QUALITY INDEX METHOD (QIM) SCHEME FOR WHOLE TILAPIAS (OREOCHROMIS NILOTICUS) STORED IN ICE

Tilapia (Oreochromis niloticus) products have an increasing demand worldwide, being Brazil a major producer. Quality control and freshness assessment are essential to assure consumer satisfaction. Therefore, a Quality Index Method (QIM) scheme was developed to evaluate the freshness of whole tilapias stored in ice. Three batches of 56 whole tilapias each (168 in total) weighting 635±45 g were stored in layers of ice for 1, 3, 6, 8, 10 and 13 days. A QIM scheme with nine attributes comprised in four parameters (overall aspect, eyes, gills and abdomen) and scored by a maximum of 19 demerits points was defined by seven experts during eight sessions (totalizing 18 h). The shelf-life of ice-stored tilapias was determined with an optimized Torry Score sheet. QIM data was compared with physicochemical and microbiological measurements to verify its efficiency. QI was linearly correlated with storage time (R2 = 0.989) and a prediction accuracy of ± 0.355 days of storage was determined by partial least squares (PLS) regression. A sensory rejection point of 11 days was estimated. The storage in ice affected a*, b*, C* and H0 values of the ventral and dorsal areas of tilapias, but no variations in L* were observed. Changes in the hardness, chewiness and adhesiveness of tilapia muscle were also detected during the storage in ice, but the springiness and cohesiveness remained low. Total volatile base nitrogen (TVB-N), 2-thiobarbituric acid-reactive substances (TBARS), pH and counts of aerobic heterotrophic mesophiles and psychrotrophs increased significantly (p < 0.05) during the storage in ice, but they were in concordance with legal limits in force. Data demonstrated the suitability of the QIM scheme for assessing the freshness of whole tilapia stored in ice.