Effects of Bromelain Tenderisation on Myofibrillar Proteins, Texture and Flavour of Fish Balls Prepared from Golden Pomfret

Abstract

An enzymatic method to tenderise golden pomfret (GP, Trachinotus blochii) flesh by marinating with bromelain (BML) solution was developed to produce GP fish balls with a texture similar to those of yellowtail fusilier (YF, Caesio cuning). Treatment with BML reduced the hardness, chewiness and gel strength significantly but increased the resilience of GP fish balls. As a result, 0.4% (enzyme-substrate ratio, w/w) BML-treated GP fish balls had the same texture properties as YF fish balls. Meanwhile, changes in myofibrillar proteins in the fish balls were determined using sodium dodecyl sulphate polyacrylamide gel electrophoresis, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and atomic force microscopy. The results indicated that BML degraded myosin light chain and troponin T effectively, without affecting actin. BML treatment generated protein fragments with significantly smaller sizes, thereby improving the tenderness of the flesh. The length, width and height of the myofibrils from 0.4% BML-treated fish ball were 6.42, 1.52 and 1.48 μm, respectively, which were not significantly different from the myofibrils of YF fish balls, indicating that the similar nanostructure determined the comparable texture properties. Gas chromatography-mass spectrometry analysis showed that 0.4% BML decreased the amount of hexanal, hexadecane, 1-octen-3-ol and 2,6,10,14-tetramethylpentadecane but increased the ratio of heptadecane from 18.14 to 38.23% in the treated fish balls, making the flavour of 0.4% BML-treated GP fish balls similar to that of YF balls. Overall, the results suggest that 0.4% BML-tenderised GP could be a promising alternative to YF to produce quality fish balls.