Effects of Brine Concentration and Drying Method on Proximate Composition, Calcium Retention, Lipid Oxidation, Spoilage Indicators, and Sensory Quality of Dried Bilih Fish (Mystacoleucus padangensis) from Lake Singkarak, West Sumatra

Abstract

Bilih (Mystacoleucus padangensis) is a small cyprinid fish that supports an artisanal fishery in Lake Singkarak, West Sumatra, Indonesia, and is commonly preserved by salting and sun drying. Because bilih is consumed whole, including the soft bones, it is a potentially valuable source of dietary calcium. However, the traditional process is poorly standardized: salt levels are set by experience, and open-air drying under humid tropical conditions is slow and exposes the product to oxidation and microbial contamination. This study evaluated the effects of three brine concentrations (5%, 10%, and 15% w/v NaCl) and two drying methods (sun drying and cabinet drying at 55°C) on the proximate composition, water activity (aw), calcium content, lipid oxidation (TBARS), total volatile basic nitrogen (TVB-N), total plate count, and sensory acceptability of dried bilih. A 3 × 2 factorial Completely Randomized Design with three replicates was used, and quality indicators were monitored during 30 days of storage at ambient temperature (28 ± 2°C). Both factors significantly affected all measured parameters (p < 0.001). Cabinet drying produced lower moisture (14.9–17.8%) and aw (0.64–0.71) than sun drying (18.1–21.4%; aw 0.71–0.78). Increasing brine concentration lowered aw and slowed spoilage-related changes in TVB-N and microbial counts, but raised lipid oxidation: TBARS at day 0 was 53% higher at 15% than at 5% brine within each drying method. Cabinet drying reduced TBARS by 37–39% relative to sun drying at all salt levels. After 30 days, only the cabinet-dried samples remained below a TVB-N value of 30 mg N/100 g at every salt level. Salt uptake diluted protein and calcium on a dry-weight basis (calcium 1,276–1,409 mg/100 g), although the products remained rich in both. Sensory acceptability was highest for 10% brine with cabinet drying (overall score 4.3/5.0), which also had the best combined rank across aw, TBARS, TVB-N, and sensory criteria. These findings support salting in 10% brine followed by cabinet drying at 55°C as a practical improvement over traditional practice for bilih processors around Lake Singkarak