Gelling Biopolymers

A higher amylopectin content of some starches leads to their higher gelatinisation temperatures, but the lowering which is observed in potato starch indicates the influence of phosphorylation in the latter. The relatively high pasting temperature and low peak viscosity of wheat starch has been attributed to its relatively high content of phospholipid impurities, which form helical complexes with the amylose chains as indicated above. 

Not all the different gelling biopolymers have equivalent rheological properties but, like starch, these properties can be modified by the presence of natural impurities and the presence of OH-substituted groups. Systematic studies of the effect of phosphate substitutions on the gelling polysaccharides remain limited, but the addition of salts (e.g. Na5P30io) to gelling systems has been observed to modify their properties (Chapter 12.4). 

---

A process using a microbially gelled biopolymer was developed and used to modify the permeability in coreflood experiments [128]. Curdlan is a microbial carbohydrate with 1,3-P-linkages. Alkaline-soluble curdlan biopolymer was... 

Lundell, C., Walkenstrom, R, Loren, N., and Hermansson, A. M. 2004. Influence of elonga-tional flow on phase separated inclusions within gelling biopolymer drops. Food Hydrocolloids 18 805-815. 

Owen, A. J. and Jones, R. A. L. 1998. Rheology of simultaneously phase separating and gelling biopolymer mixtures. Macromolecules 31 7336-7339. 

O. Gaserod, P.O. Andersen, and R. Myrvold, Gelled biopolymer based foam, US Patent 7 671100, assigned to FMC Biopolymer AS (Sandvika, NO), March 2, 2010. 

Starch can be isolated as a white powder which is almost insoluble in cold water, although it will absorb some and swell slightly. In hot water irreversible gel formation occurs (see gelling biopolymers below). 

With the exception of starch, many biopolymers cannot provide nutrition for humans and other omnivorous animals. In human foods biopolymers are used as additives that can improve texture, viscosity, fiber content, and other properties of prepared foods, without providing direct nutritional values. Examples of such utilization are the addition of pectins, agar, and other gums to foods to achieve thickening and gelling effects. Another example of potential large-scale utilization of cell wall biopolymers is the dramatic improvement in the texture and rising of breads prepared from com and other starches by the addition of xylans (78). 

This approach was satisfactorily applied to other biopolymer gelled systems, including agarose (Watase and Nishinari, 1987a), HM pectin/dimethyl sulfoxide (DMSO) gels (Watase and Nishinari, 1993), ic-carrageenan (Watase and Nishinari, 1987b) and LM pectin/Ca + and LM pectin/Ca /sucrose systems (Fu and Rao, 1999). 

Baeza, R. and Pilosof, A.M.R. Mixed biopolymer gel systems of 3-lactoglobulin and non gelling gums. Food Colloids 2000 Fundamentals and Formulation, E. Dickinson and R. Miller, eds.. The Royal Society of Chemistry, Cambridge, pp. 392, 2001. 

Formation of condensation structures is the reason for gelation of solutions of various natural and synthetic polymers. Gelation may be accompanied by conformational changes of macromolecules, which occur in the case of gelling of gelatin and other biopolymers, or in the course of chemical reactions. For instance, according to Vlodavets, partial acetalization of polyvinyl alcohol with formaldehyde in acidic medium under the conditions of supersaturation yields fibers of polyvinyl formals which further undergo coalescence and form a network with properties similar to those of leather (and artificial leather substitute). 

Proteins are biopolymers that are encountered in many applications, such as food emulsions, hair conditioners, photographic emulsions, and various medical diagnostic products. Many of these applications are frequently based on the unique surface activity of the proteins, which is reflected in functional properties such as foaming, emulsification, and gelling. The proteins are composed of polymeric chains containing many hydrophobic and hydrophilic domains, often giving the molecules an amphipathic structure somewhat similar to that of polymeric surfactants. 

Gelling Polysaccharides Gelling polysaccharides are generally more complex than structural polysaccharides in (1). They are hetero polysaccharides built from mixed monomer units and they contain many branched in addition to the straight chains as depicted in Equation 10.20e for starch. Starch, the second most abundant biopolymer, is probably the most important (below). 

---