Characterization of codfish gelatin: A comparative study of fresh and salted skins and different extraction methods

The use of alternative sources for gelatin extraction is in demand in today's industries. Fish skins are an economical and sustainable source option. However, there is a lack of information about the preservation state of skins (fresh, frozen, salted, etc.) and how that affects the gelatin yield and properties, and therefore, compromise the final product.

In this study, we present a comparative analysis between different reported gelatin extraction processes for fresh and salted codfish (Gadus morhua) skins. The extracted products were characterized based on yield of extraction, amino acid composition, molecular weight distribution, rheological properties and gel strength, as well as the cell compatibility of the gelatins envisaging future biomedical applications.

Results showed that extraction method affected the yield and gelatin properties within the same type of fish skin. Thus, it was found that water acidification step, demonstrated higher extraction yield, while other methods produced gelatins rich in OH-proline + proline, promoting enhanced gel strength and rheological properties. There is thus a compromise between yield and gelatin properties that industries need to understand before selecting their gelatin extraction method. Results, also showed that gelatins derived from salted skins demonstrated lower viscoelastic properties and gel strength, when compared with gelatins from fresh skins.

Our research represents a unique comparative compilation of different extraction methods in cod skins differently conserved, as a tool on the quest for the sustainable valorization of fish by-products, included in a circular economy framework.