bluuebunny/crossref_metadata_2025 huggingface dataset:
RESEARCH NOTE A SIMPLE TEXTURE TEST SYSTEM
Authors: DEMAN J. M. , KAMEL B. S.
Published: February 2007

A simple inexpensive texture test system is described which is suitable for quality control applications. The apparatus is constructed from a drill press stand, a mechanical force gauge and a test cell. The effect of different operators and sample thickness was investigated using apple and potato as test material. The performance of this system was compared with that of the FTC Texture Press (Kramer Shear Press) in the testing of several foods.
STRESS AND STRAIN ACTIVATED FRACTURE ELEMENTS2
Authors: PELEG M.
Published: February 2007

The characteristics of fracture elements in which the activation criterion is either a critical stress and/or strain are described. Their possible effects on the properties of phenomenological rheological models are demonstrated in the case of simplified models subjected to hypothetical deformation, stress relaxation and creep tests. It is also shown that introduction of the double criterion to models could produce rheological response patterns, especially in creep, that are more consistent with those of real materials.
COMPARISON OF STEADY SHEAR RHEOLOGICAL PROPERTIES AND SMALL AMPLITUDE DYNAMIC VISCOELASTIC PROPERTIES OF FLUID FOOD MATERIALS
Authors: BISTANY KAREN L. , KOKINI JOZEF L.
Published: February 2007

Small amplitude dynamic viscoelastic properties of apple butter, mustard, tub margarine, and mayonnaise are compared with their respective properties in steady shear flow in the range of shear rates and frequencies of 0.1‐100 sec−1 using a Rheometrics Mechanical Spectrometer. Comparison of dynamic and steady viscosities shows that dynamic viscosities (η*) are much larger than steady viscosities (η). Consequently the Cox‐Merz rule is not obeyed. Moreover the obvious nonlinearity suggests that shift‐factor type relationships are not obeyed either. The in‐phase (η') component of the dynamic viscosity shows similar behavior when compared to the steady viscosity (η).

Comparison of G′/ω2 and Ψ1 also suggests that any of the results predicted by classical theories of viscoelasticity are not obeyed. G'/ω2 is always much larger than Ψ1 and the relationship between these two material functions is nonlinear.
A STATIC METHOD FOR DETERMINING THE ABSOLUTE SHEAR MODULUS OF A SYNERESING GEL
Authors: STAINSBY GEORGE , RING STEPHEN G. , CHILVERS GRAHAM R.
Published: February 2007

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DETERMINATION OF EFFECTIVE SHEAR RATES IN ROTATIONAL VISCOMETERS WITH COMPLEX GEOMETRIES
Authors: RAO M. A. , COOLEY H. J.
Published: February 2007

The effective shear rates of a flag and a star shaped impeller were determined in a jacketed vessel by matching the viscosity of a Newtonian fluid and the apparent viscosity of a non‐Newtonian fluid, and from the slope of a plot of (1–n) versus log (P/K Nn+1d3). The results from the two methods were in good agreement. For geometries with large surface areas, the method of matching viscosities is less likely to contribute to errors.
LINEAR VISCOELASTIC BEHAVIOR OF FRANKFURTERS
Authors: SKINNER G.E. , RAO V.N.M.
Published: February 2007

Normal creep and stress relaxation experiments were performed on seven commercial brands of frankfurters. A nonlinear procedure was used to determine the model best fitting the data for each test. Re assumption of linear viscoelasticity was tested by the equivalence of model parameters. Results showed fankfurters to be linear viscoelastic materials at strain levels up to 3.8%.
RHEOLOGICAL CHARACTERIZATION OF APPLE CORTEX
Authors: MITTAL J. P. , MOHSENIN N. N. , SHARMA M. G.
Published: February 2007

The incremental creep and recovery theory was used to develop a constitutive relationship for apple cortex without assuming the nature and the characteristics of the material. Successive loading and unloading cycles of increasing duration were applied on the cylindrically shaped specimens of apple cortex. The elastic strain component was linear with stress. The viscoelastic and permanent strain components were time dependent and nonlinear functions of stress.

Three‐step creep tests and stress‐strain tests at various deformation rates were also conducted on cylindrically shaped specimens of apple cortex. Prediction of strains under these loading histories by using the constitutive equation showed a close agreement between the theoretical and experimental strains. An equivalence between the critical creep stress (found from the incremental creep and recovery tests) and the ultimate stress, obtained from the stress‐strain tests at various deformation rates, were also established.
MASTICATION: THE NEED FOR COLLABORATIVE RESEARCH
Authors: HEATH M.R. , LUCAS P.W.
Published: February 2007

A more complete understanding of the physical treatment of food in the mouth demands that both the physical qualities of the food and the relevant forces and displacements to which the food is subjected be quantified. The purpose of this article is to suggest more collaboration between oral and food texture researchers since we believe that it is only through such interdisciplinary research that progress can be made.
COMPUTERIZED VISCOMETRIC METHOD FOR STUDYING RENNET COAGULUATION OF MILK
Authors: KOROLCZUK J. , MAUBOIS J.‐L.
Published: February 2007

A viscometer (Rheomat‐30) was computerised by connecting a microcomputer (Apple II plus) through the interface: analog/digital converter (MID 1612M1). The maximal speed of the viscometer's signal readings was up to 20 records per second. This equipment was used to follow the apparent viscosity changes during the rennet coaguluation of milk.

An equation describing the evolution of the viscosity as a function of time has been drawn. It seems to be sufficient to know the initial and maximal viscosity level and the time coordinates of two points: maximum and 0.6 of the viscosity amplitude, to be able to reproduce the viscosity versus time curve.
EFFECTS OF SHEAR‐THINNING BEHAVIOR ON MIXER VISCOMETRY TECHNIQUES3
Authors: MACKEY K. L. , MORGAN R. G. , STEFFE J. F.
Published: February 2007

Brookfield RVTD and HBTD viscometers equipped with a flag impeller, having an impeller‐to‐cup diameter ratio of 0.55, and non‐Newtonian fluids 1.0% guar gum and 1.5, 2.0 and 2.5% carboxymethylcellulose were used to collect torque versus rotational speed 0.5–10.5 rad/s (0.5–100 rpm) data. Power Law consistency coefficient and shear thinning index were quantified using a Haake concentric cylinder viscometer. The proportionality constant which relates mixer shaft speed to effective shear rate (k1) was very sensitive to the shear thinning index at low values of rotational velocity. Results indicate that it is not practical to use one constant value for k1 when measuring properties of shear thinning fluids at low values of N or when using impeller‐to‐cup ratios significantly less than 1.0.
TEXTURAL PARAMETERS IN COMPRESSION TESTING OF A GEL MADE FROM FRESH AND FROZEN FISH MINCE
Authors: KNUDSEN LISBET BJERRE , BØRRESEN TORGER , NIELSEN JETTE
Published: February 2007

The relation between deformability modulus and yield stress is evaluated in compression testing of a model product made from fresh and frozen stored mince of cod. The experiments were performed with a compression rate of 120 mm/min. Preliminary experiments showed decreasing values of yield stress when compression rates were below 50 mm/min. Two moduli were calculated from the slope of the compression curve; α1, initially (small deformations) and α2 in a linear part of the curve shortly before rupture of the gel. α2 was linearly related to yield stress in gels of different water content, and in gels made from fresh and frozen raw material. α1 showed different relations to yield stress depending on quality of the raw material.
DESKTOP COMPUTER BASED COLLECTION AND ANALYSIS OF CREEP‐COMPLIANCE DATA ON FLUID FOODS
Authors: RAO M. A. , KASH S. F. , COOLEY H. J. , BARNARD J.
Published: February 2007

In a creep‐compliance test, the strain due to an imposed stress is recorded as a function of time. Subsequently, the strain is converted to creep‐compliance and the rheological parameters: compliances, retardation times, and viscosities are evaluated by a graphical method suggested by Inokuchi. A Macintosh Plus microcomputer was programmed in Basic language to collect time‐strain data from a Deer Rheometer III. A Fortran language program was written first to compute creep‐compliance from strain and subsequently to estimate rheological parameters using a nonlinear parameter estimation subroutine. Initial values for the nonlinear analysis were estimated by the computer program by means of a modified Inokuchi's method.
DYNAMIC SHEAR AND PUNCTURE PROBE MEASUREMENTS OF CANOLA PROTEIN ISOLATE GELS 1
Authors: PAULSON ALLAN T. , TUNG MARVIN A.
Published: February 2007

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INFLUENCE OF FRICTION, SAMPLE DIMENSIONS AND DEFORMATION RATE ON THE UNIAXIAL COMPRESSION OF RAW POTATO FLESH
Authors: CANET W. , SHERMAN P.
Published: February 2007

The influence of surface friction and lubrication on the compression behavior, at compression rates of 5–100mm min−l, of cylindrical samples of potato flesh have been examined with an Instron Universal Testing Machine at room temperature. The samples had length/diameter ratios of 0.2–0.8. Parameters derived from compression to failure were: failure stress; failure strain; and apparent modulus of elasticity. Stress relaxation with time was studied using samples with length/diameter ratios of 0.4–0.8 following compressions of 10 and 30%. The length/diameter ratio, rate of compression, surface friction and lubrication influenced the parameters derived from both the compression and the stress relaxation tests. Relaxation times increased following sample lubrication. The effect due to surface lubrication was smaller than in previous compression and relaxation tests on Gouda cheese. This was attributed to release of fluid from the damaged cellular tissue of the potato flesh which reduced the effectiveness of the lubricant film.
SEED COAT EFFECTS IN COOKED RECONSTITUTED BEAN TEXTURE
Authors: STANLEY D. W. , WU X. , PLHAK L. C.
Published: February 2007

The contribution of seed coat to cooked reconstituted bean texture was assessed by measuring sensory and instrumental parameters of beans with and without coats and also seed coats alone. Experiments using white beans stored for one year under tropical conditions to induce the hard‐to‐cook (HTC) defect or temperate conditions both resulted in reductions in the order of 50% in puncture force and sensory properties of beans when the seed coat had been removed. HTC bean texture was influenced less by absence of the seed coat than texture of soft beans. Seed coats softened during cooking but those from HTC beans softened less than those from soft beans. It is possible that seed coats harden during tropical storage by a lignification‐type mechanism. Beans with harder seed coats absorbed less water during soaking which may contribute further to bean hardness.
INFLUENCE OF PROTEIN CHARGE ON THERMAL PROPERTIES AS WELL AS MICROSTRUCTURE AND RHEOLOGY OF HEAT INDUCED NETWORKS FOR OVALBUMIN AND VICILIN
Authors: ARNTFIELD S. D. , MURRAY E. D. , ISMOND M. A. H.
Published: February 2007

The storage modulus (G′) and loss modulus (G″) for both ovalbumin and vicilin exhibited bimodal responses with respect to pH; lower values were obtained around the isoelectric points (IEP) and at pH extremes. Around the IEP, protein networks were characterized as highly aggregated with high tan δ (G″/G′) values. At pH values away from the IEP, the microstructure appeared as well crosslinked networks with corresponding lower tan δ values. In most cases, (except ovalbumin in acid conditions) this trend was not reversed at pH extremes. Inclusion of sodium dodecylsulfate (SDS) at pH 8.5 had an effect similar to increasing pH. For both proteins, network deterioration at high SDS concentrations was associated with protein unfolding and increased protein solvent interactions. For networks with low tan δ values (e.g. ovalbumin in alkaline conditions) the G moduli in the final network were influenced by changes during the initial cooling phase, whereas for aggregated products and most vicilin networks, changes in the G moduli during the final cooling phase were prominent. The contribution of electrostatic interactions to well crosslinked networks from both vicilin and ovalbumin was as a repulsive force in the balance required for network formation. For vicilin, electrostatic interactions also appeared to serve as an attractive force even under conditions of reasonable network formation. This may account for the difference in network quality for the two proteins.
ACETIC ACID MARINADING—THE RHEOLOGICAL CHARACTERISTICS OF SOME RAW AND COOKED BEEF MUSCLES WHICH CONTRIBUTE TO CHANGES IN MEAT TENDERNESS
Authors: RAO M. V. , GAULT N. F. S.
Published: February 2007

The tensile and adhesive characteristics of acetic acid marinaded bovine Ms sternomandibularis (StM), infraspinatus (IS), triceps brachii caput longum (TB), and psoas major (PM) were studied over the meat pH range 5.80 to 4.10 on both raw and cooked strips of muscle. In the raw muscle samples, tensile and adhesive characteristics were greatest around pH 5.0, progressively decreasing as muscle pH values approached 4.1. Cooking increased tensile strength, particularly around pH 5.0 where peak force values virtually doubled. Cooking had less influence on the adhesive characteristics of all muscle samples which tended to decrease below pH 4.5. In both raw and cooked muscle samples, intermuscular differences in adhesive characteristics were also much greater than those obtained for tensile characteristics. Irrespective of intermuscular differences in collagen content or its degree of maturity, the gradual decreases in tensile and adhesive characteristics below pH 5.0 could be related to the effect of acetic acid induced swelling on both muscle fibres and the connective tissue network. The influence of acetic acid marinading in promoting meat tenderness is due more to its effect on the behaviour of the muscle fibres during cooking than to its effect on the connective tissue network of different muscles.
VISCOELASTICITY OF GELATINIZED STARCH DISPERSIONS
Authors: EVANS I.D. , LIPS A.
Published: February 2007

Data are presented for the elastic moduli of gelatinised dispersions of a range of starch types, including native and chemically modified starches, over a much wider concentration range than examined heretofore. As found previously, there is a threshold concentration for measurable elasticity, near the close‐packing point, and a concentration region above this over which elasticity increases roughly linearly with concentration. A second, higher, “threshold” concentration at which a fairly sharp slope change occurred was also found. Three types of behaviour were found, apparently corresponding to the distinction between chemically modified starches, root and tuber starches, and cereal starches. At the second threshold concentration these, respectively, showed a significant fall in slope, little or no slope change and a marked slope increase. A recent study (Evans and Lips 1990) has provided a useful description of the elastic properties of concentrated dispersions of model deformable particles. Comparison between the behaviour of the “baseline” model dispersions with that of the starch dispersions examined here reveals significant similarities, especially when considering the behaviour of the chemically modified starches. There are some noteworthy differences which raise important questions about the structural origins of the rheological properties of starches and we briefly speculate about these.
RHEOLOGICAL CHARACTERIZATION OF STIRRED YOGHURT: VISCOMETRY
Authors: SKRIVER A. , ROEMER H. , QVIST K.B.
Published: February 2007

Rheological characteristics of stirred yoghurt, varying in dry matter content, fermentation temperature and composition of bacteria cultures, were evaluated using a Bohlin VOR Rheometer. Flow curves, covering the shear rate range 29–920 s−1, generally indicated the presence of a yield point and pseudoplastic behaviour, but also Bingham plastic behaviour was observed for some of the specimens. Systematic variations in the profile of the flow curves were observed as a result of the applied manufacturing conditions. Flow curves exhibiting pseudoplastic behaviour with a yield stress could not, over this broad shear rate interval, be described satisfactorily by the often applied Casson or Herschel‐Bulkley models, and consequently a new one, the QRS‐model was introduced. This model contains three parameters and gave a significantly better fit, with R2 values generally above 0.99.
DO IRREGULAR STRESS‐STRAIN RELATIONSHIPS OF CRUNCHY FOODS HAVE REGULAR PERIODICITIES?1
Authors: PELEG MICHA
Published: February 2007

The attractors of the jagged, normalized, dimensionless, stress‐strain relationships of three dry snacks, breadstick, pretzel and Zwieback, were constructed using the Packard‐Taken method. No unambiguous pattern could be revealed but the shape of the attractors differed from that of a totally random sequence. Although the existence of underlying characteristic periodicities could not be proven using the method with the available data it could not be ruled out either.
HARDNESS OF COOKED MILLED RICE BY INSTRUMENTAL AND SENSORY METHODS
Authors: PEREZ CONSUELO M. , JULIANO BIENVENIDO O. , BOURNE MALCOLM C. , ANZALDÚA‐MORALES ANTONIO
Published: February 2007

Fifteen milled rice varieties covering the usual range of amylose content and cooked rice hardness were used in a collaborative study to verify the sensitivity of the present objective method for measuring cooked rice hardness. The grains were cooked either in a rice cooker using a fixed water:rice ratio of 2:1, or by boiling in excess water for the predetermined optimum cooking time for each sample followed by draining. Hardness of cooked rice was measured in an Instron Universal Testing Machine (UTM) using two methods: (1) puncture of 100 individual grains and (2) extrusion through a 30 cm2 Ottawa Texture Measuring System (OTMS) cell with either a 3.2‐ or 4.8‐mm‐diam. holes plate. Hardness values were compared with sensory scores by a trained panel composed of 11 members. Sensory hardness of the rices cooked in a fixed amount of water showed very good correlation with puncture force (r = 0.94, P < 0.01) and with extrusion force through a 3.2‐mm‐diam. holes plate (r = 0.94). The correlation coefficient between puncture force and extrusion force was 0.97. Paired comparison test by the sensory panel on three pairs of rices verified consumers’ claims with respect to preference between members of each pair and agreed with results of ranking test.
YIELD STRESSES IN MOLTEN CHOCOLATES
Authors: WILSON LAURIE L. , SPEERS R. ALEX , TUNG MARVIN A.
Published: February 2007

Yield stress and flow properties of four molten chocolate samples at 40C were measured using coaxial cylinder and vane fixtures. The possibility for slip to occur during measurement was demonstrated by significant differences (p < 0.05) in Gasson parameters when measured between coaxial cylinders of different radius ratios. Significant differences in the Casson flow parameters (p ≤ 0.05) were also found when samples were sheared for 12 min as compared to 30 min. A piecewise regression technique, which fitted the Casson model to the low shear rate ranges and the Bingham model to higher shear rate ranges, could be used to best describe the flow behaviour of chocolate melts. Stress relaxation produced very low oy values, which were believed to be an artifact of the measuring fixture and instrument. In the case of the single vane method, use of different start‐up speeds had a marginal but significant effect (p < 0.05) on oy values. When the multiple vane method was employed, start‐up speeds below 0.23 rpm had no significant effect on oy. The multiple vane method proved to be simple and more rapid than obtaining the steady shear data and then fitting the Casson flow model, and thus may be more suitable for routine yield stress measurements of molten chocolate for quality assurance purposes.
BITE FORCES AND HARDNESS PERCEPTION IN PRODUCTS PRESENTING PLASTIC DEFORMATION
Authors: MIOCHE L. , QUEMAR J. C. , CULIOLI J. , WODA A.
Published: February 2007

The oral perception of the hardness of plastic deformable products was investigated. Differential sensitivity was studied over a large range of hardness during psychophysical tests in which bite forces were recorded with small intra‐oral load cells. The mechanical properties of 21 products obtained from dental waxes and modelling clays were measured. They covered a stress range from 19N/cm2 to 265N/cm2 when the plastic deformation plateau was reached. For psychophysical experiments, these products were divided into four series according to their hardness. For each series, a differential threshold was obtained for 10 individuals who were asked to make hardness comparisons by biting the samples with the incisors. During each bite, forces were recorded from an intra‐oral load cell placed beneath the sample. Differential thresholds varied between 6 and 13% depending on the series. For the 21 products taken together, a significant correlation (R = 0.98) was found between bite forces and stresses. Furthermore, significant correlations were also found within each series of comparisons except for the series of the softest products. Bite forces appeared therefore to play the main role in hardness perception of products exhibiting plastic deformation, except for the softest products for which developed forces might not correspond to the normal field of forces activated during mastication.
EVALUATION OF THE HOLE PRESSURE METHOD TO MEASURE THE FIRST NORMAL STRESS DIFFERENCE OF CORN MEAL DOUGH DURING EXTRUSION COOKING
Authors: BHATTACHARYA M. , PADMANABHAN M.
Published: February 2007

Rheological 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. N1 was 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, N1 ranged from 3 × 104 to 6 × 105 Pa for shear rates between 30 to 400 s−1. Possible sources of errors in the hole pressure measurements are discussed.
PENDULUM TEST FOR EVALUATION OF THE RUPTURE STRENGTH OF SEED PODS
Authors: LIU X‐Y , MACMILLAN R. H. , BURROW R. P. , KADKOL G. P. , HALLORAN G. M.
Published: February 2007

A small impact pendulum was developed to measure the shatter resistance of seed pods. While clamped by their stems, the pods are hit by the rigid pendulum; the rupture energy is derived from the measured angles of swing. The consistency of the pendulum was confirmed by tests on a sample of fine spring wire. The pendulum was then used in a series of trials on 13 rapeseed varieties and rupture energy results were compared with earlier bending moment and bending energy results obtained from tests using a quasi‐static cantilever arrangement. Rupture energy values were much less variable than bending energy. However, the ranking of varieties by all three strength measures was generally similar.
FIBRE FRACTURE OF BOVINE M. PECTORALIS PROFUNDUS MUSCLE COOKED PRE‐ AND POSTRIGOR
Authors: DRANSFIELD ERIC , LACOURT ANDRE , LACOURT PAULETTE
Published: February 2007

The ultimate tensile strength and extensibility in the direction of the muscle fibres of cooked meat decreased exponentially during storage of the raw meat for up to 3 days at 15C. The mode of fracture was examined by light microscopy of longitudinal sections taken after testing to break. In meat cooked soon after stunning, ‘brittle’ fracture had been induced across the fibres and the high extensibility was proposed to be due to sequential fibre fracture. At 1 day postmortem, the fractures crossed several fibres occurring in a repetitive fashion every 30 μm along the fibres. This was thought to be due to a stiff fibre embedded in an extensible surface matrix connecting the fibres. In aged meat, discontinuous fractures were prominent within each fibre and which stopped at the surface of each fibre showing further weakening of the fibre and the composite matrix. All the myofibrils remained in register. These changes are consistent with a gradual reduction in cohesion within the meat and indicates that the weakening of the focal adhesions is primarily responsible for postmortem tenderisation.
DYNAMIC VISCOELASTICITY AND STRESS RELAXATION IN STARCH PASTES
Authors: AKUZAWA SAYURI , SAWAYAMA SHIGERU , KAWABATA AKIKO
Published: February 2007

The dynamic viscoelasticity and stress relaxation of ten types of starch pastes were measured. The dynamic moduli increased with increasing frequency, and were different for each starch paste, changes in tan δ for cassava and potato starch pastes being about 0.5–0.6. The stress relaxation behaviour of all the samples tested could be represented by a four‐element mechanical model. The relationship between spinnability and stress relaxation was determined, the spinning distance increasing with increased relaxation time (τ2). No satisfactory linear relationship between spinning distance and relaxation time (τ2) was apparent with the 10 starch paste samples.
A VIDEO‐BASED METHOD FOR DETERMINATION OF AVERAGE STRESS‐STRAIN RELATIONS IN UNIAXIAL COMPRESSION OF SELECTED FOODS
Authors: ROHM H. , JAROS DORIS , DeHAAN MARGREET
Published: February 2007

A video‐based method was applied to evaluate average stress‐strain relationships during uniaxial compression experiments of selected food materials. The determination of apparent Poisson ratios of Gouda cheese resulted in numbers close to the theoretical value for incompressible materials of 0.5. In case of such foodstuffs, mathematically corrected compressional stress based on the consideration of constant specimen volume showed almost similar results to stress values estimated on the basis of the true cross‐sectional area measured from lateral extension. For compressible materials such as apples or bread, which show a certain reduction of volume under stress or strain, the apparent Poisson ratios were strain‐dependent. Average stress values calculated from compressional force and actual specimen diameter were found to be different from either engineering stress and corrected stress.
SMALL AMPLITUDE OSCILLATORY SHEAR STUDIES ON MOZZARELLA CHEESE PART II. RELAXATION SPECTRUM
Authors: SUBRAMANIAN R. , GUNASEKARAN S.
Published: February 2007

The frequency dispersion of dynamic mechanical spectra of a low‐moisture, part‐skim and a low‐fat, part‐skim Mozzarella cheese are presented. Small amplitude oscillatory shear measurements within the linear viscoelastic range (0.05% strain) were made over 12 weeks of storage. Proteolysis during storage led to softening of the cheeses and thus decreases in storage (G′;) and loss (G″) moduli. Master curves (at a reference temperature of40C) were obtained by shifting the temperature‐dependent frequency dispersion of storage modulus. There was no significant change in G’ after 4 weeks of aging. The variation of relaxation time and viscosity spectrum of both cheeses with age were obtained from the master curves using the generalized Maxwell model and nonlinear regression analysis. With maturation the viscosity distribution of corresponding Maxwell elements shifted towards smaller values, indicating that cheeses become softer and melt more easily.
METHOD TO ASSESS THE ABILITY OF ROUGH SURFACES TO ELIMINATE SLIP IN FOOD VISCOMETRY 1
Authors: HOFFNER B. , GERHARDS CH. , PELEG M.
Published: February 2007

In squeezing flow viscometry the presence or absence of friction between the specimen and the plates has a dramatic effect on the flow curve characteristics. It is therefore proposed that the method can be used to test whether a given surface, with a particular rough finish, is effective to eliminate slip of a given self‐lubricating food. The concept is demonstrated with experimental data of commercial samples of mayonnaise and mustard, which were pressed between pairs of parallel polished and rough metal plates in an imperfect squeezing flow array, and their force height relationship was recorded. In all the cases, the absolute magnitude of slope of the log‐force versus log height plot was smaller than one. This shows that these two products are self‐lubricating to such an extent that roughening of the plates surface, at least to the extent used in this work, can be an ineffective means to avoid slip. Similar results have been previously reported in three different kinds of tomato products, which suggests that the problem may not be limited to food emulsions.
TEXTURE AND STRUCTURE OF CRISPY‐PUFFED FOOD PRODUCTS PART II: MECHANICAL PROPERTIES IN PUNCTURE
Authors: VAN HECKE E. , ALLAF K. , BOUVIER J. M.
Published: February 2007

A puncture test was used to describe the mechanical and textural behavior of crispy‐puffed food extrudates. Four criteria were identified from the force‐time curves: (1) the average puncturing force, Fm, (2) the spatial frequency of structural ruptures, Nwr, (3) the average specific force of structural ruptures, fwr, and (4) the crispness work, Wc. The discriminating power of these criteria was shown through the effects of moisture content and recipe composition in the extrusion‐cooking process. Relationships between puncture criteria were also studied. The effect of water activity showed that the force related criteria described well the mechanical behavior of expanded extrudates.
MECHANICAL PROPERTIES OF AN IMMERSION FRIED POTATO STARCH‐GLUTEN GEL DURING POSTFRYING PERIOD
Authors: NORMÉN EVA , ROVEDO CLARA O. , SINGH R. PAUL
Published: February 2007

Moisture profiles in fried samples of potato starch with different gluten contents were determined during postfrying storage. Over time, moisture migrated from the core to the crust of the sample, and the moisture content of the crust region increased. The addition of gluten caused a significant increase in oil uptake in the crust. The initial hardness of the crust significantly decreased as the gluten content increased to 10 and 30%, during the first 30 min of storage. With longer storage time (> 240 min), the crust hardness tended to increase, due to an increase in firmness of the starch sample. This behavior was less pronounced for samples with 10 and 30% gluten. The range of linear viscoelastic behavior (up to 14% strain) was determined from the initial linear zone of the stress‐strain curves. Stress relaxation tests were performed in the linear and nonlinear viscoelastic regions, with a strain level of 5% and 40%, respectively. According to stress relaxation curves, samples became less elastic with the addition of gluten and more elastic with the time of storage.
EFFECTS OF GELLAN GUM, CITRIC ACID AND SWEETENER ON THE TEXTURE OF LEMON JELLY
Authors: MORITAKA HATSUE , NAITO SHIGEHIRO , NISHINARI KATSUYOSHI , ISHIHARA MIKI , FUKUBA HIROYASU
Published: February 2007

Effects of various ingredients on the texture of lemon jellies prepared from gellan gum, citric acid and sweetener were investigated by rheological measurement and sensory evaluation. The data were analyzed by use of the modification of Scheffé's mixture experiment method in converse triangle experiment area. The contours of the response surface were drawn using the best model whose terms were searched by AIC statistic, and the approximate model was calculated to consider the contours. “Hardness” estimated by both methods was large in jellies with high content of gellan gum and low content of citric acid. The content of citric acid significantly influenced “smoothness” estimated by a subjective method. The influence of citric acid varied with the content of gellan gum. The correlation coefficients of evaluation between “hardness” and “lemon flavor” or “sourness” were negative.
FORMATION OF WHEY PROTEIN POLYMERS: EFFECTS OF A TWO‐STEP HEATING PROCESS ON RHEOLOGICAL PROPERTIES
Authors: MLEKO S. , FOEGEDING E.A.
Published: February 2007

Whey protein polymers were obtained by two‐step heating of whey protein isolate (WPI) solutions with or without change of pH or protein concentration. Rheological properties of polymer solutions were studied. Viscosity of solutions heated then diluted was about 6 times higher than viscosity of equal concentration solutions heated directly. A second heating at a lower pH resulted in higher viscosity. Solutions were generally thixotropic and pseudoplastic; however, dilatant and rheopectic behavior was also observed. A 4% WPI solution could be converted to a polymer solution with a viscosity comparable to the viscosity of 1% carbohydrate hydrocolloids.
FEASIBILITY OF MEASURING MEAT TEXTURE AND EXUDATE USING PAIRED HYPODERMIC NEEDLES FOR RHEOLOGY, SPECTROPHOTOMETRY AND ELECTRICAL IMPEDANCE
Authors: SWATLAND H. J.
Published: February 2007

Meat texture and exudate were investigated using a pair of hypodermic needles curved to touch at their tips. Electrical impedance was better than fiber‐optic spectrophotometry for detecting the meat exudate released as the needles were moved apart. Separation of needles creating tension along the lengths of myofibers caused higher stress and less tip separation than needle separation perpendicularly across the myofibers.
FLOW PROPERTIES OF ORANGE DIETARY FIBER SUSPENSIONS
Authors: GRIGELMO‐MIGUEL NURIA , IBARZ‐RIBAS ALBERT , MARTÍN‐BELLOSO OLGA
Published: February 2007

The flow behavior of 7–20% orange dietary fiber (DF) suspensions at 15–65C was most adequately described by the simple power law model. The effect of the temperature on the apparent coefficient of viscosity (ηapp) followed an Arrhenius‐type relationship. The flow activation energy (Ea) was in the range 3.0–14. 7kJ/mol, depending on the concentration. The ηapp increased exponentially with concentration within the temperature range studied. The combined effect of temperature and concentration on the ηapp could be represented by an exponential equation. In all the cases, the effect of concentration on ηapp was more pronounced than that of the temperature.
SHEAR PROPERTIES AND WARNER‐BRATZLER TENDERNESS MEASUREMENT OF BEEF 1
Authors: LU RENFU , CHEN YUD‐REN
Published: February 2007

The shear properties of raw and cooked beef and their relationship with Warner‐Bratzler (WB) tenderness measurement were evaluated. Shear tests were performed on four muscles, biceps femoris (BF), longissimus dorsi (LD), semimembranosus (SM), and semitendinosus (ST), with three different aging treatments (0, 1, and 2 weeks), using a specially designed device and the WB shear device. Raw beef exhibited a nonlinear behavior characterized by linearity at small deformations, stress yield at intermediate deformations, and work hardening at large deformations. Cooked beef had a different nonlinear behavior with the slope of the force‐displacement curve increasing with displacement before the peak force. Cooking resulted in a large increase (p=0.01) in maximum shear force and strain energy. The effect of muscle type and aging on shear properties was mostly significant (p=0.05). The maximum shear force of cooked beef was correlated with WB measurement with the R2 value ranging from 0.65 to 0.34 for LD, SM, and BF except for ST with a R2 value of 0.10. Correlations of the shear properties of raw meat with WB measurement were low (R2<0.36), indicating the difficulty of predicting WB tenderness from the shear properties of raw meat.
TEXTURE OF FRIED POTATO TISSUE AS AFFECTED BY PRE‐BLANCHING IN SOME SALT SOLUTIONS
Authors: BLAHOVEC J. , VACEK J. , PATOČKA K.
Published: February 2007

Planar potato crisps were prepared from potato tubers of four varieties (Agria, Javor, Nicola and Panda). The effect of slice blanching in water and solutions of Na‐, Ca‐, and Mg‐chlorides prior to frying, as well as the effect of storage time of the tubers prior to test were also studied. The deformation curves from a three point bending test were evaluated and Young's modulus (EM), maximum relative deflection (MRD), maximum tensile stress (MTS) and surface energy (SE) were determined. The MRD and MTS correspond to rupture point values of deflection and stress, respectively. The obtained results show that almost all test parameters (MTS is an exception) depend mainly on the blanching solution and the ratio of monovalent (K and Na) to divalent ions (Ca and Mg) in the crisps. Variety dependence was observed mainly in MRD and EM. An increase in the ratio monovalent over divalent cation concentrations led to lower MRD‐ and SE‐values and at the same conditions to higher Young's moduli. EM‐values of 320–340 MPa were obtained for the two varieties with higher content of starch (Javor and Panda) while for the two varieties with lower starch content (Agria and Nicola) values of 230–250 MPa were observed. The MRD was of 0.057–0.061 for Javor and Panda and 0.075–0.080 for Agria and Nicola. The starch content could not explain the observed variety differences for maximum tensile stress and surface energy.
RHEOLOGICAL MODELS OF CHEDDAR CHEESE TEXTURE AND THEIR APPLICATION TO MATURATION
Authors: HORT JOANNE , LE GRYS GEOFFREY
Published: February 2007

Seventeen types of Cheddar cheese were assessed by a trained panel for creaminess, crumbliness (fingers), crumbliness (chewing), firmness, graininess, hardness (first bite), hardness (cutting), and springiness using Quantitative Descriptive Analysis. A maturing block of English Cheddar was also evaluated at various stages during ripening. The rheological properties of the Cheddar samples were determined using compression and cutting tests performed on an Instron Universal Testing Machine and are reported in terms of the true stress and Hencky strain. Multiple Regression techniques enabled accurate and rational rheological models of all the textural attributes except creaminess to be constructed. Models using instrumental variables where the test method had a similar action to that used by the human assessor were more accurate. The suggested models proved successful at predicting the textural characteristics of the Cheddar block at all but the earliest stages during maturation.
RHYTHMIC AND IRREGULAR MOVEMENT OF THE FIRST MOLAR WHILE EATING FOODS WITH DIFFERENT TEXTURES
Authors: TOGASHI MICHIKO , MORITA AKIKO , NAKAZAWA FUMIKO
Published: February 2007

The three‐dimensional movement of a tooth, any tooth, while naturally eating, was measured by an apparatus developed in our laboratory. The movement of the first molar on the usually used side is reported here. The mastication movements are divided into two parts, namely the rhythmical chewing period during which there are mastication pressure loads on the molar and the irregularly pulsated moving period in preparation for the swallowing followed by the rhythmical one during which there is no more pressure on it. The amplitudes of the up and down movements of the molar are 10–22mm for the rhythmical chewing period which are bigger than those for the irregularly moving period. The rhythmical chewing periods are distributed around 10–40 s depending on 14 kinds of food texture, and also on the size of the food, in a fairly similar manner for the participants. The period is longer for tough foods and bigger samples. The irregularly pulsated moving periods are widely distributed, 2–45s, and depend both on the food texture and on the participant. The irregular moving periods are longer for foods which scatter in the mouth or adhere to the teeth when chewing. The ingestion difficulty of the food was divided into two groups. One is where it is difficult to break down the food with the teeth and the other is where it is difficult to prepare for swallowing.
MECHANICAL PROPERTIES OF TWO‐PHASE DISPERSE AGAR/GELATIN MIXED GELS
Authors: FUJII KEIKO , KAJITA RIKA , KUROSAWA MIKI , FUJII TOMOYUKI
Published: February 2007

Agar/gelatin mixed gels with the same composition but with a different two‐phase disperse structure were prepared and their mechanical properties compared. The agar/gelatin mixture was first kept at temperature above the gelling temperature of gelatin but below that of agar and stirred for the selected period, before cooling it below the gelling temperature of gelatin. For the low rupture stress system the agar concentration was 0.7% (w/w), while the gelatin concentration was 4.5% (w/w) to achieve the same rupture stress as the agar gel. The mixing temperatures selected were 20 and 37C. For the high rupture stress system, the agar and gelatin concentration was 2.8 and 10.4% (w/w), respectively, to achieve the same rupture stress. The mixing temperatures selected were 37 and 40C. The both mixed gels prepared by this method consisted of a dispersed phase of agar and a continuous phase of gelatin. The rupture stress of the mixed gels decreased as the content of the dispersed phase increased. The rupture stress had a tendency to be lower as the size of the dispersed particles increased. These results suggest that the interface between the dispersed phase and the continuous phase plays an important role as Griffith's crack, with the rupture of mixed gels occurring from that place.
SENSORY CHARACTERIZATION OF TEXTURE AND FLAVOR OF HIGH VISCOSITY GELS MADE WITH DIFFERENT THICKENERS1
Authors: KÄLVIÄINEN NIINA , ROININEN KATARIINA , TUORILA HELY
Published: February 2007

Four thickeners (pectin, gelatin, starch and gelatin + starch) and two aroma concentrations (1.4 and 0.7 mL aroma / 1 kg candy base) were used for manufacturing high viscosity gel systems, i.e. strawberry candies. The salient texture and flavor attributes of the samples were identified and evaluated by a trained descriptive panel. The thickeners strongly affected texture and flavor attributes of the samples, while the two aroma concentrations did not differentiate between samples. Each thickener used produced its own characteristic texture. The gels with weak and fragile texture had stronger flavor intensities and tart flavor than the gels with strong and cohesive texture. Because of the strong interaction between texture and flavor, the results have major implications for the production of high viscosity gels such as candies.
STRESS RELAXATION AND LOW FIELD PROTON MAGNETIC RESONANCE STUDIES OF CHEESE ANALOG*
Authors: BUDIMAN M. , STROSHINE R. L. , CAMPANELLA O. H.
Published: February 2007

Cheese analog samples were prepared using two different sources of fat milkfat and vegetable oil. The rheological properties of the samples, which ranged in moisture from 42.5 to 50%, were examined using compression and stress relaxation tests. The values of peak stress (s̀ at 50% strain) from the compression tests and the initial stress (s̀o), equilibrium stress (s̀e), and elastic constant (g1) from the stress relaxation tests, were compared. All four values were higher for the samples containing milkfat as compared to the samples containing vegetable oil. For both analog formulations, moisture content was negatively correlated with values of s̀o (R2 > 0.91), s̀o (R2 > 0.80) and g1 (R2 > 0.94) at 40 mm/min crosshead speed. The CPMG‐T2 relaxation curves of the samples were determined using a low field (5.35 MHz) proton magnetic resonance sensor. The T2 relaxation data were fit to a two‐term exponential model having time constants T2a and T2b In the model, the coefficients α and β indicated, respectively, the contribution of T2b and T2b to the T2 relaxation. The T2a value was associated with the water in the analog cheese while the T2b value was associated with the oil. The T2a value was correlated (R2 > 0.95) with the relative proportion of water in each sample. It increased as the moisture content increased. There were negative correlations between T2a and s̀o, s̀e, and g1 from the stress relaxation tests.
ULTRASONICS IN EVALUATING RHEOLOGICAL PROPERTIES OF DOUGH FROM DIFFERENT WHEAT VARIETIES AND DURING AGEING
Authors: KIDMOSE ULLA , PEDERSEN LENE , NIELSEN MORTEN
Published: February 2007

The utility of low‐frequency ultrasonics in evaluating the viscoelastic properties of dough from different biscuit wheat flour qualities was studied. No distinct correlation was found between the ultrasonic characteristic (ultrasound velocity, v) and the rheological characteristics storage modulus, G' (r=0.43), or loss modulus, G″ (r=0.61), when a constant amount of water was added to the dough. Fairly high correlations were obtained between the ultrasound velocity, v, and the rheological measurements G' (r=0.93), G″ (r=0.92) and the phase angle G′ (r=0.81) with variable addition of water, corresponding to the water absorption capacity of the dough. It was not possible to distinguish between hard and soft endosperm biscuit wheat varieties using ultrasonic measurements, whether with a constant or a variable amount of water added. A high negative correlation was obtained between ultrasonic measurements and the amount of water added to the dough (r = ‐0.94), indicating that the amount of water added affected the ultrasonic measurements more significantly than differences in dough structure and rheological properties. The effect of ageing on the ultrasonic characteristics of dough samples was also studied. The ultrasound velocity, v, and storage modulus, G', increased during 40 min ageing. A high correlation obtained between ultrasound velocity, v, and the storage modulus, G' (r=0.97), indicates that ultrasonics may be a valid method of process control of rheological properties during the manufacture of dough.
BOOK REVIEWS
Authors: Koh C. J. , Bourne Malcolm , Launay Bernard
Published: February 2007

COMPUTATIONAL RHEOLOGY FOR PIPELINE AND ANNULAR FLOW. Wilson C. Chin

CRYSTALLIZATION IN FOODS. R.W. Hartel

RHEOLOGY OF FLUID AND SEMISOLID FOODS. PRINCIPLES AND APPLICATIONS
USE OF BRABENDER® VISCOGRAPH E TO MEASURE SOME RHEOLOGICAL PROPERTIES OF MINCED FISH MUSCLE
Authors: KRISTBERGSSON KRISTBERG , SIGFUSSON HALLDOR
Published: February 2007

A Brabender® Viscograph E rotational viscometer was used to measure some rheological properties of diluted mince samples from cod (Gadus morhua), halibut (Hippoglossus hippoglossus), pollock (Pollachius virens) and ocean perch (Sebastes marinus). The results were compared to measurements on undiluted samples using a Brabender® Farinograph viscometer and an Instron Universal Testing Machine. When samples were adjusted to contain the same moisture content, differences in Brabender viscosity (P ≤ 0.05) were observed both between species and between different muscles of the same species. Thermal denaturation of cod muscle proteins was manifested as an increase in Brabender viscosity at approximately 30C. The addition of 1% (w/w) NaCl resulted in lower (P ± 0.05) mince Brabender viscosity. Initial changes in mince structure caused by freezing were observed as a drop in Brabender viscosity. There was a reasonable agreement between the results obtained using the Viscograph E and those obtained using the Instron (r2= 0.791). The instruments were sensitive to both chemical and structural differences in samples. However, the Farinograph was incapable of distinguishing between muscle types or species. The Viscograph E offers the possibility to monitor Brabender viscosity changes during heating and may be used to observe the effect of additives on Brabender viscosity and muscle protein denaturation.