Principles of Good Practice for Conducting Sensory Tests

Complete block design o incomplete block design

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Unformatted text preview: essentials for an evaluation area o waiting area/room o neutral colours o positive air pressure o temperature 20- 22°C o 50- 55% humidity o standardized illumination Experimental Design • number of samples tested in one session requires a design structure • possible designs: o completely randomized design o randomized complete block design o incomplete block design • completely randomized designs (CRD) o samples are randomized across subjects • randomized complete block designs (RCBD) o samples are randomized across subjects within a block • incomplete block designs (IBD) o a subset of samples are evaluated by each subject until a certain number of evaluations are collected Context Effects and Biases in Sensory Testing • expectation error o panellists expect what they are looking for • error of habituation o people become used to something – continue doing what they are doing • minimize these by: o providing no details about samples o randomizing samples • stimulus error o irrelevant criteria are used to assist with the evaluation o minimize by: ! blind tasting ! any external cues • logical error o when two or more characteristics of the sample are associated in the minds of the panellist o minimize by: ! masking the differences • halo effect o one positive attribute affects all others • horns effect o if a negative characteristic is evaluated it will influence other attributes in a negative direction • dumping o if you don’t ask about an attribute that panellists feel strongly about, they will “dump” their evaluation of that attribute into the evaluation of an attribute you do ask about • minimize these by: o pretesting the number of questions asked o use the correct type of panel for the evaluation of the products • order of presentation of sample o biases that may occur: ! contrast effect ! error of central tendency ! time effect o minimize by: ! randomization • mutual suggestion o panellists respond to others around them o minimize by: ! ! separate sensory testing booths discouraging facial expressions and vocalizing of opinions...
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