Effects of formalin residues in marketed fish in Haryana on physicochemical and textural properties and their mitigation strategies

Formalin, a solution of formaldehyde, is widely misused in the fish trade due to its antimicrobial and tissue-firming properties. This study investigates the prevalence and impact of formalin adulteration in fish marketed across four major cities of Haryana, India-Faridabad (FDB), Yamuna Nagar (YNR), Panipat (PNP), and Bahadurgarh (BHG). Seven species, including both locally sourced and imported, were assessed across seasons to evaluate formalin content and its effects on physicochemical (pH, protein solubility, and water-holding capacity), textural property (Hardness) and Microbial load (TPC). Results revealed significantly ( p < 0.05) higher formalin levels in imported fish, particularly during warmer months (May), with pangas and catla showing peak contamination (> 30 mg/kg). Furthermore, analysis revealed that exogenous formalin adulteration significantly ( p < 0.05) lowered muscle pH, protein solubility, and water-holding capacity, while increasing hardness, reflecting protein cross-linking and structural degradation. Microbial load was lower ( p < 0.05) in adulterated samples due to formalin’s antimicrobial action. To mitigate contamination, four decontamination strategies were evaluated: tepid water immersion (50–55 °C), saline washing (5% NaCl), frying (180 °C), and tap water rinsing. Tepid immersion achieved the highest formalin reduction (up to 99.7%). Parallel association confirmed formalin’s negative impact on fish muscle integrity, underscoring the need for routine monitoring. Overall, this study highlights formalin misuse, its adverse quality impacts, effective removal methods, and regulatory implications.