Influence of different extraction techniques on recovery, purity, antioxidant activities, and microstructure of flaxseed gum

Abstract Four extraction techniques (that is, hot water extraction [HWE], alkaline–acidic extraction [AAE], ultrasound assisted extraction [UAE], and microwave assisted extraction [MAE]) were compared for flaxseed gum extraction and their influence on the yield, purity, structural characterization (monosaccharide composition, molecular weight distribution, and microstructure by transmission electron microscope), and antioxidant activity (in terms of scavenging ability of 2,2‐diphenyl‐1‐picrylhydrazyl [DPPH], 2,2'‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulphonic acid [ABTS], and reducing power) was investigated. The HWE achieved higher yield (8.96%) than UAE (7.84%) followed by MAE (7.01%) and AAE (6.44%). Moreover, the four flaxseed gum (FSG) samples exhibited the identical monosaccharide composition, but slight difference was observed in the content, whereas the molecular weight ratios exhibited significant difference. All samples displayed concentration‐dependent manner for all antioxidant assays. UAE‐FSG showed significant higher scavenging ability on DPPH free radical, ABTS free radical, reducing power, and β‐carotene bleaching assay followed by HWE‐FSG, MAE‐FSG, and AAE‐FSG. Overall results showed that UAE was favorable to the purity of FSG, whereas HWE was more advantageous to improve the extraction yield and facile as it requires no special equipment. Practical Application Extraction methods directly affect the recovery and purity of the extracted compound. Thus, this study could help in selection of appropriate extraction method for FSG. The results suggested that FSG possesses potential healthcare application in food industry because of their nutrition composition and antioxidant activities, and thus, it can be used for formulation of functional food as a natural antioxidant agent.