Sensory testing, consumer preference and market price of foods, especially for low-income consumers with minimal education

 

NRI experience includes:

 

1. Expert practical knowledge of sensory-testing and consumer-preference studies and techniques;
2. Expertise in working with rural and urban consumers (with various languages and levels of education) in developing countries worldwide;
3. Providing advice on product price in relation to consumer acceptance and affordability;
4. Working with adult and child consumers (under ethical codes of practice);
5. Statistical analysis of sensory-testing and consumer-preference data;
6. Provision of customized training programmes in sensory testing, consumer testing and methods of analysis;

 

Consumer-acceptance studies in developing countries - working with the most vulnerable consumers on the lowest incomes - are still relatively under-reported.  Programmes seeking to introduce new products, and those who are involved in their promotion and marketing, may require knowledge about consumer acceptance and sensory testing in order to ensure these programmes are more effective.  Scientists at NRI have undertaken advisory work and research in these areas worldwide for some 30 years on behalf of government departments and international agencies.  Examples of our work include consumer acceptance of sweet potato in Tanzania, cassava products in Nigeria, rice in Ghana, sorghum pastes in Tanzania and Zimbabwe, peanut butters in Zimbabwe, tea in Malawi and cocoa in Ghana.  This has involved interviewing over 2600 consumers in these countries.  For more information about our experience please click here.

 

If you would like more information please contact:

 

Keith Tomlins, Reader in Food Safety and Quality
Natural Resources Institute
University of Greenwich
Central Avenue
Chatham Maritime
Kent
Tel: +44 1634 883626
Fax: +44 1634 883567
Email: k.i.tomlins@gre.ac.uk

 

For information about NRI publications in sensory and consumer testing click here.

 

 

Sensory and consumer studies that NRI has been involved in include:

• Acceptability of orange-fleshed sweet potato by school children and mothers with pre-school children in Tanzania
• Acceptance of sweet potato in Tanzania: variation with cultivar, location and season
• Variation in sensory qualities of sweet potato during storage under tropical conditions
• Acceptability of parboiled rice (raw and cooked) in Ghana
• Acceptability, affordability and price of rice in Ghana
• Consumer acceptance of fufu flours and pastes in Nigeria
• Consumer acceptance of stiff porridges made from mixtures of sorghum, maize and cassava in Tanzania
• Consumer acceptance of stiff porridges made from mixtures of sorghum and maize in Zimbabwe
• Consumer acceptance of peanut butters in Zimbabwe
• Role of sensory evaluation during the manufacture of black tea in Malawi 
• Comparison of neural networks and statistical methods for classifying black teas
• Survey of cocoa fermentation on-farm in Ghana

Sweet potato

Acceptability of orange-fleshed sweet potato by school children and mothers with pre-school children in Tanzania.  Reducing vitamin A deficiency in Africa is a major priority, and orange-fleshed sweet potato may contribute to the solution. Pre-school children are particularly vulnerable to vitamin A deficiency.  Pregnant women and nursing mothers are another group who would benefit greatly from more vitamin A in their diet.  However, rural communities in Africa are thought to be cautious about accepting foods substantially different in colour and taste from those they are used to. This was the problem addressed in this research.  This study involved 94 school children and 59 mothers with pre-school children in the Lake Zone of Tanzania. Both groups generally preferred orange-fleshed cultivars to white ones. The mothers liked the orange-fleshed sweet potato more than the school-aged children did. This was encouraging, because foods liked by mothers are more likely to be offered to their children. The majority found the orange-fleshed varieties acceptable, but a small minority did not. The acceptance of the orange-fleshed cultivars showed that low-income rural communities are open to accepting new foods in such circumstances. Related Publications

 

Acceptance of sweet potato in Tanzania: variation with cultivar, location and season.  Sweet potato is an important staple crop in East Africa with great potential for the introduction of improved cultivars, but little is known about which sensory characteristics are desirable.  Over a two-year period, 600 consumers were interviewed at three locations (urban and rural) in the Lake Zone of Tanzania, and consumer preferences among 14 locally-available cultivars of sweet potato (in cooked form) were evaluated.  A simple questionnaire based on consumer’s first-choice preference was used because many of the interviewees had received minimal education.   A trained sensory panel profiled the cooked sweet potato samples enabling comparisons between preference, location and season.   Cluster analysis based on the sensory attributes was used to classify the cultivars into groups: some cultivars were consistently preferred over the two-year period while others were not.  The location where the cultivars were grown also influenced preference. Stepwise regression indicated that the most discriminating sensory attributes were starch and stickiness.  Target levels based on the mean intensity scores of these attributes were suggested as criteria for screening new cultivars. Related Publications

 

Variation in sensory qualities of sweet potato during storage under tropical conditions.   Five sweet potato cultivars were analysed for their sensory characteristics, and for the changes in these during storage under tropical conditions. The results suggested that differences between the sweet potato cultivars were mainly determined by textural components. Storage affected the sweet and chestnutty characteristics. Overall the changes during storage were less significant than the differences between the cultivars. Related Publications

Rice

Acceptability of parboiled rice (raw and cooked) in Ghana. Parboiled rice produced in Ghana is of poor quality and is being overtaken by imported rice. This study sought to investigate consumer preference and relate sensory attributes to consumer acceptability. A total of 300 consumers in urban centres in Ghana assessed parboiled long-grain rice in both the uncooked and cooked forms.  In the uncooked form, most consumers preferred the imported parboiled rice to that produced locally. Acceptability was influenced by location and gender. Individual preferences of consumers varied, and four different consumer consumer groups were identified on the basis of similarity of preferences. Regression models to predict consumer preference from the sensory panel scores were based on either brown colour of the cooked rice or unshelled paddy in the uncooked form, but they were not valid for all consumers. The study assisted producers in the development of products that looked good at the market and also tasted good, and that could be applied in different locations in Ghana. Related Publications

 

Acceptability, affordability and price of rice in Ghana. Small-scale producers in northern Ghana wanted to assess the acceptability and price of a prototype parboiled rice (PPR) that was targeted at urban consumers in Accra.  The PPR was evaluated in relation to three local samples and a high-value imported one. The PPR was acceptable and the market price suggested by consumers was influenced by both affordability and acceptability. Acceptance scores suggested a higher potential price for the PPR: however, consumers with different income levels discounted the prototype rice to an extent that depended on their assessment of affordability. Acceptability by consumers was related to rice consumption and purchasing behaviour, whereas affordability was associated with income, gender and quality perception. Low affordability groups knew the least about the benefits of rice. Related Publications

Cassava products

Consumer acceptance of fufu flours and pastes in Nigeria. Fufu is a fermented cassava product consumed in Nigeria and is available as pastes or flours.  A new fufu paste product had been developed that produced less environmental waste during processing.  Descriptive sensory profiles of six selected samples of flours and pastes demonstrated distinct differences in sensory profiles.  They were evaluated for consumer acceptance at three demographic locations: Lagos (n=91), Ibadan (n=121) and Abeokuta (n=99).  Fufu made from the new paste that produces less environmental waste had the highest acceptance scores, followed by flour and paste made by the traditional method, and finally three other flours (two commercially-purchased ones and one made from the paste that uses less environmental wate).  Acceptance did not differ between the three locations.  Three distinct consumer groups were identified and the number of consumers in these groups differed between the locations.  Internal preference mapping indicated that consumers associated the flours with sensory attributes such as sticky texture and raw cassava odour, while pastes were associated with soft texture, and shiny and creamy appearance. Correlations between consumer acceptance scores and sensory scores appeared to be non-linear for many attributes.  If this is confirmed, it suggests that processors need to ensure tight control of the production process. Related Publications

Sorghum and maize

Consumer acceptance of stiff porridges made from mixtures of sorghum, maize and cassava in Tanzania. Stiff porridges (ugali) based on various proportions of sorghum, maize and cassava flour were evaluated by a sensory panel, and this was followed by consumer testing by 200 consumers in two regions of the Lake Zone of Tanzania.  The project objective was to identify constraints to the increased utilization of sorghum and millets.

 

Consumer acceptance of stiff porridges made from mixtures of sorghum and maize in Zimbabwe. A sensory panel discriminated between 12 sorghum stiff pastes (sadza).  The sorghums had widely different sensory characteristics.

Peanut butters

Consumer acceptance of peanut butters in Zimbabwe.  Low-income rural producers of peanut butter required more information about consumer preferences for their product, in order to increase their market access.   Peanut butters were assessed in relation to different roasting times and shelf-life.  Consumer acceptance studies indicated two optimal roasting times: these were associated with distinct peanut flavour profiles. During the shelf-life study of six selected butters, consumer acceptability did not alter.  Sensory testing, however, was more sensitive to product changes: sensory attributes that varied were sticky texture, stale odour and sweetness. Related Publications

Tea

Role of sensory evaluation during the manufacture of black tea in Malawi. During a major study of the quality of black tea in Malawi, particular attention was paid to the role of sensory evaluation in quality control during manufacture. The impacts of internal factors (e.g. order of tasting of samples) and external factors (e.g. the design of the tasting facilities) on the reliability of taste-testing were analysed. Guidelines were developed for the setting up of tea-tasting panels and the improvement of information from existing panels. Best-practice recommendations were published for reliable and consistent quality-control by taste panels in tea factories in Malawi and elsewhere in Africa. Related Publications

 

Comparison of neural networks and statistical methods for classifying black teas. Neural network and statistical methods were compared for their effectiveness in predicting the origin and quality of black teas from sensory and chromatographic data. Both methods had similar accuracies in classifying the origin of black teas from their phenolic composition. Neural networks were less accurate than stepwise multiple regressions as a model for predicting score and price of black teas from their chemical composition and sensory attributes. The accuracy improved and the training time was reduced when training variables chosen by stepwise multiple regressions were selected. An advantage of the neural network model is that a single model could predict several parameters simultaneously. Related Publications

Cocoa

Survey of cocoa fermentation on-farm in Ghana. The influence of fermentation practices on quality was assessed by a survey of 56 cocoa farms in Ghana. Variations in the frequency of turning of the ferments were noted in relation to cocoa-producing region and cultivar. Sensory evaluation of chocolate samples made from the cocoa beans indicated that short pod-storage and fermentation with a single turn after three days produced the most acceptable cocoa. The acceptability varied by region, with the Eastern region producing the most acceptable cocoa. A composite sample was average in terms of its sensory characteristics, supporting the concept that blending facilitates the balanced flavour characteristic of Ghana cocoa. Related Publications

Related Publications

NRI publications in sensory and consumer testing

 

Tomlins, K., Ndunguru, G., Stambul, K., Joshua, N., Ngendello, T., Rwiza, E., Amour, R., Ramadhani, B., Kapande, A. and Westby, A. (2007) Sensory evaluation and consumer acceptability of pale-fleshed and orange-fleshed sweetpotato by school children and mothers with preschool children. Journal of the Science of Food and Agriculture (in press).

 

Tomlins, K., Manful, J., Gayin, J., Kudjawu, B. and Tamakloe, I. (2007) Study of sensory evaluation, consumer acceptability, affordability and market price of rice. Journal of the Science of Food and Agriculture 87: 1564-1575.

 

Tomlins, K., Sanni, L., Oyewole, O., Dipeolu, A., Ayinde, I., Adebayo, K. and Westby, A. (2007) Consumer acceptability and sensory evaluation of a fermented cassava product (Nigerian fufu). Journal of the Science of Food and Agriculture 87: 1949-1956.

 

Tomlins, K., Rukuni, T., Mutungamiri, A., Mandeya, S. and Swetman, A. (2007) Effect of varying roasting time and shelf-life on sensory testing and consumer acceptability of peanut butters in southern Africa. Tropical Science (submitted)

 

Tomlins, K., Manful, J. T., Larwer, P. and Hammond, L. (2005). Urban consumer preference and sensory evaluation of locally produced and imported rice in West Africa. Food Quality and Preference 16: 79–89.

 

Tomlins, K., Rwiza, E., Nyango, A., Amour, R., Ngendello, T., Kapinga, R., Rees, D. and Jolliffe, F. (2004)   The use of sensory evaluation and consumer preference for the selection of sweetpotato cultivars in East Africa. Journal of the Science of Food and Agriculture 84: 791-799.

 

Tomlins, K.I., Rwiza, E, J., Ndengello, T., Amour, R., Kapinga, R. E. and Rees, D. (2003) The use of consumer tests and trained taste panels to assess sensory characteristics. In: Sweetpotato Post-Harvest Assessment: Experiences from East Africa (Rees, D., van Oirschot, Q. and Kapinga, R. eds), pp. 37-50 Natural Resources Institute, Chatham, UK (ISBN 0 85954 5482)

 

van Oirschot, Q.E.A., Rees, D. and Aked, J., (2003) Sensory characteristics of five sweet potato cultivars and their changes during storage under tropical conditions. Food Quality and Preference 14: 673-680.

 

van Oirschot, Q.E.A. and Tomlins, K.I. (2002). Applying analytical sensory evaluation techniques, which translate qualitative perceptions to numerical data to research on development issues. Paper presented at the Conference on Combining Qualitative and Quantitative Methods in Development Research, 1-2 July 2002, Centre for Development Studies, University of Wales, Swansea.

 

Tomlins, K. I and Mashingaidze, A. (1996) Quality control during the manufacture of black tea: the role of sensory evaluation. Tea Research Foundation (Central Africa) Quarterly Newsletter 121: 39-47.
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Tomlins, K. I. and Gay, C. (1994). Prediction of quality and origin of black tea and pine resin samples from chromatographic and sensory information: evaluation of neural networks. Food Chemistry 50: 157-165.

 

Baker, D.M., Tomlins, K.I. and Gay, C. (1994) Survey of Ghanaian cocoa farmer fermentation practices and their influence on cocoa flavour. Food Chemistry 51: 425-431.

 

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