Extraction of collagen from the vitreous humor of yellowfin tuna (Thunnus albacares) by pepsin-based protein solubilization

Collagen is a protein of high nutritional value; currently obtaining collagen from fishery discards helps to alleviate the global production of waste. Therefore, the objective of this study was to extract collagen from the eye of yellowfin tuna (Thunnus albacares) by pepsin-based protein solubilization. To this end, the hydroxyproline concentration, solubility, protein composition, and amino acid profile of the collagen were determined. The specimens were selected to weigh between 40 and 60 lbs. The eyes were removed and solubilized using three concentrations of pepsin (6%, 8%, and 10%), then incubated for 48 hours at 18 °C. The 10% pepsin treatment exhibited the highest solubility (92.7% ± 0.15), surpassing the other treatments (91.9% ± 0.25 using 8% pepsin and 91.6% ± 0.45 using 6% pepsin). However, the hydroxyproline concentration was higher in the 8% pepsin treatment (2.62 mg/g ± 0.62), and concurrently, the percentage of collagen was 19.5% ± 4.59. In terms of proximal composition, the 6% pepsin treatment yielded a higher protein percentage than the other treatments (4.05% ± 0.03). The amino acid profile demonstrated the presence of essential amino acids. These findings suggest that discarded fishery by-products may be utilized to obtain collagen, a valuable protein for food industries.