Functional and structural properties of gliadin as influenced by pH, extraction protocols, and wheat cultivars.

Gliadin, owing to its low cost, ease to extract, high foaming capacity, easily available and high surface hydrophobicity, has found a wide range of applications both in the food and pharmaceutical sectors. The functional and structural characteristics of gliadin extracted with four extraction protocols from six wheat cultivars were investigated in this study. The surface-active properties of gliadin protein as a function of pH, extraction protocols, and wheat cultivars were compared, including solubility, zeta-potential, foaming properties, emulsion properties, surface hydrophobicity and secondary structure. Overall gliadin extracted using different extraction protocols and from different wheat cultivars was found to be higher in ß-turns (24.88-37.91 %), followed by ß-sheet (12.81-22.37 %), α-helix (15.13-20.70 %) and lower in random coil (6.53-9.08 %). Varied pH ranges, wheat cultivars, and different extraction protocols were found to have a substantial impact on solubility, zeta potential, foaming stability, emulsion capacity and surface hydrophobicity. The foaming capacity was observed to be more influenced by extraction protocols than wheat cultivars. Emulsion stability showed statistically significant (p ≤ 0.05) influence between the wheat cultivars, and a non-significant (p ≥ 0.05) difference among extraction protocols. The functional properties of freeze-dried gliadin extracted using different protocols were found to be pH-dependent. A comprehensive understanding of how the structural, surface active and functional properties of gliadin are influenced by the extraction protocols and wheat cultivars will enable us to understand the gliadin better and broaden its use for both food and non-food applications.

Characterization of gliadin, secalin and hordein fractions using analytical techniques.

Prolamins, alcohol soluble storage proteins of the Triticeae tribe of Gramineae family, are known as gliadin, secalin and hordein in wheat, rye and barley respectively. Prolamins were extracted from fifteen cultivars using DuPont protocol to study their physiochemical, morphological and structural characteristics. SDS-PAGE of prolamins showed well resolved low molecular weight proteins with significant amount of albumin and globulin as cross-contaminant. The ß-sheet (32.72-37.41%) and ß-turn (30.36-37.91%) were found higher in gliadins, while α-helix (20.32-28.95%) and random coil (9.05-10.28%) in hordeins. The high colloidal stability as depicted by zeta-potential was observed in gliadins (23.5-27.0 mV) followed secalins (11.2-16.6 mV) and hordeins (4.1-7.8 mV). Surface morphology by SEM illustrated the globular particle arrangement in gliadins, sheet like arrangement in secalins and stacked flaky particle arrangement in hordeins fraction. TEM studies showed that secalin and hordein fractions were globular in shape while gliadins in addition to globular structure also possessed rod-shaped particle arrangement. XRD pattern of prolamin fractions showed the ordered crystalline domain at 2θ values of 44.1°, 37.8° and 10.4°. The extracted prolamins fractions showed amorphous as well as crystalline structures as revealed by XRD and TEM analysis. Space saving hexagonal molecular symmetry was also observed in TEM molecular arrangement of prolamins which has profound application in development of plant-based polymers and fibres.

Comparative Quality Evaluation of Physicochemical, Technological, and Protein Profiling of Wheat, Rye, and Barley Cereals.

Agronomically important cereal crops wheat, barley, and rye of the Triticeace tribe under the genus Triticum were studied with special focus on their physical, proximal, and technological characteristics which are linked to their end product utilization. The physiochemical parameters showed variability among the three cereal grains. Lactic acid-solvent retention capacity (SRC) was found to be higher in wheat (95.86-111.92%) as compared to rye (53.78-67.97%) and barley (50.24-67.12%) cultivars, indicating higher gluten strength. Sucrose-SRC and sodium carbonate-SRC were higher in rye as compared to wheat and barley flours. The essential amino acid proportion in barley and rye cultivars was higher as compared to wheat cultivars. Barley and rye flours exhibited higher biological value (BV) owing to their higher lysine content. SDS-PAGE of wheat cultivars showed a high degree of polymorphism in the low molecular range of 27.03-45.24 kDa as compared to barley and rye cultivars. High molecular weight (HMW) proteins varied from 68.38 to 119.66 kDa (4-5 subunits) in wheat, 82.33 to 117.78 kDa (4 subunits) in rye, and 73.08 to 108.57 kDa (2-4 subunits) in barley. The comparative evaluation of barley and rye with wheat cultivars would help in the development of healthy food products.

Comparative evaluation of gliadins from four extraction protocols using advanced analytical techniques.

Gliadin, a major component of gluten, is known to trigger celiac disease; therefore, its extraction is important to study its properties as well as its presence in gluten-free products. Four gliadin extraction procedures Osborne (1924), Weiss (1993), Wallace (1989) and DuPont (2005), were investigated on six wheat cultivars using advanced analytical techniques such as dynamic light scattering (DLS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Higher zeta potential of extracted gliadin was observed in DuPont (23.53-27), followed by Weiss (16.17-20.80), Osborne (16.17-20.13), and Wallace (14.60-19.47). Particle Z-average size (15.74-184.83 nm) was found to have an inverse relationship with the Polydispersity index (0.17-184.83). The surface morphological structure of TEM studies revealed the compact globular particle arrangement of gliadin, besides rod-shaped arrangement, was also found in DuPont and Wallace extracted gliadin. XRD pattern of gliadin exposed the crystalline domain at 44.1°, 37.8°, and 10.4° diffraction peaks. The d-spacing obtained from XRD and TEM-SAED analysis supports the presence of crystalline domains in gliadin apart from the amorphous domain. The insight obtained from this work will provide a better understanding of morphology and other properties of the same protein extracted with different extraction procedures.

In Vivo Bioavailability of Lycopene from Watermelon (Citrullus lanatus Thunb) Coloring.

Diet containing watermelon coloring (5, 20, 35 and 50 mg lycopene/100g) was fed to albino rats to study in-vivo bioavailability of lycopene. The rats were fed with lycopene enriched test diets for seven days of treatment period along with control diet during pre and post treatment periods of seven days each. The body weight of each group of albino rats significantly increased during feeding trial which showed that rats were in healthy condition during the treatment. The daily lycopene intake from test diets varied from 0.03 to 0.51 mg during treatment period of seven days which decreased to 0.02-0.07 mg during post-treatment period with control diet. The lycopene absorbed by different groups of rats varied from 0.22 to 3.74 mg/kg body weight of rat during treatment period and 0.15-0.67 mg/kg body weight of rat during post-treatment periods. Lycopene bioavailability increased proportionately with the lycopene content of test diet.

Diversity in Grain, Flour, Amino Acid Composition, Protein Profiling, and Proportion of Total Flour Proteins of Different Wheat Cultivars of North India.

Wheat cultivars grown at three different locations in North India were assessed for their variability in kernel and flour characteristics. Protein and the wet and dry gluten contents of the flour varied significantly (p ≤ 0.05) from 9.32 to 12.60%, 23.46 to 43.04%, and from 8.28 to 15.00%, respectively. Wheat varieties exhibited moderate sodium dodecyl sulfate (SDS) sedimentation and solvent retention values. Flour showed a significant (p ≤ 0.05) difference in the amino acid composition. Lysine, having the lowest chemical score, was the first most limiting amino acid in all wheat varieties. The variability of total flour proteins determined by SDS-PAGE showed polymorphism both in the number and intensity of bands, particularly in the molecular weight range of 35.1-42.8 kDa corresponding to the α-, ß-, and γ-gliadin/low-molecular-weight glutenin subunit (LMW-GS) region. Pearson's correlation established between the various grain and flour parameters showed a significant correlation, which can result in better end product use.

Comparative study of structural and functional characterization of bran protein concentrates from superfine, fine and coarse rice cultivars.

Rice bran protein concentrates prepared from superfine, fine and coarse cultivars were assessed for their physicochemical, structural, functional properties and digestibility. The protein concentrates differed in structural, thermal and functional properties. Rice bran protein concentrate of fine cultivar (F-RBPC) had relatively more ß-sheets (42.81%) and less α-helix (15.03%) and ß-turns (21.98%) than that of superfine (SF-RBPC) and coarse (C-RBPC) cultivars. Thermal denaturation temperature (Td) was similar for all cultivars, whereas enthalpy of denaturation (ΔH) was high for F-RBPC. Essential and uncharged polar amino acids were the highest in F-RBPC and the lowest in C-RBPC. SF-RBPC had higher digestibility in comparison to F-RBPC and C-RBPC. Surface hydrophobicity, protein solubility and foaming capacity were greatest for F-RBPC. Whereas, SF-RBPC exhibited better foaming stability and emulsion activity and C-RBPC displayed more stable emulsion. Principal component analysis revealed that Td and ΔH were positively correlated with ß-sheets content. Foaming capacity and protein solubility were related positively with surface hydrophobicity and negatively charged or uncharged polar amino acids. Emulsion properties were negatively correlated with hydrophobicity. In vitro digestibility of protein was negatively correlated to the ratio of Arginine to Lysine.

Utilization of watermelon pulp for lycopene extraction by response surface methodology.

Lycopene extraction was optimized from watermelon pulp using response surface methodology using independent variables:solvent/meal ratio (4:1-12:1v/w), number of extractions (1-5), temperature (20-60°C) and extraction time (4-20min). Watermelon pulp had 59.95mglycopene/100g on fresh weight basis. The experimental values of lycopene with selected combinations of independent variables were 8.20-59.17mg/100g on fresh weight basis. The second order model obtained revealed a coefficient of determination (R2) of 0.986, the standard error of 0.04, the root mean square error of 0.02 and a scattered plot between experimental and predicted values. The optimum solvent/meal ratio, number of extractions, temperature and extraction time were 10:1v/w, four, 50°C and 16min respectively. The optimum conditions of lycopene extraction were confirmed experimentally.

Physico-chemical properties of acetylated starches from Indian black gram (Phaseolus mungo L.) cultivars.

Starches separated from three black gram cultivars were modified by acetylation and compared to their native starches. Acetylation was carried out by treating starches with 0.04 and 0.08 g of acetic anhydride/g of starch dry weight basis (db) at 25 °C. The extent of acetylation increased proportionally with the concentration of acetic anhydride used. Retrogradation of acetylated starch pastes decreased significantly (p ≤ 0.05) as revealed by significant decrease in syneresis, increased freeze thaw stability and increased light transmittance. The pasting curves of 10.7 % starch slurries showed that acetylation decreased the setback viscosity values by 51.2-82.8 % and pasting temperature by 3.1-5.6 °C than respective native starches. Differential scanning calorimetry observations also revealed significant decrease in gelatinisation temperature of acetylated starches than native starches. Hardness and adhesiveness of starch gels varied between 10.3 and 32.6 g and 4.6-82.3gs, respectively which were significantly lower than corresponding native starch gels.

Total phenolics, antioxidant activity, and functional properties of 'Tommy Atkins' mango peel and kernel as affected by drying methods.

Mango processing produces significant amount of waste (peels and kernels) that can be utilized for the production of value-added ingredients for various food applications. Mango peel and kernel were dried using different techniques, such as freeze drying, hot air, vacuum and infrared. Freeze dried mango waste had higher antioxidant properties than those from other techniques. The ORAC values of peel and kernel varied from 418-776 and 1547-1819 µmol TE/g db. The solubility of freeze dried peel and kernel powder was the highest. The water and oil absorption index of mango waste powders ranged between 1.83-6.05 and 1.66-3.10, respectively. Freeze dried powders had the lowest bulk density values among different techniques tried. The cabinet dried waste powders can be potentially used in food products to enhance their nutritional and antioxidant properties.

Characterisation and functional properties of watermelon (Citrullus lanatus) seed proteins.

BACKGROUND: People in developing countries depend largely on non-conventional protein sources to augment the availability of proteins in their diets. Watermelon seed meal is reported to contain an adequate amount of nutritional proteins that could be extracted for use as nutritional ingredients in food products. RESULTS: Osborne classification showed that globulin was the major protein (≥500 g kg (-1)) present in watermelon seed meal, followed by albumin and glutelin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that the polypeptides had low molecular weights ranging from 35 to 47 kDa. Isoelectric focusing revealed that the isoelectric point of most proteins was in the acidic range 4-6. These proteins are rich in aspartic acid, glutamic acid and serine. An increase in pH (5-9) significantly (P < 0.05) decreased the denaturation enthalpy of these proteins. Among functional properties, albumin exhibited a much higher dispersibility index (810.3-869.6 g kg(-1)) than globulin (227.8-245.4 g kg(-1)), glutelin (182.1-187.7 g kg(-1)) and prolamin (162.3-177.7 g kg(-1)). Digestibility was in the ranges 760.6-910.0 and 765.5-888.5 g kg(-1) for Mateera and Sugar Baby watermelon protein fractions respectively, while surface hydrophobicity ranged from 126.4 to 173.2 and from 125.8 to 169.3 respectively. The foaming and emulsifying properties of albumin were better than those of the other proteins studied. CONCLUSION: The good nutritional and functional properties of watermelon seed meal proteins suggest their potential use in food formulations.