Evaluation of barley as a source of protein for chicks. II. Nutritional assessment of barleys of differing variety and composition as complements to protein concentrates

Barley samples differing in variety, nitrogen fertiliser treatment and location of growth were compared in mixtures with gelatin by the rat net protein utilisation (n.p.u.) test and in mixtures with fish, meat, soya bean or groundnut meals by the total protein efficiency (t.p.e.) chick growth procedure. Small but significant differences were found, the order of superiority of the barleys varying according to the nature of the accompanying concentrate and in some cases there were indications that the variations in quality were related to amino-acid composition. In general the poorer the quality of the accompanying concentrate the more pronounced were the differences between the barleys.     

Hydroxypropylmethylcellulose at the oil–water interface. Part II. Submicron-emulsions as affected by pH

The emulsifying behavior of four different commercial types of hydroxypropylmethylcellulose (HPMC) was studied and correlated with the properties of the interfacial films.     

Application of the plastein reaction to mycoprotein: II. Plastein properties

Mycoprotein peptide hydrolysates have been used as starting materials for plastein synthesis. Compared to other proteins studied, mycoprotein hydrolysates were a relatively poor substrate for the plastein reaction and generally led only to thixotropic viscous solutions, rather than to gelled products, and only low yields of insoluble plastein material. Once formed, however, the insoluble fraction remained insoluble over the whole pH range of 2–11. In contrast to many other plasteins, the mycoprotein material was not solubilised by detergents such as sodium dodecyl sulphate although, like others, it was largely solubilised by 50% (v/v) organic acids or 1 M NaOH and partially solubilised by chaotropic agents such as 8 M urea, 6 M guanidinium chloride and 7 M potassium thiocyanate. A combination of 8 M urea and 50% (w/v) citric acid completely solubilised the plastein to a clear solution. Gel filtration failed to reveal any change in peptide molecular weight distribution on plastein formation while ion-exchange chromotography showed some quantitative differences but these were difficult to interpret as most of the material did not adhere to the anion-exchange column under the conditions used. Amino acid analysis revealed a marked preferential incorporation of hydrophobic peptides into the plastein fraction. Differential scanning calorimetry results showed only broad peaks which suggested heterogeneous reaction mixtures and products with no well-defined structural elements. These results are entirely consistent with plastein formation proceeding via a purely physical aggregation pathway.     

Foliar analysis as a diagnostic technique in cocoa nutrition. II.—Errors during the preparation phase prior to analysis of leaf samples

Errors arising from the preparative phase of storing the fresh harvested cocoa leaves during transit to the laboratory, washing, drying, grinding and storage of the ground material before analysis have been studied. A procedure aimed at reducing such errors is recommended.     

The Mechanism for the Synthesis of Starch and Its Relationship to Flagellin and to the Newly Proposed Structural Model for DNA. Part II.

All of the components and enzymes required for the synthesis of starch by the glycogen precursor method have now been shown to exist. In this mechanism, the genetic inducer sucrose stimulates the production of phosphorylase and the Q-enzyme. These and other enzymes in turn convert sucrose to glycogen. The external branches of the glycogen are then removed by the debranching enzyme isoamylase. The removed branches act as substrates, necessary co-enzymes, suppliers of adenosine diphosphate glucose (ADPG), and possibly genetic inducers for the production and enzymatic activity of glucosyltransferase. They are converted into ADPG by the D-enzyme plus other enzymes and then into amylose. Consequently, the percentage of amylose is directly proportional to the degree of debranching of amylopectin, which in turn is determined by how long amylopectin can be retained in the plastid solution before precipitating with isoamylase or other enzymes to form starch. The ability of the above specialized mechanisms to occur in the same solution is thus a result of selective complexing of enzymes to different polysaccharides and the production of different genetic inducers. Thus the interaction of different inducers with DNA repressors determines the time-sequence for the production of specific enzymes. The thermal stability of thermophile flagellins and the inability of 6 M guanidinium chloride (GCl) to dissociate mesophile flagellin dimers (M_w = 40,000) or thermophile flagellin trimers (M_w 54,000) supports the conclusion that protein-amylopectin complexes exist and cannot be readily dissociated. Because hydroxyls are involved in these flagellin aggregates, then the hydroxyls of much larger amylopectin molecules should also be able to form similar stable bonds with proteins. It is proposed that mutations can be caused by either elimination of active genes by feed-back mechanisms (permanent repressors) or by chemicals and radiation. New genetic strains of grains produced by radiation for resistance to pests can thus only lead to disaster. Improvement of the soil is the only means for the production of lasting resistant strains.     

Determination of sulphur in foodstuffs. II. Reduction to hydrogen sulphide

Sulphate formed by the oxygen-flask combustion of foodstuffs may be quantitatively reduced to hydrogen sulphide by a mixture of hydriodic acid, hypophosphorous acid and hydrochloric acid. The gas, swept out by nitrogen, is absorbed in sodium hydroxide solution and titrated with mercuric acetate solution using dithizone as indicator. The difficulties encountered in the method, including interferences, have been investigated and compared with a turbidimetric method. This reduction procedure is recommended where accuracy is required or where elements that interfere with the simpler methods are present.     

Bovine muscle 20S proteasome. II: Contribution of the 20S proteasome to meat tenderization as revealed by an ultrastructural approach

The role of the 20S proteasome proteolytic effects was revisited using an ultrastructural approach with the aim to explain some particular structural changes identified in type I muscles and in high pH meat. In both types of meat, major changes observed after ageing are an increase in the thickness of the Z-line followed by the appearance of an amorphous protein structure spreading out over the I-band. This was followed by a total degradation of this amorphous structure and of the Z-line. Partial transversal fragmentation of the myofibrils within the I-band can also be detected. The data reported clearly demonstrate that the 20S proteasome was able to mimic these sequential structural changes, a feature never obtained with either calpains or cathepsins. It is the first time that a direct implication of this complex in postmortem muscle is postulated.     

Wheat endosperm hardness. Part II. Relationships to content and composition of flour lipids

In Part I we analysed hardness and colour of wheat endosperm and stated that these features are quite well correlated among kernels of individual varieties. In order to enhance knowledge of the biochemical basis of endosperm hardness, this study aimed at determining how the content and the composition of free and starch lipids influence it. Wheat samples (used previously in Part I) were milled in a way that reduced the number of non-endosperm particles in flour. Simple linear correlation coefficients between endosperm hardness and its lipid composition indicated that hardness was positively correlated with the content of free glycolipids (r=0.82) and negatively with the content of surface lipids of starch, especially with their non-polar fraction (r=-0.83). The typical feature of harder wheat varieties was a substantially higher content of oleic acid in lipids of the starch surface.     

Tryptic phosphopeptides from whole casein. II. Physicochemical properties related to the solubilization of calcium

Casein phosphopeptides (CPP) were produced by tryptic hydrolysis of sodium caseinate and further purified by precipitation and chromatography on QAE-Sephadex A-25. Their physico-chemical properties were compared with the properties of an enzymically dephosphorylated equivalent preparation (DPP). Binding of Ca2+ to the peptides was measured using a Ca selective electrode and was found to increase with pH and to show 1/1 stoicheiometry Ca/Porg in CPP at pH 6.5 and 7.6. Klotz plots indicated equivalent binding sites at these two pH values, but some heterogeneity was seen at pH 3.5. In contrast, DPP did not bind significant amounts of Ca2+. CPP effectively inhibited the formation of insoluble calcium phosphates at different Ca/P ratios. The effective CPP concentration was 10 mg/l and complete stability of calcium phosphate solutions was obtained at about 100 mg/l. This stabilizing effect was dependent on the presence of organic P.     

Conditioning studies on Australian wheat. II. Morphology of wheat and its relationship to conditioning

A morphological study was carried out on three hard and three soft Australian wheat varieties. A number of staining techniques were developed to reveal the structure of the bran layers and the endosperm and hence to establish any inter-varietal differences. This information has been used to facilitate the explanation of expected differences in the rate of penetration of the water used in the conditioning of wheat prior to milling, and in the milling yields themselves. Possible explanations for these differences in behaviour include variations in the thickness and composition of the outer cuticle and testa, the extent to which the outer epidermal and inner parenchymal cells have been compressed, and the number and size of protein masses present in the sub-aleurone endosperm cells.     

Application of chemical methods for the assessment of beef quality. II. Methods related to protein breakdown

Various methods for assessing the extent that the protein has spoiled in stored beef are considered in relation to the various criteria discussed in Part I. From the point of view of routine quality control, the macro-distillation of the volatile nitrogen produced appears to be the most reliable method. From statistical correlations with odour scores, most beef can be considered to be acceptable if the total volatile nitrogen (TVN) and TVN/FF (fat-free) figures do not exceed 16.5 and 19.7 mg N/100 g respectively.     

Starch Graft Polymers. II. Preparation of Graft Polymers Containing Acrylamide and Acrylic Acid and Evaluation as Textile Print Paste Thickeners

Graft copolymers of starch and the vinyl monomers acrylamide (I) and acrylic acid (II) – prepared by γ-radiation induced grafting reactions – and a graft terpolymer of starch, I and II – prepared by base hydrolysis of a graft copolymer of starch and acrylonitrile (III) — have been evaluated as textile print paste thickeners. Preparation, characterization and evaluation procedures are presented together with results illustrating that starch poly (I) containing 39% poly (I) and starch poly (I, II) containing a mixture of 21% I and 37% II are effective thickeners in this application if used in combination with one another or with commercial thickeners such as algin (sodium alginate).     

Proteases of the soyabean. II. Specificity of the active fractions

Six proteolytic fractions of the soyabean differed in specificity on synthetic substrates. Their Michaelis constants on poly (L-glutamic acid) differed one from the other. The optimum pH values of proteolytic action were slightly lower than that of the crude extract. The fractions did not autolyse, nor did one fraction hydrolyse any other. Finally, none of the fractions exhibited trypsin-like activity, as characterised by ability to hydrolyse benzoylarginine ethyl ester, either at their optimum pH or at the pH optimum of trypsin.     

Conditions Governing Food Protein Amyloid Fibril Formation. Part II: Milk and Legume Proteins

Both intrinsic and extrinsic factors impact amyloid formation of food proteins. We here review the impact of various conditions and food constituents on amyloid fibrillation of milk and legume proteins. Much less is known about casein and legume protein amyloid‐like fibril formation than about that of whey proteins such as β‐lactoglobulin, α‐lactalbumin, and bovine serum albumin. Proteins of both sources are often studied after heating under strong acidic (pH < 3) conditions. The latter induces changes in protein conformation and often peptide hydrolysis. At higher pH values, alcohols, chaotropic and/or reducing agents induce the conformational changes required to enhance fibrillation. Different types of food proteins can impact each other's fibrillation. Also, the presence of other food constituents can enhance or reduce it. No general conclusions on the mechanisms or impact of different food constituents on food proteins can be made. Optimal conditions for AF formation, that is, heating for several days at low pH, are rare in food processing. However, this does not exclude the possibility of AF formation in food products. For example, slow cooking of hydrolyzed proteins may enhance it. Future research should focus on the prevalence of AFs in complex food systems or model systems relevant for food processing.