Oxidative stability and proximate composition of silver cyprinid (Rastrineobola argentea) used for fishmeal in East Africa

ABSTRACT

Fishmeal and oils used for feed formulation contain polyunsaturated fatty acids (PUFAs) that are easily oxidized, and affect farmed fish. In this study, the effects of season (dry or wet), drying methods (i.e., artisanal: bare ground, rock surface, meshes laid on the ground or raised racks or adopted), as well as storage time on Rastrineobola argentea used for fishmeal in East Africa were examined. Lipid oxidation and proximate composition stability were determined at 30-day intervals over a period of 90 days. Lipid oxidation stability was monitored by determining free fatty acids (FFA), peroxide value (PV) and thiobarbituric acid-reactive substances (TBARs). Changes in proximate composition were based on moisture, ash, crude protein (CP), crude fat (EE), and gross energy (GE). The relationships among lipid oxidation and proximate composition parameters were also explored. Considerable oxidative rancidity reflected by significantly high levels of FFA, PV, and TBARs in dried R. argentea was recorded in the wet than in the dry season. Drying of R. argentea on bare ground and meshes laid on the ground led to higher lipid oxidation than drying on raised racks. Lipid oxidation was also significantly higher in salted and indirectly dried R. argentea than in the unsalted and directly dried samples. Dry matter tended to decrease with storage time, as ash was high in salted samples and those dried on bare ground. There was a general decrease in EE content with storage time that coincided with peroxidation. However, CP and GE were less affected by season, processing methods and storage time. Drying R. argentea on raised racks was the best among the processing method investigated.

KEYWORDS:

• Lipid oxidation
• processing methods
• proximate composition
• Rastrineobola argentea
• seasonality
• storage time

Acknowledgments

This study was funded in part by the Swedish International Development Cooperation Agency (SIDA) and Makerere University bilateral program, as well as the United Nations University Fisheries Training Programme (UNU-FTP). Micheal Kasiga, the fisheries officer at Kiyindi landing site is thanked for logistical support. Nathan Semwanga did a commendable job in laboratory analysis. Amy Fingerle, of the Salmon River Restoration Council in Sawyers Bar, California, proofread the manuscript.

Disclosure statement

None of the authors had conflict of interest in the study and data presented in this manuscript.

Additional information

Funding

This work was supported by the Swedish International Development Cooperation Agency (SIDA) and Makerere University bilateral program [75007304];United Nations University, Fisheries Training Programme [9253-17].