Effect of κ-carrageenan on gelation and gel characteristics of Antarctic krill (Euphausia superba) protein isolated with isoelectric solubilization/precipitation

Isoelectric solubilization/precipitation (ISP) was used to extract krill protein isolate (KPI). Due to krill endogenous proteases ISP-KPI barely forms gel which is a major hurdle in wide application of this tremendous protein source for direct human consumption. The objective was to improve gelation and elucidate interaction mechanism between κ-carrageenan and KPI. κ-Carrageenan was added to KPI at 0.00, 0.75, 1.50, 2.25, and 3.00 g/150 g and heated at 90 °C for 15 min. Added κ-carrageenan improved texture of KPI gels. However, the level of addition had minimal effect. SDS-PAGE revealed severe proteolysis of KPI even during heating. Total and free sulfhydryl were not different, while surface hydrophobicity and water-holding-capacity slightly decreased and increased, respectively with added κ-carrageenan. Fourier-transform-infrared-spectroscopy showed none-to-minimal shift of β-sheet and α-helical protein structure; while CC and CO stretching as well as CH bending of κ-carrageenan showed the greatest shift, indicating that κ-carrageenan was mainly responsible for gel formation.