Bagaspati L Sadewa, Tjipto Leksono, Santhy Wisuda Sidauruk

Naniura is a traditional fermented fish product from North Sumatra that is processed using organic acids derived from Jungga citrus (Citrus hystrix). This study aimed to evaluate the effect of Jungga citrus immersion time on sensory characteristics, physicochemical properties, lactic acid bacteria (LAB) population, and crude exopolysaccharide (EPS) content of tilapia naniura. Fresh tilapia fillets were immersed in Jungga citrus juice at a 1:1 (w/v) ratio for 0, 3, 4, and 5 h, followed by marination with spices. Sensory evaluation was conducted using hedonic and quality scoring tests with 15 moderately trained panelists. Physicochemical properties (water activity and pH), total LAB counts, LAB characteristics, and crude EPS content were analyzed using standard laboratory methods. The results showed that immersion time significantly affected sensory acceptance, physicochemical properties, LAB population, and EPS content (p < 0.05). The highest hedonic acceptance was obtained at 4 h of immersion, while the highest quality scores, LAB counts, and crude EPS content were observed at 5 h. Increasing immersion time decreased pH and increased water activity, indicating enhanced acid diffusion and protein modification. LAB isolates were identified as Gram-positive, non-motile, heterofermentative bacteria. These findings indicate that Jungga citrus immersion time plays a critical role in determining the sensory quality, microbial activity, and physicochemical stability of tilapia naniura. An immersion time of 4–5 h is recommended to achieve optimal product quality, LAB development, and potential EPS production, supporting the development of safe and functional traditional fermented fish products in Indonesia.