Conlinin in flaxseed (Linum usitatissimum L.) gum and its contribution to emulsification properties

Abstract

Flaxseed gum (FG) is a mixture of natural polysaccharide and protein derived from flaxseed (Linum usitatissimum L.) that has potential for thickening foods, stabilizing emulsions, and gelling solutions. The composition and identities of proteins in FG have never been reported. In this study, gum prepared from whole flaxseed was deglycosylated by treating it with trifluoromethanesulfonic acid (TFMS). The resultant proteins were separated by 2D-gel electrophoresis. The major protein spots with estimated molecular weights (MW) of 10–11 kDa and 11–12 kDa were excised, digested with trypsin, and analyzed using matrix-assisted laser ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Peptide MS of tryptic digestion fragments was compared to MS of peptides from gene models available through National Center for Biotechnology Information (NCBI) database. Fragments consistent with the seed storage protein conlinin, the low-molecular-mass 2S storage flaxseed protein, were identified as the major spot constituents. Emulsification properties of FG were determined before and after protease hydrolysis with emulsion activity index (EAI) and emulsion stability (ES) as indicators. Both EAI and ES decreased from 98.7 ± 5.4 to 59.9 ± 3.2 m2/g and from 66.4 ± 1.1 to 42.1 ± 2.0%, respectively, after protease treatment. Conlinin is the major protein associated with FG and it plays a fundamental role in determining FG emulsification properties.