Effect of antioxidants on lipid oxidation in herring (Clupea harengus) co-product silage during its production, heat-treatment and storage

Abstract

Provided high product quality, ensilaging can be used to valorize fish filleting co-products into a silage suitable for food applications. However, a documented challenge for products from hemoglobin-rich fish raw materials is the high susceptibility to lipid oxidation, calling for stabilization by antioxidants. In a comparison among different rosemary-containing antioxidants and isoascorbic acid, we here found that the commercial mixture Duralox MANC-213 (MANC) provided the best protection against peroxide value and 2-thiobarbituric acid reactive substances (TBARS) development during ensilaging of herring filleting co-products (0–7 days, 22 °C), and also during subsequent heat-treatment (30 min, 85 °C). Increasing MANC concentration from 0.25 and 0.75 to 1.25% lowered TBARS values from 43.53 and 25.12 to 18.04 µmole TBARS/Kg silage, respectively, after 7 days of ensilaging. During storage at 4 °C/22 °C in presence of MANC, 1.25% provided the highest protection with 87–90% and 66–73% lower TBARS, at 4 °C and 22 °C, respectively, at 6 months compared to the controls. At this time point, heat-treated silages had lower protein degree of hydrolysis and free amino acids values than the non-heat-treated one. Regardless of antioxidant addition, total volatile basic nitrogen (TVB-N) formation still increased during the storage, but, overall, TVB-N values in silages were below the acceptable limit of 30 mg TVB-N/100 g fish for human consumption. Together with lipid oxidation data, this suggest that herring silage produced in presence of antioxidants can be used both for high quality feed and food applications.

Pilot-Scale Ensilaging of Herring Filleting Co-Products and Subsequent Separation of Fish Oil and Protein Hydrolysates

“…Contrary, a high TBARS value was recorded in the herring co-product even before ensilaging, which after 1 h decreased significantly ( p < 0.05) and remained constant at ~ 8–9 µmole TBARS/kg silage thereafter. Overall, the TBARS values recorded in this study were slightly lower than in our previously reported lab-scale ensilaging of herring co-products at 21–22 °C with 0.25–1.25% BORDANTIX W/S or BORDANTIX O/S antioxidant added; 8–9 µmole and 20–28 µmole TBARS/kg silage, respectively (Sajib et al, 2022 ). The lower TBARS values recorded in this study could possibly be due to the use of higher quality starting raw material as ensilaging was done on-site at the herring processing plant within 1–2 h after the generation of co-products.…”

“…Lab-scale ensilaging of herring filleting co-products has previously been reported, e.g., by our team (Sajib et al, 2020 , 2022 ), but also by, e.g., van’ t Land et al ( 2017 ). Briefly, ensilaging can be performed by adding 2.5% v/w formic acid (85% purity) to minced herring co-products to lower the pH below 4.0, and the protein degree of hydrolysis (DH) can then be tuned by terminating the autolysis after a specific time.…”

“…The fact that peroxides accumulated less in oils from silage subjected to heat could be due to different oxidation kinetics caused, e.g., by the lower FFA content in this oil (Chew, 2020 ). Also, it could be due to the inactivation of catalytic enzymes such as lipoxygenases (LOX) during heating of the silage (Sajib et al, 2022 ). Wu et al ( 2022 ) recently reported high LOX-activity in herring heads, which stimulated severe oxidation during their cold storage.…”

“…Samples for PV and TBARS analyses were prepared as described by Sajib et al ( 2022 ) using a chloroform:methanol (2:1) extraction according to Lee et al ( 1996 ). The PV and TBARS were then analyzed spectrophotometrically (Cary 60 UV–vis, Agilent technologies, 117 USA) using the chloroform and methanol phase, respectively, according to Undeland et al ( 2002 ) and Schmedes and Hølmer ( 1989 ), respectively.…”

“…Based on our earlier findings, most changes in DH appear within 1–3 days of ensilaging, and around 40% DH was achieved after 2 days of ensilaging at 22 °C with continuous stirring. Although susceptible to lipid oxidation (Sajib & Undeland, 2020 ), the silage could however, be stabilized during its production, heat-treatment, and storage by adding rosemary ( Rosmarinus officinalis L.) extract-based antioxidants (Sajib et al, 2022 ). For example, BORDANTIX W/S (0.25% w/w ), a commercial rosemary extract-based antioxidant mixture, lowered 2-thiobarbituric acid reactive substances (TBARS) formation by 91% after 7 days of ensilaging at 22 °C, compared to the control.…”