12 Quality and consumer acceptability S.R. P.R. Durand. hP Foods Ltd 12.1 Introduction Quality is an essential feature that will lead the consumer to select or not any food product. With numerous food scares that have hit the food market in the UK and Europe(E. coli, BSE, genetically modified organisms-based products, dioxins in animal feed in belgium) consumers have become much more aware and therefore selective in their choice to food Quality takes many aspects from safety to nutrition, sensory characteristics to service qualities. Consumers integrate these concepts to decide which product to buy according to their own criteria. A safe product is an essential requirement but will never suffice to sell a product Consumers want an attractive product in terms of organoleptic properties at a price they consider appropriate. It should satisfy their needs in terms of service provided(e.g. convenience, ease of opening)and more and more related to specific nutritional needs (vitamins, functional ingredients, low calories, low salt). In summary, quality is the combination of features in a product which ensure customer satisfaction From this definition of quality, it can be seen that customers will repeat the purchase of a chilled product if they are satisfied by its sensory quality, in one word if they are pleasurable to eat. Our senses are extremely sensitive and sophisticated to scrutinise our outside world. For example, our sense of smell, although not as sensitive as some other animal species, can detect hundreds of different odours. The topic of the first and second sections will give an overview of the way we measure quality of chilled products using our senses. It will also show how using a pool of people trained in the detection and description of sensory qualities will give the ability to product developers and quality managers to develop the best product, every time. However, understandi
12.1 Introduction Quality is an essential feature that will lead the consumer to select or not any food product. With numerous food scares that have hit the food market in the UK and Europe (E. coli, BSE, genetically modified organisms-based products, dioxins in animal feed in Belgium) consumers have become much more aware and therefore selective in their choice to food. Quality takes many aspects from safety to nutrition, sensory characteristics to service qualities. Consumers integrate these concepts to decide which product to buy according to their own criteria. A safe product is an essential requirement but will never suffice to sell a product. Consumers want an attractive product in terms of organoleptic properties at a price they consider appropriate. It should satisfy their needs in terms of service provided (e.g. convenience, ease of opening) and more and more related to specific nutritional needs (vitamins, functional ingredients, low calories, low salt). In summary, quality is the combination of features in a product which ensure customer satisfaction. From this definition of quality, it can be seen that customers will repeat the purchase of a chilled product if they are satisfied by its sensory quality, in one word if they are pleasurable to eat. Our senses are extremely sensitive and sophisticated to scrutinise our outside world. For example, our sense of smell, although not as sensitive as some other animal species, can detect hundreds of different odours. The topic of the first and second sections will give an overview of the way we measure quality of chilled products using our senses. It will also show how using a pool of people trained in the detection and description of sensory qualities will give the ability to product developers and quality managers to develop the best product, every time. However, understanding 12 Quality and consumer acceptability S. R. P. R. Durand, HP Foods Ltd
342 Chilled foods using trained people will only tell you one side of the story; how is a product characterised? In an increasingly competitive market, food manufacturers have realised the eed to ask their existing and potential customers what they like and dislike through preference tests. This will form the second side of the story and the ction dedicated to consumer acceptability will provide an exhaustive list of preference tests used to understand liking patterns. The final section will foc on combining these two sets of information, subjective and objective, to develop consumer-driven specifications that will fulfil their expectations 12.2 What defines sensory quality? The sensory quality of a product can be divided into its appearance, smell, texture. flavour and also aftertaste 12.2.1 Appearance The appearance of a product is the first assessment that a consumer will undertake to define the quality of a chilled product. Many aspects of the visual component of a food product can be used to assess its quality. The size, the shape the distribution of pieces, the surface texture, the colour and the brightness are all determining factors to assess freshness and overall quality expectation. The dullness or sheen of the surface in red meat combined with the redness of the flesh are used by consumers to assess the freshness of meat products in supermarkets. In return, supermarkets use lighting and in some instance spraying thin layer of water to improve the visual quality of meat behind counters The appearance can be divided into optical and visual structure components The optical appearance is mainly related to colour, gloss and translucency. The visual structure is linked to the texture of the product, including particle size, smoothness and surface texture. Colour is probably the first and main characteristic that a customer will use to judge the quality of a chilled product as the deterioration of food is often linked to a colour change(Piggott 1988) Colour is also involved with a psychological dimension; red is associated with power, orange and yellow with excitement and cheerfulness. The food industry is therefore spending a considerable amount of resources on eye-catching properties. In particular, farmed salmon are fed with carotenoids to give them a pink/orange colour, further enhanced when smoked, which is considered to be a sign of quality and freshness in the mind of the consumer 12.2.2 Odour: type, intensity The smell of chilled food gives a good indication of the freshness and quality An odour is detected when volatiles are inhaled into the nasal cavity and make contact with the olfactory system. Our smelling system is more modest equipment than our vision system, detecting only 10,000 odours with 5 million
quality using trained people will only tell you one side of the story; how is a chilled product characterised? In an increasingly competitive market, food manufacturers have realised the need to ask their existing and potential customers what they like and dislike through preference tests. This will form the second side of the story and the section dedicated to consumer acceptability will provide an exhaustive list of preference tests used to understand liking patterns. The final section will focus on combining these two sets of information, subjective and objective, to develop consumer-driven specifications that will fulfil their expectations. 12.2 What defines sensory quality? The sensory quality of a product can be divided into its appearance, smell, texture, flavour and also aftertaste. 12.2.1 Appearance The appearance of a product is the first assessment that a consumer will undertake to define the quality of a chilled product. Many aspects of the visual component of a food product can be used to assess its quality. The size, the shape, the distribution of pieces, the surface texture, the colour and the brightness are all determining factors to assess freshness and overall quality expectation. The dullness or sheen of the surface in red meat combined with the redness of the flesh are used by consumers to assess the freshness of meat products in supermarkets. In return, supermarkets use lighting and in some instance spraying a thin layer of water to improve the visual quality of meat behind counters. The appearance can be divided into optical and visual structure components. The optical appearance is mainly related to colour, gloss and translucency. The visual structure is linked to the texture of the product, including particle size, smoothness and surface texture. Colour is probably the first and main characteristic that a customer will use to judge the quality of a chilled product, as the deterioration of food is often linked to a colour change (Piggott 1988). Colour is also involved with a psychological dimension; red is associated with power, orange and yellow with excitement and cheerfulness. The food industry is therefore spending a considerable amount of resources on eye-catching properties. In particular, farmed salmon are fed with carotenoids to give them a pink/orange colour, further enhanced when smoked, which is considered to be a sign of quality and freshness in the mind of the consumer. 12.2.2 Odour: type, intensity The smell of chilled food gives a good indication of the freshness and quality. An odour is detected when volatiles are inhaled into the nasal cavity and make contact with the olfactory system. Our smelling system is more modest equipment than our vision system, detecting only 10,000 odours with 5 million 342 Chilled foods
Quality and consumer acceptability 343 of colours with more than 100 million receptors (Meilgaard It is however highly efficient in the detection of spoilage, Irs or taint and often more sensitive and accurate than many sophisticated instruments. When cutting a piece of meat or fish, the level of freshness can be assessed by smell. Jorgensen et al.(1988)has shown a strong relationship between the detection of malodorous volatiles and the spoilage of chilled fish during shelf-life as detected by a pool of trained people 12.2.3 Flavour Flavour is possibly the essential sensory component used to measure the quality of chilled products. If the flavour is undesirable or does not correspond to expectations, the product will be rejected. Flavour is defined as the sum of perceptions perceived in the mouth in the back of the throat and the nose via the retro-nasal route(Piggott 1988). Flavour includes the primary tastes(salty, sweet, acidic and bitter) caused by soluble substances, sensation factors such as astringency, heat or cooling effects and the aroma perception caused by volatile lbstances. Quality criteria associated with flavour relate to the expression of an expected flavour and the intensity of it. 12.2. 4 Texture Texture can be defined as the sensory perception on the physical structure of a food product. During the handling and preparation of food, texture properties can be measured by visual evaluation and touch to identify its overall quality. A hard cheese over matured will look dry with a sensation of mouthdrying and roughness in the mouth. Cheese makers use an agreed methodology to define the quality of cheese in relation to its texture characteristics exture is a complex area of the evaluation of sensory quality, as described and classified in reviews by Bourne(1982) or Civille and Liska(1975). There are three different texture characteristics 1. The mechanical dimension is related to the reaction of the food to stress such as hardness, firmness, cohesiveness or chewiness, as measured by the muscles of the hand, fingers, lips, tongue or jaw. 2. The geometrical dimension is related to the arrangement of the physical components of a product such as size, shape, fibrousness, particles or lumps 3. The surface dimension is related to the moisture and fat content of a product and how they are released during a chewing process A large part of enjoying a meat product involves its texture quality and consumers are well aware of words such as tenderness chewiness or toughnes Slaughtering methods and storage conditions have an influence on the texture quality of fresh fish as described by Love(1988). For pastry-based products such as quiche or pizza, texture is the criterion that influences and therefore best
receptors, versus millions of colours with more than 100 million receptors (Meilgaard et al. 1987). It is however highly efficient in the detection of spoilage, off-odours or taint and often more sensitive and accurate than many sophisticated instruments. When cutting a piece of meat or fish, the level of freshness can be assessed by smell. Jorgensen et al. (1988) has shown a strong relationship between the detection of malodorous volatiles and the spoilage of chilled fish during shelf-life as detected by a pool of trained people. 12.2.3 Flavour Flavour is possibly the essential sensory component used to measure the quality of chilled products. If the flavour is undesirable or does not correspond to expectations, the product will be rejected. Flavour is defined as the sum of perceptions perceived in the mouth in the back of the throat and the nose via the retro-nasal route (Piggott 1988). Flavour includes the primary tastes (salty, sweet, acidic and bitter) caused by soluble substances, sensation factors such as astringency, heat or cooling effects and the aroma perception caused by volatile substances. Quality criteria associated with flavour relate to the expression of an expected flavour and the intensity of it. 12.2.4 Texture Texture can be defined as the sensory perception on the physical structure of a food product. During the handling and preparation of food, texture properties can be measured by visual evaluation and touch to identify its overall quality. A hard cheese over matured will look dry with a sensation of mouthdrying and roughness in the mouth. Cheese makers use an agreed methodology to define the quality of cheese in relation to its texture characteristics. Texture is a complex area of the evaluation of sensory quality, as described and classified in reviews by Bourne (1982) or Civille and Liska (1975). There are three different texture characteristics. 1. The mechanical dimension is related to the reaction of the food to stress, such as hardness, firmness, cohesiveness or chewiness, as measured by the muscles of the hand, fingers, lips, tongue or jaw. 2. The geometrical dimension is related to the arrangement of the physical components of a product such as size, shape, fibrousness, particles or lumps. 3. The surface dimension is related to the moisture and fat content of a product and how they are released during a chewing process. A large part of enjoying a meat product involves its texture quality and consumers are well aware of words such as tenderness, chewiness or toughness. Slaughtering methods and storage conditions have an influence on the texture quality of fresh fish as described by Love (1988). For pastry-based products such as quiche or pizza, texture is the criterion that influences and therefore best Quality and consumer acceptability 343
344 Chilled foods its quality. The pastry tends to adsorb moistness from the other ents to become soggy prior to any development of off-flavour 12.3 Sensory evaluation techniques From the previous section, it is obvious that any test to measure quality of chilled food should involve the use of human subjects Sensory evaluation is a scientific discipline involved with the measure study and interpretation of responses to food properties as perceived by the senses of sight, smell, taste, touch and hearing(IFT 1975) ensory assessment is done either by a small pool of people( typically 8 to 30 people)who have received some training, known asobjective testing or by a larger pool of consumers who give their own opinion on a product or range of products without any prior training. This is known as'subjective testing. The objective and hypotheses defined in any project brief will determine the choice of the type of valuation to be performed, and the type of panel, the test and the overall design of the experiment. Carpenter et al.(2000) defines in detail the criteria to consider Objective testing is carried out by qualified and trained people and can be used for discriminating and describing differences between chilled products This pool of people, or sensory panel, can be employees of a company or a dedicated workforce. After initial recruitment to measure any sensory impairment such as anosmia (impairment in the sense of smell) or ageusia (impairment in the sense of taste), the panel members take part in an extensive and gradually more difficult training schedule in order to describe, discriminate and evaluate any subtle differences between the products under investigation Many sensory professionals have published training schedules for general aining sessions Jellinek 1985) to more specific and precise sensory programmes( Civille and Szczesniak 1975). Tests used to characterise food properties by sensory experts can be either discriminative or descriptive 12.3.1 Discriminative tests These types of tests are used when it is required to identify if any difference exists between two or more products. It might be required to change an ingredient supplier for cost reduction or quality reasons and the brief is to confirm that the overall flavour, texture or appearance is not affected. It is more cost effective to ask a highly trained panel of experts in their field to assess any difference rather than asking consumers. The tests are very sensitive to any direct most commonly used discriminative test. In this test, panellists are given three mples, in a pre-determined order, one is different from the other two. They are asked to identify the odd sample(BS 5929: part 5, 1988). For example, a ham manufacturer might want to assess the effectiveness of a controlled atmosphere packaging against a present system without changing the overall sensory
predicts its quality. The pastry tends to adsorb moistness from the other components to become soggy prior to any development of off-flavour. 12.3 Sensory evaluation techniques From the previous section, it is obvious that any test to measure quality of chilled food should involve the use of human subjects. Sensory evaluation is a scientific discipline involved with the measure, study and interpretation of responses to food properties as perceived by the senses of sight, smell, taste, touch and hearing (IFT 1975). Sensory assessment is done either by a small pool of people (typically 8 to 30 people) who have received some training, known as ‘objective testing’ or by a larger pool of consumers who give their own opinion on a product or range of products without any prior training. This is known as ‘subjective testing’. The objective and hypotheses defined in any project brief will determine the choice of the type of evaluation to be performed, and the type of panel, the test and the overall design of the experiment. Carpenter et al. (2000) defines in detail the criteria to consider. Objective testing is carried out by qualified and trained people and can be used for discriminating and describing differences between chilled products. This pool of people, or sensory panel, can be employees of a company or a dedicated workforce. After initial recruitment to measure any sensory impairment such as anosmia (impairment in the sense of smell) or ageusia (impairment in the sense of taste), the panel members take part in an extensive and gradually more difficult training schedule in order to describe, discriminate and evaluate any subtle differences between the products under investigation. Many sensory professionals have published training schedules for general training sessions (Jellinek 1985) to more specific and precise sensory programmes (Civille and Szczesniak 1975). Tests used to characterise food properties by sensory experts can be either discriminative or descriptive. 12.3.1 Discriminative tests These types of tests are used when it is required to identify if any difference exists between two or more products. It might be required to change an ingredient supplier for cost reduction or quality reasons and the brief is to confirm that the overall flavour, texture or appearance is not affected. It is more cost effective to ask a highly trained panel of experts in their field to assess any difference rather than asking consumers. The tests are very sensitive to any sensory variation as they involve a direct comparison. The triangle test is the most commonly used discriminative test. In this test, panellists are given three samples, in a pre-determined order, one is different from the other two. They are asked to identify the odd sample (BS 5929: part 5, 1988). For example, a ham manufacturer might want to assess the effectiveness of a controlled atmosphere packaging against a present system without changing the overall sensory 344 Chilled foods
Quality and consumer acceptability 345 properties over time. The test sensitivity can allow expensive capital expenditure requirements to be made with a high level of confidence When more than two products are compared, ranking tests comparison tests are used. Typically, a ranking test is used when no control is available or required and assessors are asked to rank products in order of intensity for a specific sensory characteristic. A multiple comparison test is used when a control sample is used as an anchor point and assessors are asked to evaluate the intensity of the difference if any Other tests might be required from time to time to evaluate the sensitivity of specific compounds and/or chemicals. These tests are important in taint evaluation or the detection of materials difficult to assess. Threshold tests are used to detect at which concentration level, a compound can be detected Dilution technique determines the smallest amount of compound that can be detected in a product. Gillette et al. (1984)use this technique to assess the level of heat in red peppers 12.3.2 Descriptive tests These tests are used to identify sensory characteristics of a chilled product and quantify them. Panellists are selected on their ability to describe and discriminate between samples. They are presented with variants of the product and asked to describe them. After a period dedicated to confirm and define agreed terms and scale, the panel is then presented with the samples, one at a time and asked to give a score. Stone et al. (1974) has described in detail one of these descriptive techniques calledquantitative descriptive analysis. Results are analysed by means of univariate and multivariate analyses. Analysis of variance(O"Mahony 1986) is used to measure any difference between samples for each attribute Principal component analysis is a technique used to reduce the amount of dimension or sensory terms into a manageable format, usually two or three dimensions. Procustes analysis is mainly used for the assessment of individuals performance and efficiency(Arnold and Williams 1986). Graphs are often used to summarise the results into condensed and meaningful information. Spider graphs(see Fig. 12.1), give a general overview of sensory differences by th overall shape of each product, providing an individual product fingerprint. Other sensory techniques have emerged in recent years in the evaluation of food quality by sensory evaluation. In particular, the time-intensity technique takes into consideration the temporal dimension of tasting behaviour( Cliff et al. 1993). This technique is particularly interesting for the assessment of spicy oroducts or for primary taste evaluation, such as sweet sensation in artificially sweetened drinks and is used by Matysiak and Noble(1991) Figure 12.1 shows an overview of how four samples of chilled smoked salmon differ in sensory terms from one another, using a spider graph. For each attribute, the samples are more intense away from the centre. In particular salmon d had a more orangy colour and sample F had the least moist surface Sample I was the least salty and smoky produc
properties over time. The test sensitivity can allow expensive capital expenditure requirements to be made with a high level of confidence. When more than two products are compared, ranking tests or multiple comparison tests are used. Typically, a ranking test is used when no control is available or required and assessors are asked to rank products in order of intensity for a specific sensory characteristic. A multiple comparison test is used when a control sample is used as an anchor point and assessors are asked to evaluate the intensity of the difference if any. Other tests might be required from time to time to evaluate the sensitivity of specific compounds and/or chemicals. These tests are important in taint evaluation or the detection of materials difficult to assess. Threshold tests are used to detect at which concentration level, a compound can be detected. Dilution technique determines the smallest amount of compound that can be detected in a product. Gillette et al. (1984) use this technique to assess the level of heat in red peppers. 12.3.2 Descriptive tests These tests are used to identify sensory characteristics of a chilled product and to quantify them. Panellists are selected on their ability to describe and discriminate between samples. They are presented with variants of the product and asked to describe them. After a period dedicated to confirm and define agreed terms and scale, the panel is then presented with the samples, one at a time and asked to give a score. Stone et al. (1974) has described in detail one of these descriptive techniques called ‘quantitative descriptive analysis’. Results are analysed by means of univariate and multivariate analyses. Analysis of variance (O’Mahony 1986) is used to measure any difference between samples for each attribute. Principal component analysis is a technique used to reduce the amount of dimension or sensory terms into a manageable format, usually two or three dimensions. Procustes analysis is mainly used for the assessment of individuals’ performance and efficiency (Arnold and Williams 1986). Graphs are often used to summarise the results into condensed and meaningful information. Spider graphs (see Fig. 12.1), give a general overview of sensory differences by the overall shape of each product, providing an individual product fingerprint. Other sensory techniques have emerged in recent years in the evaluation of food quality by sensory evaluation. In particular, the time-intensity technique takes into consideration the temporal dimension of tasting behaviour (Cliff et al., 1993). This technique is particularly interesting for the assessment of spicy products or for primary taste evaluation, such as sweet sensation in artificially sweetened drinks and is used by Matysiak and Noble (1991). Figure 12.1 shows an overview of how four samples of chilled smoked salmon differ in sensory terms from one another, using a spider graph. For each attribute, the samples are more intense away from the centre. In particular, salmon D had a more orangy colour and sample F had the least moist surface. Sample I was the least salty and smoky product. Quality and consumer acceptability 345