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.

Changes in physicochemical, nutritional characteristics and ATR-FTIR molecular interactions of cereal grains during germination.

The cereal grains such as wheat, barley, sorghum, millets were evaluated before and after germination (24 h, 48 h and 72 h) and compared for their proximate composition, antioxidant activity, total phenolic content, total flavonoid content, pasting properties, in vitro starch digestibility and FTIR spectroscopy. Germination inversely affected the protein, fat, and ash content of different cereal grains. The germinated flours have less water content and higher oil absorption capacities along with reduced starch content. The contents of rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS) in the ungerminated cereal flours ranged from 20.7 to 32.1%, 26.9 to 38.0% and 6.2 to 17.6% respectively but after germination of 72 h, the RDS content increased from 26.5 to 36.2% while SDS and RS content decreased from 26.1% (sorghum) to 16% (barley) and 14.7% (barley) to 4.6% (wheat) respectively. The drought-tolerant crops (sorghum, millets and barley) are potential sources of antioxidants and phenolic content and yielded lower hydrolysis index and estimated glycaemic index upon germination. The highest section of antiparallal ß-sheet, α-helix and ß-turns were found in wheat flour followed by sorghum flour and their proportion decreased with continuous germination. The continuous reduction of viscosity was evaluated with the progress in germination. Overall, germination is a way to get health-promoting compounds from less utilizing cereal such as millets, sorghum and barley and enhance their uses to nourish the huge population with the aim to fulfill their nutritional requirements.

Impact of ultrasonication on functional and structural properties of Indian wheat (Triticum aestivum L.) cultivar starches.

In the present study, functional and structural properties of wheat starches treated with ultrasonication for 15 and 30 min (US-15 and US-30, respectively) were studied. Functional properties such as swelling power, amylose content and oil absorption capacity increased significantly (P ≤ 0.05) upon ultrasonication. A-type crystalline nature of wheat starches remained unaffected with ultrasound treatment, whereas relative crystallinity increased after US-15 and US-30, but the percentage increase was less in case of US-30 (30.82-34.06%) as compared to US-15 (33.70-37.36%). FTIR spectral patterns showed that no new bond was formed or broken by ultrasonication in starch molecule, whereas the absorbance ratios 1022/995 cm-1 decreased significantly (P ≤ 0.05) and ranged between 0.976 and 1.056 and 1.003-1.055, for US-15 and US-30, respectively. Scraps and deformities made on granule surfaces by ultrasonic waves were clearly observed in SEM images, which were more prominent in case of large sized starch granules. Particle size analysis revealed that the percent volume of A-type granules increased with both US-15 (68.85-79.72%) and US-30 (70.96-79.89%), whereas that of B-type granules decreased after US-30 treatment.

Effect of high-intensity ultrasound treatment on nutritional, rheological and structural properties of starches obtained from different cereals.

The ultrasonication was applied to four cereal starches namely wheat, barley, rice, and maize for two ultrasonication treatment durations, i.e., 15 and 30 min (T 15 and T 30, respectively) and were evaluated for their in vitro digestibility, XRD, FTIR spectroscopy, morphological and rheological properties. Ultrasonication increased the swelling power and solubility of starches from different cereals. For ultrasonicated starches (both raw and cooked), the RDS and RS content exhibited significant (P ≤ 0.05) an increase with an increase in treatment duration. RDS content exhibited an increase after both cooking and ultrasonication and ranged between 67.8 and 81.4%, whereas RS content declined with cooking and enhanced with ultrasonication and ranged between 2.3 and 3.1% after T 30 while SDS content decreased with increase in ultrasonication duration. FTIR spectra of ultrasonicated starches showed the characteristic broad peaks at 3351 to 3404 cm-1and to assigned to OH stretching of the hydroxyl group. The rheological properties showed an increase in G' and G″ for 15 min ultrasonication and decreased with 30 min ultrasonication. The main effects of ultrasonication were led to the formation of depressions and pores on the surface of starch granules, which were appropriately observed in wheat and maize starches.

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.

Effect of Acacia Gum, NaCl, and Sucrose on Physical Properties of Lotus Stem Starch.

Consumer preferences in east Asian part of the world pave the way for consumption of lotus stem starch (LSS) in preparations such as breakfast meals, fast foods, and traditional confectioneries. The present study envisaged the investigation and optimization of additives, that is, acacia gum, sodium chloride (NaCl), and sucrose, on water absorption (WA), water absorption index (WAI), and water solubility index (WSI) of LSS employing response surface methodology (RSM). Acacia gum resulted in increased water uptake and swelling of starch; however, NaCl reduced the swelling power of starch by making water unavailable to starch and also due to starch-ion electrostatic interaction. Sucrose restricted the water absorption by binding free water and decreased amylose leaching by building bridges with starch chains and thus forming rigid structure.

Effect of incorporating hydrothermal, kilned and defatted oats on antioxidant and chapatti making properties of wheat flour.

Oats were subjected to treatments like defatting, hydrothermal cooking and kilning, milled into flour and then the control and treated flours were incorporated into wheat flour at 25% and 50% levels and chapatti making behaviour and antioxidant properties were studied. The treatments significantly affected the antioxidant properties of oats. Incorporating oat flours to wheat increased total phenolic content but lowered the antioxidant activity however both were decreased significantly upon baking. The reducing power of the oat blended flour was higher than the wheat flours and ranged from 8.0 to 15.5 µmol AAE/g and was further increased upon baking. The metal chelating activity of flour blends varied from 62.0% to 73.8% and further increased upon baking. After baking the total flavonoid content was lowered and ranged from 308 to 389 µg CE/g. The non-enzymatic browning index significantly increased up to 27.6% upon baking.

Physicochemical, morphological and pasting properties of acid treated starches from different botanical sources.

Effect of acid modification on physico-chemical, morphological and pasting properties of banana, sweet potato, lotus stem and wheat starches were studied. Results revealed that swelling power, solubility and water binding capacity of all starches decreased by acid modification. By acid modification starch granules from different varieties tended to appear fused and less smooth than the native starch granules. The pasting properties of native starches of all different varieties have significantly decreased following acid modification. Acid modified starches showed higher syneresis as compared to native starches.