Production and Physicochemical Characterization of Gelatin and Collagen Hydrolysates from Turbot Skin Waste Generated by Aquaculture Activities

Abstract

Rising trends in fish filleting are increasing the amount of processing by-products, such as skins of turbot, a flatfish of high commercial value. In line with circular economy principles, we propose the valorization of turbot skins through a two-step process: initial gelatin extraction described for the first time in turbot, followed by hydrolysis of the remaining solids to produce collagen hydrolysates. We assayed several methods for gelatin extraction, finding differences in gelatin properties depending on chemical treatment and temperature. Of all methods, the application of NaOH, sulfuric, and citric acids at 22 °C results in the highest gel strength (177 g), storage and loss moduli, and gel stability. We found no relation between mechanical properties and content of pyrrolidine amino acids, but the best performing gelatin displays higher structural integrity, with less than 30% of the material below 100 kDa. Collagen hydrolysis was more efficient with papain than alcalase, leading to a greater reduction in Mw of the hydrolysates, which contain a higher proportion of essential amino acids than gelatin and show high in vitro anti-hypertensive activity. These results highlight the suitability of turbot skin by-products as a source of gelatin and the potential of collagen hydrolysates as a functional food and feed ingredient.

Characterization of Tuna Gelatin-Based Hydrogels as a Matrix for Drug Delivery

“…The gelatin chain structure obtained by the extraction method from tuna collagen was characterized by GPC and TGA. The GPC eluogram of tuna gelatin (Dry GE) exhibits several overlapping polymeric peaks, starting at 38 min with the elution of high Mw species, up to around 60 min when light scattering signals return to baseline (Figure 2) which is in agreement with skin gelatin from other fish species obtained using an identical extraction process [23][24][25][26]. DOX is a multiring planar molecule, which can provide appropriate binding sites through π-π and hydrogen bonding interactions on the transport of other guest molecules.…”

“…In addition, the tuna gelatin hydrogel features a highly complex viscosity (Figure 13), similar to previously discussed fish gelatins [23][24][25] that is typical of a strong gel matrix in agreement with the previous cryo-SEM analyses (Figure 7). Generally, the higher viscosity of gelatin at steady conditions permits it to maintain the integrity of the gel formulation whereas the change of viscosity produced at the sol/gel transition upon shearing makes it suitable for preparing complex structures with good shape printability upon cooling [5].…”

“…Furthermore, the gelation kinetics of the tuna gelatin hydrogel were determined by monitoring the complex, loss and storage moduli as well as the viscosity on heating in the critical gelation temperature range as revealed by MDSC (10-40 • C) and its subsequent reversibility upon cooling (40-10 • C, Figure 13). A sharp transition in complex viscosity occurs in the thermal interval between 18 • C and 25 • C (Figure 13a,b) as well as the storage and loss moduli (Figure 13c,d) during the heating ramp, which is indicative of the disruption of the hydrogel elastic network and in agreement with the sol/gel transition observed around for 25GE hydrogel by MDSC that is similar to previously reported in the literature for other fish gelatin [5,24,25]. In addition, the resistance of the gel network at 20 °C (at the sol/gel transition) can assessed by studying the frequency dependence of the viscoelastic moduli (Figure 12 The hydrogel network shows a gel-like behavior as indicated by the superior stora modulus over the loss modulus (G' > G'') with a parallel like profile in the frequency ran under study [59].…”

“…22, 8, x FOR PEER REVIEW Furthermore, the gelation kinetics of the tuna gelatin hydrog monitoring the complex, loss and storage moduli as well as the vis critical gelation temperature range as revealed by MDSC (10-40 reversibility upon cooling (40-10 °C, Figure 13). A sharp transiti occurs in the thermal interval between 18 °C and 25 °C (Figure 13a and loss moduli (Figure 13c,d) during the heating ramp, whi disruption of the hydrogel elastic network and in agreement wi observed around for 25GE hydrogel by MDSC that is similar to pr literature for other fish gelatin [5,24,25].…”

Extraction and Characterization of Gelatin from Skin By-Products of Seabream, Seabass and Rainbow Trout Reared in Aquaculture

“…Such considerable amount of by-products requires realistic uses to increase resource efficiency and sustainability in fish production. Viable alternatives include recovery of edible parts from heads, frames, belly flaps and certain viscera [4]; oils rich in polyunsaturated fatty acids from heads, gills, and guts [5]; protein hydrolysates as food and feed ingredients from heads, trimmings and frames [6,7], and gelatin and collagen from both skin and bones [8][9][10]. Among these alternatives, gelatin and collagen extraction are particularly attractive because of their higher value compared with the other options [11,12].…”