Lisa Duizer1 | Chris Findlay2
Sensory evaluation has a number of different applications within the food industry, ranging from analytical testing for differences among products through to hedonic testing to understand consumer liking. Because of the breadth of tests available, sensory testing can be used for a number of different purposes. This includes new product development, product reformulation, process changes, cost reduction and quality evaluation. It is the latter use, quality testing, which is the focus of this article. Often within the food industry quality is measured via microbiological, chemical or physical testing of a food product. This reflects the relative importance of food safety, nutrition and product integrity, which for most consumers are invisible. Less well utilized is sensory quality testing. Sensory quality testing relies on input from the consumer to determine acceptance of perceived characteristics of the product1, one of the main reasons for future purchases. It also requires measurements of consistency of the product to ensure ongoing consumer satisfaction. This article outlines the requirements necessary for the establishment of a sensory based quality control program and the application of a sensory quality program in the Canadian context are illustrated through the case studies of Canadian companies.
The establishment of a sensory quality program requires considerations that are similar to any other quality control program. Standards must be established and limits of those standards must be identified. One major difference between sensory quality testing and other forms of quality testing is that the instrument used for measurements is human. Often using individuals for testing is seen to be too difficult to run; panelists are variable in their responses and testing is deemed expensive. A well-established sensory quality program however minimizes these concerns and can provide valuable information for food manufacturers.
An excellent example of an effective Sensory Quality program may be found at the Sleeman Breweries based in Guelph, Ontario. When production was entirely in that single location, the Sensory Quality program that had been developed worked very well. The expansion of operations to multiple production sites across Canada created a challenge for the existing quality systems. Typically, the Sensory Analyst would physically visit each location annually to screen and train panelists. This was an expensive and time-consuming process. The implementation of a cloud-based sensory software platform enabled Sleeman Sensory Analyst, Chris Williams, to centralize his quality assurance and product development sensory programs. In addition to providing timely and fact-based analysis and reporting, the system made the screening and training of employees from coast-to-coast practical. By using the system to determine the proficiency of potential quality panelists, Sleeman’s saved time and effort whilst ensuring qualified tasters would be trained for the panel. The ability to distribute blind coded samples not only provided training opportunities, but also calibrated the panelists to the attributes of their products. Standardization of this process has created a companywide system that delivers reliable and actionable Sensory Quality results. The accuracy, acuity and attendance of all panelists is tracked for all facilities and used to maintain the panel. The current program that runs routinely across all locations is delivered with great consistency and assures the company that products are delivering their unique sensory character and are meeting their Sensory Quality standard.
The first consideration when establishing any quality program is to define the type of quality that you are interested in. Essentially two types of quality programs can exist: a defect driven program or a “typicity” program.2 In the case of a defect driven program, quality testing can be conducted at the product level or at the ingredient level, evaluating the ingredients to be used during the manufacture of the product. The highest quality level in this scheme is defined by an absence of defects. Often in the case of a defect driven quality program, the defects can be linked to the underlying chemical and physical changes in the product. A good example of a quality system used in many countries in the world is the evaluation of virgin olive oils. In this quality program, defects present in the oil dictate the designation of the oil and can also be tracked back to handling of the olives during harvest and storage and the treatment of the oil after pressing. These quality standards have been developed by the International Olive Council (IOC) and have been published online.3
The use of a quality program to indicate ”typicity” also requires identification of defects in the products but also must include identification of key attributes within a food product which designate it as “typical of the region”. A number of sensory based quality programs have been developed for European products that have “protected designation of origin” or “protected geographical indication” including Salama da sugo (Italian fermented sausages)4, Galician turnip greens5 and potatoes6 and Spanish turrón (almond nougat)7.The identification of sensory attributes typical of the region is essential for ensuring that adulteration of products or the introduction of imitation products into the market does not occur. Such products can be identified during the quality test. In Canada, the VQAO testing established with the Liquor Control Board of Ontario is a good example of quality testing for typicity.
The Vintners Quality Alliance of Ontario (VQAO) wines are evaluated by a panel of highly trained tasters provided by the Liquor Control Board of Ontario (LCBO). According to Leonard Fransen, Manager of Quality Services at LCBO, these tasters must pass a yearly proficiency test and are independent of the wineries to avoid a conflict of interest. That independence is a primary characteristic of an effective Quality program.
A quantitative sensory method, developed with specialized sensory software, is used to assess specific wine attributes; appearance and colour, aroma (primary and secondary) and bouquet, taste and harmony for correctness, intensity and quality. The methodology utilizes descriptive indicators to quantify individual attributes rather than numeric values. This ensures consistency of evaluation results among all tasting panels by eliminating biases.
In accordance with VQAO Rules, wines must be of sound quality, representative of the type designation and free of any technical faults or defects. Varietal designated wines are assessed for varietal character and typicity. Proprietary designated wines are assessed for vinous character and typicity. These tastings are conducted in the morning in a controlled setting, following well established principles of sensory evaluation – it is much different from a wine competition since the wines are evaluated against an absolute standard.
Since its inception in 2000, the number of VQAO wines have doubled to over 1900 products with a retail value in excess of $300 million. Production comes from 151 member wineries. As, Brian Schmidt, President and Chair of VQAO, observed in their 2015 Annual Report that “VQA and our appellations have matured into a solid framework that consumers can rely on and that wineries can build their brands on.” Sensory analysis of any submitted wine is usually completed within 5 days and last year 98.3% of those wines passed on Sensory Quality testing.
To establish either a defect driven or typicity driven sensory quality program, there are two key steps that must be followed. First, it is necessary to specify the standards or specifications that the product must achieve to be classified as good quality8. To determine these standards, a descriptive analysis panel is often conducted on representative food samples. A descriptive analysis panel involves a small group of individuals (typically between 10 and 20 panel members) selected for their ability to characterize small differences in intensity of sensory attributes9. This panel does not provide measures of liking of the product. Instead they are used to evaluate the intensity of a number of important attributes within the food product. Training of the panel to evaluate attribute intensity is essential to obtaining reliable quality results10.
Selection of attributes is important when using a descriptive panel for standard specification and the importance of each attribute for product quality must be decided. This can be done with the assistance of a consumer panel11,12. Therefore, the second step in developing a sensory quality program is to determine the importance of these attributes in affecting perceived quality by the consumer. This will allow for the establishment of a range of intensities that are acceptable for each attribute
evaluated in the product. For sensory quality programs which are designed for ingredient evaluation, it may be possible to use management for the development of tolerable limits of quality. However, if the quality program is being developed for a final consumer product, a consumer panel is often used to assist with the development of these tolerable ranges. Consumers are the end user of the product and will be the population most likely to reject the product if the quality is lacking.
Consumer testing involves a large group of individuals (over 100) who will evaluate products for liking. Scales such as a 9-point hedonic scale ranging from dislike extremely to like extremely can be used to determine the degree of liking by the consumer13. For this test, products exhibiting a range of sensory attributes must be included in the evaluation. The liking data that is collected can be correlated to the trained panel data to identify the range of acceptable intensities for specific sensory properties the food product exhibits.
Once standard development and establishment of the tolerable limits for sensory attributes has occurred, a sensory quality test must then be selected which can be used to routinely evaluate the food product for sensory quality. A number of different types of tests are available for use in quality testing and have been thoroughly outlined by Muñoz et al.14. A test that is commonly used during sensory quality testing is that of quality grading. In this case, a scorecard is developed with key sensory attributes (identified during the standard development) defined and described to participants. Corresponding rating scales are also presented to participants for product evaluation. Such an approach requires that individuals be carefully trained prior to beginning the test so that they understand the different sensory attributes and their presence within the food product. The corresponding rating scales are established to indicate at which stage the product quality is deemed unacceptable (using the information from the tolerable limit development). This approach requires that a small number of individual sensory attributes is being evaluated by the participants so that it is easy to be able to identify the products that are out of specification.
Although quality grading is one of the most commonly used tests in a sensory quality program, it is not the only one available. The remaining tests can be broadly classified into those which require the use of a physical standard and those which require a mental standard2. A physical standard is presented to participants when using a difference from control test to indicate quality. Participants are presented with the “gold standard” product which is deemed to be of good quality by consumers. All other products are compared to that physical standard. A difference from control scale ranging from “no difference” to “extreme difference”15 is presented to participants for the evaluation. Overall product differences can be evaluated as can be individual attribute differences to determine how similar to the control each test product is.
When a mental standard is being used in the sensory quality test, participants must be extensively trained to remember what a good quality product is. In many instances these participants are deemed to be “expert” evaluators and there is only one or a handful of individuals who take part in the evaluations. Care must be taken to ensure that these individuals are truly sensory experts that have been extensively trained to evaluate the quality of the products16. Individuals who are merely good tasters are not adequate expert tasters2. Experts should not shift in their evaluations over time in their evaluations, so it is necessary to conduct repeat training sessions with them with known defects to ensure that there is no “drift” in their results.
Although there are many product areas for which quality can be measured, without knowledge of the quality of a product from a sensory perspective, a food producer runs the risk of selling an inferior product that does not meet consumer expectations. This may jeopardize the company’s reputation and any potential for repeat purchase of the product. Therefore the development of a sensory quality program is a necessity to support both the product and the brand.
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1Lisa Duizer, Department of Food Science, University of Guelph, Guelph ON
2Chris Findlay, Compusense Inc, Guelph ON