Effects of protein isolate from bambara groundnut (BGPI) at different levels (0–6 %, w/w) in combination with microbial transglutaminase (MTGase) at different concentrations (0, 0.3 and 0.6 U g−1surimi) on gels properties of sardine (Sardinella albella) surimi were investigated. In the absence of MTGase, the increases in breaking force and deformation of gels were obtained when BGPI at levels of 1.5–3 % was incorporated (P < 0.05). The further increases in BGPI levels (4.5–6 %) resulted in the decrease in breaking force and deformation (P < 0.05). When MTGase (0.3 and 0.6 U g−1surimi) was added, the increase in breaking force and deformation were noticed, regardless of BGPI levels, and the strengthening effect was in dose-dependent manner. The increases in hardness, gumminess and chewiness were also observed when surimi gel was added with BGPI and MTGase (P < 0.05). Water-holding capacity of gels was improved with increasing level of BGPI, and MTGase incorporated (P < 0.05). Whiteness of gels slightly decreased with increasing BGPI levels, however the addition of MTGase had no impact on whiteness (P > 0.05). Based on electrophoretic study, myosin heavy chain decreased with addition of MTGase, indicating the formation of cross-links. More compact structure was observed in gel added with MTGase (0.6 U g−1surimi) and 6 % BGPI, and was accompanied by an increased gel strength.
