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exhaustive of all the compounds in a food. More important, no chemical analysis reveals the exact pattern of the chemicals contained within a food or most other sensory materials. Not every compound is detected to the same extent by gas chromatography or liquid chromatography. Thus the exact ratios between compounds is often not known. In concentrating materials for analysis so as to bring the concentrations within the range of the instrument, the ratios among compounds are initially changed because of effects of vapor pressure or solubility in the extracting medium. The interrelations of factors affecting texture present even greater difficulties. Characteristics such as gumminess and the hardness of embedded particles need not be related to each other, thus it is not possible to speak of total texture in the same way as it is possible to speak of total flavor. There are some difficulties in measuring color, but on the whole color can be more reliably expressed physically than is true for the other sense modalities. Relations between acoustical properties and sensory characteristics have been extensively studied (49). The point of mentioning each of the senses is that a food or a perfume or the odor of a barnyard is usually judged by more than one sense. That is true even for the seemingly simple response to the odor of a barnyard. It is thought that the sensation perceived is odor, but actually generally more than odor is involved. Some of the volatile substances reaching the nose are compounds possessing trigeminal characteristics causing a stinging sensation or even pain. Considering all that is not known, it is remarkable that sensory-instrumental applications have been as useful as they are.

To make correlation methods even better, it is necessary to know more about the sensory receptors and how the brain processes information. Humans and other animals probably utilize a process somewhat like PCA. Hundreds of sensory signals are detected and these sensory signals must be combined in various ways to form patterns of varying complexity; in other words, data reduction is carried out. Like PCA components, some of the patterns may encompass signals from only a dozen or so sensory notes, other may encompass several dozen. The point is that humans and other animals are responding to several patterns representing different kinds of sensations and patterns of varying size, then somehow this semiprocessed information is ultimately taken and put together as a composite sensation that tells the mind that this food is delectable, that food is almost without taste, and that food has a trace of cinnamon in it. In the brain a whole series of complex interaction effects have taken place. They are not the chemical interactions a chemist thinks of, a reaction between this physical substance and that. They are chimera, not amenable to understanding even if all the kinds of chemical reactions that could occur among the hundreds of chemicals comprising flavor were known, because they are perceptive reactions not physical ones.

Before sensory-instrumental correlation can reach the ultimate in applicability, knowledge of sensing, brain processing of information, and all the other sciences (physiology, psychology, biochemistry, and anatomy) that impinge on the reception, the processing, and the analyzing of sensory information must be greatly expanded. At present, statistical methods are adequate. There must be enlistment of a greater number of statisticians who have an interest in sensory research and are willing to work around some of the limitations that sensory analysis imposes. That which is ideal is often not practical in sensory analysis, such as the evaluation of a large number of samples all at one session. For the time being, present-day computers can handle most of the data sets presented to them, but the day will come when computing demands will be far greater than they are now. If perceptual interactions are begun to be understood, far more will be demanded of computing capacity and complexity than presently exists. Chemical measurement of food components must be made to be "true" to avoid giving a distorted picture of the relations among the hundreds of compounds comprising foods and other natural substances of sensory importance. The characteristics of compounds that make them be sensory substances must be learned. There is fair knowledge of the functional grouping that must exist for substances to be sweet, the properties of chemicals that make them be sour or salty are known with even more certainty, but by and large it is not really known why this compound has the property of being a sensory substance and that one does not. It is necessary know as much about the laws that govern sensory properties as does a synthetic chemist who is seeking to synthesize a new compound. From knowledge of the properties of chemicals, their functional groupings, and possible pathways to foster reactions otherwise particularly difficult to make occur, the chemist can predict in advance the likelihood of success in synthesizing a new compound. Chemists, once they know the identity of a compound, have at their fingertips, or at least readily ascertainable, a whole series of other information about properties of that substance. Sensory properties are not hard facts like vapor pressure and molecular weight. They must be described in terms of perception. Their description is mutable according to who is doing the describing. The description should be an immutable property, not merely a perception. Notwithstanding as important as are all these other considerations, there is nothing to stop the far wider use of multivariate analysis of sensory—instrumental relations. There must be a will on the part of practitioners to stay at the task for some time to avoid having their results be parochial because of acquiring insufficient data. Once sufficient data has been secured, to be sure the results represent real relations, sensory-instrumental correlations can be of great practical importance for present industrial operations such as ensuring ingredients purchased meet the company's buying specifications or the finished product meets its quality specifications for marketing. Of greater importance, correlations so determined can serve as a base for the advancement of fundamental knowledge. From such correlations will ultimately arise an understanding of cause-and-effect relations. Still more important, they in turn will provide a good share of the base of knowledge required to advance comprehension of the detection of sensory signals, their analysis and data processing within the brain.

Homemade Pet Food Secrets

Homemade Pet Food Secrets

It is a well known fact that homemade food is always a healthier option for pets when compared to the market packed food. The increasing hazards to the health of the pets have made pet owners stick to containment of commercial pet food. The basic fundamentals of health for human beings are applicable for pets also.

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