Synthesis and properties of fish protein‐based hydrogel

Abstract

The novel use of fish protein (FP) in the manufacture of a superabsorbent hydrogel was investigated. Following the introduction of a large number of hydrophilic groups into fish protein by modification with ethylenediaminetetraacetic dianhydride (EDTAD), proteins were cross-linked by sulfhydryl-disulfide interchange reaction between the endogenous sulfhydryl groups and disulfide bonds to produce an insoluble gel structure. The water uptake of 76% EDTAD-modified FP hydrogel was 540 g water/g dry gel at 214 × g, and it depended on pH and ionic strength of the solution. The structural changes in proteins consequent to modification were also investigated. EDTAD-FP hydrogels had increased rigidity after glutaraldehyde treatment but displayed diminished water uptake characteristics.The total world fishery catch was about one million metric tons in 1993 (1), of which approximately 30% can be considered underutilized and unexploited by-catch (2). Typically, most of these low-cost fish resources are used in the manufacture of fish meal. Besides the underutilized trash fish, the waste generated from fish processing operations contains 27-49% protein on a dry weight basis and constitutes another valuable resource (3). Since the 1940s, a variety of chemical modifications have been employed to modify the functional properties (water absorption, emulsifying activity, emulsifying capacity, gelation and aeration capacity) of fish protein (FP) concentrate (4-6). However, these chemically modified protein products have never been introduced in the market owing to safety concerns. In the present study, a new application for FP as a superabsorbent hydrogel for nonfood uses has been investigated. The process to synthesize FP hydrogel and the swelling properties of the gel are described. EXPERIMENTAL PROCEDURESMaterials. Ethylenediaminetetraacetic dianhydride (EDTAD) and N-acetylhomocysteine thiolactone (NAHCTL) were obtained from Aldrich Chemical Co. (Milwaukee, WI). Picrylsulfonic acid (TNBS), 25% glutaraldehyde solution, and 5,5′-dithio-bis(2-nitrobenzoic acid) were from Sigma Chemical Co. (St. Louis, MO). All other chemicals were of analytical grade. Heat-sealable, water-wettable paper was purchased from Bolmet Inc. (Dayville, CT).Preparation of crude FP. The fish used in this study was walleye pike (Stizostedion vitreum), obtained from a Wisconsin fish farm. The fish were filleted immediately upon arrival, and whole muscle was chopped and blended in chilled deionized water at a meat-to-water ratio of 1:10. The pH of the fish suspension was adjusted to 12 by the addition of 2.5 N NaOH solution, and the suspension was mixed for 30 min to totally solubilize the fish protein (FP) from muscle cells. The suspension was filtered through a 0.5-mm sieve to remove insoluble material. The filtrate was dialyzed against water (the molecular weight cut-off of the membrane was 6,000-8,000 Daltons) and lyophilized.Protein determination. The protein content of the lyophilized sample was determined by subtracting the lipid and moisture content of ...

Synthesis and absorbency of a superabsorbent from sodium starch sulfate-g-polyacrylonitrile

“…Research on superabsorbents was initiated by the development of a starch-based superabsorbent, Superslurper, by the U.S. Department of Agriculture, Northern Regional Research Center, in the late 1960s. 1 Since then, modification of natural raw materials such as starch, 2 cellulose, 3,4 and protein 5 and direct synthesis from hydrophilic monomers such as acrylamide 6,7 and acrylic acid 8,9 with crosslinkers have been utilized to prepare superabsorbents.…”

Chemical Modification and Structural Analysis of Protein Isolates to Produce Hydrogel using Whitemouth Croaker (Micropogonias furnieri) Wastes

“…The isolate obtained from acid solubilization, in the rate EDTAD/protein (0.5), attained 72.4% of lysine residue modification, while the isolate obtained from alkaline solubilization reached, at the same condition, 63.5% of modification. In a similar study, however, using alkaline protein isolate from meat fish in a chemical modification with EDTAD/protein (0.5) was found to have a modification of 75.9% of lysine residues [26]. Using soy protein isolate, it reached a modification of 90% of lysine residues when EDTAD/protein (0.5) was used, which shows that soy proteins are more sensitive to chemical modification [24].…”

“…The EDTAD used was purchased from Sigma Chemical Co. The procedures were carried out as reported by other researchers [26]. The chemical modification procedure and analyses were done in triplicate.…”

“…All swelling studies were carried out at room temperature (25±2°C). The water uptake of gel was indicated by the weight of water absorbed divided by the weight of dried gel [26]. The wet pouch with swollen gel was dried in an oven at 105°C to constant weight.…”

“…The electrophoresis profiles of all EDTAD-modified isolated show significant amounts of high molecular weight protein polymer that could not penetrate the stacking and separating gel. According to Hwang and Damodaran [26], the polymerization must be due primarily to the formation of intermolecular cross-linking by the bifunctional EDTAD. The formation of other covalent bonds might be produced under alkaline reaction conditions used for modification.…”