Applying advanced instrumental methods: mealiness in fruit
9.2 Sensory evaluation and consumer’s expectations
Although awareness of texture appears to be present on a subconscious level, it plays an essential role in determining people’s feelings about foods. Very often flavour overshadows texture at the conscious level. People simply take the texture of a food for granted, considering it an integral part of the nature of the food.
They do not distinguish it as a separate and distinct characteristic. This is reflected in the limited ability to verbalise when talking spontaneously about texture.
Texture awareness is increased when expectations are violated, associations are made with non-food items or unpleasant mouth sensations are experienced.
Szczesniak (1971) observed that sex and socioeconomic group are factors which influence awareness of texture. In general, women were more texture conscious than men. Better educated people were more texture conscious and showed a better understanding of the idea of texture because of better education and expe-rience in dealing with generalised concepts and applying abstract ideas to real life cases.
Sensory evaluation has been defined as ‘a scientific discipline used to evoke, measure, analyse, and interpret reactions to those characteristics of foods and materials as they are perceived by the senses of sight, smell, taste, touch and hearing’ (Andani, 2000). Bourne (1982) summarised it as follows ‘there is no instrument available that has the sophistication, elegance, sensitivity, and range of mechanical motions as the mouth or that can promptly change the speed and mode of mastication in response to the sensations received during the previous chew’. Texture was found to be a clearly perceived attribute of foods. Most of the sensory results published on apples are based on preference or difference testing, related to pleasure or acceptability, rather than to intensity of defined attributes (Lapsley, 1989).
Sensory analyses can be conducted at different levels, each resulting in spe-cific information about fruit quality attributes such as texture and flavour. An ana-lytical sensory panel, trained in descriptive sensory analyses, will provide detailed information about the sensory attributes of the product. In consumer preference tests, the general descriptive quality perceptions of the consumer will be studied.
Repertory grid methods can be interpreted as an intermediary technique. Using consumer expectation theory, information can be gathered about what the con-sumer expects of the product and how this will influence his or her purchase intent. Each of these methods provides answers to different questions, as will be illustrated below. For each type of test, an example in the framework of texture and mealiness in apples will be discussed.
9.2.1 Analytical sensory panel
In the early 1970s, Civille and Szczesniak (1973) developed a tool to describe and quantify textural characteristics of foods. This technique was not an instru-mental technique but involved a panel of people trained to assess texture. Nicot (1992) summarised all the practical aspects which have to be considered when
performing a sensory study with a trained panel. The experimental design depends on the nature of the product, the environmental factors which have to be controlled in the room where the tests are performed, the way the samples are presented to the panel and how they are encoded (Williams and Carter, 1977;
Dürr, 1979). There are many problems associated with the sampling of the fruit, such as variation within one fruit and between fruits of the same batch. More-over, there may be wide variability between the subjects who rate the samples.
The differences between human beings reflected, for instance, by the equipment they have available for the process of chewing, their neurophysiology for con-veying the information to the brain and their capacity for describing experiences to the investigator, should be taken into account or corrected for during the analy-ses of the data. Another source of variability is the response of the panellist and the method used by the investigator to elicit and record the response. Some indi-vidual differences are unavoidable while others to some extent are under the experimenter’s control.
In the framework of a European project (EU FLAIR CT95-0302) on meali-ness of fruits, a panel was trained at the Institute of Food Research (Reading, UK) and the IATA (Valencia, Spain) to assess mealiness in apples (Nicolaï et al., 1999). Different degrees of mealiness were induced by storing Granny Smith, Golden Delicious, Late Top Red, Cox Jonagold and Boskoop apples in air and 95% relative humidity at 20°C for variable times. A discussion session was held to select descriptors that would characterise the samples. Remarkably, mealiness was not one of the descriptors used by the trained panel as it was not a term they could comprehend. First the extent to which the peel influenced perceptions was evaluated. Removing the peel had some effect on attributes related to taste, but did not seem to affect the ratings of the texture-related attributes. It was decided to restrict further sensory work to peeled samples. The attribute scores observed for the texture attributes pulpy, granular, floury, juicy, hard and crispy for the dif-ferent cultivars and storage conditions demonstrated that these descriptors were used to describe different degrees of mealiness. Hence, mealiness was not per-ceived as a one-dimensional parameter but as an umbrella term which encom-passed the descriptors floury and granular. The latter attributes were found to be negatively correlated to attributes such as hardness, crispiness and juiciness (Nicolaï et al., 1999).
9.2.2 Consumer preference patterns
In contrast to a trained analytical panel, consumers often do not have a stan-dardised vocabulary to describe objectively what they are perceiving when assessing product attributes. Instead of describing their perceptions by means of specific product attributes, because of their limited vocabulary, they use hedo-nically based terms like ‘nice’ and ‘tasty’ to express their perceptions (Andani, 2000).
Andani (2000) studied whether consumers perceived mealiness in apples as a negative quality attribute, and whether their preference pattern leant more to
‘fresh’ than ‘mealy’ apples. The participants were given three apple cultivars (Cox’s, Boskoop and Jonagold) at three different stages of mealiness (fresh, mid-point and mealy). To obtain these stages the apples were stored in mealiness inducing conditions (20°C and ± 95% relative humidity, RH) for a certain period depending on the required mealiness level. Each of 150 subjects was asked to rate the apples for how much they liked the fruit on a nine-point hedonic box scale labelled from ‘dislike extremely’ to ‘like extremely’. To analyse and visu-alise the preference data structure, the preference mapping methodology was applied (Carroll, 1972; Greenhoff and MacFie, 1994). The multidimensional character of the preference mapping technique offers a number of advantages over univariate analysis algorithms. The information from each participant for all assessed products is taken into account in the analysis, the scores for products are not averaged over consumers, but each individual is represented on the map (Earthy, 1996). Hence, no information is lost by averaging, and natural segmen-tation of consumers over the map is illustrated (McEwan, 1988/9).
Based on this preference mapping methodology, the author observed a sepa-ration along the first preference dimension between Jonagold and Cox on the one hand and Boskoop on the other hand. Boskoop had a low consumer acceptance or preference level. The data suggested that preference was driven by dislike of Boskoop more so than liking of Cox and Jonagold. The same apples samples were tasted by the sensory panel to identify the specific product attributes causing the consumer preference segmentation. It was found that the dislike of Boskoop apples was caused by the ‘bitter’, ‘acid’ and ‘unripe’ flavour of the Boskoop variety, suggesting this dislike was more related to flavour than texture. Although less clearly than the cultivar (flavour) segmentation, the consumer preference pattern leant more to non-mealy apples, indicating that the consumers perceived mealiness as a negative quality attribute. Andani (2000) reported that more
‘mealy’ samples were perceived as having a ‘granular’ texture. Thus the results supported the hypothesis, which states that consumers would perceive mealiness in apples as a negative quality attribute, and show a greater liking for ‘fresh’
than ‘mealy’ fruit. For the same three cultivars, Jaeger et al. (1998) looked at cross-cultural differences between British and Danish consumers in relation to preferences for fresh and aged apples. The preference patterns were similar for British and Danish consumers and reflected no cross-cultural differences (Jaeger et al., 1998).
In a study among Spanish consumers living in Madrid it was found that the consumer in general sees mealiness as a negative characteristic (López et al., 1996). Flavour is regarded as more important than appearance. Men prefer more sweet apples while in general women prefer more acidic fruits. Young people also preferably eat more acidic fruits.
9.2.3 Repertory grid method
The repertory grid method is another technique to assess how consumers perceive product attributes like mealiness in apples. This technique is used to gather
consumer information about products at a level between the trained sensory panel and the consumer’s preference or acceptability judgement. Kelly (1955) was the first to use a repertory grid method. He developed the technique to iden-tify the constructs that people use to structure their perceptions of the social world. The subjects are asked to say in which way two stimuli are alike and different from a third. The process is repeated until the subject does not know any more new items. In 1981, Olsen (1981) first applied this technique to food acceptability. He added a second part to the method by asking the subjects to define a scale to measure the amount of each construct perceived in the objects. Hence, each person uses his own constructs and scales for evaluating the objects.
A repertory grid study was conducted among consumers of four different coun-tries (Belgium, UK, Spain and Denmark) and five different languages (Dutch, French, English, Spanish and Danish) (De Smedt, 2000; Andani, 2000). The par-ticipants were given apples (Cox’s, Boskoop and Jonagold) of three different mealiness stages (non-mealy, midpoint and mealy). The data in this study were analysed using generalised procustes analysis (GPA). GPA is a member of the family of methods that are concerned with the analysis of data arising from several individuals. The purpose is to know how the individuals differ and, equally, to what extent they may agree in their perceptions of the same phenom-ena. GPA is an empirical statistical technique which allows the investigator to relate in a multivariate space different sets of attributes or constructs generated by the different consumers with the tasted samples. It also deals with the problem of individual panellists who constantly under or over score an attribute (Dijksterhuis and Gower, 1991). Figure 9.1 gives a plot of the consensus solu-tion of the GPA. The first dimension separates the Boskoop apples from the other cultivars and runs from bottom right to top left. The second dimension runs from the top right to the bottom left and aligns well with the degree of mealiness. On the consensus plot, the distribution of the sample means for each consumer group around the global sample mean can be seen. It can be concluded that no one consumer group was significantly different from the other groups when describing their perception of the samples as the position of the groups around the sample is rather tight.
From this study it could be concluded that there is a consensus among differ-ent consumer groups in the way they perceive mealiness. However, the way dif-ferent consumers describe their perception is quite difdif-ferent. Flemish (Dutch speaking Belgians), Walloons (French speaking Belgians), Danes and Spaniards all use a translation of the word ‘mealy’. Apart from this, they all have their own attributes to describe mealiness. English consumers on the other hand do not use the term ‘mealy’. It is not a term they can comprehend. They will describe mealy apples as coarse, spongy, dry and crumbly. No clear difference was found between the Flemish and the Walloon consumers in Belgium in their ability to generate descriptors. Both groups generated approximately the same number of descrip-tors. The Flemish consumers used the mealiness category more widely than the Walloon consumers. In general, consumers from different countries perceive the
differences between the samples similarly, which means that there is a cross-cultural consensus with respect to the perception of mealiness.
9.2.4 Consumer expectations and acceptability
Consumers have prior expectations, supported by previous experience, about the quality attributes of a product (Deliza and MacFie, 1996). For fruits, these expec-tations are based to a large extent on the external fruit appearance, manual texture perception and aroma (Christensen, 1983; Cardello and Segars, 1989), which may be used by the consumer as a guide to freshness, ripeness, quality and variety (Richardson-Harman et al., 1998). Different expectation theories are proposed in the literature (Deliza and MacFie, 1996) to analyse the consumer’s expectations.
Experiments were organised both in the UK and in Spain to quantify which external features of the apple influence the expected perception of the sensory properties (Andani, 2000; Nicolaï et al., 1999). The features were skin colour, density and ‘texture’ to touch. The participants gave more weight to what they perceived ‘in mouth’ rather than the external features of the apple. From other studies, it was found that it was not possible to manipulate the subjects’ percep-tions. It was also confirmed by means of consumer studies that, at least in Spain, there clearly exists a market segment who prefer mealy apples. Andani (2000) studied the relation between gender and the importance of texture in apples. The
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Fig. 9.1 GPA consensus plot showing variation between the different consumer groups (GPA with isotropic scaling) for three apple cultivars (Cox, Jonagold and Boskoop) in three mealiness stages (1: fresh, 2: midpoint, 3: mealy). D: Danish, E: English, S: Spanish,
N: Dutch, F: French (source: Andani, 2000).
results suggested that texture is significantly more important to females (92%) than to males (61%). Up to 69% of the females rated texture to be ‘very impor-tant’ compared to 49% of the males. Neither sex judged the texture to be ‘not very important’, emphasising the importance of texture and, hence, mealiness, to the consumer.