Harry T. Lawless

Sensory Evaluation of Food

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Multidimensional scaling of sorting data applied to cheese perception

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Effect of citric acid and citric acid-sucrose mixtures on swallowing in neurogenic oropharyngeal dysphagia.

Abstract A series of experiments examined the feasibility of using sorting data as input to multidimensional scaling (MDS) to create perceptual maps of cheeses. One study used a fairly diverse set of cheeses. Cheese names were also sorted for conceptual mapping. In a second study, only blue-veined cheeses were sorted. After sorting cheeses, intuitively sensible perceptual maps were obtained from MDS with low stress. Duplicate cheeses and those with highly similar characteristics were plotted close together. Regression of attribute scale data into the space revealed major dimensions corresponding to flavor and texture attributes (e.g. smooth and soft vs. firm and crumbly). Two consumer groups, one experienced and knowledgeable about cheeses and the other a group of cheese consumers with no special knowledge, training or expertise, participated. Data from the two knowledge groups were similar, except that the more knowledgeable group had a larger number of significant attributes when regressed through the MDS space for blue cheeses. The sorting task was rapid and simple for participants. The overall result substantiates the applicability of the MDS/sorting technique for perceptual modeling of food categories.

Descriptive analysis of complex odors : reality, model or illusion'?

The ability of sour and sweet–sour mixtures to improve swallowing in 11 nursing home residents with neurogenic oropharyngeal dysphagia was investigated using fiberoptic endoscopic evaluation of swallowing. Citric acid (2.7%) significantly reduced aspiration and penetration compared with water. Teaspoon delivery of liquids significantly reduced aspiration and penetration compared with natural cup drinking. Subjects tended to appropriately self-regulate the cup volume they consumed after the first trial. A significant increase in spontaneous dry swallows was observed after both taste stimuli. The mechanisms for improved swallowing due to citric acid are not understood but may be due to increased gustatory and trigeminal stimulation of acid to the brainstem in neurologically impaired subjects.

Effects of color and odor on judgments of sweetness among children and adults

Abstract The primary sensory tool for specifying the characteristics of a complex aroma, fragrance, flavor or other odorous mixture of volatiles is descriptive analysis. Descriptive analysis uses a trained panel to specify the intensities of specific attributes, based on a psychophysical model for intensity scaling. However, the use of descriptive techniques for complex and well-blended aromas gives rise to several problems. The psychophysical intensity model based upon independent odor notes may be a poor way to characterize odor experience, bringing into question whether descriptive analysis is an adequate tool for sensory analysis of complex smells. These problems include the following: (1) disagreement among experts in the most prominent odor notes of a single product and other individual differences problems, (2) a correspondence between similarity scaling and intensity scaling, (3) the substitution of applicability measures for intensity, (4) the need to use mid-tier, general odor terms for profiling complex fragrances, and (5) blending and integration effects. Data will be presented on citrus–woody mixtures showing that ratings of similarity and intensity are highly correlated, suggesting a common underlying process for both ratings. A related issue concerns whether odors and their mixtures are perceived as unitary or analyzable percepts. With these same stimuli, the perception of singularity vs. mixed-ness of stimuli is difficult to predict. Sensory scientists should question the validity of descriptive data for such stimuli and avoid the simplistic mistake of equating data with perception. The use of simple and apparently independent intensity scales may produce the illusion that the odor experience is a collection of independent analyzable “notes” when it is not. ©

The taste of calcium and magnesium salts and anionic modifications

Abstract Judgments in one sensory modality or dimension are often affected by information in other sensory dimensions even if they do not physically or physiologically interact. Examples of such psychological contextual effects are the enhancing effects of color and odor on judgments of sweetness. Children might be expected to be more influenced by irrelevant dimensions and thus might show increased context effects when asked about specific attributes. Two experiments investigated the effect of color change in a fruit beverage on sweetness judgements and the effects of an added aromatic flavor (vanilla) on judgments of sweetness, creaminess and liking of milk. Three groups of American children were tested, in age groups of 5 to 7, 8 to 10 and 11 to 14-years-old, and their responses and contextual effects were compared to those of adults. The strongest and most consistent effect across age groups was the enhancement of rated sweetness by added vanilla flavor in milk. Children did not show the expected effect of darker red colors raising sweetness judgments in the fruit beverage, and the 11 to 14-year-old group showed a trend in the opposite direction from adults (lighter red color judged as sweeter). The concept of sweetness may be more strongly associated to sweet aroma characteristics at an early age than to specific colors. The differences between adults and the 11 to 14-year-old group could arise from a number of sources, including product experiences, developmental and/ or cohort effects, and are worthy of further study.

Effects of oral chemical irritation on taste

Abstract Taste properties of divalent salts are complex. The first study examined the taste profiles of calcium chloride, magnesium chloride and magnesium sulfate. These divalent cation salts were characterized primarily by bitter taste, with additional sensations described as salty, metallic, astringent, sour and sweet, generally in decreasing order of intensity. A second study examined the taste properties of calcium salts other than chloride. Calcium gluconate, calcium glycerophosphate and calcium lactate had lower salty and bitter responses than equimolar concentrations of calcium chloride, an effect suggesting anionic inhibition.

Principles of Good Practice

Oral irritation was induced by rinses with capsicum oleoresin and with piperine, constituents of red and black pepper, respectively. The perceived intensities of two concentrations of each of four tastants representing the four classical taste qualities were evaluated after rinsing with these irritants. Comparing taste intensity after rinses with capsicum and after control rinses with emulsifying agents or water, there were significant decrements in taste intensity of citric acid and quinine, and on one concentration of sucrose, but no effect on salt. The effects of piperine were more broad, with significant decrements in perceived intensity relative to emulsion controls for all substances.

Dimensions of sensory quality: A critique

In later chapters of this textbook, we will often state that a particular method should be performed using standard sensory practices. This chapter will describe what we mean by “standard sensory practices” Table 3.1 provides a checklist of many of the good practice guidelines discussed in this chapter; this table can be used by sensory specialists to ensure that the study has been thought through. It should be remembered that a good sensory specialist will always follow the standard practices because that would help ensure that he or she will obtain consistent, actionable data. However, an experienced sensory scientist will occasionally disregard the standard practice guidelines. When one breaks these rules, one always has to be fully aware of the consequences, the risks entailed, and whether one still can get valid data from the study.

Gender, age, vessel size, cup vs. straw sipping, and sequence effects on sip volume.

Abstract This essay argues that quality is a complex term used in different ways. In addition to sensory quality, there are factors such as nutritional content, safety, shelf-life and reliability, that contribute to the consumers overall opinion of a food product. Product quality is multidimensional. Some sensory quality determinations have taken an analytic approach through the identification of defects by experts or descriptive measurement of conformance to a target. However, consumer opinion must be one benchmark for good quality. Yet this also presents problems. Consumers are rarely analytical — they perceive products in an integrated fashion, show halo effects and use language imprecisely. Product strategists would do well to focus on specific aspects of consumer appeal. A comprehensive approach to quality entails a consideration of consumer needs and expectations, careful translation of consumer language, and optimization of attributes through good sensory measurement.