Impact of sarcoplasmic proteins on texture and color of silver carp and Alaska Pollock protein gels

Isoelectric solubilization and precipitation (ISP) relies on extreme pH shifts to solubilize, precipitate and recover myofibrillar protein (MP), whereas sarcoplasmic proteins (SP) are water soluble. SP were recovered from silver carp (SC) and added to ISP-recovered SC MP or Alaska Pollock (AP) to investigate the impact on texture and color of their cooked gels. MP was solubilized at pH 12.3 using Ca(OH)2 and precipitated at pH 5.5 with acetic acid. Protein (ISP recovered SC MP or AP) was combined with transglutaminase (TGase) at 0 or 5 g, starch at 15 or 20 g, polyphosphates at 3 g, and SP at 0, 77 mg or 144 mg per kg final protein gel paste. Gels without added SP (5 g TGase only) were harder, gummier, chewier, more cohesive and resilient (p < 0.05), for both SC and AP. Interestingly, addition of SP in SC gels showed similar results as adding 5 g TGase for some textural measurements, including springiness and Kramer and Torsional stress (p > 0.05). This was likely due to the calcium content and endogenous TGase activity in ISP-recovered protein. Future studies comparing effects of SP and endogenous TGase on protein gels with different calcium content would be beneficial.