Comparison of Variable-Blade to Allo-Kramer Shear Method in Assessing Rainbow Trout (Oncorhynchus mykiss) Fillet Firmness

A variable-blade (VB) attachment was compared to the Allo-Kramer (AK) shear attachment for texture analysis of rainbow trout fillets from 2 experiments; effects of attachment configuration, storage regimen, and cooking temperature are evaluated. In the 1st experiment, AK detected differences in force measurement, and VB showed that the perpendicular orientation yielded the highest response (P < 0.05). Fillets refrigerated (4 degrees C) for 0 d were firmer than fillets stored for 14 d (337.36 compared with 275.90 g/g). Raw fillets were firmer than cooked fillet (333.79 compared with 279.46 g/g). In the 2nd experiment, frozen storage at 25 degrees C for 30 d after refrigerated storage (R3F30 and R7F30) decreased VB shear force (P= 0.0019) and AK energy of shear (P= 0.0001) by 1.5- and 2-fold compared to those evaluated after refrigerated storage for 3 and 7 d (R3 and R7), respectively. Cooking increased VB and AK texture for all storage regimens (P < 0.05). In both studies, instrumental texture did not correlate with alkaline-insoluble hydroxyproline (P > 0.05). Shear direction affected force generated by the VB attachment, and this attachment could discriminate shear force differences due to cooking and frozen-storage. Practical Application: Fillet texture was determined by a recently developed device and compared to texture determined by the Allo-Kramer shear attachment; both responses were related to collagen content. The VB attachment defined fillet texture as affected by cooking and storage condition.