TASTE THRESHOLDS, TASTE SENSITIVITY AND THE EFFECTS OF ADRENALECTOMY IN RATS

A number of behavioral experiments have attempted to measurethe absolute taste thresholds in the rat. Certain aspects ofthe procedures and methods of data analysis used in these experimentsare reviewed with the suggestions that: (1) Although comparisonshave commonly been made between the taste threshold values reportedin different experiments, these are not valid because of theabsence of a common definition of threshold. (2) The high thresholdmodel on which these experiments are based may be inappropriate.(3) It is possible to measure taste sensitivity rather thantaste thresholds, and (4) Had these points been considered inprevious experiments different conclusions might have resultedregarding the effects of adrenalectomy on NaCl sensitivity.     

COMPARISON OF SIMPLIFIED METHODS FOR EVALUATION OF SENSORY THRESHOLDS OF ADDED SUBSTANCES

Results obtained in the determination of sensory thresholds with three different simplified methods were compared. The methods were: a modification of the ascending method of limits (1), one based on the method of the constant stimuli (2), and one based on the use of scales (3). The study was carried out on two sensorially simple systems, sucrose and aspartame aqueous solutions. The thresholds values for sucrose obtained by method 1 (1.41 g/L) and by method 2 (1.60 g/L) were similar and within the range obtained by method 3 (0.6–1.6 g/L). For aspartame the values obtained with methods 1 and 2 were also similar (0.004 and 0.005 g/L, respectively), but they were below the minimum value of the corresponding range (0.008–0.016 g/L) calculated with method 3. These results suggest that the sensory methods provoked less variability in thresholds values than other noncontrolled factors. The limitations and advantages of each method are discussed considering: experimental work, precision of results and practical validity.     

INFLUENCE OF COLOR ON TASTE THRESHOLDS

Increasing molar concentrations of sweet, sour, bitter and saltywere evaluated in colorless and colored (red, green, yellow)water solutions by 28 untrained students. Green color statisticallyincreased sweet taste threshold sensitivity while yellow colordecreased taste sensitivity. Red color did not affect the tastesensitivity of sweet. In the case of sour, both yellow and greencolors decreased sensitivity with red having no affect. Redcolor decreased bitter taste sensitivity with yellow and greencolor having no effect. No significant differences due to coloraffected salty taste sensitivity. Thus, psychological colorassociation can alter reports of certain basic taste sensations. ^*Scientific Series Paper Number 1764 of the Colorado State UniversityExperiment Station.     

SENSORY THRESHOLDS: CONCEPTS AND METHODS

A sensory threshold can be defined generally as a stimulus intensity that produces a response in half of the trials. The definition of the population threshold is discussed. Five main classical statistical procedures for estimating thresholds are reviewed. They are the probit, the logistic, the Spearman-Karber, the moving average and the up-and-down procedures. Some new developments in statistical methods for estimating thresholds are outlined. The newly developed methods include the generalized probit and logistic models, the model based on the Beta-Binomial distribution, the trimmed Spearman-Karber method, the kernel method and the sigmoidally constrained maximum likelihood estimation method. The authors propose a new procedure based on the Beta-Binomial distribution for estimating population threshold.     

SENSORY EVALUATION OF IRRADIATED BEEF AND BACON

Vacuum-packed beef and bacon were treated with gamma- radiation (1–10 KGy) from CO⁶⁰ and stored for 3 months at + 4°C. The samples were evaluated by a trained sensory laboratory panel, directly after irradiation, and after 3 months. Samples given 1.0 KGy and higher doses were found to be significant different from nonirradiated samples at both times of testing. A higher intensity of off-taste, rancidity, metallic taste and sweetness, and a lower intensity of juiciness and color saturation were found in all the irradiated samples. Off-taste and rancidity were found to increase with increasing doses, and were best explained when analyzed by Principal Component Analysis (PCA).     

SENSORY AND INSTRUMENTAL EVALUATION OF STRAWBERRY YOGURT COLOR

Eleven samples of strawberry yogurt prepared with different red color concentrations using Ponceau 4R (E-124) were evaluated by instrumental and sensory methods. Color intensity evaluation was carried out by a panel of eight assessors specifically trained to measure strawberry color in yogurt. Color acceptability was measured with 120 regular and frequent consumers of yogurt. Color was measured with a Minolta Chroma Meter CR-200b, obtaining parameters L*, a* and b*. Principal component analysis was performed on the instrumental variables. Regression models between the instrumental first principal component, red color concentration, sensory intensity, and acceptability allowed determining quality control limits for red color attribute. These limits may be controlled by selecting either instrumental or sensory methods, being the latter easy to implement and providing dependable results.     

EVALUATION OF RANGE-GRAZED AND CONCENTRATE-FEDBEEF BY A TRAINED SENSORY PANEL, A HOUSEHOLD PANEL AND A LABORATORY TEST MARKET GROUP

A trained sensory panel and a household panel evaluated leaner range-grazed and higher grading concentrate-fed beef for sensory characteristics. The findings were compared to those from a laboratory test market study designed to determine the consumer appeal of branded range-grazed beef when compared to concentrate-fed beef. Broiled steaks from concentrate-fed steers were scored more flavorful, more tender, more juicy and more desirable overall than those from range-grazed steers by the trained sensory panel and by the household panel. In the laboratory test market study steaks from range-grazed steers were nearly equal in acceptance to those from concentrate-fed steers because consumers, although accustomed to concentrate-fed beef in their marketplace, compromised palatability for meat they perceived to be leaner and more healthful.     

DESCRIPTION OF THE SENSORY CHARACTERISTICS OF SPANISH UNIFLORAL HONEYS BY FREE CHOICE PROFILING

Different Spanish unifloral honeys (eucalyptus, sunflower, rosemary, thyme, lavender, citrus, anise, quercus, and lemon blossom) and one multifloral honey were studied by Free-Choice Profiling (FCP) analysis. Generalized Procrustes Analysis (GPA) applied to the FCP data allowed discrimination between samples and provided information on the attributes responsible for the differences observed. The honeys had significantly different sensory characteristics. Textural attributes were the predominant factor in discriminating between samples, and appearance (color included) was also correlated with GPA dimensions to a lesser extent.     

EFFICIENCY OF A CYCLIC DESIGN AND A MULTIDIMENSIONAL SCALING SENSORY ANALYSIS TECHNIQUE IN THE STUDY OF SALT TASTE

Multidimensional scaling (MDS) procedures produce maps of stimulus points, the dimensions of which may be sensory and/or physicochemical attributes. Our objective was to test the efficiencies of a cyclic design and a MDS method in the study of saltiness perception. Two levels of NaCl (0.1% and 0.2%, w/v) were added to two nonionic and two ionic gum solutions prepared to two concentrations. Subjects scaled dissimilarities between pairs of solutions and rated each sample for flavor attributes. Solution pairs were selected using cyclic designs. Repeated measures ANOVA determined that added NaCl was the only significant factor affecting saltiness perception. In contrast, from KYST-2A MDS maps, we concluded that saltiness perception was influenced by gum property, gum concentration, presence of calcium and potassium, and related to binding of the sodium ion (Na⁺) as determined by ²³Na nuclear magnetic resonance (NMR) spectroscopy. The MDS cyclic design successfully reduced the number of samples and subjects when using experienced subjects.