Comparing masticatory performance and mixing ability.

Masticatory performance has often been measured by determining an individual's capacity to comminute a test food. Another method to determine masticatory performance, which is now widely used, evaluates the ability to mix and knead a food bolus. Two-coloured chewing gum and paraffin wax have been used as test foods for the quantification of the mixing ability. The aim of our study was to compare the results obtained with the comminution of an artificial test food and the results obtained from mixing of a two-coloured chewing gum. The degree of mixing of the colours of the chewing gum was quantified with an optical method. Twenty young subjects with a natural dentition (average age 24 years) and twenty elderly subjects, mostly with complete dentures (average age 72 years), participated in the study. Significant differences in masticatory performance between the two groups were detected with both methods. However, the comminution test was better in discriminating the masticatory performance of the two groups. The mixing ability test with the two-coloured chewing gum proofed to be a good method to determine masticatory function in subjects with a compromised masticatory performance (elderly subjects). However, the method appeared to be less suitable for subjects with a good masticatory performance (young subjects).

Food memory and its relation with age and liking: an incidental learning experiment with children, young and elderly people.

The present study compared incidental learning and food memory in children, young adults and elderly people for three sensory modalities (taste, texture and aroma). The relation of gender and liker-status (i.e. how much we like a product) with food memory was also investigated. Participants received a complete meal including a custard dessert used as target under incidental learning conditions. 24h later, participants were confronted with a series of samples consisting of the target and slightly modified versions of the target (distractors) and were unexpectedly asked to perform an "absolute memory" ("Did you eat this sample yesterday?") and a "relative memory" test ("Is the present sample less/equal/more pleasant than the one you ate yesterday?"). Participants also performed a hedonic and a discrimination test. Memory for the custard was poor and did not depend on age, but it was related to gender, and to how much participants liked the product. Females and high-likers outperformed males and low-likers in the absolute memory task, but they were not better in discriminating the products on both the hedonic and the perceptual dimension. Results also showed that, contrary to common belief, not all sensory aspects that can be discriminated in perception and in liking, are equally well remembered.

Do tastants have a smell?

The stimuli used in taste research are usually considered to be odourless. This was tested in two experiments with aqueous solutions of two representative compounds for each of the five taste qualities including umami. In the first experiment elderly and young subjects rated the intensity and pleasantness of three concentrations of the stimuli, while wearing or not wearing a noseclip. Saliva production was also measured. Blocking olfaction only influenced salivation for umami. It reduced taste intensity ratings, but as in an earlier experiment with the same compounds in food products, this effect was stronger in the young, who also liked the stimuli better wearing the noseclip. In the second experiment, another group of young people tried to detect the odours of the tastants dissolved in demineralized, double-distilled or Evian water. A considerable number of subjects could regularly detect seven of the ten tastants by olfaction and the extent to which they did correlated significantly with the reduction in taste intensity ratings for the different tastants found in the first experiment. We suggest that most tastants can be smelled and that this smell contributes to taste intensity ratings.

Texture and flavour memory in foods: an incidental learning experiment.

Memory plays a major role in the formation of food expectations. How accessible and how accurate is incidentally acquired and stored product information? In the present experiment the memory for variations in texture (and flavour) was tested with a new and ecologically valid method. Subjects (N=69: 35 women, 34 men, age 19-59 yrs) came to the institute before having had breakfast and received a breakfast of several items (including breakfast drinks, biscuits and pâté). Subsequently, during the day, they answered questions about their hunger feelings every hour and returned for a taste experiment at the end of the day. When unexpectedly confronted with a series of multiple samples of four texture variations of each of the breakfast items mentioned above, they had to indicate which of these variations they had eaten at breakfast. Signal detection measures showed that most subjects recognised the eaten versions well for all three of the food items. Women remembered better than men. Both men and women used an equally conservative criterion.

An analysis of human response to the irritancy of acetone vapors.

Studies on the irritative effects of acetone vapor in humans and experimental animals have revealed large differences in the lowest acetone concentration found to be irritative to the respiratory tract and eyes. This has brought on much confusion in the process of setting occupational exposure limits for acetone. A literature survey was carried out focusing on the differences in results between studies using subjective (neuro)behavioral methods (questionnaires) and studies using objective measurements to detect odor and irritation thresholds. A critical review of published studies revealed that the odor detection threshold of acetone ranges from about 20 to about 400 ppm. Loss of sensitivity due to adaptation and/or habituation to acetone odor may occur, as was shown in studies comparing workers previously exposed to acetone with previously unexposed subjects. It further appeared that the sensory irritation threshold of acetone lies between 10,000 and 40,000 ppm. Thus, the threshold for sensory irritation is much higher than the odor detection limit, a conclusion that is supported by observations in anosmics, showing a ten times higher irritation threshold level than the odor threshold found in normosmics. The two-times higher sensory irritation threshold observed in acetone-exposed workers compared with previously nonexposed controls can apart from adaptation be ascribed to habituation. An evaluation of studies on subjectively reported irritation at acetone concentrations < 1000 ppm shows that perception of odor intensity, information bias, and exposure history (i.e., habituation) are confounding factors in the reporting of irritation thresholds and health symptoms. In conclusion, subjective measures alone are inappropriate for establishing sensory irritation effects and sensory irritation threshold levels of odorants such as acetone. Clearly, the sensory irritation threshold of acetone should be based on objective measurements.

Taste perception with age: generic or specific losses in threshold sensitivity to the five basic tastes?

Detection thresholds for NaCl, KCl, sucrose, aspartame, acetic acid, citric acid, caffeine, quinine HCl, monosodium glutamate (MSG) and inosine 5'-monophosphate (IMP) were assessed in 21 young (19-33 years) and 21 elderly (60-75 years) persons by taking the average of six ascending two-alternative forced choice tests. A significant overall effect was found for age, but not for gender. However, an interaction effect of age and gender was found. The older men were less sensitive than the young men and women for acetic acid, sucrose, citric acid, sodium and potassium chloride and IMP. To detect the compound dissolved in water they needed a 1.32 (aspartame) to 5.70 times (IMP) higher concentration than the younger subjects. A significant decline in thresholds with replication was shown. The age effect found could be attributed predominantly to a generic taste loss.

Approach to setting occupational exposure limits for sensory irritants in The Netherlands.

This article describes how scientists in the Netherlands set occupational exposure limits (OELs) for sensory irritants. When they tackle this issue, a number of key questions need to be answered. For example, did the studies indeed measure sensory irritation and not cytotoxicity? When the irritant is an odorant, can interference of olfactory stimulation be excluded? In the case of subjective measurements, can psychological irritation be excluded? When adaptation is an issue, did the studies indeed measure adaptation and not habituation? When OELs are established in the Netherlands, each of these issues is carefully addressed before a value is suggested. When setting an OEL in the Netherlands, human data carry more weight than animal data of comparable quality. As in the United States, documentation for the recommended OEL is written and a discussion of all available relevant and reliable data culminating in the selection of the key study for deriving the health-based recommended occupational exposure limit is provided. Special effort is dedicated to reconciling differences between the animal and human data. If the toxicological database is considered to be inadequate, the committee acknowledges this limitation and will not recommend a limit value due to insufficient data.

Asymmetry in the disconfirmation of expectations for natural yogurt.

Effects of expectations conveyed by a product description or an empty package on the evaluation of four types of natural yogurt were studied in a laboratory setting. Hedonic and perceptual responses for the correctly or incorrectly identified products generally showed assimilation: they fell between the responses to the unlabelled products and the responses for the expected properties evoked by presenting only product descriptions or empty packages. Hedonic judgments remained close to the expectation when the product performed better than expected, whereas they were relatively close to the evaluation for the unlabelled product when the product performed worse than expected. The asymmetry was largest for the buying intentions of subjects who received product packages. This is in accordance with the theory that positive disconfirmations are regarded as "gains" and negative disconfirmations as "losses". The asymmetry is likely to be more important in actual buying behaviour than in the experimental settings generally studied, as here.