Herbert Stone

6 – Descriptive Analysis

Publisher Summary This chapter deals with the descriptive analysis, which is the most sophisticated concept in the sensory analysis of products. Descriptive methods were designed to analyze products with a high degree of reliability and precision. Results from a descriptive analysis test provide complete sensory descriptions of an array of products, the basis for mapping product similarities and differences, and a basis for determining sensory attributes. The chapter classifies six test methods for descriptive analysis, according to whether the results are qualitative or quantitative. The test methods described in the chapter are: flavor profile, texture profile, quantitative descriptive analysis (QDA method), spectrum descriptive analysis, free-choice profiling, and diagnostic descriptive analysis. The development of the methodology has been traced from the use of a product expert through the more formal and rigorous approach applied in the QDA method. The QDA methodology emphasizes on the behavioral basis of the judgment process and combines with a rigorous approach to assess response reliability.

Comparison of sensory and consumer results with electronic nose and tongue sensors for apple juices

Abstract Research was conducted to compare apple juice quality measured by consumers, a trained sensory panel [using the quantitative descriptive analysis (QDA) method], and instrument analysis using “α-ASTREE” Liquid Taste Analyzer (electronic tongue) and the Prometheus (electronic nose—sensor array and mass spectrometry). Results from these analyses demonstrate that the electronic tongue and electronic nose, in combination, can be used to predict the sensory characteristics and their relationship to the quality of apple juices measured by consumers. Applications of these findings are important for Quality Control and Quality Assurance (QA/QC) as they demonstrate that these instruments may be used to track “consumer-defined quality” of apple juice, as long as key measures have been identified a priori. That is, sensory, consumer, physical/chemical, and electronic tongue and nose research must be conducted initially to identify key measures used to define quality for the target consumer.

OLFACTORY DISCRIMINATION AND WEBER'S LAW.

Experiments with two odorants, acetic acid and propionic acid, have provided additional evidence that jnds are a constant fraction of the stimulus strength. A linear plot of the difference limens and stimulus intensities has yielded a K of 0.28 for olfactory discrimination in man. The treatment of data derived from tests above the 50% limen and the over-all concept of jnd discrimination are discussed.

The role of sensory evaluation in the food industry

Abstract Increased competition and new opportunities stimulated by progressively vanishing trade barriers and expanding world markets, have greatly accelerated the food industrys world-wide requirement for new products, quality improvements, extended shelf-life, increased productivity, and lower production and distribution costs. Success within the framework of these new challenges will be directly related to the industrys ability to develop more precise knowledge about consumer attitudes and perceptions related to food products, and how these are best measured and implemented. Sensory evaluation is a critical component to that process. Historically, sensory evaluation has often been associated with product experts, and later as a more passive member of the product development team. Currently, the new challenges facing the food industry are progressively transforming sensory to a more proactive role, responsible for generating new product ideas based on unique sensory properties or unique consumer segments identified only through sensory behavior. However, the survival of sensory evaluation as an independent information resource is not guaranteed. Sensory evaluation must develop and improve its methods and more clearly delineate its responsibilities and role in the food industry. This paper focuses on the new and changing role for sensory evaluation in the food industry.

The role of the trigeminal nerve in olfaction

Abstract The effect of reversible blocking of the trigeminal nerve on olfactory stimulation was studied in rabbits with chronically implanted electrodes. In one series of experiments, blocking the trigeminal nerves at the level of the ganglia increased olfactory bulb excitability, but no cortical desynchronization was evident on odor presentation. Respiration and heart rate remained relatively unchanged during odor presentation. In the trigeminally blocked animal, olfactory bulb-induced sinusoidal wave activity was significantly increased in frequency and amplitude when compared with this activity in the unblocked animal following odor presentation. The present evidence supports the concept of a central regulatory control over olfactory afferent inputs; the trigeminal nerve plays an important role in this system.

Temperature and ph effects on the relative sweetness of suprathreshold mixtures of dextrose fructose)

Increasing the temperature from 5 deg to 50 deg C did not significantly alter the relative sweetness of aqueous solutions of dextrose, fructose, and their combination, as measured by the method of magnitude estimation, with a panel of 12 experienced Ss. Reducing pH from 5.8 to 2.7 caused about a 50% reduction in relative sweetness for all stimuli tested. The slopes of these lines tended to decrease slightly, whereas the Y-intercept values showed the greatest change. In all experiments the slopes of the lines were reasonably stable, averaging 1.40 vs 1.3 reported by Stevens (1961) for sucrose. The results of these experiments are discussed in relation to previously reported data on taste interactions.

Changes in absolute detection threshold and in subjective intensity of suprathreshold stimuli during olfactory adaptation and recovery

Olfactory adaptation and recovery to methyl isobutyl ketone at a concentration 10 times the absolute detection threshold (Ito) was intensively studied in two human Ss. A combined psychophysical procedure was used that allowed comparisons of changes in threshold (It) with changes in the subjective intensity of suprathreshold stimuli. Information was also obtained on the effect of the adapting stimulus on the psychophysical power function for this odorant. A threshold detection procedure was used to estimate changes in It; an unstructured magnitude-estimation procedure was used to monitor changes in the subjective intensity of suprathreshold stimuli and the psychophysical power function. The data provided additional information on the behavioral course of olfactory adaptation and recovery and suggested that this combined method can be used profitably for further investigations of this kind. Complementary to the work of Cain and Engen (1969), the results suggested an increase in the exponent of the power function with increasing adaptation.

The olfactory-trigeminal response to odorants

Abstract The olfactory-trigeminal response produced by two odor stimuli, isopropyl alcohol and octane, was studied in awake, restrained rabbits with recording electrodes permanently implanted in one olfactory bulb and in the anterior sensory motor cortex for measurement of spontaneous activity. Surface electrodes were used to measure respiration and EKG. Xylocaine hydrochloride injected via cannulae permanently implanted at the root of both trigeminal nerves was used as a blocking agent. That the results obtained with the xylocaine-treated rabbits after odor stimulation were due to trigeminal block, and not to changes in the central nervous system by infiltration of the drug to adjacent tissue, was proven by the results obtained with an animal whose trigeminal nerves were lesioned with electrical current. The response to odorants was characterized by changes in respiratory and heart rates, by a typical cortical “arousal” reaction, and by changes in bulbar activity. Blocking the trigeminal nerves by injection of xylocaine or by lesioning produced changes only in the cortical EEG and bulbar spontaneous activity, according to stimulus concentration. Respiration and heart rate remained unchanged during odor presentation. These data support the hypothesis that the olfactory response to many odorants is really an “olfactory-trigeminal” response. Further, the aversive response of the rabbit to high concentrations of odor stimuli is inhibited when the trigeminal nerves are blocked.

Introduction to Sensory Evaluation

Sensory evaluation is a scientific discipline that is used to measure, analyze, evoke, and interpret the reactions to those characteristics of foods and materials as they are perceived by the senses of sight, smell, taste, touch, and hearing. Sensory evaluation involves the measurement and evaluation of the sensory properties of foods and other materials. Sensory evaluation also involves the analysis and the interpretation of the responses by the sensory professionals. Linking of sensory testing with other business functions is essential, because it is essential for the sensory professional to understand the marketing strategy. Sensory evaluation principles have their origin in physiology and psychology. The information derived from experiments with the senses has a major influence on test procedures and on the measurement of human responses to stimuli. Sensory information is used as a part of marketing decision to identify and quantitatively model the key drivers for a products acceptance, and is now generally recognized as a core resource for any sensory program.

A comparison of olfactory adaptation among seven odorants and their relationship with several physicochemical properties

A study was made comparing olfactory sensitivity before and after 100 sec of adaptation for stimuli representing several odorant classes with varying physicochemical properties. Measures taken were absolute detection thresholds and magnitude estimates of suprathreshold stimuli. Significant rank-order correlation coefficients (<.90) were found between nonadapted and adapted absolute detection thresholds, vapor pressure, and percent adaptation.