Protein Quality Of Wheat Research Articles

Reliability of Two Laboratory Techniques to Predict Bread Wheat Protein Quality in Nontraditional Growing Areas1

This investigation was undertaken to evaluate the reliability of two laboratory techniques, sodium dodecyl sulphate sedimentation (SDSS) test and SDS‐polyacrylamide gel electrophoresis (SDSPAGE) of the high molecular weight (HMW) glutenin subunits, identify the protein quality factors from different sources of highprotein bread wheat (Triticum aestivum L.) selections. Spring wheat germplasm included high protein hexaploid derivatives from Triticum dicoccoides, and selections from Argentina with good bread milling and baking properties. Winter wheat materials were from the Oregon State University International Winter ✕ Spring Wheat Program. Electrophoretic analysis (SDS‐PAGE) of the HMW glutenin subunits was a reliable indicator of loaf volume at specific protein levels. Elevated protein levels were not always required for high loaf volumes, but usually gave slightly better expansion. The HMW glutenin banding patterns were independent of environment factors. Bands 5 and 10 contributed by the D genome, with either bands 1 or 2* from the A genome and bands 7 and 8 or 17 and 18 coded by the B genome, were correlated with high loaf volume. Fivegram wholemeai samples, suspended in 100 mL of a solution containing 0.96 g lactate L−1 and 20 g SDS L−1 and a reading time of 30 min gave the best sedimentation values to discriminate between wheat lines giving high or low loaf volume. For the experimental materal used, SDSS values were found to be dependent upon variations in protein content.

Evaluation of the protein quality of wheat grains (Grizza 155) and eight related products by the dose-response bioassay

The amino acid analysis revealed that wheat grains, white and dark flour, baladi bread prepared from white or dark flour, bread prepared from formulae enriched with gluten and biscuits are poor in lysine with chemical scores ranging between 20 and 49. The assessment of the protein quality of wheat and related products was done by slope ratio bioassay. Results based on slopes relative to those of reference casein + methionine ranked bread prepared from dark flour and cooked wheat (belila) as the highest in their protein quality, followed by their parent; wheat (RNV = 44). Dietetic bread with gluten had RNV = 20-24; owing to its high protein content (38%), its utilizable protein approached that of good proteins (8%). Very high significant correlation existed between the two measures of response; gain in weight and net increase in body water as response of nitrogen intake.

The effect of level of protein intake in isoenergetic diets on energy utilization

Energy intake is known to affect the efficiency of nitrogen (N) utilization. Less is known about the effect of protein intake on energy metabolism by the growing human. Initial observations were made on a single child consuming successive isoenergetic diets in which protein intake was varied in five levels between 1.0 and 2.0 g/kg per day. Rate of weight gain varied from 2.1 (low protein) to 8.4 (high protein) g/kg per day. The estimated percentage of N in the weight gained was relatively constant during all five dietary periods. Six children were subsequently studied while consuming diets in which protein provided 4, 5.3, 6.4 to 6.7, and 8% of energy intake during randomly assigned dietary periods. Mean rate of weight gain varied from 2.8 ± 2.4 (4% protein energy) to 6.7 ± 1.2 (6.4–6.7% protein energy) g/kg per day (P < 0.05). As protein intake increased from 6.4 to 6.7 to 8% of energy, no further increase in rate of weight gain appeared to occur. Assuming the cost of weight gain to be 5.6 kcal/g, a mean of 16.8 ± 7.9% of energy used for weight gain at the upper levels of protein intake was “wasted” at the lowest level of intake. Reanalysis of studies in which protein quality of wheat protein was improved by incremental supplements of lysine also demonstrated a similar effect of protein quality on weight gain. In addition, the estimated percentage of N in the weight gained did not differ significantly among dietary periods. The data suggest that energy utilization is remarkably sensitive to both the quantity and quality of protein in the diet. These findings have implications in a number of clinical settings in which there are attempts to improve weight gain by “pushing calories” without providing adequate protein. In addition the data raise questions concerning the current Food and Agriculture Organization/World Health Organization recommendations for protein and energy intakes by children in the 6-month to 3-year age groups.

Improvement of wheat protein quality and quantity by breeding.

Substantial genetic, variability for grain protein content in wheat has been identified. In appropriate combinations known genes can increase protein content of wheat grain by 5 percentage points. Productive high protein experimental lines with good agronomic traits and satisfactory processing attributes have been identified. A high protein hard red winter variety developed in Nebraska was released for commercial production in 1975 under the name "Lancota". The high protein of Lancota resides entirely in the starchy endosperm portion of the kernel and is fully transmissible to white milled flour. The high protein of Lancota results from elevated NO3 reductase activity, increased N-absorption by the roots, and more complete translocation of N to the grain. Despite strong environmental influence on wheat protein level, genes for high protein have been demonstrated to effectively increase protein content in many different production environments. Lysine % of protein decreases but lysine % of grain increases as protein is increased. Genetic variability for lysine of sufficient magnitude to overcome the normal depression of lysine % of protein as protein is increased has been uncovered. Experimental lines have been developed in the ARS-Nebraska program in which genes for high protein and high lysine were combined. The lines have been widely distributed for use in other breeding programs.

Critical Available Soil Phosphorus Level of Indian Soils in Relation to Protein Quality of Wheat

AbstractMore information is needed on the relation between the protein quality of wheat and the phosphorus level of the soil on which it is grown. Protein quality of ‘Kalyan Sona’ wheat (Triticum aertivum L.) grown in the greenhouse on 14 alluvial soils was measured by the lysine, methionine, and tryptophan contents of the grain. Quality was inferior when available soil P levels were below 12.5 ppm. Based on this critical level of P, the soils were separated into two groups. The ‘t’ test for protein quality characters of wheat grown on these two groups of soils was highly significant. The importance of soil testing in respect to the need for phosphatic fertilization in maintainng the quality of wheat protein was brought out.

Influence of irrigation and nitrogen fertilization on the amino acid composition of spring wheat

Sprinkler irrigation on clay soils in southern Finland decreased the protein content of spring wheat flour in five field experiments in the years 1967—70, by 16 ± 4 per cent on an average. The amino acid composition, however, was improved, because the proportion of lysine was increased by 6 ± 4 %. Accordingly, the content of lysine in flour was decreased by irrigation only by 10 ± 5 %. An increase of fertilizer nitrogen from 68 to 144 kg/ha increased the protein content of wheat flour by 19 ± 5 %, but the proportion of lysine in the amino acid composition decreased by 9 ± 4 %. Therefore, the lysine content in flour was increased by nitrogen fertilization only by 8 ± 5 %. It seemed as if urea and ammonium nitrate limestone would have had about the same effect on the quantity and quality of wheat protein. As a consequence of the reversed influences of irrigation and nitrogen fertilization on the wheat protein it was possible, by means of irrigation and an additional nitrogen fertilization, to produce 65 per cent higher grain yields without any noteworthy changes in the contents of protein or amino acids.

Protein Quality of Wheat and Soybeans after Rhizopus oligosporus Fermentation

Protein quality of wheat and soybeans fermented with Rhizopus oligosporus has been studied by rat assay methods and amino acid analysis. The fermentation process did not significantly change the essential amino acid composition of wheat or of a mixture of wheat and soybeans. The growth of rats fed fermented wheat improved significantly over those fed unfermented wheat; also the protein efficiency ratio (PER) of wheat was increased by fermentation. These improvements were partly attributed to the increase in availability of lysine in wheat by fermentation. A mixture of wheat and soybeans (1:1) gave a good pattern of amino acids. The mixture as a protein source supported growth well as did casein; also, the fermentation process raised the PER value of the mixture so that it was comparable to casein.