SDS-PAGE analysis of protein profile in mackerel tuna (Euthynnus affinis) preserved with bilimbi (Averrhoa bilimbi) extract

Mackerel tuna (Euthynnus affinis) is a valuable source of animal protein but is highly perishable due to its high water content. To extend its shelf life, natural preservatives offer a promising alternative to synthetic additives. Bilimbi (Averrhoa bilimbi) has potential as a natural preservative owing to its bioactive compounds, such as saponins, flavonoids, and polyphenols, which possess antioxidant and antimicrobial properties. This study aimed to evaluate the effect of bilimbi extract on the protein profile of mackerel tuna using SDS-PAGE electrophoresis to determine the most effective concentration for preservation. An experimental approach was used, with samples consisting of tuna flesh subjected to 24-hour storage, both untreated and treated with bilimbi extract at concentrations of 50%, 75%, and 100%. SDS-PAGE analysis was employed to assess protein degradation, supported by organoleptic evaluation to observe changes in appearance, texture, odor, and overall acceptability. The results demonstrated that treatment with 50% bilimbi extract preserved the protein integrity and sensory quality of the fish most effectively, showing characteristics closest to those of fresh tuna. These findings suggest that bilimbi extract at 50% concentration is optimal as a natural preservative for mackerel tuna, maintaining both protein structure and organoleptic quality during storage.