composition are not obvious, except that part of the oxadiazole rings were opened. After UV-accelerated aging, the degree of orientation and the crystallinity of the fiber and the intrinsic viscosity of polymer solution were well maintained. The condensed and macromolecular structures of the fiber were well protected.     

Structures and pesticidal activities of derivatives of dinitrophenols. XII.—In vitro activity of C3 to C13 α-branched alkyldinitro-phenols and their esters and ethers against the spores of Venturia inaequalis and other fungi

The activity in vitro of 2-(C₃ to C₁₃ α-branched alkyl)-4,6-dinitrophenols and 4-(C₄ to C₁₃ α-branched alkyl)-2,6-dinitrophenols and of their various esters and ethers was determined against the spores of Venturia inaequalis (Cooke) Wint., Botrytis cinerea Pers., Fusarium bulbigenum, Cooke & Massee, var. lycopersici (Brushi) Wollenw. and Cercospora melonis Cooke. Several alkyldinitrophenols were highly active against Venturia and the 2-alkylphenols were generally more active than the 4-alkylphenols. The alkyldinitrophenols were not effective against the spores of Botrytis, Fusarium and Cercospora.. Esterification of several lower alkyldinitrophenols to methyl carbonates gave compounds with enhanced activity, but methyl carbonates of C₇ to C₁₁ alkyl dinitrophenols showed considerably reduced activity. Esterification to ethyl- or other alkyl-carbonates gave compounds with considerably reduced activity against Venturia. Esterification of 2-isopropyl- and 2-t-butyl-4,6-dinitrophenols to crotonates gave compounds with enhanced activity against Venturia, but crotonates of other phenols showed reduced activity. The acrylates of several C₆ to C₈ alkyl dinitrophenols proved highly active. Ethers of active phenols showed considerably reduced activity.     

SPECIFIC HEAT CAPACITY OF AUSTRALIAN HONEYS FROM 35 TO 165C AS A FUNCTION OF COMPOSITION USING DIFFERENTIAL SCANNING CALORIMETRY

Modulated temperature differential scanning calorimetry was used to investigate the specific heat capacity (C _p ) of 10 Australian honeys within the processing and handling temperatures. The values obtained were found to be different from the literature values at certain temperatures, and are not predictable by the additive model. The C _p of each honey exhibited a cubic relationship (P < 0.001) with the temperature (T, C). In addition, the moisture (M, %), fructose (F, %) and glucose (G, %) contents of the honeys influenced their C_p. The following equation (r² = 0.92) was proposed for estimating C_p of honey, and is recommended for use in the honey industry and in research:      

A Kinetic Approach to Evaluate the Structure‐Based Performance of Antioxidants During Lipid Oxidation

Thermal kinetic parameters of fish oil oxidation, as affected by o‐hydroxyl, o‐methoxy, and alkyl ester derivatives of p‐hydroxybenzoic acid in various concentrations (0.02% to 0.16%) at 35 to 55 °C, were calculated. The average extent of increase (2% to 10%) in the values of free energy of activation, ?G⁺⁺, as well as the average extent of change in the Arrhenius equation parameters, including activation energy (E_a, –40.5% to 13.6%) and frequency factor (A, –55.0% to 4.3%), could be employed well to show structure‐based performance of antioxidants. Temperature coefficient (T_C) and Q₁₀ number, which were considered as the quantitative measures of thermal sensitivity of the lipid system, showed changes from –40.3% and –27.2% to 13.5% and 11.5%, respectively, in the presence of the antioxidants.     

Physical aging of glassy normal and waxy rice starches: effect of aging time on glass transition and enthalpy relaxation

Physical aging and glass transition characteristics of amorphous normal and waxy rice starches (11 and 15% moisture contents) were investigated under differential scanning calorimetry as function of aging time. Normal rice starch showed higher T_g than waxy rice starch. The T_g and ΔC_p at glass transition gradually increased with aging time, whereas fictive temperature was slightly reduced regardless of moisture content and starch type. The relaxation enthalpy and relaxation peak temperature increased with aging time until structural equilibrium was reached. Enthalpy increase was more significant in the early stage of aging whereas temperature increase was constant during the aging period tested (120 h). Aging kinetic analysis using Cowie and Ferguson model revealed that the amorphous normal and waxy rice starches behaved in different modes for the physical aging. Relaxation distribution parameter (β) of both starches was in a range of 0.3<β<0.7, but higher at a lower moisture content, and for normal starch than for waxy starch. Maximum relaxation enthalpy for normal starch (1.10 and 2.69 J/g, respectively, at 11 and 15% moistures) was higher than those of waxy starch (0.77 and 2.48 J/g). Based on the characteristic time (t_c), normal starch has slower progression toward an equilibrium than waxy starch. Overall results proved that physical aging kinetics were highly dependent on starch structure and composition.     

GC evaluation of flavour compound sorption from water solutions by corn starch cryotextures obtained by freezing

Sorption of essential oil aroma components, n-alcohols and linalool by starch corn cryotexture was studied. Results show that terpene hydrocarbons of Rosmarinus officinalis L. essential oil are sorbed quantitatively from 0.05% water solution by cryotexture due to hydrophobic interactions with starch polysaccharides. Aroma compounds with oxygen atoms within the molecule are sorbed two times less. A templating effect with glucose, sucrose, maltose and some essential oil components was observed. Sorption of n-alcohols C₄, C₆, C₈, linalool and their mixture with alkyl acetates in concentration 0.5 — 15 mmol/l was carried out. Individual octanol is sorbed by cryotexture on 88%, hexanol on 20%, linalool on 25%. Butanol is not sorbed at the chosen concentration. Synergism in sorption of hexanol from mixture with octanol and alkyl acetates was observed, while a suppression effect of octanol sorption was found for the same mixture.     

Reduction of fumonisin B1 in extruded corn breakfast cereals with salt,malt and sugar in their formulation

The objective was to determine the effect of added sodium chloride, barley malt and sucrose on the stability of fumonisin B₁ (FB₁) present in corn flour. Two levels of both sodium chloride (0.4% and 2%) and barley malt (0.8% and 5%) were added to the unextruded corn flour, and six levels of sucrose (3–10%) were used. The addition of sucrose at the lowest salt content (0.4%) as well as salt, either at 0.4% or at 2%, led to a significant decrease of FB₁ levels in extruded samples, whereas malt, either at 0.8% or at 5%, did not significantly affect FB₁ stability. Decontamination rates depended on the concentrations of added ingredients and ranged from 2% to 92%. The greatest reductions in FB₁ content were achieved with extrusion cooking with a high salt content, whilst the lowest reductions were the result of processing corn flour with low contents of both salt and sucrose. Salt at 2% was the most effective ingredient in reducing FB₁ content of the final extruded food.     

Gelatinisation Properties of Cassava Starch in the Presence of Salts,Acids and Oxidising Agents

The effect of various cations, anions, acids and oxidising agents on the gelatinisation properties of cassava starch was studied and wide variation was observed in the pasting and swelling properties. Sodium chloride and sodium thiosulphate slightly lowered the peak viscosity of cassava starch with increase in concentration, whereas with sodium sulphite, calcium chloride and sodium hypochlorite, a more significant decrease in the viscosity and breakdown was observed. Ferrous sulphate, alum, aluminium chloride and acids enhanced the peak viscosity at lower concentrations followed by a decrease at 1% and above. Sodium metabisulphite elevated the viscosity at 0.05 and 0.1%, while sodium hypochlorite lowered the viscosity and breakdown. DSC studies showed that aluminium chloride, sodium sulphite, and sodium thiosulphate brought about an increase in T_onset, T_end and ΔH values at higher concentrations. A decrease in swelling volume was observed from 0.05 to 1% concentration of sodium chloride and above that there was a gradual increase. With sodium sulphite, a significant increase in swelling volume was observed at 2.5 and 5% levels. With 0.05 and 0.1% aluminium chloride and sodium metabisulphite an increase in swelling volume was noticed, but at higher concentrations there was a drastic fall. Sodium chloride, sodium sulphite, sodium thiosulphate and calcium chloride brought about decrease in starch paste clarity with increase in salt concentration, whereas ferrous sulphate, aluminium chloride, sodium hypochlorite, hydrochloric acid and acetic acid improved the starch paste clarity.     

Relationships Between Selected Properties of Seeds,Flours, and Starches from Different Chickpea Cultivars

ABSTRACT

Five desi (PBG-1, PDG-4, PDG-3, GL-769, and GPF-2) and one kabuli type (L-550) chickpea cultivars were evaluated for their seed mass, volume, hydration capacity, swelling capacity, cooking time, and instrumental textural properties (hardness, cohesiveness, gumminess, and chewiness). Flour was prepared from these chickpea cultivars and various physicochemical and functional properties were determined. The pasting (pasting temperature, peak viscosity, breakdown, and final viscosity) and gelatinization (T _o, T _p, T _c, and ΔH _gel) properties of these flours were measured using Rapid Visco Analyzer (RVA) and Differential Scanning Calorimeter (DSC), respectively. Starch was also isolated from chickpea cultivars and evaluated for amylose content, swelling power, solubility, and syneresis values. Physicochemical, cooking, and instrumental textural properties of seeds of different chickpea cultivars were related to physicochemical, gelatinization, and pasting properties of their flours and physicochemical properties of their starches. Selected properties of chickpea seeds were significantly correlated with the properties of their starches and flours. Hardness value of soaked chickpea seeds was positively correlated to cooking time, seed mass, seed volume, hydration, and swelling capacity (p < 0.01). Water solubility index (WSI) of chickpea flours was positively correlated to seed mass, volume, hydration capacity, and hardness value (p < 0.05). Selected instrumental textural parameters of seeds had positive correlation with ΔH _gel of flours (p < 0.01). Peak viscosity of flours showed positive correlation to breakdown, final viscosity, bulk density, and negative correlation to cohesiveness of soaked seeds (p < 0.01). Final viscosity showed negative correlation to bulk density and water absorption index (WAI) (p < 0.01) of flours.     

Proteinaceous Surfactants Produced from Gelatin by Enzymatic Modification: Evaluation for Their Functionality

Proteinaceous surfactants were prepared by applying the “one-step process” which permitted covalent incorporation of amino acid esters directly into proteins during treatment with papain. Gelatin was used as a hydrophile and n-alkyl esters of L-leucine as lipophiles. Each of the hydrophile-lipophile mixtures was incubated with papain under the following conditions: medium, 1M carbonate (pH 9) or a 20:80 mixture of acetone-1M carbonate (pH 9) containing 2 mM 2-mercaptoethanol; concentration of gelatin in the medium, 33% (w/w); L-leucine ester vs gelatin ratio, 0.1 mole/100g; papain vs gelatin, 1% (w/w); incubation period, 15 min; and temperature, 37°C. The enzymatic reaction was stopped by adding 1N HCl and the product purified by dialysis followed by washing with hot acetone or dichloromethane to remove low-molecular species. Each product was found to be a mixture of peptides having a wide range of molecular weight, with an average at approximately 7,500 daltons. The amounts of the alkyl moieties covalently incorporated were in a range 1.1–1.2 moles per 7,500g of the products. Their surfactancy varied depending particularly on the carbon number of the alkyl moiety; the products resulting from the incorporation of C₄–C₆ alkyl esters of leucine showed greater whippability, whereas the incorporation of the C₁₀–C₁₂ alkyl esters gave products having a higher ability to stabilize an o/w type emulsions.     

Microstructural characteristics of turbot (Scophthalmus maximus) muscle: effect of salting and processing

The effect of salt concentration on the processing and characteristics of turbot muscle was investigated in this study. The turbot muscle samples were salted with 1%, 5%, 10%, 15%, or 20% w/w salt at 4°C for 3 h. Low-field nuclear magnetic resonance was utilized to characterize water distribution and water holding capacity in the samples. Nuclear magnetic resonance transverse (T₂) relaxation identified three water components (T₂₁, T₂₂, and T₂₃) which all exhibited characteristics correlated with water holding capacity. Textural analysis indicated that hardness and elasticity increased with increasing salt concentration. Histological imaging showed that with the increase of salt concentration, the muscle fiber diameter and area increased first and then decreased. The porosity of salted samples was higher than that of fresh ones. It was shown that salting at lower salt concentrations would lead to partial degradation of the fibrin in the tissue samples and the swelling of proteins. In treated samples, 5% w/w salt was shown to produce the best results. This study provides theoretical basis for the development of salted turbot meat products.     

Physicochemical,Thermal, Morphological and Pasting Properties of Starches from some Indian Black Gram (Phaseolus mungo L.) Cultivars

The starches separated from thirteen different black gram cultivars were investigated for physicochemical, thermal, morphological and pasting properties. Amylose content, swelling power, solubility and water binding capacity of starches ranged between 30.2–34.6%, 16.0–22.3 g/g, 14.8–17.3% and 73.5–84.5%, respectively. The diameter of starch granules, measured using a laser‐light scattering particle‐size analyzer, varied from 12.8 to 14.3 μm in all black gram starches. The shape of starch granules varied from oval to elliptical. The transition temperatures (T_o, T_p and T_c) and enthalpy of gelatinization (ΔH_gel) determined using differential scanning calorimetry, ranged between 66.1–71.3, 71.0–76.2, 75.9–80.4°C and 6.7–9.4 J/g, respectively. Pasting properties of starches measured using the Rapid Visco Analyser (RVA) also differed significantly. Pasting temperature, peak viscosity, trough, breakdown, final viscosity and setback were between 75.8–80.3°C, 422–514, 180–311, 134–212, 400–439 and 102–151 Rapid Visco Units (RVU), respectively. Turbidity values of gelatinized starch pastes increased during refrigerated storage. The relationships between different properties were also determined using Pearson correlation coefficients. Amylose content showed a positive correlation with swelling power, turbidity and granule diameter. Swelling power showed a negative correlation with solubility and setback. T_o, T_p and T_c showed positive correlation with turbidity, pasting temperature and were negatively correlated to peak and breakdown viscosity.     

Phase and State Transitions in Granular Starches Studied by Dynamic Differential Scanning Calorimetry

Phase and state transitions of granular starches heated in water are studied by dynamic differential scanning calorimetry (DDSC). The DDSC results of various granular starches show a stepwise heat capacity (C_p) change in the storage C_p curve, which starts at the beginning of melting or immediately preceding gelatinization and ends before the melting reaches its peak temperature. Annealing reduces the magnitude of this stepwise change in storage C_p. After the amorphous phase is selectively removed by acid, the stepwise storage C_p is greatly reduced. The stepwise storage C_p increase is not observed when recrystallized linear short chains from enzyme‐debranched waxy maize starch are heated in water. The results show that the stepwise change in C_p observed on the granular starch is a unique property associated with the phase transition of granular structure and reflects a glass transition of the rigid amorphous regions in starch granules. The glass transition of the mobile amorphous phase in granular starch is believed to extend over a broad range of temperatures before gelatinization. A small glass transition below 0°C is directly detected by DDSC and is attributed to part of the mobile amorphous fraction in granular starch.