WITH THE GROWING CONSUMPTION of wine in this country and the rapidly developing interest of the general public in wine appreciation, maintenance of uniform quality and improvement in quality have become matters of increasing importance to California wine makers. At present our only method of distinguishing quality is by sensory examination-visual observation, smelling, and tasting-and this is the province of professionals, calling for skill, training, and experience. To some extent objective tests can be applied to supplement and support sensory judgments, but quality ratings still rest largely on the estimates of expert tasters. While much has been written about the various aspects of wine judging, the information is scattered and not always easily available. Furthermore, because of their subjective nature, standards tend to vary, and a major problem of wine tasting has been to achieve, by various types of testing, uniform and reliable judgments. The purpose of this publication is to provide a complete guide to the sensory examination of all kinds of wines. The standards proposed herein are generally accepted measures of quality, and an attempt has been made, insofar as possible, to provide objective criteria that will be useful both to amateur and experienced tasters. The first section is devoted to a discussion of the senses and the way they function, since this is considered fundamental to their intelligent utilization. The chemical characteristics of wines are discussed under color, smell, and taste, and the available data on their detection or differentiation are summarized. A list of words for purely descriptive work is given in connection with each of these. A brief description of the main types of wine produced in California then follows. Various types of tasting for different purposes are suggested. Difference testing is discussed, and the statistical procedures for determining significance are outlined. Finally, scoring and ranking pro-1
The relative sensitivities of the two-sample and triangular designs, in cases where quality may be stated unambiguously, have been much discussed. From a classical standpoint, using a binomial mathematical model, the triangular technique should be more efficient than the two-sample (9). This arises from the differences in the chance probability for each design.The two-sample comparison consists in the presentation of two samples (different in intensity of quality) to the taster, who is required to denote one as being higher in intensity. The chance probability for this occurrence to he correct is one-half. The triangular test comprises three samples, two identical and one different in intensity of taste quality. The taster is required to determine the odd sample. By chance, this probability is one-third.When the tests are given in the above manner, actual experimental results have shown that the triangular design is not as sensitive as the twosample method in the determination of thresholds (2,4). This phenomenon has been explained as being due, to a large extent, to the inherent limitations of flavor perception ( 2 ) . However, this view is not unanimous. Protracted tasting is not necessarily the cause for fatigue or sensory adaptation (11). An attempt has been made to increase the efficiency of the triangular design by including the partially correct judgments in tests of significance (3).Using these designs, the levels of significance for thresholds have been established by employing only the probability of committing an error of the first kind ; i.e., the chance that the hypothesis of no real difference may be rejected when it is true. However, it has been emphasized that a consideration of the error of the second kind (the chance that a taster may overlook a real difference when it exists) is of at legst as great importance as that of the error of the first kind (1).It is the purpose of this paper to demonstrate, by experiment, inherent differences existing between the two-sample and the triangular designs.
The purpose of this paper is to report a taste-preference experiment with raisins which emphasizes the distinction between difference testing and preference ratings based on organoleptic examinations of foods, beverages, perfumes and similar substances. The experiment involves simple, singlepaired comparisons, because such procedures are fundamental in most ranking procedures.It is sometimes assumed that products can be classed as better than similar products by mass testing that consists of having the products ranked according to preference by a great number of persons. The tables giving the number of favorable responses necessary to indicate statistical significance assume the same direction of preference for all testers and ability to detect the difference if any exists. These two assumptions will now be discussed in some detail, and applied to the experiment with raisins. MASS CONSUMER PREFERENCE TESTING BASED ON ONE TEST PER CONSUMERIf none of the testers can distinguish a difference, then the products will be equally preferred and in a series of trials about half the time each will be scored over the other. The probabilities of each number of .scorings of A over B, say, will be given by ( )where n is the number of testers employed. If the difference can be detected by each tester, but one-half the testers prefer A over B and one-half prefer B over A, and we consider a sample of n tasters drawn at random from such a population of testers, then the probabilities of each number of scorings of A over B will be again given by (1). That is, the two cases are indistinguishable on the basis of an experiment which simply records the preference for the two products.If all preferences are in the same direction we have the usual one-tailed test (5) if the questions are: is A preferred to B or is B preferred to A, and the usual two-tailed test if it is merely asked if one product is preferred to another. The probabilities involved are either the right or left tails or both tails of (1). If the difference can be dCtected and part of the preferences are one way and part the other, say the proportion that prefer A is p and proportion that prefer B is q, and p + q = 1, then the probabilities of given numbers of A over B in preference expressions are given by:(q + pjll.(2)The distribution (2) can be quite skewed either to the right or to the 810
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