Psychophysically

The aroma of fmit, the taste of candy, and the texture of bread are examples of flavor perception. In each case, physical and chemical stmctures ia these foods stimulate receptors ia the nose and mouth. Impulses from these receptors are then processed iato perceptions of flavor by the brain. Attention, emotion, memory, cognition, and other brain functions combine with these perceptions to cause behavior, eg, a sense of pleasure, a memory, an idea, a fantasy, a purchase. These are psychological processes and as such have all the complexities of the human mind. Flavor characterization attempts to define what causes flavor and to determine if human response to flavor can be predicted. The ways ia which simple flavor active substances, flavorants, produce perceptions are described both ia terms of the physiology, ie, transduction, and psychophysics, ie, dose-response relationships, of flavor (1,2). Progress has been made ia understanding how perceptions of simple flavorants are processed iato hedonic behavior, ie, degree of liking, or concept formation, eg, crispy or umami (savory) (3,4). However, it is unclear how complex mixtures of flavorants are perceived or what behavior they cause. Flavor characterization involves the chemical measurement of iadividual flavorants and the use of sensory tests to determine their impact on behavior. 

A persistent idea is that there is a very small number of flavor quaUties or characteristics, called primaries, each detected by a different kind of receptor site in the sensory organ. It is thought that each of these primary sites can be excited independently but that some chemicals can react with more than one site producing the perception of several flavor quaUties simultaneously (12). Sweet, sour, salty, bitter, and umami quaUties are generally accepted as five of the primaries for taste sucrose, hydrochloric acid, sodium chloride, quinine, and glutamate, respectively, are compounds that have these primary tastes. Sucrose is only sweet, quinine is only bitter, etc saccharin, however, is slightly bitter as well as sweet and its Stevens law exponent is 0.8, between that for purely sweet (1.5) and purely bitter (0.6) compounds (34). There is evidence that all compounds with the same primary taste characteristic have the same psychophysical exponent even though they may have different threshold values (24). The flavor of a complex food can be described as a combination of a smaller number of flavor primaries, each with an associated intensity. A flavor may be described as a vector in which the primaries make up the coordinates of the flavor space. 

Methods are described for determining the extent to which original natural color is preserved in processing and subsequent storage of foods. Color differences may be evaluated indirectly in terms of some physical characteristic of the sample or extracted fraction thereof that is largely responsible for the color characteristics. For evaluation more directly in terms of what the observer actually sees, color differences are measured by reflectance spectrophotometry and photoelectric colorimetry and expressed as differences in psychophysical indexes such as luminous reflectance and chromaticity. The reflectance spectro-photometric method provides time-constant records in research investigation on foods, while photoelectric colorimeters and reflectometers may prove useful in industrial color applications. Psychophysical notation may be converted by standard methods to the colorimetrically more descriptive terms of Munsell hue, value, and chroma. Here color charts are useful for a direct evaluation of results. 

Psychophysical Methods for Measurement and Designation of Reflectance Color in Foods... 

The indirect methods discussed thus far have dealt with measurement of color only as it can be correlated with physical characteristics of materials and the effect of these materials on radiant energy. As has been pointed out, the reflectance spectro-photometric curve describes a property of the material. A change in the reflectance spectrophotometric properties may not always result in a change in visual color. The reason is that color of the object is not an unchangeable characteristic of the object itself, dependent only upon these reflectance properties, but is also dependent upon the quality of the illuminating light and the sensitivity of the observer s eye. Thus the measurement and description of visual color are psychophysical problems... 

Conversion of Psychophysical Notation into Colorimetrically More Descriptive Terms... 

The methods described make possible the objective measurement of color of foods and a designation in standardized psychophysical terms. However, the psychological significance of food colors is not directly apparent from results expressed... 

One reason for the seemingly slow progress of understanding is the interdisciplinary nature of sweetness research. The conclusions that can be drawn, from, for example, physiological and psychophysical experimentation, must be related to what is known of the structural chemistry of the stimulus and how it may interact at the molecular level. All too often, it is not appreciated that one particular line of experimentation cannot be viewed in isolation, but must relate to other disciplines. Only by fully understanding all of the associated events leading to sweetness perception shall we understand the mechanism of sweetness perception itself. 

Much of our present day knowledge of sweetness intensity, both at the threshold level, where taste begins, and above the threshold level, derives from the application of psychophysical techniques. It is now evident that the psychophysical procedure used measure separate aspects of sweetness perception. Hedonic responses cannot be predicted from intensity of discrimination data, and vice versa. The taste-panel evaluation of sweetness is of fundamental importance in the development of worthwhile structure-taste relationships. Therefore, it is vital that the appropriate psychophysical method and experimental procedure be adopted for a particular objective of investigation. Otherwise, false conclusions, or improper inferences, or both, result. This situation results from the failure to recognize that individual tests measure separate parameters of sensory behavior. It is not uncommon that the advocates of a specific method or procedure seldom... 

The recognition of the importance of MP in maintaining the health of the retina has led to the development of a number of methods for determining its concentration in situ. These methods, necessarily noninvasive, are routinely employed in dietary supplementation studies with lutein or zeaxanthin to monitor the uptake of the carotenoids into the retina. Every method exploits the optical properties of lutein and zeaxanthin, specifically their absorbance at visible wavelengths. The detection of a light signal, modified by the carotenoids, is accomplished either by the retinal photoreceptors themselves (psychophysical methods) or by a physical detector such as a photomultiplier,... 

Anstis, S. M. and P. Cavanagh (1983). A minimum motion technique forjudging equiluminance. In Colour Vision Psychophysics and Physiology, J. D. Mollon and L. T. Sharpe (eds.). London Academic Press, pp. 66-77. 

West, P. and J. Mellerio (2005). An innovative instrument for the psychophysical measurement of macular pigment optical density using a CRT display. International Color Vision Society Annual Meeting, Lyons, France. 

Doty, R.L. (1977) A review of recent psychophysical studies examining the possibility of chemical communication of sex and reproductive status in humans. In Muller-Schwarz D and Mozell, M.M., Chemical Signals in Vertebrates. Plenum, New York, pp. 273-286. 

Johansson, G. 1973. Visual perception of biological motion and a model of its analysis. Perception Psychophysics, 14,201-211. 

The input value of the dispersion model represents the odour load as established by a psychophysical experiment. The experiment relates a human sensation to a physical quantity. The human sensation to be recorded usually encompasses questions concerning the detectability, the intensity or the quality of the odour. In the case of odour pollution, the physical quantity is often expressed as the dilution number or the relative concentration. 

FRITTERS, J.E.R., BEUMER S.C.C., KLARENBEEK, J.V. and JONGEBREUR, A.A. (1979). Psychophysical methodology in odour pollution research the measurement of poultry house odour detectability and intensity. Chem. Sens, and Flav. 4, 327-340. 

Measurement of the strength of odours by dynamic dilution olfactometry and observers is a complex task. The observers require adequate training and sound psychophysical procedures are needed to maximise the validity of the measurements. 

This paper describes some investigations into the physical operation of olfactometers, with reference to two commercially produced models, a Prosser and a TO4. It should be noted that the findings reported here are not necessarily typical of other copies of these olfactometers. The type of psychophysical procedure, eg suprathreshold or threshold measurements is not included in this paper. 

The perception of odour is due to the presence of volatile compounds in the inhaled air. Measurement of this perception can be carried out directly by psychophysical methods or indirectly by analysing the air for the odorous volatile compounds. Both methods however present a number of limitations and difficulties. 

Although knowledge on the correlation of odorous compounds concentration and odour impression is still limited, it is used in all types of olfactometry. Indeed diluting this concentration by adding pure air is a general practice. Also many investigations were performed where chemicals are added to air and used in psychophysical experiments. Many speakers in this workshop will present data in this field. Here only chemical analysis will be dealt with. 

Does this mean that machines are going to decide if an odour is present or not By no means, while the population will always be the reference, and psychophysical measurements will be necessary to make chemical analysis possible. 

Mowrey, D. B., and D. E. Clayson. Motion sickness, ginger and psychophysics. Lancet 1982 655-657. 

Breslin, P.A. et ak. Psychophysical evidence that oral astringency is a tactile sensation. Chem. Senses 18, 405, 1993. 

Some 30 phencyclldlne-llke compounds are known to produce psychophysical effects resembling those of SNA. Of these, ketamine (Ketalar, Ketaject), a chlorophenyl methylamlnocyclohexanone, is currently used fairly widely as a dissociative anesthetic In humans. Therefore, Its use can provide clinical information about undeslred effects of single doses of the phencyclidine series. 

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