Antioxidant Properties of Flaxseed Protein Hydrolysates: Influence of Hydrolytic Enzyme Concentration and Peptide Size

Abstract

Flaxseed is an emerging source of protein raw materials for bioactive protein hydrolysate production; however, there is insufficient information on the structural properties of its antioxidative peptides. The aim of this work was to determine the peptide composition and relationships to antioxidant properties of flaxseed protein hydrolysates (FPH) obtained using two protease (thermoase) concentrations (2.5 and 3.0%). The FPH were passed through ultrafiltration membranes to yield fractions with <1, 1-3, 3-5, and 5-10 kDa peptide sizes, which were also tested for antioxidant properties. Mass spectrometry data yielded several peptide sequences located within the flaxseed conlinin, but a lesser number was found in the 3.0% thermoase-FPH. 2,2-Diphenyl-1-picrylhydrazyl radical scavenging was lowest (54%) for the 3.0% thermoase-FPH while membrane separation enhanced the values up to 65% for the <1 kDa peptides. Metal chelation and iron-reducing ability were also significantly (P < 0.05) enhanced after membrane fractionation. In contrast, the hydroxyl radical scavenging ability was unchanged (2.5% thermoase-FPH) or significantly (P < 0.05) diminished (3.0% thermoase-FPH) after membrane fractionation, except for the 5-10 kDa peptides that had notably (P < 0.05) higher values. We conclude that the <1 and 1-3 kDa peptides may be useful agents to suppress oxidative stress within living tissues while the 3-5 and 5-10 kDa could be suitable preservatives to enhance food shelf life.

Thermoase‐hydrolysed pigeon pea protein and its membrane fractions possess in vitro bioactive properties (antioxidative, antihypertensive, and antidiabetic)

“…Comparatively, the findings from the present study is similar to the observation of other researchers, which suggest stronger DRSA for LMW peptide fractions than HMW peptides and crude hydrolysate (Arise et al, 2016;Jha, Mandal, Bhattacharyya, & Ghosh, 2014;Sonklin, Laohakunjit, & Kerdchoechuen, 2018). Nwachukwu and Aluko (2018) been identified as important assays to predict antioxidant activities (Islam et al, 2013). Therefore, the strong ability of PPHT and peptide fractions to scavenge these radicals is a pointer to their potential relevance as sources of natural antioxidant and functional ingredients.…”

“…Comparatively, the findings from the present study is similar to the observation of other researchers, which suggest stronger DRSA for LMW peptide fractions than HMW peptides and crude hydrolysate (Arise et al., 2016; Jha, Mandal, Bhattacharyya, & Ghosh, 2014; Sonklin, Laohakunjit, & Kerdchoechuen, 2018). Nwachukwu and Aluko (2018) reported that membrane ultrafiltration improved DRSA of thermoase hydrolysate of flaxseed protein, although, there was no significant difference ( p > .05) in the activity of the different peptide sizes. Similarly, Rong, Girgih, Malomo, Ju, and Aluko (2013) earlier reported that membrane ultrafiltration promoted antioxidant activities of rapeseed peptides.…”

Structural and functional properties of food protein-derived antioxidant peptides

“…The FRAP assay is routinely used to determine ability of antioxidative food protein‐derived hydrolyzates and peptides to serve as reductants by donating their excess electrons to the Fe 3+ ‐2,4,6‐tripyridyl‐S‐triazine complex, and reducing it to the more stable divalent ferrous ion, Fe 2+ (He et al, ; Nwachukwu & Aluko, ; Torres‐Fuentes et al, ). In a study of protein hydrolyzates and peptides from Corolase PP‐hydrolyzed sea lettuce flakes ( P. palmata ), the high reducing power of the decapeptide, SDITRPGGNM was linked to the terminal Met residue (Harnedy et al, ) because sulfur‐containing amino acids, such as Cys and Met are known to be highly effective in reducing the Fe 3+ ‐ferricyanide complex (Udenigwe & Aluko, ).…”

“…In addition, antioxidant peptides could also serve as additives in foods in order to curb the oxidation of food products (Qiu, Chen, & Dong, ). This is especially useful to prevent oxidative rancidity of foods containing oils where the formation of ketones and aldehydes could impair the food's organoleptic properties, shorten its shelf life and result in considerable economic losses (He et al, ; Nwachukwu & Aluko, ; Qiu et al, ). The ability of such protein‐derived antioxidative agents to play a role in the prevention and/or amelioration of ROS‐induced oxidative damage has been increasingly linked to their structural properties (Aluko, ; Samaranayaka & Li‐Chan, ; Zou et al, ).…”

Structure-informed separation of bioactive peptides

“…Examples of membrane fractionation technologies include nanofiltration and ultrafiltration, the latter being the most utilized to date for peptide fractionation. A plethora of studies have demonstrated the significance of ultrafiltration for fractionating peptides from several food protein hydrolyzates such as pea protein hydrolyzates (Li et al, ), egg ovomucin hydrolyzates (Sun, Chakrabarti, Fang, Yin, & Wu, ), flaxseed protein hydrolyzates (Nwachukwu & Aluko, ), and chicken feather keratin hydrolyzates (Yeo et al, ).…”