Multi-session sensory designs using mutually orthogo-nal latin squares balanced for carryover effects

Sensory trails play a vital role in food and nutrition experiments in establishing certain sensory facts about agricultural/animal produce. To draw definite conclusion from the study, it is important to eliminate or minimize all sources of error and control all factors that may influence the inference. Hence, in addition to the potential sources associated with the preparation of the test products, variability due to measurement or assessment process,order effects,carryover effects and assessor fatigue are to be considered. An experimental design for sensory evaluation should be capable of accommodating all these variables. However, when there are a large number of products two operational constraints, viz. assessor constraint and preparation constraint, may limit the choice of experimental designs. Assessor constraint sets a maximum number of products that an assessor can evaluate within a session before onset of sensory fatigue and preparation constraint limits the number of products that can be prepared for a given session without loss of experimental control. Therefore, many times it may become necessary to split sensory evaluation into sessions. Here, a general method is developed based on initial sequences to construct designs for multi-session sensory trials balanced for carry over effects. In the proposed designs, all panelists will have to evaluate only a subset of samples in each session and they will not have to taste the same product more than once during different sessions.