PREDICTION OF THE QUALITY OF SOME TURKISH WHEAT GENOTYPES BY ELECTROPHORETIC SEPARATION OF PROTEIN FRACTIONS

An exploratory study was conducted to compare Konya‐Bezostoya and Tokat‐Bezostoya, bread making varieties of wheat, and Sofu, a Turkish local strain used for pasta making plus four breeding lines to ascertain which of the breeding lines most likely merits carrying forward for further refinement of the line. The wheat was analyzed for weight per unit of volume, kernel weight, impurities, kernel size and shape and hardness; for moisture, ash and protein content; sedimentation values and wet and dry gluten content to provide background information on kernel characteristics. The chief purpose of the study was to examine the electrophoretic properties of the standard varieties and breeding lines to relate genetic characteristics to bread‐ or pasta‐making potential. Glutenin profiles and gliadin subunits were among the factors studied. Low and high‐molecular‐weight (HMW) alleles were considered. Two of the     

RHEOLOGICAL BEHAVIOUR OF MIXED GELS OF WHEAT STARCH AND ETHYL(HYDROXYETHYL)CELLULOSE

Gelatinisation of wheat starch (6%) in the presence of a nonionic amphiphilic polymer, ethyl(hydroxyethyl)cellulose (EHEC) has been studied. Concentration (0.1–1 wt %) and molecular weight (approximately 80,000–350,000) of EHEC were shown to influence the rheological behaviour of the pastes at 60C, and the gels after 340 min storage at 25C. Two separated regions in the mechanical spectra (0.01–10 Hz) were observed for the mixed gels at 25C with the highest concentration of EHEC. This behaviour suggested long range (overall gel properties) and the influence of short range (molecular entanglements) interactions.     

INFLUENCE OF THE STARCH GRANULE SURFACE ON THE RHEOLOGICAL BEHAVIOUR OF WHEAT FLOUR DOUGH

The influence of the properties of the starch granule surface on the rheological behaviour of wheat flour doughs was studied in dynamic oscillation measurements (frequency sweep and strain sweep) and in stress relaxation measurements. A flour with a high protein content (15%) was diluted with wheat starch to obtain a protein content of 10%. The granule surface of the substituted starch was modified in three different ways: by heat treatment, by adsorption of a wheat protein fraction and by adsorption of lecithin to the granule surface. The effects of these modified starches were compared with the results obtained for nonmodified starch and protein or lecithin (in liposomes) added to the flour. Owing to the low concentration of the added protein and lecithin, no effect was observed when they were added to the bulk of flour. However, as a starch-surface modification the same components influenced the rheological parameters studied. Also the heattreated starch had an effect on the rheological behaviour. The study established the importance of the properties of the starch-granule surface in wheat flour dough.     

THE EFFECT OF TEMPERATURE ON SOME RHEOLOGICAL PROPERTIES OF WHEAT FLOUR DOUGHS

Abstract. Doughs from three flours were sheared between a cone and plate at constant rates in the range 6 times 10^-4-2 times 10^-2 s^-1.
At temperatures between 25 and 40C, the apparent viscosity decreased with increasing temperature and with increasing rate of shear. The effects of the temperature and of the rate of shear were independent one of another, and can be described by an Arrhenius type equation and a power equation, respectively. At temperatures between 45 and 60C, the apparent viscosity increased rapidly with increasing temperature; this is ascribed to starch gelatinization. In this temperature range, the apparent viscosity decreased more rapidly with increasing rate of shear than at lower temperatures.
At temperatures between 25 and 45C, the shear modulus decreased with increasing temperature and slightly increased with increasing rate of shear. From the former fact it is concluded that the elasticity of dough has an origin different from rubber elasticity. In this temperature range, the shear modulus can be described by an equation similar to that for the apparent viscosity. At temperatures between 45 and 65C, the modulus increased with increasing temperature, though to a lesser extent than the apparent viscosity.
Changes in the rate of stress relaxation are in accordance with the effects of temperature and rate of shear on the apparent viscosity and the modulus.     

RHEOLOGICAL BEHAVIOUR OF COCOA DISPERSIONS

The steady-shear viscosities of cocoa mass and cocoa suspensions were measured over a wide range of temperature and cocoa powder content. The effects of gasification, moisture and lecithin contents were also investigated. The viscosity of cocoa mass followed the Quemada or the Casson model. Both viscosity and yield stress decreased with increasing temperature. Degasification also lowered the viscosity and yield stress. The viscosity of concentrated cocoa suspension increased with increasing powder content and exhibited shear-thinning behaviour, and followed the Kreiger and Dougherty model. While the relative intrinsic viscosity was nearly constant, the maximum volume fraction increased with increasing shear stress or shear rate. Addition of moisture in suspension increased the viscosity due to partial gelation of starch; while addition of lecithin decreased the viscosity due to the lesser number of flocs in the suspension.     

RHEOLOGICAL BEHAVIOUR OF INFANT FOODS

The rheological properties of four different infant foods were studied. Flow of all samples showed time dependence, which was qualitatively evaluated and quantitatively described by the Weltman and Hahn models. Rheological data were obtained at a constant shear rate of 57.6 s⁻¹. These foods showed coefficients of thixotropic breakdown between 4.34 Pa. s and 16.69 Pa. s. Values of the Hahn equation parameter were: p from 1.25 to 1.93 Pa and a from 0.019 to 0.031 s⁻¹. The results showed that the Weltman equation was better than the Hahn equation in describing the thixotropic behaviour of these foods. After eliminating time dependency, flow was adequately described by the Herschel-Bulkley model.     

A SIMPLE, RAPID AND SIMULTANEOUS PREPARATION OF GLANDLESS COTTENSEED 7S AND 11S PROTEIN FRACTIONS AND CHARACTERIZATION OF SOME PHYSICOCHEMICAL PROPERTIES

A simple and rapid method for simultaneous preparation of individual protein fractions from glandless cottonseed storage proteins was developed. With gel filtration chromatography, using Sephacryl S-300 HR and 10% NaCl solution as an eluent, 3 fractions, FI, FII, FIII were obtained. FII and FIII produced single peaks by gel filtration rechromatography and anion exchange chromatography. FII and FIII showed both a single major and a barely noticeable minor band, respectively, on polyacrylamide gel electrophoresis. Analytical ultracentrifuge patterns showed impurites less than 2% in FII and a single symmetrical peak for FIII. Sedimentation coefficients were computed to be 10.7S and 6.8S for FII and FIII, respectively; molecular weights by osmometry were 2.39 × 10⁵ and 1.40 × 10⁵ g/mole for FII and FIII, respectively. Both fractions were high in acidic and low in sulfur-containing amino acids, and contained phytate and gossypol at less than 10 and 2 ppm, respectively.     

A COMPARISON OF THE RHEOLOGICAL CHARACTERISTICS OF DIFFERENT FRACTIONS OF CHICKEN MYOFIBRILLAR PROTEINS1

ABSTRACT Suspensions of myofibrils and salt-soluble (SSP) or insoluble (SIP) proteins of chicken breast muscle in 0.6 M NaCl at pH 6.0 were heated to induce gels. Dynamic oscillating measurements showed multiple transitions in the shear storage modulus and loss modulus for all three protein fractions in the temperature range of 40–65C. However, changes in these viscoelasticities were most pronounced for SSP and least appreciable for SIP. Gel penetration test also revealed a descending order of SSP < myofibrils < SIP in gel strength. The three fractions of myofibrillar proteins appeared to follow a similar gelation mechanism but vary in the density of the gel networks.     

EFFECT OF ADDITIVES ON RHEOLOGICAL CHARACTERISTICS AND QUALITY OF WHEAT FLOUR PAROTTA

Effects of oxidizing agents (potassium bromate [20 and 40 ppm], ascorbic acid [100 and 200 ppm] and potassium iodate [20 and 40 ppm]), reducing agents (potassium metabisulphite [100 and 200 ppm] and cysteine hydrochloride [50 and 100 ppm]), enzymes (fungalα‐amylase [10 and 20 ppm] and protease [10 and 20 ppm]) and dry gluten powder (1, 2 and 3%) on rheological characteristics of dough and quality of parotta were studied. Addition of oxidizing agents and dry glutenincreased values for farinograph stability, extensograph and mixograph areas, apparent biaxial extensional viscosity, compressive stress, hardness and cohesiveness, while reducing agents and enzymes decreased the aforementioned characteristics and increased force decay parameter and adhesiveness of the dough. Among the different additives studied, incorporation of 100‐ppm potassium metabisulphite, 50‐ppm cysteine hydrochloride and 10‐ppm protease increased the overall quality score of parotta.     

RHEOLOGICAL AND PHYSICOCHEMICAL PROPERTIES OF DERIVATIZED WHEY PROTEIN CONCENTRATE POWDERS

ABSTRACT

The gelling ability of whey proteins provides important textural and water holding properties in many foods. However, because many products cannot be heated to the temperature needed for thermal gelation of whey proteins, cold-set gelation of whey proteins could be very advantageous to the food industry. A derivatization procedure for the production of a cold gelling whey protein isolate (WPI) consisting of protein hydration, pH adjustment, thermal gelation, freeze drying, and milling was applied to three commercial whey protein concentrates (WPC). The resulting derivatized WPC powders were reconstituted in water and evaluated through a range of rheological and physical property studies. The effects of temperature, concentration, and shear on viscosity as well as water holding capacity and intrinsic viscosity were assessed. Although the composition of the starting materials influenced the functionality of the final derivatized powders, all samples exhibited a dramatic increase in thickening and water holding ability. All samples were able to form cold-set weak gel structures suitable for contributing viscosity and texture to a wide range of food systems.     

RHEOLOGICAL BEHAVIOUR OF KIWI FRUIT JUICE CONCENTRATES

The rheological behaviour of diluted kiwi concentrates (22.5–63.0 °Brix) over the temperature range 4 to 70C, was studied. The values below 55.7 °Brix fit the power law while above 55.7 °Brix fit the Herschel-Bulkley equation. Maximum and minimum consistency index values were 62225 and 16 mPa. s ⁿ . Concentrates showed a yield stress at 55.7 °Brix, from 5 to 11 Pa, and 63.0 °Brix, from 19 to 53 Pa. Yield stress was correlated with temperature by means of a linear equation. Arrhenius activation energies were in the range of 28.97 to 33.89 kJ/mol. The average value of the flow behaviour indexes varied from 0.85 (sample at 22.5 °Brix) to 0.59 (sample at 63.0 °Brix). Simple equations are proposed to describe the combined effect of temperature and soluble solids content on consistency index and rheological behaviour index.     

FLOW BEHAVIOUR OF LARD AND OF ITS FRACTIONS AT 15°C. RELATIONSHIP WITH THBJRMAL BEHAVIOUR AND CHEMICAL COMPOSITION

The rheological behaviour of lard and of its fractions at 15°C was studied by means of penetrometry and viscometry in order to characterize the variations of the yield value and of the viscosity in the temperature range from – 20 to 70°C. The Casson rheological model is suitable to describe the flow behaviour of these three fats until completely melted. The variations of the rheological parameters could be described by relationships of the form log x = a 10³/T+ b. Comparison of the rheological behaviour, the thermal behaviour, determined by means of differential scanning calorimetry, and the solid fat content, determined by means of nuclear magnetic resonance, showed good relationship between the results over the whole melting range.     

RHEOLOGICAL BEHAVIOUR OF BUTTER AT LARGE DEFORMATIONS

Eleven traditionally produced butter samples were evaluated for rheological properties at large deformations by lubricated and nonlubricated uniaxial compression with varying sample geometries and compression rates, by stress relaxation in shear and creep experiments in compression at 5–20C each. Compression forces required to deform cylindrical samples in nonlubricated conditions were higher than in lubricated cases. Correction of shape changes in nonlubricated stress-strain curves resulted in good agreement with lubricated experiments at low compression rates up to stress maxima or yielding. As frictional forces were relatively smaller at high deformation rates, lower stresses were obtained in nonlubricated conditions. Samples with higher height/diameter ratios showed more pronounced stress maxima. A biaxial extensional viscosity, η be , was computed for nonbrittle, soft samples. Typical slopes in logarithmic plots of viscosity against strain rate were approximately -1. At strains of about 0.01 creep compliance depended on compression stress. The average ratios of recovered to initial instantaneous compliance were between 0.31 and 0.59, and increased with sample temperature. A calculated ηBE from creep compression showed fair agreement with ηBE from static compression experiments. At comparable strains, a conversion of creep compliance to the stress relaxation modulus by an approximate method showed a good fit of experimental results.     

QUALITY CHARACTERISTICS OF MEAT BATTERS AND FRANKFURTERS CONTAINING WHEAT GERM PROTEIN FLOUR1

Frankfurters were extended with wheat germ protein flour (WGPF) at 3.5, 5.0. and 7.0%. Water added during formulation was increased by 2% for every 1% of WGPF added. Batters containing WGPF had higher pH and adhesiveness values. Viscosities of the batters were not affected by addition of WGPF. Batters containing WGPF had lower cooking losses, and lower percent water and fat separated. Positive effects, such as lower cooking losses, higher processing yields and lower percent fat, were not consistent at levels of WGPF beyond 3.5%, probably because of higher levels of added water. Total yields of the samples containing WGPF were higher than those of control samples. No differences were observed in protein and amino acid contents of samples. Lower fat content was found in samples extended with 7.0% WGPF. Frankfurters containing WGPF had lower shear force and firmness values. Differences in color of frankfurters were also observed.     

RHEOLOGICAL BEHAVIOUR OF BUTTER AT SMALL DEFORMATIONS

Thirteen continuously churned commercial butter samples were evaluated for rheological properties at small deformations. The methods performed included dynamic experiments in shear and compression, stress relaxation in shear and static compression at 5–20C each. Linear viscoelastic behaviour was observed up to a critical strain of 0.001. The structure breakdown due to shear strains between 0.001 and 0.01 was found to be fully recoverable. No qualitative differences in the rheological behaviour were observed between the samples. Temperature-induced variations were mainly ascribed to changes in the solid fat content. Correlations between selected rheological measures in the linear viscoelastic region (i.e., complex modulus G* [Pa], relaxation modulus G(t) | _t ≃ 0[Pa], and modulus of deformability M_D[Pa]) were found to be causal and only slightly affected by the solid fat content.     

RHEOLOGICAL BEHAVIOUR OF CLARIFIED MANGO JUICE CONCENTRATES

The rheological behaviour of clarified mango juice was measured at temperatures 15–85C and concentrations 15–66 °Brix, using a rotoviscometer. Mango juice free of pectin and pulp behaves as a Newtonian fluid. The effect of temperature can be described by an Arrhenius-type equation. The activation energy for viscous flow was in the range of 1.64–8.44 kcal/g-mol, depending on the concentration. The effect of concentration was modelled better by an exponential relationship than a power-law relationship. Simple equations are proposed for describing the combined effect of temperature and soluble solids content on the juice viscosity.