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
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
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
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
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
12.3.3 Use of a trained panel for measurement of sensory quality
Taint and off-flavours
In foods these are a major threat to manufacturers and retailers, as it can become
extremely damaging and costly. A tainted product reaching the consumer can
create problems for the food producer or retailer much more damaging than the
complaint itself. Direct costs such as loss of production, cleaning of factory,
damaged commercial relationships between suppliers, manufacturers and
retailers (e.g. de-listing by retailers), litigation proceedings and even factory
shutdown may occur. Other more substantial financial implications may arise,
such as loss of customer goodwill and damaged brand image may manifest
themselves through lower sales and loss of market share. Taint and off-flavours
are caused by the presence of a chemical at very low concentration in a food
product, usually a volatile organic compound, which imparts a flavour
unacceptable to the consumer. Taint is an unpleasant odour or flavour imparted
to food through external sources and off-flavour (or off-odour) is an unpleasant
flavour (or odour) to food through internal changes, such as enzymatic or
microbial activities. Unlimited sources of taint and off-flavours exist making it
extremely difficult for manufacturers or retailers to control. Raw materials,
packaging materials, factory environment (e.g. flooring, paint, cleaning agents),
microbial spoilage are all known sources of taint and off-flavour. Water can also
be a major source of contamination. It may contain chlorophenols or
chloroanisol; this accounts for the largest number of known cases of taint.
Sensory evaluation coupled with the use of sophisticated apparatus such as Gas
Chromatography Mass Spectrometry (GCMS) is required to evaluate and
identify the taint and its source. Such a combination was used by Farmer et al.
(1995) to evaluate off-flavours in wild and farmed Atlantic salmon. The author
found that the main difference was between wild salmon caught in rivers and
those from the sea rather than between wild and farmed salmon. River-caught
Fig. 12.1 Differences in sensory profile between four different chilled smoked salmon.
346 Chilled foods
wild salmon showed enhanced earthy flavour and odour notes, with 2-
methylisoborneol and geosmin being the major compounds involved.
Sensory monitoring of quality
The quality of chilled products should be consistent during production and food
companies are using various techniques to ensure food quality conformity.
These techniques have a common ground in that one or more parameters are
measured against an agreed quality specification. For example, pH, salt or
sugar levels might be measured to ensure no drift to the final composition of a
product. These measurements, although important in their own right, will not
allow the definition of flavour characteristic or texture quality. Sensory
evaluation is therefore used to ensure integrity of a series of set quality
parameters. The stages involved in setting up such routine sensory quality
monitoring include the establishment of a product standard that represents the
customer requirements. The product standard is translated into key sensory
characteristics. The second stage involves the definition of acceptance ranges
for each parameter, taking into account commercial risks against consumer
loyalty. In the case of sensory quality assessment, a panel is selected and
trained to recognise products that fall within and outside the acceptable range
for each sensory parameter. It is essential that employees involved are
committed to quality and that more than one assessor is used for each
assessment to ensure precision and reliability. Standard procedures are set up
and may include go/no-go quality rating or grading such as the CCFRA frozen
and canned products specification (Rodway et al. 1999), difference test or more
precise but lengthy descriptive analysis.
A specification sheet that includes acceptance ranges (Table 12.1) and a
quality monitoring chart for a flavour parameter (Fig. 12.2) are provided as an
example for the assessment of the quality of a chilled apple pie. The members of
a panel are asked individually to assess each sample for each attribute using a
10-point scale, from not present to very strong. A consensus score or mean score
is then entered into the collation sheet showing the non-acceptable range for
each attribute (shaded areas). One or more scores outside the non-shaded area
indicate a product that does not meet quality criteria and further investigation is
required to confirm the findings. Figure 12.2 displays the trend of the change of
strength of flavour characteristic for a chilled apple pie product over a
production time span of six months. For each production batch evaluated, a
score outside the two specification limits is considered as unacceptable. The
strength of flavour varies considerably over this production period and an
investigation should be organised to understand reasons for this variability and
how to correct it.
Storage effect/definition of shelf-life
Shelf-life of chilled products can be defined as the period between manufacture
and consumption during which the product is in an acceptable condition, both in
Quality and consumer acceptability 347
terms of safety and quality. During storage, a chilled product will undergo
changes linked to chemical, microbiological and physical reactions. It has been
shown that for many products, sensory evaluation has proven to be the most
sensitive technique to assess these changes. Similar techniques to those
described for quality monitoring can be applied to sensory shelf-life evaluation.
Claasen and Lawless (1992) found that sensory analysis by descriptive
technique to measure the end of life of liquid milk was more sensitive than
more traditional analytical techniques.
Table 12.1 Specification sheet for collation of data for flavour and texture of chilled
apple pie
Flavour 0 123456789
Strength of apple
Sweetness
Acidic
Oily/fatty pastry
Off-flavours
Texture
Doughiness of pastry
Crispness of apple
Greasy mouthfeel
Fig. 12.2 Quality monitoring over a six month period for strength of flavour of a chilled
apple pie.
348 Chilled foods
Strength apple flavor
Upper specification
Lower specification
12.4 Determining consumer acceptability
There is no doubt that the taste of food is an essential criterion for the
acceptability of a product by the consumer. The best marketing and advertising
campaign for a new chilled product might convince a consumer to buy it for the
first time. However, should this product not attain expected values, the
consumer will not purchase the product again. Although taste undoubtedly plays
an important part in food choice, it is not the only essential element. Attitudes,
belief, nutritional awareness, brand and image, convenience, price and other
socio-cultural aspects (e.g. religion, education) are all important criteria the
market researcher will take into account. Although expert sensory panels are
useful to understand the sensory properties of a chilled product, when consumer
acceptability and behaviour is concerned, tests involving consumers must take
place.
12.4.1 On-site trials for screening purposes
These tests are used by many food companies to assess the sensory quality of
their products, including products under development versus competitors’ ones.
These tests are very useful for the screening of several samples prior to a full-
scale assessment, in order to reduce costs and optimise tight deadlines. A
minimum number of consumers are required in order to be confident of the
result. It is advisable to involve at least 50 employees. The main negative aspect
to this type of assessment is the knowledge employees have acquired working in
contact with the product and inevitably biases may occur in their choice. The
researcher should minimise these biases hiding recognisable clues when
possible.
12.4.2 Home placement tests
These tests imply that consumers are asked to try and assess one or more
products while at home. The advantage is that the assessment is carried out
within a normal life situation and is therefore more likely to represent the true
behaviour and liking for a product. It also has the advantage of getting an
opinion from the whole family rather than just one individual. However, the
drawback is that the control of the response is poor. In particular, different
cooking procedures and processes may be used by different consumers, making
a direct comparison more complicated. Also, when two or more products are
assessed, the cooking procedure between products or the time interval between
cooking and eating may differ.
In a home location test, samples may be delivered to homes or collected at a
central location. After a certain period, the researcher will interview the
consumer by phone or face-to-face by calling in. Questions such as liking for
each product by each member of the household, type of cooking and serving,
expectation, likelihood of purchase may be asked.
Quality and consumer acceptability 349
12.4.3 Central location or hall tests
When a consumer test must be controlled more closely, or the number of
products exceeds two or three, a central location test in busy town centres is
preferred. Interviewers stop potential participants and ask specific questions to
ensure that they meet agreed criteria, i.e. that they fall within set quotas and to
ensure their willingness to participate. This test tends to be preferred by food
companies for being cheaper to run than home location tests. Hedonic scales are
usually used to measure liking of products. Consumers are asked their liking for
each product and also the preferred sample overall. The objective of the research
will dictate the type of samples to be assessed and the questions asked.
12.4.4 Food choice and attitude
The above techniques all use hedonic scales that mainly reflect the preference
for the product. However, when one is interested in the reasons for choosing
certain foods, it is important to encompass other components to determine
attitude towards foods. In particular, the cognitive and intention components.
Many researchers have tried to incorporate more than one factor to explain what
dictates choice. When consumers want to treat themselves to a high-quality
piece of meat, they may be more inclined to go to a local butcher and select,
often after discussion and advice, a quality sirloin steak.
The experience of buying and the context in which it is carried out becomes
an integral part of the decision process and choice. Lange (1999) studied how
name and packaging information could affect orange juice liking under
economical constraint. The author observed differences between hedonic
responses under blind conditions when various information and economical
constraints were given. Other researchers have investigated the influence of
health and nutrition information on liking (Ka¨hko¨nen and Tuorila 1995).
Contextual analysis has been extensively studied by Schutz (1994) to identify
how, when, where and by whom specific food products are eaten.
12.4.5 Qualitative research
Qualitative research is carried out when the objective of the study is to understand
behaviour and attitude rather than preference, although a combination of both is
often considered. Focus groups and individual interviews are two types of
qualitative techniques. In a focus group test, eight to ten consumers are recruited
and asked to participate in a discussion around a specific topic. To manage such a
group, a moderator is used who leads the discussion using specific elicitation
techniques to gain information related to the topic. In particular, it is useful to use
open-ended questions and probing questions to get the most useful information
from the group. A carefully prepared questioning plan is used by the moderator to
guide the discussion towards the main areas of interest.
In a recent study, a focus group technique was used to investigate whether a
new concept of pre-cooked bacon would succeed in the market-place. Reactions
350 Chilled foods
to the idea, the product and various packaging formats formed the basis of the
question guide. Convenience and healthiness were found to be the main aspects
that would attract the consumer to this new concept. In particular, the issue was
not whether bacon was healthy but rather the cooking method used, e.g. frying
...‘anything’s bad if you fry it’. Also, a microwavable bacon that would retain
its sensory characteristics, i.e. crispness, was appealing to the housewives in
particular.‘I spend half my time in the kitchen and I think that’s wonderful’.
Individual interviews are used when topics are more sensitive or when no
group interaction is either wanted or needed. Various elicitation techniques are
used, often similar to those used for focus groups. One technique that is used
mainly in an interview environment is the Repertory Grid Method. Objects
under study are arranged into groups of three, such that each object appears at
least once and one object is carried over to the next trio. Two of these three
objects are similar according to the criterion defined by the researcher and
different from the last object. Each interviewee is asked to describe how one
object differs from the other two. Scaling has sometimes been used to assess the
level of difference or similarity for each consumer and each descriptor (Gains
1994).
12.5 Future trends and conclusion
Better understanding of consumer needs and expectations is an essential aspect
to build consumer loyalty and generate new custom. This chapter has shown that
both sensory and consumer assessments are required to fully understand
consumer behaviour. It has recently emerged from researchers and also food
companies that the use of an integrated approach to product quality and new
product development lead to sustainable market success. Consumer-driven
specification becomes very much a current trend in the food industry. After
years of production-driven specification, food companies have realised that
customer complaints increase while loyalty does not. The potential of consumer
input into the development of food quality specifications has been described by
McEwan (1999) to relate sensory characteristics (as defined by a trained panel)
and the acceptability range as defined by the consumer. The research involved
canned grapefruit, and it was shown that the main deterrent to quality
acceptability was found to be any physical defect that was perceived to have a
negative effect on the texture and flavour. On the other hand, ragged edges and
broken segments were thought to have less adverse effects than previously
thought by the industry. Bech et al. (1997) has put in place an overall consumer-
driven quality tool, House of Quality, where consumer needs are translated into
measurable sensory attributes using frozen peas as a vehicle for the
demonstration. These principles can be applied to chilled foods.
Consumer integration at an early stage of product development is becoming
widely spread amongst food manufacturers, reducing time and cost, often related
to product failure when rejected at first glance by the consumer. In the UK, it is
Quality and consumer acceptability 351
estimated that 90% of new products introduced to the market each year will be
de-listed from the retailers after six months on the shelves.
New and exciting techniques have seen great potential in recent years. In
particular, preference mapping used to relate sensory data to consumer acceptability
has proved very useful to both marketing and product development teams alike
(Risvik et al. 1997). This technique allows researchers to focus more closely to the
optimum product from a sensory point of view as defined by the consumer.
Major food scares have had in recent years a huge and detrimental effect on
food acceptability, and in particular beef and GMO-related products. Consumers
have made their voice heard and this has resulted in major and essential policies
developed by governments. Food manufacturers have realised the importance of
understanding consumer behaviour better and identifying the mechanisms for
food choice and acceptability. Traceability is becoming a very hot topic for food
manufacturers and retailers. The integration of total quality systems and closer
control is being put in place in ever growing international and complex markets
(see Chapter 15).
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