Proteomic analysis of bighead carp surimi washed by the conventional process and pH-shift process

The proteomic technique utilizing two-dimensional gel electrophoresis (2-DE) and MALDI-TOF/TOF MS was applied to investigate bighead carp muscle proteins washed by the conventional and two variants of pH-shift (acid-aided and alkali-aided) processes. Conventional washing yielded the highest gel strength, water holding capacity (WHC) and whiteness. Alkali treatment increased breaking force, while both pH-shift methods decreased gel strength, WHC and whiteness. There were 14 differential protein spots related to muscle tissues and muscle protein structure. The conventional process significantly reduced myosin heavy chain fast skeletal type 3 and actin 3b, but upregulated myosin heavy chain fast skeletal type 1, myosin low-temperature type S1 heavy chain and tropomyosin alpha-1 chain. The pH-shift process decreased low-temperature light meromyosin and desmin in surimi ( p < 0.05). The pH-shift process upregulated Sk-tropomodulin and myosin regulatory light chain. The acid-aided process led to the higher density of myosin heavy chain fast skeletal type 3 ( p < 0.05), while the alkali-aided process led to the higher densities of myosin heavy chain fast skeletal type 1 and 10°C light meromyosin in surimi ( p < 0.05). These results indicated that specific MHC isoforms and structural proteins are differentially retained under different pH environments, directly influencing the gel properties.