摘要:

ABSTRACTRheological properties of food dough melt, such as steady shear viscosity (η) and first normal stress difference (N1), were measured using an in‐line slit die rheometer attached to a laboratory model single‐screw extruder. The flow rate through the rheometer was varied by altering the screw speed. Alternatively, a sidestream valve, to vary the flow rate through the rheometer at fixed screw speed, was also used to obtain rheological data. The slit die rheometer was tested with corn meal at three different experimental conditions: 25% and 35% moisture contents at 180C barrel temperature and 35% moisture content at 150C barrel temperature. N1was measured using the hole‐pressure and exit‐pressure method. Exit pressure measurements were found to be erratic and unreliable. Hole pressure increased monotonically with increasing flow rate and was found to be affected by the processing history. The magnitude of the hole pressure ranged between 2% and 21% of pressure of the flush mounted transducer. For the experimental conditions used in this study, N1ranged from 3 × 104to 6 × 105Pa for shear rates between 30 to 400 s−1. Possible sources of errors in the hole pressure measurements a

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00759.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe rheological behaviour of kappa‐carrageenan/galactomannan blends, at ratios ranging from 1/99 to 5/95 in the presence of KCl, was investigated by means of viscosity and oscillatory shear measurements. These experiments were performed at 1% total polymer concentration and at 15C. The results were compared to those of the galactomannans alone (locust bean gum or guar gum

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00760.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe properties of gels prepared by heating solutions of bovine serum albumin (BSA) for 30 min at 121C in the presence and absence of glucono‐delta‐lactone (GDL gels) and xylose (Maillard gels) were compared. During formation the pH of the Maillard and GDL gels decreased to 4.9 whereas the pH of the gels formed in the absence of GDL or xylose remained near neutral. Maillard gels show much less syneresis compared with the GDL gels and contained nondisulphide covalent crosslinks as evidenced by very low protein solubilities in mixtures of sodium dodecyl sulphate and β‐mercaptoethanol. Both the GDL and Maillard gels could be formed at much lower protein concentrations than the neutral conventional gels. The stress relaxation of the gels in compression was measured and the response analyzed using Peleg's equation. The parameters in this equation were not strongly dependent on protein concentration or degree of deformation. The neutral pH gels were far more elastic than the low pH gels, but despite the difference in crosslinking mechanisms the viscoelastic behaviour of the Maillard and GDL gels was similar. However, the break strength and asymptotic residual modulus of the Maillard gels were higher. It is suggested that the stress relaxation occurs in weaker, noncovalently linked regions of the gel, whereas the nondisulphide covalent crosslinks in the Maillard gels reinforce strong regions already containing disulphide li

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00761.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTBone shaped specimens (length 83 mm, width 20 mm and the “neck” region 10 mm) cut from slices of white, brown and whole wheat breads were tested in tension using a Universal testing machine. The ends of each specimen were taped with masking tape and held by two pairs of alligator grips to avoid slippage and failure in the grip zones. The tensile parameters determined were the shape characteristics of the prefailure force‐displacement (F vs. D) curve C1, and C2, using the equation F = C1D/(C2+ D) as the model, the ultimate force and the break elongation. They were on the order of 0.2–0.7N, 9–28 mm, 0.1–0.3 N and 4–30 mm, respectively. Because of inherent nonuniformity of the bread crumb cellular structure, the data scatter was too large to enable monitoring textural changes in the breads during seven days of storage at ambient temperature. The method's performance could probably be improved if a large number of specimens were tested and/or the specimen size reduced so it can be taken from regions where the structure is more or

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00762.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTSet‐style yogurts were produced from cow's milk under standard conditions by using 11 commercially available starter cultures. Samples were prepared in control beakers and within the Couette device of a dynamic rheometer. Repeatability of rheometer yogurt fermentations proved to be satisfactory. Within the linear viscoelastic region a significant inverse relationship between storage modulus and tan δ of yogurt samples was found. Specific properties of starter cultures clearly affected response in dynamic frequency sweeps and in stress relaxation experiments. Dynamic and relaxation data showed good agreement. Relaxation spectra H(τ) were obtained from dynamic measurements and stress relaxation by approximation methods. Both the shape of H‐τ curves and the magnitude of H was affected by starter cultures. As compared to literature data on model casein gels and microstructural findings on yogurt the results imply that (a) a permanent network exists in yogurt, (b) interactions with long relaxation times contribute less to viscoelasticity in the case of yogurt produced with viscous starter cultures, and (c) attachment of mucogenic bacteria to the protein matrix via exogenic polysaccharides decreases yogurt fi

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

ABSTRACTThe steady‐state flow behaviour of oil‐in‐water emulsions stabilized by a sucrose palmitate was studied. Droplet size measurements were also carried out. The influence of sucrose ester (1–10% w/w) and oil concentrations (55–85% w/w) were analyzed. Influence of ageing was also studied. The Sisko and Carreau models were used to fit the experimental results depending on oil concentration. A master flow curve was obtained for all the oil and sucrose ester concentrations studied. The resulting master curve may be described fairly well by using a form of the Carreau model which includes a shift factor for both oil and sucrose ester concentration. The influence of the oil volume fraction on the shift factor was represented by a Frankel‐Acrivos equation. A correlation between rheological properties and particle size parameters has also been

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

RHEOLOGIE DER LEBENSMITTEL (FOOD RHEOLOGY). D. Weipert, H.‐D. Tsheuschner and E. WindhabBARLEY CHEMISTRY AND TECHNOLOGY. A. W. MacGregor and R. S. Bhat

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00765.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

GENERAL PRINCIPLES:Cell Wall Compitions and Enzymes of Potatoes, Jicamas and Chinese Water Chestnuts. R. PresseyGENERAL PRINCIPLES:Stress Relaxation Behavior of Apple Pomace and Effect of Temperature, Pressing Aid and Compaction Rate on Juice Yield. S. H. I. Al‐Mashat and C. A. ZuritzGENERAL PRINCIPLES:Linear Programming and Response Surface Methodology to Optimize Surimi Gel Texture. J. S. Chen, C. M. Lee and C. CrapoGENERAL PRINCIPLES:The Relationship of the Microstructure of Cooked Ham to its Properties and Quality. K. Katsaras and K. D. BudrasINSTRUMENTAL MEASUREMENTS:Dynamic Rheological Measurement of Structure Development in High‐Methoxyl Pectin/Fructose Gels. M. A. Rao and H. J. CooleyINSTRUMENTAL MEASUREMENTS:Evolution of Mechanical Characteristics of Tomatoes of Two Varieties During Ripening. R. Thiagu, N. Chand and K. V. R. RamanaMETHODOLOGY&INSTRUMENTATION:Experimental Evidence of Slip Development in Capillaries and a Method to Correct for End Effects in the Flow of Xanthan Solutions. L. de Vargas, J. Perez‐Gonzalez and J. de J. Romero‐BarenqueMETHODOLOGY&INSTRUMENTATION:Measurement of Biaxial Extensional Viscosity of Wheat Flour Doughs. H. Huang and J. L. KokiniMETHODOLOGY&INSTRUMENTATION:Development and Evaluation of an Automated Grain Breakage Tester for Determining Corn Breakage Susceptibility. S. A. Watson, W. D. Kreider, M. J. Sciarini and H. M. KeenerMETHODOLOGY&INSTRUMENTATION:Evaluation of a Modified Stein Breakage Tester for More Rapid Determination of Corn Breakage Susceptibility. S. A. Watson and H. M. KeenerSENSORY ASSESSMENT:A Study of Texture‐Flavor Interactions Using Free‐Choice Profiling. I. Jaime, D. J. Mela and N. BratchellFACTORS AFFECTING TEXTURE:Physical and Sensory Characteristics of Low Fat Ground Beef Patties. M. F. Miller, M. K. Andersen, C. B. Ramsey and J. O. ReaganFACTORS AFFECTING TEXTURE:Carbohydrate or Protein Based Fat Mimicker Effects on Ice Milk Properties. K. Schmidt, A. Lundy, J. Reynolds and L. N. YeeFACTORS AFFECTING TEXTURE:Rheological Behavior of Frozen and Thawed Low‐Moisture Part‐Skim Mozzarella Cheese. H. A. Diefes, S. S. H. Rizvi and J. A. BartschFACTORS AFFECTING TEXTURE:Base‐Mediated Firmness Retention of Sweetpotato Products. W. M. Walter, Jr., H. P. Fleming and R. F. McFeetersFACTORS AFFECTING TEXTURE:Rheological Relationships Between Surimi Sol and Gel as Affected by Ingredients. B. Yoo and C. M. LeeFACTORS AFFECTING TEXTURE:Changes in Rheological Properties of Hydroxypropyl Potato Starch Pastes During Freeze‐Thaw Treatments. III. Effect of Cooking Conditions and Concentration of Starch Paste. H. R. Kim, P. Muhrbeck and A.‐C. EliassonFACTORS AFFECTING TEXTURE:Amylopectin‐Staling of Cooked Nonwaxy Milled Rices and Starch Gels. C. M. Perez, C. P. Villareal, B. O. Juliano and C. G. BiliadensFACTORS AFFECTING TEXTURE:The Role of Xanthan Gum in White Layer Cakes. R. A. Miller and R. C. HoseneyFACTORS AFFECTING TEXTURE:Effects of Flour Type and Dough Retardation Time on the Sensory Characteristics of Pizza Crust. D. M. Larsen, C. S. Setser and J. M. FaubionGENERAL PRINCIPLES:Sedimentation of a Single Particle in Systems of Xanthan with Locust Bean Gum in Relation to the Rheological Behaviour. H. Luyten W. Kloek and T. van VlietINSTRUMENTATION&METHODOLOGY:Development of a Single‐Kernel Wheat Characterization System. C. R. Martin. R. Rouser and D. L. BrabecINSTRUMENTATION&METHODOLOGY:Measurement of Single‐Kernel Wheat Hardness Using Near‐Infrared Transmittance. S. R. DelwicheINSTRUMENTATION&METHODOLOGY:Modal Analysis of the Dynamic Behavior of Pineapples and Its Relation to Fruit Firmness. H. Chen and J. Dr BaerdemaekerINSTRUMENTATION&METHODOLOGY:Breakage Susceptibility of Corn of Different Stress‐Crack Categories. S. Gu

ISSN:0022-4901    

DOI:10.1111/j.1745-4603.1994.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY