Hydrocolloids Research Papers - Academia.edu (original) (raw)

Based on physico-functional properties, gelatin is a biopolymer of great interest in food industry. Especially, its rheological and thermal properties diversify its applications. Mammalian gelatin is the main contributor to total gelatin production, but fish gelatin is also a potential alternative. The extraction method, fish type and intensity of the treatment determines the fate of produced gelatin. However, fish gelatin presents some less desirable properties due to the lesser amount of proline and hydroxyproline residues compared to the mammalian gelatins. Nonetheless, it has a good film forming ability and has been suggested as an alternative to the petroleum-based polymers. This review focusses on extraction, physicochemical properties and film forming ability of fish gelatin. Additionally, studies related to possible improvement in film barrier and mechanical properties are also enlisted. Furthermore, a minor description of legislation regarding toxicity issues of the frequently used active additives (plant extract and nanoparticles) in gelatin films is also presented. Fish gelatin applications should be expanded with the growing technological advances in industrial processes. 1. Introduction: As the global demand for gelatin is continuously on the rise, many potential sources are being sought for combating this growing need. In 2009, the global production of gelatin reached 326 thousand tons; majorly derived from pig skin, bovine hides, bones and others sources contributing 46%, 29.4%, 23.1% and 1.5%, respectively. Due to the fact that half of the production is harvested from porcine source, concerns about Halal or Kosher market strongly dominate. Moreover, in the case of bovine gelatin, the prevalence of spongiform encephalopathy necessitates a look up for possible alternatives (Karim and Bhat, 2009). Thus, fish (skin and bone) and other marine sources, along with insects (melon and sorghum bugs) are being exploited simultaneously. Nevertheless, fish, being in bulk and abundant, accounts more significantly than the insects. A number of studies have addressed the properties of fish skin gelatins, indicating that their properties differ from those of mammalian gelatins and vary among fish species. Technically, the term gelatin, applies for a series of proteins obtained from collagen after partial hydrolysis, obtained from bones, skin, hides, ligaments and cartilages, etc. (Gómez-Guillén and Montero, 2001). In the conversion process of collagen to gelatin, acid or alkali pretreatment hydrolyze the cross-linking bonds between polypeptides and irreversibly results in gelatin (Yang et al., 2008). The gelatin is water soluble and forms thermo-reversible gels with the melting temperature near to the body temperature (Norziah et al., 2009). The quality of resultant gelatin is determined by its physicochemical behavior that is further based on the species as well as the process of manufacture. Moreover, the specific amino acids and their respective amounts determine physical and functional behavior of gelatin. The higher the level of proline and hydroxyproline, the higher will be the melting point and gel strength (Karim and Bhat, 2009). According to one report (Farris et al., 2009) fish gelatin holds around 20% of proline and hydroxyproline than the bovine or porcine gelatins, which lower the gelling and melting by 5-10°C. Generally, compared to mammalian gelatin, fish gelatins hold lower gelling and melting temperatures, and lower gel strength as well (Norland, 1990). Gelatin is one of the most commonly used food additive and is an ingredient of many recipes. The proteinaceous nature of gelatin makes it an ideal food ingredient with high digestibility in certain types of diets (Johnston-Banks, 1990). As an additive, it improves water holding capacity, texture, elasticity, consistency and stability of foods (Zhou and Regenstein, 2005). Additionally, it has been used as a stabilizer, emulsifier, clarifying agent and as a protective coating material. Desserts, ice cream, jelled meat, confectionary, dairy and bakery foods are few of the main consumption areas for gelatin. Moreover, in pharmaceutics, it is used in manufacturing of capsules, tablet coatings, emulsions, ointments and skincare products. Despite the vast applicability of gelatin, theories about structure-function relationship are still under discussion. A 3D model is widely presented using fringed micelle model where microcrystallites are interconnected to amorphous segments of randomly-coiled regions. Some others suggest the presence of quaternary structures that are self-limiting in size, making triple helix or partial triple helix or turn and sheet motifs (Pena et al., 2010).