![]() Followed by the production from bovine hides and accounts for 29.4%, and bovine bones and accounts for 23.1%. The global production of gelatin from porcine skin is considered the highest and accounts for 46% of the overall production. Gelatin is derived from many sources and there is an increasing demand on it due to its many applications. Preparation method of gelatin from collagen. These different steps are summarized in Figure 1. The second step involves heating through water which comprises the actual extraction of gelatin, and the last step includes filtration and drying of gelatin, grinding into solid powder which can be used to prepare sheets. This leads to different gelatin types, such as Gelatin A and Gelatin B, which have different features, and different applications. ![]() ![]() ![]() Acidic treatment is preferable for collagen of the skin of both fish and pigs, which has less crosslinking of covalent bonds, whereas the alkaline treatment is preferable for collagen of the bovine hides that has more covalent bonds and are more complex. The difference in treatments is based on the source of collagen. The conversion process of collagen to gelatin involves three main steps the first step involves washing of the source of collagen and pre-treatment with alkali, acid, or enzymes such as pepsin. Gelatin is obtained by partial hydrolysis and incomplete breakage of the crosslinking of collagen molecule. These are necessary for its function as the main protein in skin, bones, and tendons. The unique structure of collagen gives it a group of desired characteristics, such as rigidity, flexibility, and strength. Type IV originates from the basement membranes, and so forth. While type II is derived from cartilages and Type III is the embryonic type. Type I is the most abundant and comes from the skin, tendons, bones, cornea of the eye, lung, and blood vessels. There are very slight differences in the components of amino acids of which collagen is constituted according to its source, which results in variable types of collagen (type I, II, III, V, XI, XXIV, XXVII). These amino acids are organized in a repeated sequence. Furthermore, the most abundant sequence of amino acids in the triple helix structure is proline (22%), glycine (33%), alanine (11%), hydroxyproline and hydroxylysine. The three chains are connected with each other through hydrogen and covalent bonds, which gives collagen its distinguished level of strength. Collagen comprises almost all the 20 amino acids. Each strand has a molecular weight around 105 KDa and is 300 nm long. It is made of three strands and is considered a large protein that has a molecular weight around 350 KDa. Collagen is the main constituent of connective tissues, bones, cartilages, tendons, skin, and scales. Gelatin is derived from the parent protein, collagen, which is a ubiquitous fibrous protein found extensively in the tissues of mammalian species. Additionally, expansion into cosmetic applications and drug delivery is needed. However, extensive research is still needed to characterize gelatin hydrolysates, elucidate the Structure Activity Relationship (SAR), and formulate them into dosage forms. It can be easily modified to enhance its mechanical properties. It has unique rheological properties, making it more suitable for certain applications than mammalian gelatins. The main outcomes are that fish gelatin is immunologically safe, protects from the possibility of transmission of bovine spongiform encephalopathy and foot and mouth diseases, has an economic and environmental benefits, and may be suitable for those that practice religious-based food restrictions, i.e., people of Muslim, Jewish and Hindu faiths. It also covers its pharmaceutical applications including manufacturing of capsules, coating of microparticles/oils, coating of tablets, stabilization of emulsions and drug delivery (microspheres, nanospheres, scaffolds, microneedles, and hydrogels). It covers cosmetic applications, intrinsic activities, and biomedical applications in wound dressing and wound healing, gene therapy, tissue engineering, implants, and bone substitutes. This review is comprehensive, specific to fish gelatin/hydrolysate and cites recent research. Its packaging application in food industry is extensively covered but other applications are not covered or covered alongside with those of collagen. There are several reviews that separately cover different aspects of fish gelatin including its preparation, characteristics, modifications, and applications. ![]()
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