ReviewGelatin alternatives for the food industry: recent developments, challenges and prospects
Introduction
Among commercial hydrocolloids used in the food industry, gelatin has been regarded as special and unique, serving multiple functions with a wide range of applications in various industries. Gelatin has long been used as a food ingredient (e.g., gelling and foaming agent), in the preparation of pharmaceutical products (e.g., soft and hard capsule, microspheres), in the biomedical field (wound dressing and three-dimensional tissue regeneration) and in numerous non-food applications (e.g., photography). It is a product obtained by partial hydrolysis of collagen derived from animal skin, white connective tissue, and bones (Morrison, Sworn, Clark, Chen, & Talashek, 1999). So far, the main sources for commercial gelatin are limited to pig skins or cow skins and bones, perhaps due to the relatively low cost of the final gelatin product.
The issue of gelatin replacement has existed for many years for the vegetarian, halal and kosher markets, but has gained increased interest in the last decade, particularly within Europe with the emergence of bovine spongiform encephalopathy (“mad cow disease”) in the 1980s (Morrison et al., 1999). Since then, there has been much concern about using gelatin derived from possibly infected animal parts. Since most commercial gelatins are obtained from either pigskin or cow hide, there has been considerable interest in finding and using alternative substitutes. As a result, academia and industry have been trying for many years to develop alternatives to gelatin that possess most or all of the unique functional properties of mammalian gelatin. Driven by the foreseeable demand for halal/kosher gelatin, industries are now striving to develop gelatin-free products in which mammalian gelatin is no longer used, either as a processing aid or as an ingredient. The search for new gelling agents to replace mammalian gelatin led to patents for fish gelatin production (Grossman & Bergman, 1992) as well as several published methods for fish gelatin extraction (Gómez-Guillén et al., 2002, Gudmundsson and Hafsteinsson, 1997). In addition, various patents have been published on the development of gelatin alternatives or substitutes from plant hydrocolloids such as starch/modified starch, pectin, carrageenan and agar.
A number of review articles (Babel, 1996, Baziwane and He, 2003, Djagny et al., 2001, Ledward, 1986, Veis, 1964, Wasswa et al., 2007, de Wolf, 2003) and books (Schrieber and Gareis, 2007, Ward and Courts, 1977) on gelatin have been published. To our knowledge, a comprehensive review on gelatin alternatives is not yet available. Therefore, in this paper we will discuss the unique properties of gelatin, the rationale of developing gelatin alternatives, the various studies and approaches that have been undertaken to develop gelatin alternatives, and some challenges and prospects. Direction for future studies will also be suggested.
Section snippets
Rationale for developing gelatin alternatives
Religious and vegetarian lifestyle choices may prohibit certain consumer groups from eating foods like yogurt, whipped desserts, low-fat margarine spreads, marshmallows, ice cream, and other products containing gelatin, an animal-based ingredient. The worldwide production of gelatin in 2007 was about 326 000 tons, of which 46% were from pigskin, 29.4% from bovine hides, 23.1% from bones, and 1.5% from other parts (GME, 2008a, GME, 2008b). Production of gelatin from pig skins is not acceptable
The chemistry and structure of collagen and gelatin
Collagen is the source protein from which gelatin is prepared in bulk quantities. It functions as extracellular, structural protein in bone, tendon, skin and the connective tissue of various organs. The characteristic feature of collagen is the presence of one or more domain(s) with exceptional amino acid composition (33% glycine and 22% proline) and exceptional structure: the (rigid) triple extended helix. The triple-helix structure is characterized by three extended left-handed polyproline
Functional properties and uses of gelatin
Gelatin displays multiple functional roles in food processing and formulations. The functional properties of gelatin can be divided into two groups (Schrieber & Gareis, 2007). The first has properties that are associated with gelling, for example, gel strength, gelling time, setting and melting temperatures, viscosity, thickening, texturizing, and water binding. The second group relates to the surface behavior of the gelatin, for example, emulsion formation and stabilization, protective colloid
The unique properties of gelatin
Gelatin offers many special properties that are not easily imitated by other hydrocolloids. An ideal gelatin alternative should, therefore, posses all or at least some of the following properties:
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“Melt-in-the-mouth” property—The physical characteristics of gelatin, such as melting slightly below the physiological temperature of humans, gives the polymer the special “melt-in-mouth” perception leading to intensive flavor and aroma release. This behavior is one of the most important
Possible approaches for the development of gelatin alternatives
It is evident that the task of finding an ideal alternative to mammalian gelatin is very difficult, if not impossible. According to Morrison et al. (1999), the approach to developing gelatin alternatives for the food industry should be application/process-specific. It is unlikely that a universal ingredient will replace gelatin in every food application. Morrison et al. (1999) have proposed some examples of gelatin alternatives (Table 4). In the following discussion, several gelatin
Fish gelatin
Gelatin from marine sources (warm- and cold-water fish skins, bones, and fins), which has not been previously explored, is a possible alternative to bovine gelatin (Kim and Mendis, 2006, Rustad, 2003, Wasswa et al., 2007). One major advantage of marine gelatin sources is that they are not associated with the risk of bovine spongiform encephalopathy outbreaks. Fish gelatin is acceptable for Islam and with a minimum restriction for Judaism. Furthermore, fish skin is a major by-product of the
Development of thermoreversible gel from polysaccharides
An interesting and perhaps significant development in the search for gelatin alternatives is the development of starch gel that is thermally reversible. A number of studies (Hansen et al., 2008, Kaper et al., 2005, Lee et al., 2006, van der Maarel et al., 2005) and patents (Buwalda et al., 2005, Euverink and Binnema, 2005, Trzasko et al., 1986) have been published on the development of thermally reversible gel from starch/modified starch. Most of these studies or inventions are based on the
Other potential polysaccharide-based gelatin alternatives
Many gelatin alternatives proposed for the food industry are polysaccharides, which gel based on cation-induced junction zones, and which do not have the defined melt-set characteristics of gelatin, such as gellan, alginate or carrageenan-based gels. The polysaccharide-based gelatin alternatives generally have less flexible molecular backbones, leading to higher viscosities than gelatin (Morrison et al., 1999).
The ability of some hydrocolloids to form a synergistic gelation could be exploited
Direction for future studies
As has been highlighted in the preceding discussion, current commercial application of fish gelatin as an alternative to porcine/bovine gelatin is limited due to inherent properties such as low melting point and weak gel strength of fish gelatin gels. Currently fish gelatin is being used mainly for niche markets only (Schrieber & Gareis, 2007). To get around these shortcomings, modification via cross-linking has been attempted. Enzyme-catalyzed reactions that are known to cross-link proteins
Conclusions and future outlook
Gelatin, a multifunctional hydrocolloid, is used extensively in food and non-food industries for a variety of applications. However, there is an ever-growing concern among consumers regarding the origin of these gelatins mainly due to religious sentiments and the risk of potential contamination with viruses and prions (such as the BSE prion) as it is widely extracted from animal sources. Fish gelatin is a promising alternative. Even though fish gelatin will not be able to completely replace
Acknowledgments
We gratefully acknowledge and are indebted to our anonymous referees for comments and constructive suggestions for improving the manuscript.
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