The issue of gelatin replacement has been around for many years for the vegetarian, halal and kosher markets, but has recently gained increased interest especially within Europe with the emergence of the bovine spongiform encephalopathy virus. The total gelatin market in western Europe alone is 60,000 tonnes per annum, of which 80% is in foods.
The textural and rheological properties of gelatin when utilised in various food applications is discussed. Various gelatin alternatives are proposed, and the mechanism to alter the functional properties of mixed or single polysaccharide systems is discussed. One possible gelatin alternative for the food industry is gellan gum.
Recent studies have shown that both the levels of glycerate and acetate substituents in gellan gum can be controlled independently. A range of gellan gums with varying structural and functional properties are studied. Changes in the glycerate parameters have a profound effect on the structural and rheological characteristics of gellan gum gels. These new gellan gum products have unique properties and will lead to a range of functionality in food systems with one versatile hydrocolloid ingredient.
Gelatin is a product obtained by partial hydrolysis of collagen derived from the skin, white connective tissue and bones of animals. Industrial preparation of gelatin can occur by one of two routes: an acid pre-treatment, which produces type A gelatin, and an alkali pretreatment, which produces type B gelatin . Gelatin is a high-molecular-weight polymer, which derives most of its functionality from the collagen triple helix that is the basis of the polypeptide gel network. The molecule has a well-defined order-disorder conformation transition,that results in low hot viscosities, and the unique reversible set-melt characteristics of the gel. Also the flexibility of this network gives the elastic properties associated with gelatin gels.
The issue of gelatin alternatives has been around for many years, but has recently gained increased interest especially within Europe with the emergence of the bovine spongiform encephalopathy virus that has infected cattle. This resulted in the bannins of gelatin and beef sales from the United Kingdom to other European Union countries, from 1996 until recently, and has heightened consumer knowledge of the source of gelatin,forcing certain producers to incorporate gelatin alternatives when formulating existing or new processed foods.
Additionally the low melt-set characteristics of gelatin based gels can also be a disadvantage when the formulated product is not refrigerated, especially in hotter climates.
The polysaccharide-based gelatin alternatives generally have less flexible molecular backbones, leading to higher hot viscosities than gelatin.
Many gelatin alternatives proposed for the food industry are polysaccharides, which gel based on cationinduced junction zones, and which do not have the well defined melt-set characteristics of gelatin, such as many gellan, alginate or carrageenan based gels. There are notable exceptions, such as xanthan/locust bean gum gels, which are thermoreversible, but which have relatively high hot viscosities, even compared to polysaccharide gelling systems. The approach to developing gelatin alternatives for the food industry should be application/process specific. It is unlikely that a universal ingredient, or a system of polysaccharide gums, will replace gelatin in every food application.
One possible gelatin alternative for the food industry is gellan gum. Gellan gum is the extracellular polysaccharide produced by the organism Sphingomonas elodea during aerobic fermentation.
The biopolymer is produced with two acyl substituents present on the 3-linked glucose, namely, L-glyceryl, positioned at O(2),and an acetyl substituent at O(6). Gellan gum is currently commercially available in both the high-acyl (HA) and the low-acyl form (LA). When hot solutions of gellan gum are cooled in the presence of gelpromoting cations, gels ranging in texture from brittle to elastic are formed, through principally cation-mediated helix-helix aggregation . A wide range of gel textures can be produced through manipulation of blends of HA and LA gellan gum.
It has been shown that the textural properties of gellan gum are dependent on its acyl content.Partially deacylated products studied include low acetate (cold KOH treatment) and intermediate acyl products (hot KOH treatment). In these studies acetyl substituents were removed in preference to glyceryl residues.
New studies have shown the ability to form acetate-rich gellan gum by chemical treatment. These new products may also be achieved through new strain development.
A comparison is made between these new intermediate acyl products and simple blends of HA and LA gellan gum products.
