摘要:

ABSTRACTThe theory of rubber elasticity is reviewed to study several properties of the three dimensional protein gels, e.g., the number of sulfhydryl binding sites per protein polypeptide. Alternatively, the theory of gelation can be used to explore the protein aggregating reactions, to evaluate the required number of protein aggregates and the rate that the different size proteins aggregate when gelling.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00029.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTCompressive moduli of elasticity and stress relaxation characteristics of soft goat milk cheese were compared with those of cow milk judged to be of comparable consistency. The true stress applied to a cheese sample was calculated from the variation of cross‐sectional area of a cylindrical specimen during compression. Stress relaxation data were developed by measuring the force decay resulting from imposed compression of 5, 10, 20 and 40. The compressive elastic moduli for goat milk cheese were found to be lower than those for cow milk cheese. For cheese prepared from fresh goat milk, at least two distinct periods of stress relaxation were found for each compression level. Cheese prepared from reconstituted dehydrated goat milk showed one period of stress relaxation for each compression leve

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00030.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTTomato pastes (26–30 °Brix) at 40C were highly shear thinning fluids (n = 0.28) with large magnitudes of Casson yield stresses (78–212 Pa). Dynamic shear data revealed weak gel‐like behavior of the pastes: magnitudes of G′ were higher than those of G″, and both increased with oscillatory frequencies. The Cox‐Merz rule was not applicable to the steady and dynamic shear data on the pastes, but the two types of data conformed with the use of shift factor on frequency. Solids and liquid fractions in the pastes were satisfactory for correlating the dynamic properties, consistency index, and Casson

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00031.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTSymmetrized dot‐pattern displays (SDP) of the kind used in speech analysis and medical diagnosis can also be used to visualize textural differences between and among crunchy foods. Meaningful interpretation of the patterns in terms of textural characteristics, however, will require further study of two topics: how the display parameters, notably the number of points and symmetry axes affect the resulting image perception, and how factors such as the specimen's geometry and moisture content, for example, affect the pattern's morphological feature

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00032.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTMechanisms that can be responsible for the ability of wheat flour doughs to retain gas are discussed. It is concluded that the relevant types of physical instabilities are Ostwald ripening (disproportionation) and coalescence of gas cells. The extent of Ostwald ripening is probably primarily controlled by surface rheological properties; it certainly affects crumb structure, but it cannot explain the differences in gas retention among doughs from various cereals or various wheat cultivars. It is argued that surface forces only provide a stabilizing mechanism for dough films between gas cells, i.e., against coalescence, for films that are much thinner than the diameter of a starch granule. It is concluded that variation in the potential for gas retention among wheat flour doughs is largely due to variation in bulk rheological properties. We propose a new rheological criterion for the extensibility of dough films between gas cells (and thereby for gas retention) that is based on the strain hardening of the dough in biaxial extension exceeding a specific lower limit. The criterion is translated into measurable parameters. Preliminary experiments on doughs with poor and with satisfactory baking performance illustrate its potential importance.

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00033.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe influence of tomato fruit ripeness on area‐ and perimeter‐dependent properties and dominant failure mechanisms of pericarp tissue were investigated. Tissue discs from mature‐green and red‐ripe fruit were punctured with a flat‐ended cylindrical probe and compressed with a flat plate at a constant rate of deformation. Approximately linear force‐deformation curves were obtained to tissue failure by both puncture and flat plate compression, interrupted by a region of pseudoplastic deformation at a relatively low initial bioyield force. Based on estimated area‐ and perimeter‐dependent coefficients and firmness (force/deformation) values, initial bioyielding of tissue appeared to be associated with an abrupt increase in cell‐to‐cell compaction. Puncture of mature‐green tissue led to premature failure induced by shearing or rupture of tissue at the probe perimeter. The contribution to puncture of perimeter‐dependent or shear‐associated forces and a putative “zone of influence” increased markedly with ripening, while the contribution of area‐dependent or compression associated forces generally decreased. A concomitant decrease in failure force and firmness with ripening reflected a general loss of both tissue compression and shear strengths. These results suggested that the dominant mode of tissue failure changed with ripening, from cell relaxation and rupture to cell debonding. The data obtained in this study emphasize the need to exercise caution in the interpretation of force‐deformation parameters

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00034.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTFailure mechanisms of tomato pericarp tissue were investigated by measuring puncture and viscoelastic properties of tissue from fruit stored at 22C (nonchilled) or 5C (chilled) for 28 days, or at 5C for 15 days prior to transfer to 22C for an additional 13 days (prechilled) to facilitate ripening. The puncture properties of tissue remained unchanged during 28 days of chilling. However, tissue shear strength and rigidity increased with chilling, as demonstrated by increases in storage and loss moduli, and decreases in oscillatory strain and the loss tangent. Puncture failure force, failure firmness and storage and loss moduli of nonchilled and prechilled tissues decreased to low, constant levels by 12 and 9 days, respectively. Simultaneously, pseudoplastic and failure strains and oscillatory strain each increased. These data suggest that the loss of tissue compressive strengths and transition in the dominant mode of failure from cell relaxation and rupture to cell debonding occurred at a faster rate during ripening of prechilled (i.e., chill‐injured) compared to nonchilled frui

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00035.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

ABSTRACTThe effects of turgor pressure on puncture and viscoelastic properties of mature‐green tomato pericarp were examined using tissue discs soaked in a range of osmotica (0.0–0.6 M mannitol) for at least 36 h at 4C. Turgor pressure was estimated from the osmotic potential of soaking solutions that induced incipient plasmolysis. Based on volume changes, the osmotic potential and turgor pressure of fresh tissue were estimated to be −0.56 ± 0.08 MPa and 0.20 MPa, respectively. However, puncture and viscoelastic properties corresponded to a turgor pressure of 0.15 MPa. The discrepancy between calculated and actual turgor pressures was attributed to the presence of apoplastic solutes. The data from this study revealed a general increase in cell wall stress, strain and elasticity with increasing turgor. With increases in turgor above that of untreated tissue both wall extensibility and elasticity became limiting and thus cell wall stiffness increased. Conversely, a decrease in turgor below that of untreated tissue led to an increase in viscoelasticity. Increases in bioyield and pseudoplastic bioyield strains with a variation in turgor from that of untreated tissue were consistent with cell debonding as a dominant mechanism of tomato tissue bioyielding. The reduced failure force, deformation and firmness with increasing turgor were consistent with cell rupture as a predominant mechanism of failure of mature‐green tomato pericar

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00036.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

FOOD EXTRUSION SCIENCE AND TECHNOLOGY. Jozef L. Kokini, Chi‐Tang Ho and Mukund Karwe, eds.SURIMI TECHNOLOGY. T.C. Lanier and C.M. Lee, eds.DEVELOPMENTS IN CARBOHYDRATE CHEMISTRY. Richard J. Alexander and Henry F. Zobel, eds.RHEOLOGICAL METHODS IN FOOD PROCESS ENGINEERING. James F. Stef

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00037.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

GENERAL PRINCIPLES: Functional Properties of Some Succinylated Protein Preparations. M.Z. Sitohy, S.F. Sharobeem and A.A. Abdel‐GhanyGENERAL PRINCIPLES: Change of Foam Properties of Gelatin Solutions Under Different Conditions. E. GaborGENERAL PRINCIPLES: Minor Surface‐Active Lipids of Olive Oil and Viscosity of Protein Films at the Olive Oil – Water Interface. V. KisseoglouGENERAL PRINCIPLES: Nonstarch Polysaccharides from Sunflower (Helianthus annuus) Meal and Palm‐Kernel (Elaeis guineensis) Meal – Investigation of the Structure of Major Polysaccharides. E.‐M. Diisterhoft, M.A. Posthumus and A.G.J. VoragenGENERAL PRINCIPLES: Changes in Intramuscular Collagen of Cod (Gadus morhua) during Postmortem Storage in Ice. P. Montero and I.A. MackieGENERAL PRINCIPLES: Effect of Aqueous Ethanol Washing on the Physicochemical and Functional Properties of Safflower (Carthamus tinctorius) Seed Proteins. R. Tasneem and V. PrakashINSTRUMENTAL MEASUREMENTS: Dynamic Measurement of Tissue Rigidity during Freezing and Cooking of Vegetables. S.V. Ramana and A.J. TaylorINSTRUMENTAL MEASUREMENTS: Viscosity of Locust Bean (Cerutonia siliquu) Gum Solutions. F. Garcia‐Ochoa and J.A. Casas.SENSORY EVALUATION: Production of a Yogurt‐Like Product from Plant Foodstuffs and Whey. Sensory Evaluation and Physical Attributes. K. Shirai, M. Gutierrez‐Duran, V.M.E. Marshall, S. Revah‐Moiseev and M. Garcia‐GaribayFACTORS AFFECTING TEXTURE: Rheological Changes during Thermal Gelation of Meat Batters Containing Surimi from Alaska Pollack (Therugru chulcogrumrna) or Sardine (Surdina pilchardus). J. Carballo, M. Cavestany and F. Jimenez‐ColmeneroFACTORS AFFECTING TEXTURE: Production of a Yogurt‐Like Product from Plant Foodstuffs and Whey. Substrate Preparation and Fermentation. K. Shirai, G. Pedraza, M. Gutierrez‐Durán V.M.E. Marshall, S. Revah‐Moiseev and M. García‐GaribayFACTORS AFFECTING TEXTURE: Effects of Cultivar and Growth Season on the Gelatinisation Properties of Cassava (Munihot esculentu) Starch. M. Asaoka, J.M.V. Blanshard and J.E. RickardFACTORS AFFECTING TEXTURE: A Study on the Cooking and Eating Quality Characters of Some Egyptian Rice Varieties. A.A. El‐Hissewy and A.A. El‐KadyFACTORS AFFECTING TEXTURE: Effect of Cooking on Nutrients, Microbial and Sensory Properties of Skimmed Milk and Rayeb Kishk. A.A. Salama, A.A. Damir and M. Safwat MohamedRELATIONSHIP TO STRUCTURE: Implication of Cell Wall Degrading Enzymes in the Heat‐Induced Softening of the African Pear [Ducryodes edulis(G D

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1992.tb00038.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY