Consumer research and product optimization for glue stick development in Thailand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Product Development at Massey University
This study, on the development of a new glue stick product based on tapioca starch for Thai consumers, had a major emphasis on the use of consumer input in the product optimization. At the beginning of the development process consumers identified the problems of existing products and generated the important attributes of glue stick products. Then product prototypes were made using mixture experimental designs and quantitative relationships between the ingredients and the product attributes were determined. For evaluating the sensory attributes of prototypes, a trained panel was employed during the development of the first prototypes and then a consumer panel in the second prototype development. Consumers not only evaluated the product attributes of the prototype products using line scales but also indicated their ideal product attribute levels. Physical attributes of the products were also measured. Multiple regression was used to generate the empirical equations showing the relationships between the ingredients and the product attributes. These linear relationships were then used to develop the constraints for a linear programming model. The consumer ideal product profile as well as the sensory profiles of the commercial products were employed to create upper and lower acceptable limits of the attributes' constraints. The raw materials and the physical properties were also included in the linear programming model. Acceptability maximization and cost minimization were used to generate the optimum formulations. The prototype products from these formulations were tested by a small consumer panel to select the one with highest acceptability. A pilot scale plant was designed and built and then a small quantity of the final formulation was produced. The final product, from the successful pilot scale production, was tested in a home-use test by 108 students and 64 office workers in Bangkok. The consumers evaluated the performance of the developed product in comparison with their 'usual brand'. The results from the consumer testing showed that the developed glue stick was generally accepted by the target consumers. However, some improvements of the product in terms of colour, aroma and packaging are still necessary. The product could be made commercially in Thailand in a simple plant using a closed stainless steel vessel with steam jacket, condenser and central anchor type mixer. Suitable packaging equipment is needed in order to maintain the high temperature of the mix while discharging the glue mixture into moulds. The product should be able to compete with the glue sticks already in the Thai market since it has the distinctive feature of adjustability and could be sold at a lower price.