Linear programming and consumers' ideal sensory attributes in product optimization : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Product Development at Massey University
Sensory attribute/ingredient relationships and consumers' ideal product profile were used to develop constraints for linear' programming in hand cream optimization using rice bran oil to replace mineral oil. At the beginning of the process, consumer testing was conducted in order to elicit the important attributes of the product as perceived by the consumers. Simultaneously, the strengths and weaknesses of hand creams on the market were identified, and an ideal product profile developed for hand creams.
A fractional factorial design, 26 2, was used to identify the main effects of the ingredients on the product attributes. A quantitative sensory profile technique and a trained sensory panel were employed in the product sensory evaluation of the samples. The mean scores of each sensory attribute were regressed against the levels of the ingredients in the formulations. Only the main effects of the ingredients were identified according to the design of the experiment. Most sensory attributes, consistency, spreadability, oiliness, shine and stickiness, had significant linear relationships with the ingredients. Moistness, softness and absorbability did not.
The linear relationships were then used to develop sensory constraints for the linear programming model. Upper and lower limits of these constraints were set from the consumers' ideal product profile, by adding and subtracting 1 from the ideal attribute levels. Other constraints were on ingredient levels based on formulation needs. LP88 computer program was used to solve this hand cream problem, the objective being minimum cost.
A hand cream was made using the optimum formulation from the linear programming and tested with the trained sensory panel. Ideal ratio scores (i.e. ratio of the sample mean score to the ideal score) of this hand cream's
attributes were not more than 0.3 away from the ideal. The product was then tested with a consumer panel of 20 hand cream users. In consumer testing, the optimum product was tested along with the leading commercial products in order to compare consumer acceptability on these products and to test if the optimum product could compete with the products already in the market. The results showed the consumers preferred the optimum product to the commercial products and the optimum product was closer to the ideal.
From the linear programming model used in this study, the attribute levels of the hand cream can be modified by adjusting the constraints and studies can be made of the effect of changes in ingredients on product attributes.