Y. Victor Wu

Utilization of protein-rich ethanol co-products from corn in tilapia feed

Corn distiller’s grains with solubles (CDGS), which is the residue from ethanol fermentation of corn, were incorporated in tilapia (a warm-water fish) diets that contained either 36% protein without fish meal or 32% protein with and without fish meal. A 103-day feeding study indicated that the three diets containing CDGS resulted in higher weights of tilapia than fish fed a commercial fish feed containing 36% protein and fish meal. The difference in weight gains between 32 and 36% protein diets was not significant. Incorporating fish meal (6%) in diet had no advantage over a diet without fish meal.

HYDROGEN ION EQUILIBRIA OF WHEAT GLUTENIN AND GLIADIN.

Abstract Hydrogen ion titration curves of twice-precipitated wheat glutenin and gliadin have been obtained in 3 M urea plus 0.15 M KCl at 25 °C. The data have been analyzed by equations treating the electrostatic effect as an empirical factor. The ionizing groups per 10 5 g. glutenin, and their intrinsic p K s at 25 °C. are: 38 carboxyl (4.76), 13 imidazole (6.6), 2 α-amino (8.4), 1 sulfhydryl (9.4), 23 tyrosyl (10.42), and 12 lysyl (10.6); those for gliadin are: 22 carboxyl (4.85), 14 imidazole (6.45), 2 α-amino (8.0), 1 sulfhydryl (10.0), 16 tyrosyl (10.31), and 5 lysyl (10.7). The guanidyl groups with p K greater than 13 do not affect the titration curves except through the net charge Z of glutenin and gliadin. The ionizing groups all appear to be normal. Empirical values of the electrostatic factor, w , are significantly larger for carboxyl groups than for tyrosyl groups. This change in w suggests that the conformations of both molecules depend on pH.

Conformational studies of wheat gluten, glutenin, and gliadin in urea solutions at various pH's

Abstract Viscosity, sedimentation velocity, ultraviolet difference spectra, and optical rotatory dispersion measurements were carried out on wheat gluten, glutenin, and gliadin in 3 M urea plus 0.11 M KCl plus 0.02 M buffer at pH 3–10 at 25 °C or room temperature. An increase in intrinsic viscosity and a decrease in sedimentation coefficient for glutenin at pH 10 compared with that at pH 4 are consistent with an increase in asymmetry of the protein molecule. Parameters from optical rotatory dispersion studies on glutenin also indicate a conformational change at pH 10. Some increases in intrinsic viscosity were also observed for gluten and gliadin at pH 10, but the increase for gliadin might not be significant. The absence of tyrosine and tryptophan peaks in the ultraviolet difference spectra of gluten, glutenin, and gliadin suggests that these two amino acids are not involved in any interaction with other groups.

Effect of ionic strength on the molecular weight and conformation of wheat gluten proteins in 3 M urea solutions

Abstract 1. 1.|The influence of ionic strength upon the physicochemical properties of wheat gluten proteins in 3 M urea solution was studied by osmotic pressure, optical rotatory dispersion, intrinsic viscosity, and sedimentation velocity measurements. The number-average molecular weights of wheat gluten and gliadin by osmotic pressure at 25° between pH 4.7 and 7.5 are 67300 and 46600, respectively, and are constant with changes in ionic strength between 0.0025 and 0.15. Gluten and gliadin are considerably aggregated in aluminum lactate buffer of pH 3.2–3.4 and have molecular weights of 224000 and 81200, respectively, but in 3 M urea plus aluminum lactate buffer the molecular weight of gluten is not much higher than 67300. 2. 2.|The sedimentation coefficient of glutenin and gliadin in 3 M urea plus KCl is not altered by changes in ionic strength between 0.0025 and 0.5 (pH 4.8–5.8). Because the osmotic molecular weight and sedimentation coefficient are constant, other physical changes noted are caused by structural changes other than aggregation. Both proteins appear to contain a mixture of α-helix and random-coil structure based on the interpretation of optical rotatory dispersion data in terms of Moffitt—Yang , Cotton effect, and Shechter—Blout calculations. Gliadin contains more helix than glutenin. Based on these measurements there appears to be an increase of helical content in glutenin with an increase in ionic strength but with no significant change in gliadin. Intrinsic viscosities measured in these solvents suggest that glutenin and gliadin molecules have relatively high axial ratios. The intrinsic viscosities decrease with increasing ionic strength and the change is greater with glutenin. These observations are consistent with a more constrained structure for gliadin as compared with glutenin.

Molecular weights of wheat γ1- and γ3-gliadins in various solvents

Abstract The molecular weights of wheat gliadin and its components were determined by a computer technique from sedimentation equilibrium data obtained in an ultra-centrifuge equipped with photoelectric scanner. The solvents included 3 M urea plus 0.15 M KCl at pH 6.3, 1 M acetic acid plus 0.01 M KCl at pH 3.0, 0.01 M HCl plus 0.05 M KCl at pH 2.2, 1 M acetic acid plus 0.05 M KCl at pH 3.0, 6 M guanidine · HCl at pH 4.6, 0.0167 M aluminum lactate buffer at pH 3.1, 6 M guanidine · HCl at pH 2.9, 8 M urea plus 0.15 M KCl at pH 6.3 and 3.0, and 3 M urea plus 0.15 M KCl at pH 3.1. The minimum molecular weights for γ1- and γ3-gliadins, obtained in 3 M urea plus 0.15 M KCl at pH 3.1, were 30 300 and 34 700, respectively. The respective molecular weights of gliadin and low molecular weight gliadin (gliadin with the high molecular weight component removed by a crosslinked dextran column) were 49 200 and 30 300 in 3 M urea plus 0.15 M KCl at pH 3.1. The molecular weights of γ1- and γ3-gliadins are determined for the first time.

Molecular weights of wheat γ2-, β6-, α7-, α8- and α9-gliadins

Abstract The molecular weights of wheat γ 2 -, β6-, α7-, α8- and α9-gliadins were calculated with the aid of a computer technique from sedimentation equilibrium data obtained in an ultracentrifuge equipped with photoelectric scanner. The dissociative solvents, all at pH 3.1 by addition of HCl, included 3 M urea, 0.15 M KCl; 8 M urea, 0.15 M KCl and 6 M guanidine-HCl. The minimum molecular weights for γ 2 -, α7- and α9-gliadins, obtained in 6 M guanidine-HCl, were 34 600, 30 400 and 30 900, respectively. The β6- and α8-gliadins gave minimum molecular weights of 33 000 and 36 900, respectively, in 3 M urea, 0.15 M KCl.

Optical rotatory dispersion studies on wheat gluten proteins: Gluten, glutenin, and gliadin in urea and hydrochloric acid solutions

Abstract Conformations of gluten, glutenin, and gliadin were studied by optical rotatory dispersion in 3 M urea plus 0.11 M KCl plus 0.02 M buffer at several pH values, and in 0.002 N HCl. Wavelength ranged from 600 to around 220 mμ or lower. A significant negative Cotton effect at 233 mμ was observed for each protein in all solvents studied. Values of b0 from Moffit-Yang plots were interpreted conventionally (b0 = −630 for 100% right-handed α-helix). Optical rotatory dispersion data were also treated by a modified two-term Drude equation according to the method of Shechter and Blout. The results indicate that gliadin contains more α-helix than glutenin and that all three proteins contain more α-helix in hydrochloric acid than in urea solutions. Glutenin and gliadin are probably mixtures of random coil and helix.

Food Applications of Oat, Sorghum, and Triticale Protein Products

Oat, sorghum, and triticale protein products offer considerable potential as food supplements. Each has special characteritics applicable to improved food product development. High protein or high lysine lines of these grains have been developed in recent years. Oat, sorghum, and triticale protein fractions have been separated from their grains by wet and dry milling procedures and also by air classification. Recent research is reviewed here concerning production and applications of the protein products.

Effects of Lysine on Growth of Tilapia Fed Diets Rich in Corn Gluten Meal

ABSTRACT Tilapia is a warmwater fish with mild flavor. Nearly 8.6 million kg are produced domestically, and ≈22.7 million kg are imported. Corn gluten meal (60% protein fraction) is a product obtained from wet-milling of corn. Diets (36% protein) containing 36–44% corn gluten meal with different levels of lysine and fish meal were formulated and fed to tilapia in aquaria for 12 weeks. Weight gain (WG) of tilapia fed diets containing the highest level of lysine (7.4% protein) with 4% fish meal was equal to that of fish fed a commercial control diet. Diets with lower lysine resulted in lower WG. The feed conversion ratio (FCR) and protein efficiency ratio (PER) of tilapia fed experimental diets containing adequate levels of essential amino acids and fish meal were the same as for fish fed the commercial control diet (also containing fish meal). Fish fed diets containing lower lysine levels had less favorable FCR and PER. This study shows that corn gluten meal is utilized at high levels in tilapia diets, par...

HYDROGEN-ION EQUILIBRIA OF WHEAT GLUTEN IN GUANIDINE-HYDROCHLORIDE SOLUTIONS.

Abstract Hydrogen-ion titration curves of wheat gluten have been studied in 2 and 4 M guanidine-hydrochloride (G-HCl) at 25 °C. The data were analyzed by equations treating the electrostatic effect as an empirical factor. The ionizing groups per 10 5 gm gluten and their intrinsic p K s at 25 °C in 2 and 4 M G-HCl are: 29 carboxyl (4.54, 4.48), 15 imidazole (6.49, 6.56), 2 α-amino (8.5, 7.7), 1 sulfhydryl (10.0, 9.5), 20 tyrosyl (9.97, 9.97), and 9 lysyl (10.4, 10.4). The number and intrinsic p K of guanidyl groups cannot be determined in G-HCl solutions. The ionizing groups all appear normal. The empirical electrostatic factor w at acid pH was considerably larger than it was at alkaline pH, and a larger decrease in w was observed in alkaline than in acid solutions when the solvent was changed from 2 to 4 M G-HCl. These changes in w suggest that the conformation of gluten depends on pH and that the conformation in acid solution is more stable. Different methods for purifying G-HCl are discussed.