摘要:

An instrument to measure the development of protein gels during thermal coagulation was developed. Very small oscillatory movements, sufficiently small to avoid damaging forming structures, were imposed on the sample trapped within a specially constructed cell, and the torques transferred through the sample sensed with strain gauges. Temperatures were controlled with one heating and one refrigerated (20°C) bath and the sample properties determined through both heating and cooling cycles. Egg white (EW) whey protein concentrate (WPC) and beef wiener emulsion (BWE) were tested. EW and WPC were characterized by delayed onset of gelation followed by high temperature thickening. Cooling further stiffened the gel in both cases. B WE was characterized by an initial decrease in transmitted torque as fat melting was detected. This was followed by a rapid rise in transmitted torque as the protein coagulated, followed by a further increase or stiffening on cooling. Detailed parameters describing the thermal gelation of the three materials are given

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00701.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Textural attributes of Cheddar and Cheshire cheeses, falling within narrow compositional ranges, were assessed by sensory panels, and from force‐compression curves generated by compression between two plates, and, for Cheddar cheese only, by penetrometry. Individual sensory measurements did not relate well to any instrumental one, and were better at discriminating between cheeses. Samples of each cheese variety were fractured in different ways and the fracture surfaces were examined in a scanning electron microscope. Fracture surfaces were formed by cutting directly through the matrix, tearing of the matrix along planes high in fat or cracking at grain boundaries. It is suggested that consideration of fracture mechanism may aid the selection and development of useful instrumental methods for texture assessment of chees

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00702.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The separate effects of sweetness and viscosity of sucrose on the sensory properties of vermouth were evaluated in systems: (1) varying in sucrose concentration and viscosity (2) with constant sucrose concentration but varying in viscosity, and (3) constant viscosity, but varying sucrose concentration. Twenty‐one trained judges rated oral viscosity, sweetness and bitterness, while the physical viscosity of the Newtonian systems was measured by capillary viscometry. Both perceived sweetness and oral viscosity increased, while bitterness decreased as sucrose was increased, and as the physical viscosity of the vermouths increased. However, samples in which viscosity was increased by the nonsweet Polycose® were rated sweeter and less bitter than vermouth solutions of the same sucrose concentration, but lower physical viscosity. Similarly, when vermouths of identical viscosity were compared, the vermouths with higher sucrose concentration were judged to be more viscous. Viscosity alone contributed 20‐30% of the perceived increase in sweetness due to sucrose addition. The effect of viscosity in reducing bitterness was of the same magnitude. The increase in perceived viscosity caused by addition of sucrose arose from approximately equal contributions of physical viscosity and sweetness of suc

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00703.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

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 ra

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00704.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The textural attributes of 8 different heat‐induced protein gel preparations evaluated by torsion failure testing and Instron texture profile analysis (TPA) were compared to sensory ratings by a trained texture profile panel. The gels presented a wide range of textural properties as determined by the instrumental and sensory parameters. Among the instrumental parameters, true shear strain at failure was the most frequent and significant predictor of sensory notes. Initial shear modulus and 50% compression force had the poorest correlations with sensory notes. Comparison of the two instrumental tests produced high correlations between shear stress at failure and TPA hardness; true shear strain at failure and TPA cohesiveness; and, initial shear modulus and 50% compression force. High correlations were also observed among various panel notes. Canonical correlation analyses showed that sets of linear combinations of parameters from each one of the 3 tests (torsion, TPA or sensory) were highly correlated to sets from either of the other two. Regression equations relating each of the instrumental tests to sensory notes were developed. Of the torsion failure parameters, the logarithm of true shear strain most commonly appeared in the equations. Of the TPA parameters, cohesiveness and its logarithm were the terms that were most frequent. High R2values were obtained for regression equations developed for predicting torsion failure parameters based on TPA parameter

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00705.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The gelation of casein after modification by dialdehyde starch (DAS) was studied by measuring its mechanical and swelling properties, the amount of sol fraction, its melting behaviour, amino acid analysis and polyacrylamide gel electrophoresis. Depending on the concentration of protein and DAS, fusible and infusible gels are formed. The transition from fusible into infusible gels takes place after increasing the amount of DAS, owing to an enhanced blockage of basic amino acid residues and crosslinking of polypeptide chains. The higher the concentration of protein, the lower is the concentration of DAS necessary for gelation. When the DAS concentration is high enough to form a pervading crosslinked network the crosslinking proceeds relatively fast and is nearly completed after one day. The correspondence of the time dependence of chemical andphysical parameters, the irreversible blocking of basic amino acids, especially lysine, the decrease of swelling and nitrogen extractability, the elastic component of creep compliance indicates that during a 7 day storage period the gels are completely crosslinked. Using a corrected Flory relation it was shown that an average of 3.5 crosslinks exist per one polypeptide chain. This number is similar to the number of blocked lysine groups of the same gels (3.6 ‐ 4.5). The melting and creep behaviour of the gels, and especially the effect of sodium do‐decyl sulphate on the creep compliance, point to the formation of a heterogeneous network which includes noncovalently connected mi‐croassociations and covalently connected polypeptide chains as structural ele

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00706.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Cylindrical specimens of height to diameter ratios between 0.12 to 1.0 of potato flesh, bologna sausage and process American cheese were uniaxially compressed to failure. The flatter the specimen the stiffer it appeared. This was also true with respect to strength. The magnitude of strain at failure also increased with the specimen's flatness. Application of two correction procedures for the calculation of a dimensionally independent modulus did not always yield consistent results, demonstrating that the stiffness‐strength‐shape relationships can depend not only on the material but also on the particular character of the end constrai

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00707.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00708.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Sensory Evaluation Practices.H. Stone and J. L.Functional Properties of Food Components.Y. PomeranzEconomics and Management of Food Processing.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1985.tb00709.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY