Impact of Oil Frying on the Physicochemical Properties and Nutritional Quality of Hilsa Fish ( Tenualosa ilisha )

This study investigated the effects of frying duration on the physicochemical properties, nutritional composition, and sensory quality of Hilsa ( Tenualosa ilisha ) fried in mustard oil at 170°C–180°C for 0–12 min. Frying resulted in significant moisture loss (68.50%–41.35%) accompanied by increased fat content (12.32%–27.25%) due to oil absorption. Although protein content increased on a wet basis (18.52%–21.26%), dry‐basis protein declined markedly (58.79%–35.55%), indicating thermal degradation. Prolonged frying caused substantial reductions in essential amino acids, particularly lysine and histidine, and significant losses of polyunsaturated fatty acids including a 59% decrease in eicosapentaenoic acid (C20:5n‐3, EPA). Conversely, saturated fatty acids increased from 42.64% to 49.17%, along with a rise in trans fatty acids. Lipid oxidation intensified with frying time, as evidenced by increases in peroxide value (5.11–6.84 meq O 2 /kg) and acid value (3.95–6.85 mg KOH/g), alongside a decline in iodine value (57.34–38.68 g I 2 /100 g). Color analysis showed significant darkening ( L * decreased from 65.22 to 41.24) and increased redness ( a * from 2.56 to 5.32), whereas textural properties indicated increased hardness (12.50–36.52 N) and chewiness, with reduced springiness and cohesiveness. Mineral contents increased due to moisture loss and concentration effects. Sensory evaluation identified 3–6 min as the optimal frying duration, yielding the highest scores for flavor, texture, and overall acceptability.