The ability of ferrous chelates including hairtail protein hydrolysates to prevent and reduce fatigue was studied in rats. After hydrolysis of hairtail surimi with papain, the hairtail protein hydrolysates (HPH) were separated into three groups by range of relative molecular weight using ultrafiltration membrane separation. Hairtail proteins were then chelated with ferrous ions, and the antioxidant activity, the amino acid composition and chelation rate of the three kinds of ferrous chelates including hairtail protein hydrolysates (Fe-HPH) were determined. Among the three groups, the Fe-HPH chelate showing the best conditions was selected for the anti-fatigue animal experiment. For it, experimental rats were randomly divided into seven groups. Group A was designated as the negative control group given distilled water. Group B, the positive control group, was given glutathione. Groups C, D and E were designated as the Fe-HPH chelate treatment groups and given low, medium, and high doses, respectively. Group F was designated as HPH hydrolysate treatment group, and Group G was designated as FeCl2 treatment group. The different diets were orally administered to rats for 20 days. After that time, rats were subjected to forced swimming training after 1 h of gavage. Rats given Fe-FPH chelate had higher haemoglobin regeneration efficiency (HRE), longer exhaustive swimming time and higher SOD activity. Additionally, Fe-FPH chelate was found to significantly decrease the malondialdehyde content, visibly enhance the GSH-Px activity in liver and reduce blood lactic acid of rats. Fe-HPH chelate revealed an anti-fatigue effect, similar to or better than the positive control substance and superior to HPH or Fe when provided alone.

The novel ferrous-chelating hairtail peptides may be a suitable fortificant for improving iron-deficiency status. Our findings demonstrated that this multi-tracer technique has many applications in nutritional research. © 2015 Society of Chemical Industry.

Five types of low‐value fish protein hydrolysates (FPH) and ferrous‐chelating peptides [Fe(II)–FPH] were prepared from Pacific mackerel, Spanish mackerel, hairtail, Japanese anchovy and horse mackerel. The hydrolysis degrees of FPH and ferrous chelation percentages of all types Fe(II)–FPH were calculated. The antioxidant activities were measured using 2,2‐diphenyl‐1‐picryl‐hydrazyl (DPPH)‐scavenging activity and hydroxyl radical‐scavenging activity. All FPH samples demonstrated low antioxidant activity. After ferrous chelation, the DPPH‐scavenging activities of Spanish mackerel‐Fe(II)–FPH and hairtail‐Fe(II)–FPH were significantly higher (P < 0.05 and P < 0.01, respectively) than other FPH, and the hydroxyl radical‐scavenging activity of hairtail‐Fe(II)–FPH was significantly higher (P < 0.05) than that of hairtail‐FPH. Among all the tested, hairtail‐Fe(II)–FPH showed the highest ferrous chelation percentage and antioxidant activity. The ferrous‐chelating peptide fractions recovered from low‐value fish, especially small, low‐value hairtail, can be used as a source of natural antioxidants for food products. Practical Applications Efficient utilization of low‐value fish is important for the economic viability of the aquatic food industry. Enzymatic hydrolysis and modification by trace metals, such as ferrous ion, is one of the most effective technologies for recovering value‐added proteins from low‐value fish without losing their nutritional value. In this study, five types of low‐value fish were hydrolyzed by alcalase and modified by ferrous chloride. 2,2‐Diphenyl‐1‐picryl‐hydrazyl and hydroxyl radical‐scavenging activities were studied. The potential antioxidant activities of ferrous‐chelating peptide fractions recovered from low‐value fish, especially hairtail, can be used in a wide range of food additives, diet nutrients and pharmaceutical agents.