Characteristics of hemoglobin and its pro‐oxidative activity in washed silver carp ( Hypophthalmichthys molitrix ) mince as affected by pH

Abstract

The objectives of this study were to investigate the pro‐oxidative activity of hemoglobin and its effect on lipid and protein oxidation changes in silver carp washed mince over 12 days of storage at 4°C under different pHs (6.0, 6.5, 7.0, 7.5, 8.0). The results suggested that the formation of Methemoglobin decreased the relative oxygenation of hemoglobin in acidic pH (6, 6.5) as compared to neutral or alkaline pH (7, 7.5, and 8.0). Hemoglobin promoted lipid oxidation more effectively under acidic conditions (pH 6.0) rather than alkaline pH (8.0), as indicated by the higher peroxide values and thiobarbituric acid‐reactive substances. Moreover, hemoglobin was found to be more conducive in initiating protein oxidation by increasing the carbonyl and dimeric tyrosine content while decreased the total sulfhydryl content in washed mince system under acidic conditions, which was linked to a higher auto‐oxidation rate. These results suggested that the lipid and protein oxidation in fish mince were more likely mediated by hemoglobin, whose pro‐oxidative activity could be influenced by its pH level. Practical applications This study demonstrates that hemoglobin pro‐oxidative activity is mainly affected by pH. The shift of pH from acidic to alkaline could attenuate hemoglobin autoxidation. This work provides a means to slow down lipid and protein oxidation during storage of fish mince by adjusting to slightly alkaline pH, which could maintain the freshwater fish mince quality.

Undesirable discoloration in edible fish muscle: Impact of indigenous pigments, chemical reactions, processing, and its prevention

“…During postmortem changes, the decreasing pH induces deoxygenation of Hb. In addition, Fe 2+ of Hb moiety is converted to met form (Fe 3+ ) and resulted in the formation of metHb (Javed et al., 2021). Moreover, metHb can react with peroxides to form a hypervalent perferryl‐Hb (“Fe 4+ = O”) radical, which could accelerate lipid oxidation and discoloration in fish muscle (Lee et al., 2015).…”

“…Various techniques are commonly used in fish bleeding after capture such as cutting the gill arches, throat (ventral aorta), or the arteries in the neck (dorsal aorta), and direct evisceration (Olsen et al., 2014). Bleeding has been known to remove 50% of blood from the fish body (Harrysson et al., 2020; Javed et al., 2021). For small pelagic species like herring, sardines, and sprat, it is difficult to apply those techniques owing to large volumes of very small fish.…”

AI-2/Lux-S Quorum Sensing of Lactobacillus plantarum SS-128 Prolongs the Shelf Life of Shrimp (Litopenaeus vannamei): From Myofibril Simulation to Practical Application

“…The decline in the shrimp freshness is a complex combination of biochemical, physical, and structural changes in the proteins, lipids, and other components. During storage, the myofibrillar was hydrolyzed by spoilage microorganisms and endogenous enzymes, the tyrosine in the protein was oxidized and complexed, and the content of the dimer tyrosine increased gradually [ 24 ]. The dimer tyrosine and sulfhydryl have a strong correlation with the texture of muscle foods [ 25 ].…”