Evaluation of pork colour: Sensory colour assessment using trained and untrained sensory panellists

M. longissimus dorsi and M. psoas major minced pork patties from three dietary treatment groups of DLY (Duroc/Landrace/Yorkshire) cross bred pigs were packaged in polythene bags and placed in a retail refrigerated display cabinet at 5±1 °C, under fluorescent light (1000 lux) for up to 5 days. Each dietary treatment group consisted of pigs (n = 7) fed either a low vitamin E diet (80 mg DL-α-tocopheryl acetate/kg of feed), supplemental iron [7 g iron (II) sulphate/kg feed] or supplemental vitamin E (200mg DL-α-tocopheryl acetate/kg of feed) + supplemental iron. Samples were subjected to visual colour evaluation by a trained sensory panel (n = 8) and an untrained panel (n = 8) on days 0, 1, 3 and 5 of display. The signal to noise (S/N) ratios for assessors and replicates for the trained assessor group were higher than those of the untrained assessor group indicating greater reliability in the trained assessor results. The trained assessor group produced relatively normal percentile distributions for sensory terms in the assessment of both M. longissimus dorsi and M. psoas major muscles. The untrained assessor group displayed more skewed or non-symmetric distributions for M. longissimus dorsi, but produced a normal distribution for M. psoas major. Quantitative and qualitative analysis of the sensory profiling by both the trained and untrained groups of test subjects showed that in general sensory training contributed to a more effective visual sensory evaluation of M. longissimus dorsi in terms of metmyoglobin development. However, this is not the case for M. psoas major where both groups of assessors produced comparable results. Use of uniploar scaling did not improve the discriminative ability of assessors, both trained and untrained, in assessment of blue and yellow. The untrained group of assessors were even less effective in the use of these scales. It appeared that the sensory visual assessment of meat products can be performed effectively without training when the product colour is familiar to the assessors. However, training of panellists becomes relevant when a more unfamiliar product of unfamiliar colour is to be assessed and the unintuitive aspect of discrimination may play a greater role in the objective sensory colour assessment of meat.