Sensory Evaluation Practices

Herbert Stone, Rebecca N. Bleibaum, Heather A. Thomas

• Publisher: Academic Press
• Year: 2012
• eBook ISBN: 9780123820877
• Edition: 4
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Understanding what the consumer wants and will accept are two of the most significant hurdles faced by anyone in new product development. Whether the concern is the proper mouth-feel of a potato chip, the sense of freshness" evoked by a chewing gum, or the weight and texture of a cosmetic, if the consumer doesn't find the product acceptable, it won't sell. Sensory evaluation testing is the process that establishes the consumer acceptability of a product. It can help identify issues before general production is begun and potentially bring to light issues that hadn't previously been considered a factor in the success of the project.

Chapter 1

Introduction to Sensory Evaluation

Chapter Outline

1.1 Introduction and objective

1.2 Historical background

1.3 Development of sensory evaluation

1.4 Defining sensory evaluation

1.5 A physiological and psychological perspective

1.1 Introduction and objective

Since publication of the third edition in 2004, developments continue to be made in the sensory sciences and their application in the product evaluation process. In today’s highly competitive, global business environment, company executives acknowledge the need for actionable product sensory information to supplement what they already believe they know about consumer behavior. This is especially the case for foods, beverages, and most other consumer products, including the ubiquitous electronic devices that have such a large impact on our daily lives. As noted elsewhere (see, for example, Stone and Sidel, 2007, 2009), brand managers and marketing researchers (also known as consumer insights professionals), like sensory scientists, look for ways to increase their knowledge about consumer responses to products before and after purchase. Of major interest is identifying variables besides those that are typically measured (e.g. preference) to gain a competitive advantage. Product sensory information has long been one of those variables often overlooked or not well understood, but it is now becoming a more integral part of a product’s business strategy. This has led to increased participation of sensory professionals as part of project teams versus being on the outside, waiting for test requests to arrive, if at all, without knowing the background or the basis for a request. Where successful, it has yielded benefits for the sensory professional in the form of improved status, increased compensation, and, for some, a stronger and earlier voice in a company’s product decision-making process. Direct and indirect rewards also were realized, including willingness to support university research, more course offerings, and an increasing demand for newly trained sensory professionals. Another development has been a media connection. In the past, the likelihood of media mention of sensory evaluation was rare; today, there are many books, blogs, and other media outlets describing results from “sensory tests” or interviews with individuals possessing unique sensory skills. Although one may question some of these claims/curiosities, this exposure has brought more attention to the field and that is a positive effect. Changes within the profession also continue to take place, such as more professional meetings and symposiums discussing research results. Other changes are more focused on the ways in which professionals design, analyze, and report results. There has been a major increase in use of direct data capture and a concomitant reduction in use of paper ballots—a more rapid turnaround from data collection to reporting results. The availability of relatively inexpensive software has enabled professionals to more easily undertake design studies. However, none of this has come without some costs—for example, use of software not appropriate for behavioral data or using data that are not appropriate for a particular analysis. This makes it relatively easy for the inexperienced professional to satisfy a request but significantly increases the likelihood of decisions errors. As Groopman (2009) noted as part of a discussion about the state of clinical trials but equally relevant to sensory tests, “Statistical analysis is not a substitute for thinking.” Just because one obtains a graphical display or a series of tables with associated statistical significances does not mean it has any meaning or external validity. Considering the major increases in computing power and the trivial cost, one can undertake a wide range of analyses with little or no knowledge as to their relevancy or if the data set is appropriate for that analysis (May, 2004). One needs to appreciate that output will always be obtained regardless of the quality and quantity of the original data. When unexpected product changes are obtained and not understood, it is the responsibility of the sensory staff to explain the result and minimize confusion. We explore these issues in more detail later in this book.

As mentioned previously, using sensory information as a part of a product marketing strategy has given it unprecedented attention. Identifying specific sensory and chemical measures that have a significant effect on preference and purchase intent has important consequences for a company. In those instances in which this information has been used, its significance has been recognized and the product success in the marketplace is appreciated. Clearly, it is a powerful approach to enhancing product preference versus using a simple trial-and-error process. However, this has only been possible with the use of quantitative descriptive analysis to identify the sensory differences and similarities among competitive products and the availability of user-friendly software. The next logical step in this process has been to incorporate imagery into the process. Exploiting this information to the fullest extent possible has enabled companies to grow their market share as well as implement cost savings through better use of technology, etc. (Stone and Sidel, 2007, 2009). All this has been possible as a direct result of using sensory resources effectively, a better understanding of the measurement process, combined with a more systematic approach to the testing. Much of this progress has been achieved within the technical and marketing structures of companies that recognized the unique contributions of sensory evaluation. In the past, such developments were the exception; today, it is a more common occurrence, again reflecting the increased awareness of sensory information. For a summary of these developments, the reader is directed to Schutz (1998). However, much more needs to be done, in part because the links between sensory, marketing, and production are not strong and in part because there is a lack of appreciation for the principles on which the science is based. For some, sensory evaluation is not considered a science capable of providing reliable and valid information. This is not so surprising, given that this perception is fostered in part by the seemingly simplistic notion that anyone can provide a sensory judgment. We are born with our senses and barring some genetic defects, we are all capable of seeing, smelling, tasting, etc. It certainly seems simple enough, so why should a technologist or a brand manager believe results from a test that are inconsistent with their expectations and their own evaluations? As a result, demonstrating that there is a scientific basis to the discipline continues to be a challenge. Further challenges develop when tests are fielded without qualified and sufficient numbers of subjects, again leading to incorrect recommendations. It is no longer a surprise to hear statements such as “We don’t have the time or money to do it right, but we will be able to do it over again later.” It takes a lot of effort to overcome this kind of thinking. Since the previous editions of this book, advances continue to be made, albeit at a slow pace, not because test procedures are inadequate but, rather, as noted previously, because the science is not readily acknowledged as such. In all fairness, it should be noted that sensory professionals have not been effective spokespeople for their work or for the science. In one company, sensory evaluation will be used successfully, but in another it will be misused or the information will be ignored because it is inconsistent with expectation. Unfortunately, this latter situation has encouraged use of other information sources or the development of competing test capabilities in the hopes of obtaining acceptable information without fully appreciating the consequences.

Throughout the years, numerous efforts have been made and continue to be made to develop a more permanent role for sensory evaluation within a company. Reviewing the technical and trade literature shows that progress in the development and use of sensory resources continues. There has been a noticeable increase, and much of the impetus continues to come from selected sectors of the economy, notably foods and beverages, and their suppliers (Jackson, 2002; Lawless and Heymann, 2010; Meiselman and MacFie, 1996; Piggott, 1988). In their seminal textbook on sensory evaluation published more than 45 years ago, Amerine et al. (1965) correctly called attention to three key issues: the importance of flavor to the acceptance of foods and other products, the use of flavor-related words in advertising, and the extent to which everyday use of the senses was largely unappreciated, at that time. Perhaps a secondary benefit of today’s concerns about food safety has been awareness by consumers of the sensory aspects of the foods they purchase.

Current interest in sensory evaluation reflects a more basic concern than simply being able to claim use of sound sensory practices. A paper published more than three decades ago (Brandt and Arnold, 1977) described the results of a survey on the uses of sensory tests by food product development groups. The survey provided insight into some of the basic issues facing sensory evaluation then and now. Of 62 companies contacted, 56 responded that they were utilizing sensory evaluation. If this question were asked today, one would expect the number to be close to 100%. Since publication of that survey, there have been many similar surveys with additional results reflecting greater interest in and use of sensory evaluation. However, descriptions of tests being used revealed then, as now, that confusion existed about the various methods; for example, it was found that the triangle test (a type of discrimination test) was the most popular, followed by hedonic scaling (a type of acceptance test) and paired comparison (either an acceptance test or a discrimination test). Because these and other methods mentioned in the survey provide different kinds of information, it is not possible to evaluate the listing other than to assume that most companies use a variety of methods.

Not surprisingly, there was confusion about acceptance test methods and the information that each provides. For example, single-sample presentation is not a test method, but 25 of the 56 companies responded that it was one of the test methods in use. It is in fact a serving procedure, and such responses may reflect poorly worded or a misunderstood question in the survey. Single-sample testing would be referred to as a monadic test. Another example of the confusion is “scoring,” which was said to be in use by only 7 of the 56 companies contacted. However, all sensory tests involve some kind of scoring. Statistical tests included in the survey elicited similarly confusing responses. The failure to clearly define the terms confirms that the consumer packaged goods industry uses sensory evaluation but there is confusion as to what methods are used and for what applications. As previously mentioned, sensory evaluation is still not well understood, methods are not always used in appropriate ways, and results are easily misused. There continues to be a lack of qualified professionals, but more are being trained. Books on sensory evaluation continue to be published; however, the science still has not achieved a status commensurate with its potential. Similarly, its role within individual companies is far from clear. One of the goals of this text is to provide a perspective on all these issues and how one should develop resources and integrate them into the business environment. This is not to imply that the scientific basis of sensory evaluation is overlooked. Rather, it is not as well understood as it should be considering its widespread use and strategic potential.

This edition continues to emphasize the importance of a systematic approach to the organization, development, and operation of a sensory program. Primary emphasis is directed toward the more practical aspects of sensory evaluation and approaches to implementing a respected and credible program, but we do not neglect the fundamental, underlying issues, including but not limited to experimental design, the reliability and validity of results, and related topics. From a sensory science perspective, reliability and validity are essential to developing a credible program and providing actionable recommendations that enable a company to build a strong brand consistent with its brand strategy (Aaker, 1996). From a business perspective, it is these latter issues that loom as most important because they build trust that others will place on these recommendations and the extent to which managers will act on them. Sensory professionals must communicate information clearly to ensure that superiors, peers, and subordinates understand what was done and what the results mean in terms of meeting that test’s specific objective and how the research facilitates the product link with the business strategy.

The importance of the relationship between reliability and validity of results and the credibility assigned to sensory recommendations and, in a global sense, the credibility of a sensory program are at stake. Although it is logical to assume that a test result should speak for itself, and that it will be understood, this is not the usual situation. It takes a conscious effort to gain the confidence of a brand manager and consumer insights advisors so that recommendations will be acted on sufficiently. When it succeeds, it is reassuring, but more often it does not, which raises questions as to why sensory information is not better understood and used more effectively. There is no single or simple answer. However, it is clear that the ease with which one can evaluate a product makes it easy for a product manager to disregard information that does not satisfy expectations and substitute one’s own judgment. That and an unwillingness to appreciate the complexity of the judgmental process leads to decision problems and product failures. However, it is the responsibility of the sensory professional to be sure that tests are organized and fielded using best practices, that replication is an integral part of every sensory analytical test, that subjects are qualified and understand the task, that the scorecard is relevant to the test objective, etc. Product evaluation is a complex multistep process in which a group of individuals respond to stimuli (a set of products) by marking a scorecard (electronically or by paper ballot) according to a specified set of instructions. There are many steps in the process where errors can occur, and not all of them are obvious. Of particular importance is the matter of whether the test objective is understood and the requester can explain how the results will be used; that is, what questions will be answered? Failure to obtain such information is a clear sign of problems when reporting results. Once there is agreement on the objective, a test plan can be established, a design prepared, and actual fielding initiated. As already emphasized, there are many challenges faced by sensory professionals; some are self-induced, whereas others come from requesters specifying the test method, the type of scale, or output that yields a single numerical value. The concept of number biases impacting responses seems to have been lost or not at all understood. Measurement or scaling is another area of confusion. Requests to use only a company’s “standard scale” so that it is possible to compare results reflect a poor understanding of the measurement process, as is the request to use a “universal scale” for which there is no evidence. These measurement issues are discussed in detail in Chapter 3.

Subjects have a major impact on a program’s credibility. How they were selected and what kind of training, if any, they received are important considerations, as are their responses, in terms of both their sensitivity and their reliability. To a degree, a panel of subjects can be considered as functioning like a null instrument, recording what is perceived.

Within the sensory community, there is the implication of a human (or group of humans) functioning like an instrument, which has obvious appeal in a technical sense. However, there is an equally large body of scientific evidence that recognizes individual variability in perception based on genetic differences at the receptor level, differences in sensory acuity, and experiential differences that all impact perception. The human instrument position within sensory science is sensitive, particularly to those who mistakenly envision an invariant system yielding the same numerical values time and time again. It has particular appeal among those that lack an understanding of psychology, human behavior, and the perceptual process. The realities of the situation are, of course, quite different. Subjects, no matter what their level of skill or number o...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Foreword
• Preface
• Chapter 1. Introduction to Sensory Evaluation
• Chapter 2. The Organization and Operation of a Sensory Evaluation Program
• Chapter 3. Measurement
• Chapter 4. Test Strategy and the Design of Experiments
• Chapter 5. Discrimination Testing
• Chapter 6. Descriptive Analysis
• Chapter 7. Affective Testing
• Chapter 8. Strategic Applications
• Chapter 9. Epilogue
• References
• Index
• Food Science and Technology International Series