Location: Cereal Crops ResearchTitle: Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal
|LAN, YANG - NORTH DAKOTA STATE UNIVERSITY|
|CHEN, BINGCAN - NORTH DAKOTA STATE UNIVERSITY|
|RAO, JIAJIA - NORTH DAKOTA STATE UNIVERSITY|
Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2020
Publication Date: 2/1/2020
Citation: Lan, Y., Ohm, J., Chen, B., Rao, J. 2020. Physicochemical properties and aroma profiles of flaxseed proteins extracted from whole flaxseed and flaxseed meal. Food Hydrocolloids. 104:105731.
Interpretive Summary: The flaxseed is a valuable source of proteins. However, there is currently a lack of information on the structural and functional properties of proteins extracted from flaxseed. This study aimed to compare the structural and functional properties, and aroma profiles of proteins extracted from whole flaxseed (WF) and flaxseed meal (FM). Results showed that two samples differed significantly in protein extraction rate and properties of protein extracts. The protein isolate obtained from WF showed higher protein content (92%) than the protein concentrate attained from FM (61%). FM protein concentrate contained larger proportion of small size protein fractions than WF protein isolate. Both proteins showed high solubility (>90%) in alkaline solutions (pH >7.0) and the low solubility (<10%) in acidic solution (nearby pH 4.2 for WF protein isolate and 3.0 for FM protein concentrate). The WF protein isolate presented better foaming properties than FM protein concentrate. The FM protein concentrate exhibited higher stability to heating than FM protein isolate. Some unpleasant volatile compounds were only identified in FM protein concentrate. These results will be a valuable information in the utilization of flaxseed protein extracts in food industry.
Technical Abstract: This study aimed to investigate the structural and functional properties, and aroma profiles of proteins extracted from whole flaxseed (WF) and flaxseed meal (FM). On account of protein content in the extracts, flaxseed protein isolate (FPI) and flaxseed protein concentrate (FPC) were claimed to represent protein extracted from WF and FM, respectively. Results showed that two proteins differed significantly in extraction and protein recovery yields, purities, molecular and structural properties. Both SDS–PAGE and size exclusion chromatography results suggested that FPC consisted of larger proportion of low molecular weight fractions with greater heterogeneity than FPI. The isoelectric point (IEP) of two proteins was significantly different, being pH 4.2 and 3.0 for FPI and FPC, respectively, which was attributed to the presence of mucilage in FPC. Both proteins showed high solubility (>90%) at alkaline conditions (pH >7.0) and the lowest solubility (<10%) occurred nearby 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.