摘要:

ABSTRACTThe importance of maintaining the purity of rheological terms and using them only when measurements and definitions are in accordance with the accepted rheological definitions is pointed out. It is shown that if rheological terms and methods of measurements and analyses are used correctly, they can be employed in food texture studies even though conditions upon which the theory is based are not fully met. It is proposed that the term “modulus of elasticity” be replaced by the term “modulus of deformabtiity” which considers both recoverable and unrecoverable deformations that often take place when a food sample is subjected to even very small strains. It is also submitted that mechanical properties reflecting the behavior of the material under small strains do not necessarily correlate significantly with mechanical properties which reflect the yielding and fracturing or failure of the material. Published data are examined to test the validity of this hypothesis. In general, correlations between well‐defined failure type instrumental tests and panel tests are good, whereas correlations between small‐strain instrumental tests and panel tes

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01191.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTThe resistance to bruising of Jonathan, Delicious and Granny Smith apples decreased with increasing storage time during the 1975 and 1976 seasons. Impact bruise volumes were approximately equal for the three varieties in April. Subsequent testing in June, August and October showed that bruise volumes increased markedly for both Jonathan and Delicious apples and by a small amount for Granny Smith apples. Jonathan apples deteriorated most rapidly and had broken down by October. The resistance to bruising of the three varieties was unaffected by pulp temperature over the range 2°C—30°C. Jonathan, Delicious and Granny Smith apples exhibited strong linear correlations between bruise volume and energy absorbed for all storage times, thus confirming earlier results for Granny Smith app

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01192.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTAqueous sugar glasses, simulating the structure of commercial boiled sweets, were investigated in their temperature transition range by force deformation and texture profile tests using the Instron Universal Testing Machine. Cylindrically cast and thermally equilibrated aqueous glucose‐sucrose model systems having 2—2.3% moisture (w/w) and containing glucose to sucrose ratios (%w/w) of 100/0, 70/30, 55/45 and 35/65 were used. Force‐deformation tests revealed that the Young's modulus was independent of the glucose‐sucrose ratio and decreased drastically with temperature from 820 MN/m2at 3°C to 30MJV/m2at 30°C.Texture profile tests were carried out on a model system (35/65 glucose‐sucrose blend) and on a commercial hard boiled sweet. Experimental profiles for both systems were largely similar and permitted evaluation of the textural parameters of hardness and cohesiveness. Composite force‐strain or force‐penetration curves were constructed from series profile tests on the same sample and demonstrated that (a) high values of hardness were found with a flat probe and low temperatures; (b) low values of hardness were found with cone and wedge probes and high temperatures. Cohesiveness generally decreased as the initial applied strain increased, because higher strains resulted in greater sample fracture and/or plastic flow. On the other hand, temperature and probe type had little effect on cohesiveness.The difficulties experienced in bridging the gap between the empirical and the fundamental approaches to texture profiling of foo

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01193.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTA device is described for measuring the transverse deformation of cylindrical samples during axial compression. The device is fitted to an Instron Universal Testing Instrument and requires only standard Instron electronics and data recording systems. Calculations showing that the transverse deflection gives a good estimate of Poisson's ratio are valid for both isotropic and anisotropic materials.Correlation coefficients for magnitude estimates of three sensory texture attributes in beef increase from 0.5 to 0.9 when Poisson's ratio is substituted for the uniaxial “modulus of elasticity.” This indicates that Poisson's ratio may be a very promising objective parameter for predicting the sensory texture quality in m

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01194.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTRheological properties of 10.0% and 20.0% (wt/wt) aqueous dispersions of sunflower proteins have been examined at pH 10.0 by shear stress‐shear rate and stress relaxation‐time studies, respectively. The 10.0% isolates exhibited non‐Newtonian power law flow behaviour, with the power exponent decreasing during sample ageing to a mini‐muni at about 180 min and then increasing. The 20.0% isolates exhibited uiscoelasticity with the stress relaxation modulus increasing with ageing times up to about 290 min and then decreasing. Both series of observations can be explained in terms of aggregation, hydration and chain entanglement of protein molecules, with protein hydrolysis becoming a major factor after longer agein

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01195.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTUsing a precision sialometer, unilateral parotid saliva was collected from six subjects while they masticated and swallowed pieces and powders from four types of Swedish crisp breads. Significantly more saliva was required for oral manipulation of the powders than for the corresponding pieces, as the greater surface area of the former required more saliva for lubrication in preparation for deglutition. Significant differences were observed in response to the four types of bread, related to both their texture and their taste. Despite wide among‐subject variation in the amount of saliva secreted, there was agreement in all cases on the direction of the response. The results indicate that the measurement of the relation between the amount (and possibly the composition) of saliva secreted and the texture and chemical properties of foods can be quantitated, and merits further investigatio

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01196.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTAn accessory for indicating the position of the crosshead of the Instron Universal Testing Machine relative to the machine frame is described. A linear displacement transducer allows the crosshead position to be selected within 0.35 mm or returned to a previous setting within at least 0.0083 mm. This facilitates accurate crosshead positioning and reproduction of the settings for different tests. The transducer also has the potential to indicate or record test sample deformations.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTA series‐parallel model is introduced in which a yield element is incorporated in the parallel branch. Before the yield stress is reached, the stress‐strain behavior is determined by the series branch to exhibit the linear uiscoelasticity of the material. When the yield stress is reached, the stress in the model which was sustained by the yield element is suddenly transferred to the spring and dashpot in parallel. As a consequence, a stress rate discontinuity was created. It is this feature which makes possible the simulation of the yield behavior of the food material. Data from Instron tests on American cheese are used to illustrate the mo

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01198.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

ABSTRACTTextural qualities of seven different commercial frankfurters were measured using a compression/penetration test. Four plunger diameters and three penetration speeds were evaluated to select statistically optimum test conditions. A plunger with a 0.635 cm diameter and the penetration speed of 5.08 cm min‐1were chosen based on the lowest mean square error. The textural qualities, i.e. skin toughness, internal texture and surface layer firmness, were determined for each product. These measurements exhibited distinct relationships with the square of fat/protein ratio of the frankfurters. In addition, the area‐dependent and perimeter‐dependent coefficients were obt

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01199.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

Book Reviewed in This Article:Quality Detection in Foods.Compiled by J. J. GaffneyFood Colloids.H. D. Graham.Food Quality Assurance.W. A. Gould.Natural Gums for Edible Purposes.A. A. Lawrence.Food Products Formulary, Volume 3. Fruit, Vegetable and Nut Products.D. K. Tressler and J. G. Woodroof.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1977.tb01200.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY