Effects of radio frequency heating on water distribution and structural properties of grass carp myofibrillar protein gel

•Radio frequency (RF) heating reduced the total time for preparing the gel.•RF heating of electrode gap of 140 or 160 mm increased water holding capacity.•RF (160 mm) heating increased immobilized water but reduced free water.•RF (140 and 160 mm) heating promoted α-helix turning into random coil.•The RF-heated (140 and 160 mm) gels were more compact with clear network structure. This study explored effects of radio frequency (RF, 27.12 MHz, 3 kW) heating replacing the first stage (electrode gaps of 120, 140 and 160 mm) or/and the second stage (95 mm) of the water bath heating on water distribution and structural characteristics of grass carp myofibrillar proteins gels. Compared with control, RF heating (140) during the first stage significantly reduced the total time to prepare gels from 70 min to 45.3 min and increased springiness and water holding capacity from 62.9% to 68.3%. It may be attributed to the appropriate RF heating contributing to α-helix turning into random coil and cross-linking via hydrophobic interactions and disulfide bonds, thus forming smooth gels with clear network structures. Structural changes further affected water distribution (immobilized water increasing from 97.8% to 98.7%). Namely, RF (140 mm) heating improved water distribution and structural characteristics of gels, which provided basic information for RF heating surimi gels.