bluuebunny/crossref_metadata_2025 huggingface dataset:
THE WEDGE FRACTURE TEST A NEW METHOD FOR MEASUREMENT OF FOOD TEXTURE
Authors: VINCENT J. F. V. , JERONIMIDIS G. , KHAN A. A. , LUYTEN H.
Published: February 2007

The fracture properties of foods are relevant to texture but can be difficult to measure because of limitations of size or shape. Many established engineering tests for the measurement of crack growth and unstable propagation of cracks require specific test geometries, sizes and compliances of the specimen. With food materials this is rarely possible. The wedge penetration technique can usefully be adapted to foods to determine fracture parameters of brittle and semi‐brittle foods such as moderately hard cheeses and raw and cooked fruits and vegetables.
CUTTING RESISTANCE OF A RESTRUCTURED FRUIT BAR AS INFLUENCED BY WATER ACTIVITY
Authors: OWEN STEVEN R. , TUNG MARVIN A. , DURANCE TIMOTHY D.
Published: February 2007

The cutting resistance, of thin rectangular strips of a restructured dehydrated fruit bar was measured over a range of water activity, 0.30‐0.97. There was a 100‐fold increase in cutting force as the product was dried from an initial cutting resistance of 4.4 N at aw, = 0.86 to a maximum of 452 N at aw= 0.33. Below a water activity of 0.33, samples became brittle and showed lower cutting resistances; for example, 68 N at aw= 0.30. The major ingredients in the fruit product affecting cutting resistance were the level of apple puree and maltodextrin.
EFFECT OF POLYSORBATE‐60 ON THE STABILITY OF O/W EMULSIONS STABILIZED BY PROPYLENE GLYCOL ALGINATE AND XANTHAN GUM
Authors: YILMAZER G. , KOKINI J. L.
Published: February 2007

The effect of polysorbate‐60 in improving the stability of model oil‐in‐water emulsions formulated with xanthan gum and propylene glycol alginate was studied at two levels of the surfactant; 0.15% and 0.30%. Creep measurements and steady shear measurements as well as surface tension and oil droplet size measurements were conducted to relate rheological and surface properties to improved stability. Higher polysorbate‐60 concentration resulted in lower surface tension values which shifted the oil droplet size distribution to a smaller size range; this distribution was a function of aging time at 0.15% weight concentration PS‐60. The decay in rheological parameters, particularly Newtonian viscosity, was slower at 0.30% surfactant concentration.
ORAL PERCEPTION OF HARDNESS IN VISCOELASTIC PRODUCTS
Authors: MIOCHE L. , AUROY P. , LEPETIT J. , COMPAGNON D.
Published: February 2007

The problem of hardness perception was examined by means of a psycho‐physical approach. The differential sensitivity was studied over a wide range of hardness (approximately 100 to 600 × 104 Pa) with products displaying mainly elastic behavior.

A series of five silicon elastomer samples were prepared, each series containing 6–8 samples of varying degrees of hardness. The rheological characteristics of these products were measured. Differential threshold and magnitude estimation tests were carried out by 10 subjects who were asked to make hardness comparisons by biting or squeezing the samples. There was no significant difference in sensitivity between molars and incisors as shown by the differential thresholds which varied between 4 and 11% depending on the hardness range. Pressing between the fingers gave less accurate performances than biting. The difference in sensitivity detected by the threshold measurements was not shown in the magnitude estimation tests.
RHEOLOGICAL PROPERTIES OF GOAT MILK CHEESE: METHOD OF TRUE AXIAL STRESS VERSUS APPARENT AXIAL STRESS
Authors: RISCH ERIC
Published: February 2007

Compressive 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 level.
THE EFFECTS OF TURGOR PRESSURE ON PUNCTURE AND VISCOELASTIC PROPERTIES OF TOMATO TISSUE
Authors: JACKMAN ROBERT L. , MARANGONI ALEJANDRO G. , STANLEY DAVID W.
Published: February 2007

The 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 pericarp tissue.
EFFECT OF STRAIN LEVEL AND STORAGE TIME ON THE RECOVERABLE WORK OF COMPRESSED BREAD CRUMB 1
Authors: NUSSINOVITCH A. , STEFFENS M. , CHINACHOTI P. , PELEG M.
Published: February 2007

Cylindrical specimens of bread crumbs were subjected to a compression‐decompression cycle using a computer interfaced Universal Testing Machine during 11 days of storage at ambient temperature. The strain (% deformation) was set at various levels in the range of 20–80%. The overall work per unit volume, calculated from the area under the stress‐strain curve, increased exponentially with the imposed strain while the percent recoverable work, calculated from the area under the decompression curve, decreased exponentially with the strain. The loss of elasticity that accompanies bread aging was clearly manifested in the percent recoverable work, irrespective of the imposed strain. It declined in a manner that could be described by a power law or an exponential decay model at the same degree of fit as judged by statistical criteria.
VISCOELASTIC BEHAVIOUR OF AMYLOSE‐FATTY ACID GELS
Authors: RAPHAELIDES S.N.
Published: February 2007

Rheological measurements were used to study the gelation of amylose in O.01M KOH (pH 12) in the presence of fatty acid potassium salts. Creep compliance‐time experiments indicated that addition of the fatty acids caused considerable changes in the rigidity of the amylose gels. The effect was dependent on fatty acid concentration, molecular conformation and lipid acyl chain length. Dynamic measurements on aged amylose‐potassium stearate gels showed that the development of rigidity modulus was rapid and dependent on the fatty acid concentration.
RHEOLOGICAL INDICES OF FRUIT CONTENT IN JAMS: EFFECT OF FORMULATION ON FLOW PLASTICITY OF SHEARED STRAWBERRY AND PEACH JAMS
Authors: COSTELL E. , CARBONELL E. , DURAN L.
Published: February 2007

The effect of formulation factors on Casson yield values measured at low shear rates (0.08 ≤γ≤ 1.01s‐1) (σ01) and at medium shear rates (2.58 ≤γ≤ 387.30s‐1) (σ02) was analyzed in previously sheared strawberry and peach jams. Twenty three samples of each fruit jam were prepared according to a second order composite rotatable design. Composition ranges were: fruit content, 25–55%; soluble solids content, 60–70° Brix; added pectin in strawberry jams, 0.3–0.7% and in peach jams, 0.1–0.5%. Variation of σ01 values in strawberry jams depended mainly on the interactions between fruit and soluble solids and between fruit and pectin, while in peach jams, it depended on fruit‐soluble solids and soluble solids‐pectin interactions. Patterns of change of σ02 values with composition were similar to those observed for σ01 in both strawberry and peach jams. Predictive power of σ01 and σ02 values for estimation of fruit content was low, but taken in conjunction with soluble solids content and total pectin values, 79.5% of the variability of fruit content in strawberry jams and 91.1% of same in peach jams could be explained.
RHEOLOGICAL PROPERTIES OF WHEY PROTEIN CONCENTRATE GELS
Authors: COONEY M.J. , ROSENBERG M. , SHOEMAKER C.F.
Published: February 2007

The rheological properties of heat whey protein concentrate gels were studied by dynamic oscillation rheometry. A whey protein concentrate of 75% protein was used to make solutions of 10.3, 12.5 and 14.5% protein (w/w), which were heated to 90C for gel formation. Specific attention was focused on the temperature dependence of the mechanical properties of the gels during cooling and reheating. In all cases the magnitude of the complex modulus |G*| was found to increase with decreasing temperatures from 90 to 30C. The tan δ, which is related to the relative viscoelasticity of the gels, increased with decreasing temperatures from 90 to 60C. At temperatures between 60 and 30° C, tan δ remained constant. The dependence of |G*| and tan δ on temperature was found to remain constant during heating and cooling between 30 and 70C, indicating that rheological changes were reversible within this temperature range.
EFFECTS OF STARTER CULTURES ON LINEAR VISCOELASTIC AND PHYSICAL PROPERTIES OF YOGURT GELS
Authors: ROHM H. , KOVAC ALESA
Published: February 2007

Set‐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 firmness.
IDENTIFICATION OF THE MAIN TEXTURAL CHARACTERISTICS OF CANNED PEACHES AND THE EFFECTS OF PROCESSING VARIABLES
Authors: APOSTOLOPOULOS C. , BRENNAN J. G.
Published: February 2007

The texture profile of canned peach fruits was studied using magnitude estimation as a scaling method. Their sensory characteristics were assessed using as a modulus either a model fruit or a real fruit sample. The sequence of appearance of the textural characteristics was determined during 4 stages of assessment (nonoral, first bite, during mastication, after effects). Four different varieties of peach fruits were canned and the effect of four processing variables (level of heat treatment, degree of ripeness, sugar concentration in the processing liquid and hardness of the processing liquid) on the texture profile of the fruits was examined. The results showed that an increase in the severity of the heat treatment and the degree of ripeness of the fruit resulted in a decrease in the firmness, crunchiness and chewiness of the canned fruit. Fibrousness was similarly affected but to a lesser extent. Freshness and juiciness were also negatively affected by these variables. An increase in the sugar concentration and hardness of the processing liquid resulted in an increase in the firmness, crunchiness and chewiness of the canned fruit. Fibrousness, freshness and juiciness were similarly affected but to a lesser extent.
MODELLING THE GELLING BEHAVIOUR OF LINSEED POLYSACCHARIDE: EFFECT OF SALTS AND pH
Authors: SUSHEELAMMA N.S. , CHAND NAGIN , RAJALAKSHMI D.
Published: February 2007

The rheological properties of linseed polysaccharide gels in the presence of citric acid, calcium and magnesium carbonates were studied using a factorial design and the Herschel‐Bulkley model. The yield stress and consistency index increased with the concentration of calcium and magnesium ions, while the flow behaviour index decreased, imparting stability to the gel. With citric acid, s̀o and k reached a maxima and then decreased, while n increased after an initial dip. The effect of pH (3.4–9.3), sucrose (45–55%), and polysaccharide (0.6–0.8%) on rheological constants were modelled using polynomials where up to fifth power of pH was required. Ln(s̀o), ln(k), and n were fitted to the standardised (normalised) forms of pH, In (sucrose) and In (polysaccharide) with multiple correlations of 0.95, 0.97 and 0.98, respectively. The two optima (with pH) were computed using Nelder and Mead's flexible polyhedral search method. Both required 55% sucrose and 0.8% polysaccharide with pH of 4.3 and 7.3, respectively. The models at the two optima are discussed through 3‐D graphs. The technological implications of the dual optima have been indicated. This is, probably, the first report where two optima, with pH, have been observed for a gel forming polysaccharide.
CHARACTERISATION OF PATTERNS OF CHEWING BEHAVIOUR IN HUMAN SUBJECTS AND THEIR INFLUENCE ON TEXTURE PERCEPTION
Authors: BROWN WENDY E. , LANGLEY KEITH R. , MARTIN ALAN , MacFie HALLIDAY J.H.
Published: February 2007

Electromyography was used as a noninvasive and unobtrusive technique to characterise chewing patterns for a range of foods. Differences between subjects for a variety of aspects of chewing sequence are recorded for a range of foods (carrot, apple, roast pork, salami, biscuit and toast). Identifiable subgroups of subjects differing in chewing behaviour existed within the random sample of 52 dentate subjects. The five subgroups accounted for 52%, 21%, 11%, 10% and 6% of the sample population. Major discriminating factors between the behavioural groups lie in their chewing time and the muscle work rate during chewing. Sensory ratings for firmness and rubberiness of model foods differed significantly between the subjects exhibiting different chewing behaviours. Chewing behaviour may influence consumers’ perceptions about the texture of a food.
MEASUREMENT OF FLOW ABILITY OF BUTTER BY CAPILLARY RHEOMETRY
Authors: SHUKLA A. , RIZVI S.S.H.
Published: February 2007

Capillary rheometry was used to study and compare the rheological behavior of butters made from supercritically fractionated high melting triglyceride (HMT) and anhydrous milk fat (AMF) at different temperatures. Application of shear rates in the range of 17.37 to 346.93 S−1 showed a strong dependency of flow behavior on the capillary diameter, indicating slippage at the walls. Shear rates were corrected for wall‐slippage using capillaries with different diameters but the same length, and for non‐Newtonian behavior using the Rabinowitsch procedure. Shear stresses were corrected for entrance effect using capillaries of the same diameter but different lengths. Power law consistency indices (K), determined from loglog plots of corrected shear stresses versus shear rates, were found to have a negative correlation with temperature. Higher K values were observed for HMT butter depicting its more solid‐like behavior due to greater concentration of high melting triglycerides. A slight increase in the K values was observed on storage probably due to rearrangement of fat crystals and formation of secondary bonds between them. Flow indices were found to be relatively insensitive to both time and temperature of storage. From the flow curves (apparent viscosity versus shear rates), master curves were generated using the time‐temperature superposition principle.
STIFFNESS ASSESSMENT FROM JAGGED FORCE‐DEFORMATION RELATIONSHIPS1
Authors: PELEG M. , NORMAND M.D.
Published: February 2007

Brittle and crunchy foods are notorious for their irregular and irreproducible force‐deformation relationships which cannot be converted to stress‐strain relationships because of geometric considerations. However, a fairly consistent assessment of their stiffness can still be extracted from their jagged force‐deformation curves. For example, either the averaged force at a given deformation (e.g., 20%), determined directly or calculated by fitting the curves of several specimens with a polynomial model, can be considered a legitimate stiffness measure albeit a relative one. But since the magnitude of such parameters is affected by occasional force lows and minima as well as failure and sliding events at preceding deformations, they can only provide a low estimate of the material actual stiffness. Application of an algorithm that identifies the peak forces in the force‐deformation relationship produces a new relationship that has a fairly regular and much smoother shape. Derivation of stiffness parameters from such curves is not only easier because of the regular shape and reduced number of points but also provides a closer estimate of the material actual stiffness.
CONSTITUTIVE MODELS OF FOODS
Authors: KOKINI J.L. , WANG C‐F. , HUANG H. , SHRIMANKER S.
Published: February 2007

Linear and nonlinear viscoelastic properties of food materials are important to product design and process design if they can be quantitatively defined. This paper covers prediction of dilute and concentrated solution, linear viscoelastic properties and models for nonlinear viscoelastic properties. The usefulness of various constitutive models in predicting these properties are discussed and demonstrated.
EFFECT OF POSTRIGOR SARCOMERE LENGTH ON MECHANICAL AND STRUCTURAL CHARACTERISTICS OF RAW AND HEAT‐DENATURED SINGLE PORCINE MUSCLE FIBRES
Authors: WILLEMS MARK E.T. , PURSLOW PETER P.
Published: February 2007

Light microscopy during tensile tests was used to examine the effect of postrigor sarcomere length (SL) on mechanical and structural characteristics of raw and heat‐denatured (1 h at 80C) muscle fibres of porcine longissimus lumborum and the structural deformation mechanisms of such fibres inducing mechanical differences. The effect of the collagenous network associated with single coldshortened muscle fibres on maximum stress was analysed. Muscle bundles developed rigor at 2C (cold‐shortened = CS), at22C (control = C), and at 22C
EFFECT OF STORAGE ON THE RHEOLOGICAL BEHAVIOUR OF BABY FOODS
Authors: ALONSO M.L. , ZAPICO J.
Published: February 2007

The effect of storage temperature on rheological behaviour of four varieties of baby foods was studied. After 24‐month storage at 15C and 25C, the constant A in Weltman model increased significantly for the vegetables, meat and fish samples, and decreased significantly for the fruit samples. After 24‐month storage at 5C and 15C there were no significant changes in flow behavior index, consistency index and yield stress of the Herschel‐Bulkley model for the vegetables, meat, fish and fruit samples. Increase in storage temperature decreased the consistency index and yield stress of the fruit samples.
RHEOLOGY OF SODIUM CASEINATE‐CARRAGEENAN MIXTURES
Authors: KEOGH M. KIERAN , LAINÉ KARINE I. , O'CONNOR J. FINBARR
Published: February 2007

The main effects and interactions of mixtures of sodium caseinate, k‐ or t‐ carrageenan, sodium chloride, calcium chloride and hydrogen ions on the rheological properties in aqueous systems cooled to 5 C were quantified. Response surface methodology was used to display the results for five different response variables: gelation temperature, consistency index (k*), dynamic power law factor (n*), critical strain (γc), and syneresis. The gelation profiles observed for both k‐ and t‐carrageenan systems demonstrated that the sol‐gel transition in sodium caseinate‐carrageenan mixtures was due to electrostatic interactions of free carrageenan loops or tails with the intervention of cations. Caseinate molecules did not play a major role in this process. The electrostatic nature of the interactions was further demonstrated by the significant influence of salts and pH on the consistency and brittleness of the gels (represented by k*and γc, respectively). Consistency and brittleness were inversely related as well as consistency and syneresis. Syneresis was negligible in t‐carrageenan gels and was reduced by sodium caseinate and sodium chloride in the k‐carrageenan systems.
ON THE APPARENT FRACTAL DIMENSION OF SOUND BURSTS IN ACOUSTIC SIGNATURES OF TWO CRUNCHY FOODS1
Authors: TESCH RALF , NORMAND MARK D. , PELEG MICHA
Published: February 2007

The jaggedness of the filtered and compressed acoustic signatures of cheese balls and croutons at various levels of water activity was determined in terms of an apparent fractal (Kolmogorov) dimension. The plot of the mean dimension vs water activity had a characteristic sigmoid shape that could be adequately described by a modified version of the Fermi equation. Regression analysis yielded that the apparent fractal dimension, DfK, of the cheese balls and croutons when dry was around 1.45 and 1.38, respectively. The inflection point, awc, that is, the water activity level where half the drop in DfK occurred, was awc= 0.50 and awc= 0.55, respectively. The steepness of the jaggedness versus water activity relationship in terms of the aw range where about 90% of the drop of jaggedness occurred was 0.27 in the cheese balls and about 0.29 in the croutons.
BOOK REVIEW
Authors: BOURNE MALCOLM
Published: February 2007

The Science of Cookie and Cracker Production. Edited by Hamed Faridi, Chapman and Hall, New York. 516 pp. 1994. $99.95.
RHEOLOGY OF PURE AND MIXED KAPPA‐CARRAGEENAN GELS IN LACTIC ACID FERMENTATION CONDITIONS
Authors: ARTIGNAN JEAN‐MICHEL , CORRIEU GEORGES , LACROIX CHRISTOPHE
Published: February 2007

Texture profile analysis and rupture tests, respectively, at a deformation of 5 and 80%, were carried out on commercial kappa‐carrageenan gel cylinders (3% w/v concentration) and on mixed gel cylinders (kappa‐carrageenan/iotacarrageenan or locust bean gum [LBG], in different proportions), to select the best gel composition as an immobilization matrix for continuous lactic acid fermentations of dairy media. Mixed gel cylinders were soaked in a model system for lactic fermentations consisting of 36 dairy media: milk, whey and whey permeate, with 4 lactate concentrations (5, 20, 35 and 50 g/L of medium), combined with 3 pH values (6.5, 6.0, 5.5). GENUGEL X‐0909 n°5180850 was the most resistant of all commercial kappa‐carrageenans available; mixing this kappacarrageenan with LBG in the respective proportions of 2.75%/0.25% gave the best rheological properties to the resulting mixed gel. Our study of the impact of fermentation parameters showed that pH has a significant effect on hardness, cohesion and percentage of deformation at rupture in milk (but not in the other 2 media). A pH drop of milk from 6.5 to 5.5 resulted in more brittle gels which may be explained by an increase in the amount of soluble calcium cations. Generally, soaking in milk produced the most brittle gels due to its calcium content, whey produced the hardest gels and whey permeate, the softest. An increase in the amomonium lactate concentmtion significantly improved hardness, rupture force and percentage of deformation at rupture, while reducing cohesion and resilience: NH4+ cations would account for this effect. The differences in rheological behuviour of immobilization gel beads during continuous Eactic fermentations of milk and whey permeate would be due to the cation content and more specijically to the higher calcium concentmtion in milk.
LOW‐LEVEL BRUISING OF STORED APPLES DUE TO QUASISTATIC LOADING UP TO CONSTANT COMPRESSION STRAIN
Authors: BLAHOVEC J. , PATOČKA K. , BAREŠ J.
Published: February 2007

Gold Delicious and Spartan apples were compressed between two plates and the bruise‐spot volume was subsequently inspected. Fruits were loaded and unloaded at a strain of about 8%. Tests were performed from harvest to the end of storage under: normal conditions (cold storage at 2C for Spartan and OC for Golden Delicious) and modified conditions (the same temperatures but the Biofresh solution was applied to the fruits before being cooled in storage). The contact Hertz theory can be used to describe the compression curve up to the bioyield point. The parameter BMR (bioyield stress to apparent modulus of elasticity ratio) was used for classification of the whole storage period; it was divided into three parts: softening Ia, weakening Ib, ripened II. There was a linear relation between bruise volume and the absorbed energy for fruits tested at all storage times. But over Ib and II the bruise volume was a relatively stable exponential function of the absorbed energy only. The lowest value of the energy absorbed by a fruit without any bruising decreased in Ia and was relatively stable in other parts. The effect of the Biofresh solution on the mechanical parameters was very limited, affecting only the hysteresis losses in Golden Delicious apples.
BI‐CYCLICAL INSTRUMENT FOR ASSESSING TEXTURE PROFILE PARAMETERS AND ITS RELATIONSHIP TO SENSORY EVALUATION OF TEXTURE
Authors: MEULLENET J‐F.C. , CARPENTER J.A. , LYON B.G. , LYON C.E.
Published: February 2007

The most popular instrumental imitative test is the Texture Profile Analysis (T.P.A.). It was originated in the General Foods Laboratories (Szczesniak et al. 1963) and adapted to the Instron by Bourne (1978). T.P.A. involves a double compression test that uses flat plates attached to an Instron Universal Testing Machine (I.U.T.M.). Several instrumental parameters can be extracted from the force/deformation curve generated by the test (e.g. hardness, cohesiveness, springiness, and chewiness). Recently developed in our laboratory, the Bi‐cyclical Instrument for Texture Evaluation (B.I.T.E. master) uses the I.U.T.M. to generate its motion and features a set of artificial dentures as well as a tri‐dimensional movement simulating a chewing motion. Five parameters were extracted from the force/deformation curve to evaluate their potential use for the prediction of cohesiveness.
FACTORS AFFECTING FRACTURE PROPERTIES OF SHORT‐DOUGH BISCUITS
Authors: BALTSAVIAS A. , JURGENS A. , VLIET T. VAN
Published: February 2007

Fracture properties of short‐dough biscuits were determined in three‐point bending tests. Biscuits exhibited an essentially elastic behaviour and fractured at small strain. Span length did not influence the parameters measured, in accordance with theory. Biscuits fractured with the bottom side upwards had slightly higher fracture stress and fracture strain than those in the inverted position. Presumably, air cells at the bottom side acted as sites of stress concentration. Fracture strain was strain‐rate dependent over the range studied possibly due to local plastic deformation. Reducing the fat content increased the fracture stress of the biscuits, which indicates that the method provides a useful tool for discriminating among short‐dough biscuits of various composition.
APPLICATION OF STRESS‐CONTROLLED ANALYSIS TO THE DEVELOPMENT OF LOW FAT SPREADS
Authors: EVAGELIOU VASILIKI , ALEVISOPOULOS STEFAN , KASAPIS STEFAN
Published: February 2007

Creep testing was carried out on low fat commercial spreads at 3% (Promise) and 22.5% (Delight) fat content. A ‘full fat’ product (Flora margarine) and gelatin gels were also analysed to provide background understanding of the viscoelastic behaviour in the low fat samples. Increasing levels of applied stress deform both the Flora margarine and the gelatin gels which creep and eventually achieve steady flow. The linear creep compliance‐time dependency for a given stress/level of initial deformation was imitated by a mechanical model combining a Maxwell element in series with one or more Voigt elements, which exposed the elastic nature of gelatin associations as opposed to the ‘plasticity’ of a fat lattice. Deviations from linearity in gelatin gels and Flora margarine lead to a catastrophic disruption of networks and the termination of experiments due to excessively high angular velocities on the rheometer. The nonlinear regime in low fat spreads, however, produces a three part deformation‐time profile comprising creep with steady shear flow, accelerated rate of deformation, and a second level of flow (‘terminal'). The accelerated rate of deformation signifies the catastrophic disruption of the biopolymer matrix and results in a viscoelastic solution with suspended fat aggregates. The viscosity of this system (‘terminal') is much lower than the preceding steady shear viscosity before the yield point. Eventually, the fat aggregates break down leading to the sequence of viscosity collapse, excessive angular velocity, and experiment termination. The understanding achieved on phase behaviour and structural properties was used to develop economically water continuous spreads (5%–7.5% fat) without the undue gel‐like behaviour of Promise imparted by the gelatin component. The prototype spreads possess a stress‐strain profile under compression similar to that of Flora margarine at refrigerator temperature.
STUDY OF RESTRICTED DIFFUSION BY NMR IN FREEZE‐DRIED STARCH GELS
Authors: CORNILLON P. , McCARTHY M.J. , REID D.S.
Published: February 2007

Pulsed‐gradient spin‐echo NMR diffraction patterns were used to determine the pore size in freeze‐dried corn starch gels (7 and 12% w/w) with octane used as the probe molecule. The pore diameters are approximately 200 μm and appear isotropic for this measurement. This technique can provide an effective measure of the pore size without altering the sample structure.
ELECTROMYOGRAPHIC STUDY ON COOKED RICE WITH DIFFERENT AMYLOSE CONTENTS
Authors: KOHYAMA K. , OHTSUBO K. , TOYOSHIMA H. , SHIOZAWA K.
Published: February 2007

The texture of six varieties of cooked rice with different amylose contents was measured with a Texturometer. Masticatory behavior of the rice was evaluated using electromyography (EMG) of masticatory muscles. Differences in mastication patterns among the seven subjects examined were greater than between rice varieties. Masticatory behavior was more related to the adhesiveness and stickiness of rice as measured using a Texturometer than to the hardness. The number of chews and masticatory time, total duration of mastication and total muscle activities were highly correlated with each other, and were greater in cooked rice with a high amylose content, which showed low adhesiveness and stickiness values using a Texturometer. Cooked rice with a high amylose content was masticated with high masseter muscle activities. The ratio of jaw‐opening muscle activity to the preceding jaw‐closing muscle activity was low in high‐amylose varieties, which corresponds to the ratio of stickiness to hardness using a Texturometer. Between‐sample differences in mastication parameters were more apparent in the early stage of mastication, and no significant diference was observed in the late stage.
RELATIONSHIP BETWEEN INSTRUMENTAL AND SENSORY ANALYSIS OF TEXTURE AND COLOR OF POTATO CHIPS
Authors: SEGNINI SANDRA , DEJMEK PETR , ÖSTE RICKARD
Published: February 2007

The instrumental and sensory analysis of the texture and color of commercial potato chips were compared. The instrumental measurement was a puncture test with an Intron Universal Testing Machine, and the parameters used were fracture force, deformation and stiffness. The instrumental color quantification was a computerized video image analysis technique, and the color was expressed as L*a*b* values. Sensory evaluation of texture and color was performed by a sensory panel especially trained in evaluating potato chips. The sensory attributes were “hardness”, “chewiness”, “crunchiness”, and “tenderness” for texture analysis, and “yellow color”, “burnt aspect”, “sugar colored aspect” and “transparency” for color analysis. The factor analysis of the sensory attributes indicated that texture can be divided into two principal components, one represented by “hardness”, “crunchiness” and “chewiness”, and the other by “tenderness” alone. The factor analysis of the color can be divided into two principal components, one including “yellow color” and “burnt aspect”, and the other “sugar colored aspect” and “transparency”. Discriminant analysis showed that “tenderness” and “crunchiness” could predict correctly over 90% of the data. Fracture force correlated well with all of the sensory attributes (R2 > 0.76), and L* with the sensory color attributes (R2 > 0.79). The “Tenderness” was the individual sensory attribute which had the highest correlation (R2= 0.95) with fracture force.
NEW PROCEDURE FOR ESTIMATING THE MODULUS OF DEFORMABILITY OF CHEESE FROM UNIAXIAL COMPRESSION TESTS
Authors: WATKINSON PHILIP J. , JACKSON L. FRASER
Published: February 2007

The gradient of the inflection at the lowest strain in a stress versus strain curve was used to estimate the modulus of deformability (Ed) of cheese from the commonly used uniaxial compression test. The procedure required a sufficiently high sampling rate (e. g. 50 Hz at an initial strain rate of 0.0332 s−1) to give data that provided fine structure to the measurements which is not usually reported. This procedure was based on the empirical observation that there was an initial concave up region prior to the usually reported concave down region of the curve for all samples studied. Numerical estimation of the gradient was used to locate the inflection point, and to estimate the gradient at that point. The procedure gave a well‐defined measurement in the region of interest at small strain. It did not assume that all samples had the same strain region for compaction‐dominating and fracture‐dominating processes. Thus, in effect, it took account of the different strains at which Ed should be measured and eliminated differences in Ed between samples induced by differences in these processes. This procedure was compared with three existing procedures, for three cheeses. The procedure used responded differently to each cheese at the 1 % level. Values of Ed from the inflection point were similar to those from the gradient over 0.5 to 1.5 times the inflection strain, and higher than those from the gradient over 0 to 0.04 strain or from the linear term in a fiph order polynomial fit to the data up to fracture. The ranking of Ed for each cheese was the same for each procedure and the relative magnitude of Ed for each cheese was similar for each procedure.
INSTRUMENTAL MEASUREMENT OF ADHESIVENESS IN SOLID AND SEMI‐SOLID FOODS. A SURVEY
Authors: FISZMAN S. M. , DAMÁSIO M. H.
Published: February 2007

The literature on the methodology for instrumental determination of adhesiveness in various groups of solid and semi‐solid foods and the definition of the related parameters is reviewed. A specific analysis is made of the various ways of presenting the sample to the equipment, the shapes, sizes and materials of probes, degrees of penetration or compression, and devices specially designed for measuring adhesiveness in particular foods. Information is provided about various forms of sensory measurement evaluation of adhesiveness.
NMR VELOCIMETRY STUDY OF THE TEMPERATURE DEPENDENT RHEOLOGY OF BUTTER, SEMISOFT BUTTER AND MARGARINE
Authors: BRITTON M. M. , CALLAGHAN P. T.
Published: February 2007

A new rheological characterization technique is described in which nuclear magnetic resonance (NMR) velocimetry is used to measure velocity profiles across the annular gap of a Couette cell, for materials that exhibit yield stress and power law shear thinning properties. The materials studied were butter, semi‐soft butter and margarine over a temperature range from 25C to 42C. The method enables the observation of heterogeneous behavior across the different stress regimes that are present in the Couette gap and flow visualization makes it possible to clearly identify the existence or absence of slip effects at the wall. The results show that the power law exponents are strongly temperature dependent for the edible fat materials investigated.
VISCOELASTIC BEHAVIOR OF FRIED POTATO CRUST*
Authors: LIMA ISABEL , SINGH R. PAUL
Published: February 2007

A restructured potato model system was fried for 5, 10 or 15 min at 170, 180, or 190C and tested in a dynamic mechanical analyzer. Stress relaxation phenomena was described by a two‐element Maxwell model with a parallel spring. The viscoelastic behavior of the crust resulted from its porous structure of open and closed foam cells embedded in oil. Relaxation of stress in the fried crust was a result of slippage of the dispersed oil through the crust and from rearrangements of the air cells. Elastic modulus of the fried crust increased for higher frying times and temperatures and were the most significant elements in distinguishing between samples.
DATABASE OF PHYSICAL PROPERTIES OF FOODS: SUBGROUP OF MECHANICAL AND RHEOLOGICAL PROPERTIES
Authors: HOUŠKA M. , NESVADBA P. , MAYER Z.
Published: February 2007

An online database of numerical values of selected rheological and mechanical properties of foods has been constructed as part of a general database covering physical properties of foods. The objective is to provide an easy access to data for food engineers and others interested in physical properties. The collected data include viscosity, elasticity modulus, puncture force and more than 70 properties for over 600 foods. Each entry consists of a bibliographic reference. Tables may be attached to the bibliographic record, describing the food in terms of its composition and structure; the measurement method used, a validation and assessment code for the quality of the measured data and a matrix of the numerical values of the given physical property listed as a function of independent variables such as temperature, shear rate, pressure or composition parameters. This paper describes the organisation and management of the database and the processes of interrogating the database and contributing data by users. The database is on http://www.nelfood.com
ANALYSIS OF REPEATED STICKINESS MEASURES OF WHEAT DOUGH USING A TEXTURE ANALYZER
Authors: GRAUSGRUBER HEINRICH , HATZENBICHLER EVELYN , RUCKENBAUER PETER
Published: February 2007

Stickiness of wheat dough using 51 international wheat genotypes was measured ten‐times per sample using a texture analyzer and the improved Chen‐Hoseney stickiness cell. Repeated measures analyses were carried out with the parameters adhesive force, adhesiveness, and stringiness of the force‐time curves using the SAS MIXED procedure. The data revealed a high variability among observations from replicates of the same sample preparation. It is suggested to analyze a large (seven to ten) number of repeated measures per sample to account for the variation. Triplicate measures that result in reliable means with low standard errors for the particular lab conditions and test settings can be found by a repeated measure analysis.
COMPARISON OF BETALAIN EXTRACTION FROM BEET (BETA VULGARIS) BY LOW DC ELECTRICAL FIELD VERSUS CRYOGENIC FREEZING
Authors: ZVITOV R. , SCHWARTZ A. , NUSSINOVITCH A.
Published: February 2007

A low DC electrical field (40 V/cm) applied to beet tissue as a novel method for extracting the naturally occurring betalain pigments removed soluble solids, minerals and pigment with almost no alteration of the gross textural properties of the tissue. Scanning electron micrographs revealed minor changes in the surface of the electrically treated tissue versus major changes in the tissue after freeze‐thaw treatment. Cryogenic freezing (∼20 s) and thawing (one cycle) of the same tissue induced considerable damage, as evidenced by reduced values of stress at failure and loss of the tissue's elastic properties. Intact and DC‐electrically treated tissue specimens had the same stress at failure (∼ 1500 kPa) and the same degree of elasticity (∼ 30%), in contrast to the tissue that passed through freeze‐thawing (∼ 14%) and lost its elastic textural properties. Electrical extraction, which can be applied to thinly cut tissue, has a major advantage over other methods since the tissue remains almost intact, and thus can be used for other commercial applications, such as baking and filling.
INFLUENCE OF CARRAGEENAN AND TOTAL SOLIDS CONTENT ON THE RHEOLOGICAL PROPERTIES OF LACTIC BEVERAGE MADE WITH YOGURT AND WHEY
Authors: PENNA A.L.B. , OLIVEIRA M.N. , TAMIME A.Y.
Published: February 2007

The purpose of this work was to study the influence of carrageenan level (X1) and total solids content of yogurt/whey mixture (X2) on starter culture fermentation time, physicochemical properties (pH, fat and total solids contents) and rheological characteristics of lactic beverages using response surface methodology. The physicochemical characteristics of the lactic beverages were similar to those of commercial products. All beverages showed non‐Newtonian fluid behavior with thixotropy and yield stress. The total solids content of the lactic beverages had a greater influence on the rheological behavior of these products than the carrageenan level. Wide ranges of consistency measurements were observed by varying the stabilizer level and total solids content.
SIMULTANEOUS INSTRUMENTAL MEASUREMENT OF FIRMNESS AND JUICINESS OF APPLE TISSUE DISCS
Authors: HARKER F. ROGER , WHITE ANNE , FREETH BRUCE , GUNSON F. ANNE , TRIGGS CHRIS M.
Published: February 2007

Discs of apple tissue were compressed to 75% of their original height. Throughout compression, the force‐distance curve was collected and the electrical impedance of the discs was measured at two frequencies of alternating current—1 kHz and 1 MHz. Electrical impedance was separated into its resistive and reactive components, and at these particular frequencies changes in resistance predominated. Measurements at 1 kHz indicate the resistance of extracellular regions of the discs (ruptured cells as well as those regions external to the plasma membrane), while measurements at 1 MHz indicate the resistance of the entire disc (combined intracellular and extracellular regions). Juice was released from the discs as a result of damage to cells and the extrusion of cellular fluid into intercellular air spaces. This resulted in a decline in electrical resistance at 1 kHz, but little change to the resistance at 1 MHz. Changes in juice release as determined by electrical measurement were related to the mechanical properties of the discs. Generally, the release of juice occurred after the inflection point on the force‐distance curves, but much earlier than mechanical failure (indicated by maximum force). The extent of tissue damage was determined from the relative decrease in resistance at 1 kHz, and was found to vary among apple cultivars and in response to fruit ripening.
WATER ABSORPTION EFFECTS ON BIAXIAL EXTENSIONAL VISCOSITY OF WHEAT FLOUR DOUGH
Authors: OSORIO FERNANDO , GAHONA ERIC , ALVAREZ FRESIA
Published: February 2007

Biaxial extensional viscosities of wheat flour dough at three water absorption levels were determined as a function of biaxial strain rates using lubricated squeezing flow. The shape of the curves obtained in this study showed a sharp increase followed by a gradual increase which could indicate the presence of viscoelastic effects, which is not the usual case reported in the published literature for other products when using this technique. Plasticizing effect of water coupled with the effect of the starch and the interaction among the other components of wheat flour dough could explain the rheological behavior of flour dough during lubricated squeezing flow testing. Values of biaxial extensional viscosities of wheat flour dough for the three water absorption levels obtained in this study showed significant differences in the entire deformation range (P < 0.05).
MECHANICAL PROPERTIES AND SENSORY TEXTURE ASSESSMENT OF CHEESES
Authors: GOH S.M. , CHARALAMBIDES M.N. , WILLIAMS J.G.
Published: February 2007

The viscoelastic behaviour of hard and semi‐hard cheeses was investigated in relation to sensory assessment of texture. The experiments consisted of two separate studies which involved sensory and uniaxial compression tests on eight cheeses in each study. The stress‐strain data of the cheeses were approximated well by a power law relationship, showing that the strain and the time dependent variables were separable. The cheeses exhibited similar time dependent behaviour, so the degree of correlation between sensory and instrumental measurements was not influenced significantly by changing the deformation rate in the instrumental tests. Sensory firmness appeared to correlate with instrumental stiffness measurements in one study, but not in the other. This was probably due to the use of different panels and methods of sensory assessment.
EFFECT OF DEGREE OF COMPRESSION ON TEXTURE
Authors: AL‐HAQ MUHAMMAD IMRAN , SUGIYAMA JUNICHI
Published: February 2007

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CELLULAR STRUCTURE OF PEANUT‐BASED EXTRUDED SNACK PRODUCTS USING SCANNING ELECTRON MICROSCOPY
Authors: CHOI I.‐D. , PHILLIPS R.D. , JEONG H.‐S.
Published: February 2007

A mixture of partially defatted peanut flour (12% fat) and rice flour was extruded to produce indirectly, puffed extrudates using a corotating twin‐screw extruder. Extrudates were dried to obtain half‐products of 11‐12% moisture content, and the half‐products were expanded by deep‐fat frying. The effects of three levels of peanut flour (30, 40, and 50%), screw speed (200, 300, and 400 rpm) and feed rate (4, 5, and 6 kg/h) were studied by characterizing the cellular structure of expanded snack products using Scanning Electron Microscopy (SEM). Average cell size (mm2) and the number of cells per unit area (cm2) were determined from the interior cross‐section area of snack products. Those parameters were influenced mainly by the level of peanut flour followed by screw speed and feed rate. Increasing peanut flour from 40 to 50% produced less puffed final products resulting in small cell size compared to snacks of 30 ‐ 40% peanut flour. The maximum cell size was produced in the snack products extruded with peanut flour of 30 ‐ 40% at screw speed of 250 ‐ 330 rpm and feed rate of 4.7 ‐ 5.7 kg/h. While the number of cells was relatively similar regardless of screw speed and feed rate, increasing peanut flour increased the number of cells. The cell walls became thicker with increasing feed rate.
EFFECT OF SUGAR AND FAT REPLACERS ON THE TEXTURE OF BAKED GOODS
Authors: ESTELLER MAURICIO SERGIO , AMARAL RENATA LIRA , LANNES SUZANA CAETANO DA SILVA
Published: February 2007

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YIELD STRESS OF HOT CEREALS BY THE VANE METHOD
Authors: DEJONGH JULIE J. , STEFFE JAMES F.
Published: February 2007

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