Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal

The aim of this study was to determine the structural and functional properties, and aroma profiles of flaxseed proteins extracted from golden whole flaxseed (WF) and flaxseed meal (FM). Results showed that two kinds of proteins differed significantly in terms of extraction and protein recovery yields, purities, as well as molecular and structural properties. Flaxseed proteins obtained from WF and FM reached different purities of isolate (FPI) and concentrate (FPC), respectively. Both SDS–PAGE and size exclusion chromatography (SEC-HPLC) results suggested that FPC consisted of a larger proportion of low molecular weight fractions with greater heterogeneity than FPI. The isoelectric point (IEP) of the two proteins was significantly different, being pH 4.2 and 3.0 for FPI and FPC, respectively. This was because of the presence of mucilage in FPC. Both proteins showed the high solubility (>90%) at alkaline conditions (pH > 7.0) and the lowest solubility (<10%) near individual IEP. FPI presented higher foaming capacity than FPC at both neutral (pH 7.0) and acidic pH (pH 3.5) while FPC exhibited higher thermal stability than FPI. Both flaxseed proteins presented overall neutral to positive flavors and FPC exclusively contained (Z)-3-hexen-1-ol, 1-octen-3-ol, and (E)-3-octen-2-one, which can be used to differentiate FPC from FPI.