MODIFICATIONS AND APPLICATIONS TO FOODS OF THE GENERAL FOODS SENSORY TEXTURE PROFILE TECHNIQUE

The primary attributes of the General Foods sensory texture profile technique are standardization, reproducibility, and ease of correlation with instrumental measurements. Since the original publication in 1963, the method has undergone modifications and refinements such as: addition of an initial stage for evaluation of surface properties, evaluation of certain mechanical characteristics of elasticity and cohesiveness on specific products, and development of texture profile techniques and terminology for the evaluation of semi-solids. Application of this expanded texture profile method is demonstrated using foods such as vanilla cookies, frankfurters, and whipped toppings.     

VIEWS ON RELATING INSTRUMENTAL TESTS TO SENSORY ASSESSMENT OF FOOD TEXTURE. APPLICATIONS TO PRODUCT DEVELOPMENT AND IMPROVEMENT 1,2

Well-defined measurements of the mechanical properties of food and the reduction of sensory attributes to the fundamental primary entities, together with the definition of their correlation functions, provide the basis for the eventual development of instruments calibrated in terms of human sensory response and having a high probability of predicting the consumer reaction. Since mechanical measurements of most foods are time-dependent, the understanding of conditions prevailing during sensory testing (rate of shear, etc.) will aid in selecting the optimum conditions for instrumental testing. Recent progress in this area has been made with fluids and some solid foods. The method of magnitude estimation assists the researcher in discovering the underlying laws relating physical product changes to perceived textural changes. At the same time, magnitude estimation also aids the product developer to determine empirical, ad hoc relations between physical levels of mechanical variables and textural perceptions, even if the true, underlying relationships are not known. Ad hoc equations can be used (in conjunction with optimization techniques) to determine the combination of mechanical variables that (a) produce a specific sensow texture profile, and (b) maximize texture/product acceptability.     

INSTRUMENTAL AND SENSORY CHARACTERIZATION OF COOKED POTATO TEXTURE

Uniaxial compression, Texture Profile Analysis (TPA) and chemical measurements were related to sensory texture evaluation of potato quality during storage. Principal component analysis grouped the varieties into three types of variation: mealiness versus firmness and springiness (PC1), moistness versus adhesiveness (PC2) and hardness versus adhesiveness and moistness (PC3). In uniaxial compression the variable 'stress', 'work up to fracture' and 'total work during compression' described the same type of information in the data. These uniaxial data and most of the TPA data were highly correlated. Uniaxial compression data (stress, strain, modulus of deformability), starch structural data (area, roundness, aspect ratio), specific gravity and pectin methyl esterase activity discriminated between the varieties and harvest times. Partial Least Squares Regression showed stress, strain, modulus of deformability and specific gravity to be the most important variables in distinguishing between two groups of sensory texture attributes explaining 65% of the total variance in the sensory data. Coefficients of correlation between predicted and measured sensory attributes were in the range 0.36–0.79. The TPA data were not found to be relevant substitutions for the sensory attributes.     

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.     

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   

INSTRUMENTAL AND SENSORY MEASUREMENT OF BEEF PATTY AND SAUSAGE TEXTURE

Beef sausages and beef patties of different texture were produced by varying the fat content in the raw mix over the range 5–30%. Batter shear stress and strain increased linearly with increased fat level (P<0.09 and 0.001, respectively). Although batter shear stress was not related to sensory scores, shear strain was directly related to moistness and inversely related to grittiness scores (P<0.05). Batter sensory moistness increased and firmness and grittiness deceased linearly with fat content (P<0.001). Changes in fat content did not affect the peak force of cooked patties, and there were poor correlations between patty peak force and sensory scores. Patty juiciness and softness increased and patty cohesiveness and chewiness decreased with fat content (P<0.001). Batter cook yield increased and patty cook yield decreased with increasing fat level (P<0.001). Sensory scores, using trained panelists, were more sensitive to the effect of fat content on patty and sausage texture than instrumental measurements.     

PROCESSING PARAMETER EFFECTS ON SENSORY AND INSTRUMENTAL TEXTURE CHARACTERISTICS OF REDUCED-FAT GROUND BEEF PATTIES

Effects of fat content (8 or 24%), processing temperature (–2, 1, 4C), plate size (2, 5, 5 mm), mixing time (3, 5, 8 min), and patty formation pressure (50, 100, or 150 kg) on characteristics of low-fat ground beef patties were evaluated. Reduced fat patties required less force to break when ground at –2C (2 mm plate) than when ground at 4C. Rubberiness increased as plate size increased. Rubbery scores were lowest at 4C/2 mm plate. Reduced-fat patties had lower cook losses. Increasing grinding temperature from –2 to 4C decreased break force, Kramer shear and cohesive texture. Break force was highest for patties mixed 8 min at –2C. Patty forming pressure affected breaking strength, cohesiveness, and cook loss. Production of reduced-fat ground beef patties by grinding through a 2mm plate at 4C, mixing for 2 min and forming patties at 150 kg pressure minimized rubbery texture and instrumental measures of patty hardness.     

A REVIEW OF SENSORY AND INSTRUMENTAL METHODS USED TO EVALUATE THE TEXTURE OF FISH MUSCLE

The texture of fish muscle is an important quality attribute that depends on several parameters, both intrinsic and extrinsic. Its evaluation by sensory means is the result of a combination of several parameters that cover every impression from when the fish first comes into contact with a surface in the mouth, until it is completely masticated. This makes texture difficult to describe and evaluate. In addition the muscle structure of fish is not homogenous, and this has important implications on texture measurements by instrumental means. Numerous instrumental and sensory methods have been used to evaluate the texture of fish and fish fillets, with varying results and there exists no universal recommended method.     

UNIAXIAL COMPRESSION OF UF-FETA CHEESE RELATED TO SENSORY TEXTURE ANALYSIS

Rheological characteristics of seven Feta cheeses with different textures and produced from ultrafiltered milk (UF-Feta cheeses) were evaluated by uniaxial compression and sensory texture analysis. The effect of uniaxial deformation rate (50–2500 mm/min) on four rheological parameters: Stress at fracture s?_f), Hencky strain at fracture (?_f), deformability modulus (E) and work to fracture (W_f) was examined. Three Principal Components (PC) described 76, 16 and 4% respectively, of the variation in the uniaxial compression data set (4 parameters at 12 deformation rates). Statistically α_f, E and W_f described the same type of information in the data set. Six sensory texture attributes of the UF-Feta cheeses were evaluated by a sensory texture panel: nonoral firmness, nonoral brittleness, nonoral spreadability, oral crumbliness, oral firmness and oral stickiness. One PC described 93% of the variation in the sensory texture data and grouped the sensory variables into two negatively correlated groups: nonoral firmness nonoral brittleness, oral firmness and oral crumbliness versus nonoral spreadability and oral stickiness. Correlations and Partial Least Squares regression (PLS) between instrumental and sensory texture variables showed that nonoral and oral firmness were the nonoral and oral sensory variables best predicted from instrumental measurements. α_f, E and W_f were all able to predict nonoral and oral firmness. Of the instrumental parameters, α_f generally gave the best correlation to nonoral firmness at all deformation rates. Above a deformation rate of 50 mm/min correlations between α_f and nonoral firmness were almost independent of deformation rate, and at any deformation rate correlations between α_f and oral firmness     

INSTRUMENTAL TEXTURE STUDIES ON CHOCOLATE IV: COMPARISON BETWEEN INSTRUMENTAL AND SENSORY TEXTURE STUDIES

Texture characteristics of solidified plain chocolate and milk chocolate were determined in instrumental and sensory studies. The instrumental parameters included compression strength, melting properties, maximum tensile force during hesion testing and the maximum size of dispersed solid components. To classify the sensory texture impressions into intensity ranges, by using appropriate samples, a reference scale was derived allowing a sensory panel to assign unknown chocolate samples to the respective intensity ranges. Instrumental control of the reference samples ensures satisfactory relations between instrumental and sensory data.     

RELATIONSHIP BETWEEN INSTRUMENTAL AND SENSORY ANALYSIS OF TEXTURE AND COLOR OF POTATO CHIPS

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.     

INSTRUMENTAL AND SENSORY TEXTURE ASSESSMENT AND FRACTURE MECHANISMS OF CHEDDAR AND CHESHIRE CHEESES

Textural attributes of Cheddar and Cheshire cheeses, falling within narrow compositional ranges, were assessed by sensory panels, and from force-compression curves generated by compression between two plates, and, for Cheddar cheese only, by penetrometry. Individual sensory measurements did not relate well to any instrumental one, and were better at discriminating between cheeses. Samples of each cheese variety were fractured in different ways and the fracture surfaces were examined in a scanning electron microscope. Fracture surfaces were formed by cutting directly through the matrix, tearing of the matrix along planes high in fat or cracking at grain boundaries. It is suggested that consideration of fracture mechanism may aid the selection and development of useful instrumental methods for texture assessment of cheese.     

RELATIONSHIP BETWEEN INSTRUMENTAL AND SENSORY PARAMETERS OF COOKED SWEETPOTATO TEXTURE1

This study compared two instrumental methods, namely uniaxial compression and texture profile analysis (TPA), with sensory evaluation in describing the textural properties of cooked sweetpotatoes. The steamed cooked samples (1.35 × 2.2 cm cylinder) of four cultivars and six selections were subjected to a trained texture profile panel for sensory ratings and the two instrumental methods for determination of the mechanical properties. Factor analysis indicated that the 15 sensory variables were grouped into 3 main factors, namely moistness-firmness (factor 1), particles (factor 2), and fiber (factor 3). Among the instrumental parameters, shear stress of compression and fracturability, hardness, and gumminess of TPA correlated highly (R = 0.73–0.95) with both the mouthfeel and mechanical-type sensory notes. These parameters of the two instrumental methods were linearly related (R²≥ 0.95) and could be converted from one to another with a high degree of reliability. Regression equations based on shear stress significantly explained (R²= 0.71–0.91) eight of the sensory notes. These instrumental parameters can be good predictors of cooked sweetpotato texture.     

MICROSTRUCTURAL CHARACTERISTICS AND COMPRESSION RESISTANCE AS INDICES OF SENSORY TEXTURE IN A CRUNCHY SNACK PRODUCT

Identically formulated drum dried and cold formed half-products were puffed in hot air or by frying to determine microstructure-texture relationships. Structural attributes measured were cell size (CS), number of cells per unit area (CN), cell wall thickness (CW) and product specific volume (SV). Sensory attributes of crunchiness, hardness and density were also evaluated. Puffed product microstructure depended more on the half-product preparation process than the method of puffing. Similarly prepared half products had the same microstructural attributes whether fried or hot air puffed. Sensory scores for crunchiness were not significantly different among all samples but scores for hardness and density were significantly different between hot air puffed and fried products even when microstructural attributes were similar. Higher compression force values reflected lower sensory scores for crunchiness and hardness of puffed products. Compression force was significantly correlated with microstructural attributes of CS, CW and SV.