Feasibility of Enzymatic Protein Extraction from a Dehydrated Fish Biomass Obtained from Unsorted Canned Yellowfin Tuna Side Streams: Part II.

The enzymatic extraction of proteins from fish biomasses is being widely investigated. However, little or almost no research has paid attention to the exploitation of unsorted fishery biomasses. This work is part of a larger study, Part I of which has already been published, and focuses on an extensive characterization of two collagenous samples, namely gelatin (G) and hydrolyzed gelatin peptides (HGPs), extracted from a dehydrated fish biomass coming from unsorted canned yellowfin tuna side streams. The results indicate crude protein fractions of 90-93%, pH values between 3 and 5, white-yellow colors, collagen-like FTIR spectra, and 17% in terms of total amino acid content. Viscosity and the study of dynamic viscous-elastic behavior were analyzed. Thermo-gravimetric analysis was performed to assess the residual ashes. Both samples were investigated to determine their molecular weight distribution via size-exclusion chromatography, with a higher total average molecular weight for G compared to HGPs, with values of 17,265.5 Da and 2637.5 Da, respectively. G demonstrated technological properties similar to analogous marine gelatins. HGPs demonstrated antioxidant activity as per FRAP assay. All the results open up new perspectives for the potential use of these substances in biodegradable packaging, dietary supplements, and skin care cosmetics.

Antioxidant Marine Hydrolysates Isolated from Tuna Mixed Byproducts: An Example of Fishery Side Streams Upcycling.

The aim of this research is to propose simple and scalable processes to obtain bioactive peptides extensively hydrolyzed starting from a tuna mixed biomass. The upcycling of this powdered biomass is challenging since it comes from the unsorted industrial side streams of the tuna canning process (cooked residues from fillet trimming) after a patented mild dehydration useful for preventing its degradation until its exploitation. Two different protocols were proposed, with and without the inclusion of an exogenous enzyme (Enzymatic-Assisted Extraction, EAE), with no relevant differences in yields (24% vs. 22%) and a comparable amino acid composition. Nevertheless, the former protocol (with EAE) provided peptides with an average molecular weight of 1.3 kDa, and the second one (without EAE) provided peptides with an average molecular weight of 2.2 kDa. The two corresponding types of tuna protein hydrolysates (Enzymatic Hydrolysates (EH) and Non-Enzymatic Hydrolysates (NEH)) were characterized by proximate compositions, pH, color profile, amino acid analysis, FTIR spectra, and molecular weight distribution. In addition, several biological analyses were performed to assess their potential use as nutraceutical supplements: special attention has been paid to antioxidant activity using three different methods to quantify it. EH showed the most promising antioxidant activity which could be exploited also in other fields (e.g., biomaterials, cosmetics).

Feasibility of Enzymatic Protein Extraction from a Dehydrated Fish Biomass Obtained from Unsorted Canned Yellowfin Tuna Side Streams: Part I.

This study presents for the first time a scalable process for the extraction of valuable proteins starting from samples of unsorted mixed tuna scraps which were previously dehydrated by an industrial patented process. The aims of this work were both to avoid the onerous sorting step of tuna leftovers, which generally consists of isolating skin and bones for collagen/gelatin extraction, and to improve the logistic of managing highly perishable biomass thanks to the reduction in its volume and to its microbiological stabilization. In view of a zero-waste economy, all the protein fractions (namely, non-collagenous proteins NCs and ALKs, gelatin, and hydrolyzed gelatin peptides, HGPs) isolated in the proposed single cascade flowchart were stabilized and preliminarily characterized. The extraction flowchart proposed allows one to obtain the following most promising compounds: 1.7 g of gelatin, 3.2 g of HGPs, and 14.6 g of NCs per 100 g of dehydrated starting material. A focus on oven-dried gelatin was reported in terms of proximate analysis, amino acid composition, color parameters, FT-IR spectrum, pH, and viscoelastic properties (5 mPa·s of viscosity and 14.3 °C of gelling temperature). All the obtained extracts are intended to be exploited in food supplements, feed, fertilizers/plant bio-stimulants, packaging, and the cosmetic industry.