PREDICTION OF SENSORY TEXTURE OF FETA CHEESE MADE FROM ULTRAFILTERED MILK BY UNIAXIAL COMPRESSION AND SHEAR TESTING

The ability to predict sensory texture properties of Feta cheese made from ultrafiltered milk (UF-Feta) from uniaxial compression, small shear deformation measurements (frequency sweep, strain sweep, relaxation) and indices of proteolysis was studied. In principal component analysis (PCA) some of the instrumental variables were highly correlated, e.g. the moduli from uniaxial compression and shear measurements; and strain at fracture from uniaxial compression and indices of proteolysis. PCA of the six sensory attributes determined by a trained panel showed that mainly one type of information was present in the sensory results. Partial Least Squares regression (PLS) of all results revealed that stress at fracture from uniaxial compression was the individual instrumental parameter having the highest correlation with the sensory texture attributes. Of these, the three firmness attributes were best predicted by the instrumental parameters. As the shear measurements were not very useful for prediction of sensory texture properties by themselves, and as the increase in prediction precision by inclusion of these measurements was marginal, it is suggested that either stress at fracture alone, or together with three other parameters from uniaxial compression should be used to describe texture properties of UF-Feta cheese.     

MECHANICAL PROPERTIES AND SENSORY TEXTURE ASSESSMENT OF CHEESES

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.     

Vane Rheometry for Textural Characterization of Cheddar Cheeses: Correlation with Other Instrumental and Sensory Measurements

The relationship between instrumental (vane method, texture profile analysis (TPA), uniaxial compression) and sensory texture measurements of Cheddar cheeses was investigated. A Haake VT 550 viscotester equipped with a four-bladed vane rotor was used for the vane test. Instrumental TPA was performed with a TA.XT2 Texture Analyser, and compression variables were calculated from TPA data. Vane parameters were significantly correlated with respective variables of compression and TPA (r=0.56-0.91), and sensory tests (r=0.54-0.88). Multivariate analysis indicated that seven sensory attributes of ten commercial Cheddar cheeses were satisfactorily predicted (calibration regression coefficient,R_cal >0.62) by variables of the vane, uniaxial compression and TPA tests. In particular, cheese firmness and cohesiveness evaluated by sensory panel were well described by vane stress and apparent strain. The results validate the vane method as an alternative to the existing cheese testing methods for rapid evaluation of cheese texture.     

RELATIONSHIPS BETWEEN SENSORY AND RHEOLOGICAL MEASUREMENTS OF TEXTURE IN MATURING COMMERCIAL CHEDDAR CHEESE OVER A RANGE OF MOISTURE AND pH AT THE POINT OF MANUFACTURE

Textural characteristics of 10 Cheddar cheeses with a range of moisture contents and pH values were investigated by sensory and instrumental methods, over a 9‐month maturing period. A trained panel of nine assessors described the sensory texture characteristics of the cheeses using 11 texture parameters. Instrumental parameters were derived using texture profile analysis. Relationships between sensory, instrumental, compositional and maturation properties of the cheeses were determined with the aid of principal component analysis and multiple linear regression. Nine sensory parameters significantly correlated with instrumental parameters, e.g., sensory rubbery correlated with instrumental firmness (R = 0.696, P < 0.001), chewiness (R = 0.679, P < 0.001), fracture stress (R = 0.669, P < 0.001) and springiness (R = 0.643, P < 0.001). Sensory firmness corresponded closely with instrumental firmness (R = 0.539, P < 0.001) and fracture stress (R = 0.518, P < 0.001). Sensory and instrumental texture parameters were significantly affected by changes in moisture content, pH and maturation.     

Prediction of sensory textural properties from rheological analysis for process cheeses varying in emulsifying salt,protein and moisture contents

Textural characteristics of process cheeses varying in emulsifying salt (disodium phosphate), protein and moisture contents were evaluated by rheological compression using texture profile analysis and by sensory evaluation. The primary objective of this study was to predict sensory textural parameters using instrumental rheological parameters. All sensory parameters correlated with one or more instrumental parameters, e.g. rheological firmness versus sensory firmness (R = 0.98, P < 0.001), rheological chewiness versus sensory rubbery (R = 0.92, P < 0.001) and rheological chewiness versus sensory chewy (R = 0.86, P < 0.001). Partial least squares calibration models were developed for each of nine sensory parameters using instrumental parameters. Principal component analysis of instrumental and sensory parameters illustrated relationships among parameters. It was shown that instrumental parameters could be used to supplement sensory evaluation of process cheese texture. Increasing emulsifying salt content increased firmness, springiness and chewiness and decreased adhesiveness, mouthcoating and mass formation. Increasing protein content resulted in increased fracture strain and stress and chewiness and decreased melting. Increasing moisture content increased cohesiveness and decreased firmness and chewiness. Copyright © 2007 Society of Chemical Industry     

Instrumental and sensory evaluation of crispness: I—In friable foods

Using the Constant Loading Rate Texture Testing instrument it was possible to extract from the deformation/time and force/time curves together with the sound emitted from the samples during the test, those variables included in both the definition of crispness and the assumption that in the case of friable foods crispness may be regarded as ‘compressive brittleness’.Significant correlations (P<0·01) were obtained between sensory crispness and the instrumental variables: equivalent sound level L_eq (r = 0·701), ratio of work done during fracture to total work W_F/W_T (r = 0·878) and fracture or collapse rate (r = 0·570).A poor correlation between sensory crispness and both sensory hardness (r = 0·398) and instrumental fracture force (r = 0·018) indicates that a hard friable food material is not necessarily a crisp one, whereas the highly significant correlation between sensory crispness and both sensory sound intensity (r = 0·908) and instrumental L_eq (r = 0·701) indicates the importance of sound in the sensory and instrumental evaluations.The results of regression analysis showed a number of almost equally well fitting equations with the ratio W_F/W_T and L_eq as the dominant variables in predicting sensory crispness in friable foods.     

Instrumental and Sensory Texture Attributes of High‐Protein Nutrition Bars Formulated with Extruded Milk Protein Concentrate

Previous instrumental study of high‐protein nutrition (HPN) bars formulated with extruded milk protein concentrate (MPC) indicated slower hardening compared to bars formulated with unmodified MPC. However, hardness, and its change during storage, insufficiently characterizes HPN bar texture. In this study, MPC80 was extruded at 2 different conditions and model HPN bars were prepared. A trained sensory panel and instrumental techniques were used to measure HPN bar firmness, crumbliness, fracturability, hardness, cohesiveness, and other attributes to characterize texture change during storage. Extrusion modification, storage temperature, and storage time significantly affected the instrumental and sensory panel measured texture attributes. The HPN bars became firmer and less cohesive during storage. When evaluated at the same storage conditions, the texture attributes of the HPN bars formulated with the different extrudates did not differ significantly from each other. However, textural differences were noted most of the time between the control and the HPN bars formulated with extruded MPC80. An adapted HPN bar crumbliness measurement technique produced results that were correlated with sensory panel measured crumbliness (r = 0.85) and cohesiveness (r = –0.84). Overall, the HPN bars formulated with extruded MPC80 were significantly softer, less crumbly, and more cohesive than the control during storage.     

PREDICTION OF THE SENSORY TEXTURE OF A YAM THICK PASTE (AMALA) USING INSTRUMENTAL AND PHYSICOCHEMICAL PARAMETERS

Amala is a traditional thick paste consumed in West Africa (Nigeria, Bénin, Togo). It is prepared from blanched dried yam flour and has a particular texture. The texture attributes of amala pastes obtained from market and prepared in laboratory were sensorily evaluated. Both compression and extrusion tests were done from which maxima force and slope were calculated. The physical (particle size), starch characteristics and functional properties (solubility, swelling power [Sp], viscosity) of yam flours were also determined to establish a predictive model for amala sensory texture attributes. The main amala sensory attributes were stickiness, firmness and smoothness. Stickiness and firmness could be assessed by uniaxial extrusion test: These attributes were highly correlated with the maximum extrusion slope (r = ?0.60 and r = 0.53, respectively). Stickiness was associated with yam flour Sp, which in turn was related to gelatinization temperature and enthalpy changes. In addition, soluble matter and soluble amylose were found to be indicators of amala sensory stickiness. No clear relationships were observed between sensory firmness and yam flour physicochemical characteristics or functional properties.     

SENSORY TEXTURE PROFILE, GRAIN PHYSICO-CHEMICAL CHARACTERISTICS AND INSTRUMENTAL MEASUREMENTS OF COOKED RICE

Three samples of raw-milled rice, and 4 differently parboiled rices were used to study and to relate sensory perception to instrumental measurements. Variance analysis showed that some physico-chemical characteristics indicated great differences among rice samples: thickness of cooked grain, length/width ratio, water uptake, elastic recovery, white core rate and amylose and protein contents. The most discerning sensory attributes were: elasticity, stickiness, pastiness, mealiness, length of grain, firmness, crunchiness, time in mouth, brittle texture and juiciness. The correlation circle of the principal component analysis (PCA) showed high correlation between some sensory characteristics and instrumental measurements. Melting texture, surface moistness, juiciness, were positively correlated with water uptake (r = 0.70, 0.61, 0.71). Granular texture, crunchiness, brittleness and mealiness were significantly affected by white core presence (r = 0.81, 0.74, 0.86, 0.83). Elasticity was dependent upon elastic recovery and firmness measured by the Viscoelastograph, but not linearly. Length of cooked grain was correlated with the length/width ratio of raw grain (r = 0.83). Pastiness, compactness, stickiness were slightly influenced by the thickness of raw grain (r = 0.81, 0.67, 0.72). To a weaker extent, the sensory firmness was associated with the firmness measured by extrusion force using an Ottawa cell (r = 0.58). PCA showed greatdifferences in texture between rices. Two of the parboiled rices were very elastic, another was firm, granular, crunchy and mealy. The remaining two, cooked longer, were moister and more melting. Among the 3 samples of raw-milled rices, differences in grain length feeling and melting-granular-brittle characteristics. were distinguished.     

Effects of variousMicrococcus strains on the ripening and organoleptic characteristics of Arzúa cow's-milk cheese

Ten batches of Arzúa, a soft cow's-milk cheese produced in northwest Spain, were prepared from pasteurized milk. Two (control) batches (CB) were made with a commercial starter containingLactococcus lactis subspecieslactis andcremoris. Another eight batches (MB) were made with the commercial starter plus one of eightMicrococcus spp. strains previously isolated from raw-milk Arzúa cheeses. In all MB, β-casein degradation over the 30-day ripening period was more pronounced (mean 31%) than in the CB (mean 12%). α_S1-Casein degradation was highly variable in the MB, though mean degradation over the ripening period (75%) was similar to that observed in the CB (73%). Similarly, volatile fatty acid (VFA) content was highly variable in the MB, with the mean content at 30 days (3.8 mEq per 100 g) being higher than in the CB (1.6 mEq per 100 g). Rheological characterization of the cheeses (by uniaxial compression) revealed significant differences between batches, with some samples fracturing under the compression pressure applied and others not. Sensory evaluation also revealed significant differences. “Non-milk” aromas were more frequently detected in batches made with lipolytic micrococcal strains. Betweenbatch differences in tastes and texture were also detected. Multiple correlation analysis of the data obtained at day 15 of ripening revealed statistically significant positive correlations (r>0.70) between α_S1-casein content and dry matter content, between α_S1-casein content and sensorially evaluated firmness, and between VFA content and sensorially evaluated rancidity. Statistically significant negative correlations between sensorially evaluated firmness and the ratio of α_S1-I content to α_S1-casein content were detected. The results of this study suggest a need for further studies aimed at selecting those strains which could be most suitable for the production of Arzüa cheeses; due to their effects on texture, α_S1-caseinolytic strains seem to be more appropriate than β-caseinolytic ones.     

Temporal Texture Profile and Identification of Glass Transition Temperature as an Instrumental Predictor of Stickiness in a Caramel System

Stickiness is an important texture attribute in many food systems, but its meaning can vary by person, product, and throughout mastication. This variability and complexity makes it difficult to devise analytical tests that accurately and consistently predict sensory stickiness. Glass transition temperature (T_g) is a promising candidate for texture prediction. Our objective is to elucidate the temporal profile of stickiness in order to probe the relationship between T_g and dynamic stickiness perception. Nine caramel samples with diverse texture and thermal profiles were produced for sensory testing and differential scanning calorimetry. Sixteen trained panelists generated stickiness‐relevant terms to be used in a subsequent temporal dominance of sensation (TDS) test with the same panelists. Following the TDS study, these panelists also rated samples for overall tactile and oral stickiness. Stickiness ratings were then correlated to TDS dominance parameters across the full evaluation period and within the first, middle, and final thirds of the evaluation period. Samples with temporal texture profiles dominated by tacky, stringy, and enveloping attributes consistently received the highest stickiness scores, although the correlation strength varied by time period. T_g was found to correlate well with trained panelist and consumer ratings of oral (R²_trained = 0.85; R²_consumer = 0.96) and tactile (R²_trained = 0.78; R²_consumer = 0.79) stickiness intensity, and stickiness intensity ratings decreased with T_g of completely amorphous samples. Further, glassy samples followed a different texture trajectory (brittle‐cohesive‐toothpacking) than rubbery samples (deformable‐tacky‐enveloping). These results illuminate the dynamic perception of stickiness and support the potential of T_g to predict both stickiness intensity and texture trajectory in caramel systems.     

A COMPARISON OF THREE INSTRUMENTAL TESTS FOR PREDICTING SENSORY TEXTURE PROFILES OF CHEESE

Multivariate analysis techniques were used to seek correlations between texture sensory attributes assessed by a trained professional panel and instrumental measurements (compression, puncture and penetration) carried out on various types of cheeses. Twenty-nine cheeses were assessed by the panel and instruments. Correlation was sought using Partial Least Squares regression. Hardness (R=0.87), springiness (R=0.98) and cohesiveness of mass (R=0.89) were best predicted by instrumental data from a cone penetration test. The prediction of cohesiveness was acceptable using any of the three instrumental tests performed (0.76相似文献   

Effect of ultra-high pressure homogenisation of milk on the texture and water-typology of a starter-free fresh cheese

Fresh starter-free cheeses were made from ultra-high pressure homogenised (300 MPa and inlet temperature of 30 °C), pasteurised (80 °C for 15 s) or homogenised–pasteurised (15 + 3 MPa at 60 °C, 80 °C for 15 s) milks to compare their textural, microstructural, colour and water-related characteristics by means of uniaxial compression and dynamic oscillatory tests, confocal laser scanning microscopy, spectrocolorimetry, and thermogravimetry, respectively. Sensory analysis was performed by a sensory panel. Major differences among treatments were revealed by both instrumental and sensorial methods. Cheeses from homogenised milks were firmer, less deformable, grainier, pastier, whiter, and had higher water-holding capacity but lower water-mouth feeling than cheeses from pasteurised milk. The effect of ultra-high pressure homogenisation (UHPH) was greater than that of conventional homogenisation. Differences on the composition, i.e. water typology and protein content, and the microstructure could explain the sensory characteristics of the cheeses.

Industrial relevance

UHPH treatment of milk is being studied as an alternative to conventional heat-treatment since it reduces microbial load and inactivates enzymes. Moreover, UHPH has been proven to affect protein interactions resulting in an increase of curd-firming rate and gel firmness during coagulation. Thus structural changes intrinsically related to the arrangement of cheese components, such as texture, syneresis and colour, are expected in fresh cheeses produced from UHPH-treated milk.     

Viscoelasticity and texture of spreadable cheeses with different fat contents at refrigeration and room temperatures

The effect of the 2 common consumption temperatures, refrigeration temperature (10°C) and room temperature (22°C), on the viscoelasticity, mechanical properties, and perceived texture of commercial cream cheeses was studied. Two samples with different fat contents, regular and low fat, from each of 4 selected commercial brands were analyzed. The selection criteria were based on identification of brands with different percentages of fat content reduction between the regular- and low-fat samples (35, 50, 84, and 98.5%). The fat content of regular-fat samples ranged from 19.8 to 26.0% (wt/wt), and that of low-fat samples ranged from 0.3 to 13.0% (wt/wt). Viscoelasticity was measured in a controlled-stress rheometer using parallel-plate geometry, and the mechanical characteristics of samples were measured using the spreadability test. Differences in the intensity of thickness, creaminess, and roughness between the regular- and low-fat samples of each commercial brand were evaluated at each of the selected temperatures by using the paired comparisons test. At 10°C, all samples showed higher viscoelastic modulus values, firmness, and stickiness, and lower spreadability than when they were measured at 22°C. Differences in viscoelasticity and mechanical properties between each pair of samples of the same brand were greater at 10°C than at 22°C because of the influence not only of fat content but also of fat state. Ingestion temperature did not modify the sensory differences detected between each pair of samples in terms of creaminess and roughness, but it did modify the differences detected in thickness. The joint consideration of sample composition, fat state, and product behavior during oral processing could explain the differences detected in thickness perceived because of measurement temperatures.