ABSTRACT

In this chapter, we examine the relationship among the structure of pectic polysaccharides, their physical chemistry, and functional behavior relevant to food use. Pectins are found in the primary cell wall of higher plants1-3 where they have a range of functions, including contributing to the mechanical properties of the cell wall and its hydration characteristics and acting as a barrier to the invasion of pathogens. Pectin structure shows variation with botanical origin, cell wall type, and cell wall development. Extracted pectins find use in the food industry as gelling, thickening, and film-forming agents. Commercially useful pectins come from a relatively limited range of materials such as apple pulp or citrus peel. It is inevitable that the extraction procedure modifies the polysaccharide to some extent, and it may be further modified, after extraction, by chemical or enzymatic means. Studies on pectin may have a number of motivations, including trying to explain its role in the plant cell wall or understanding its behavior as a food ingredient. Cell wall studies often focus on the complexity of pectin structure and its variation with plant type and cell development. Food-related studies are often more concerned with the functional behavior of extracted polysaccharides of somewhat simpler structure. In this chapter, we draw on literature from both areas, as both are relevant to understanding the relationship between pectin structure and its functionality. The functionality that forms the focus of this chapter is the contribution of pectic polysaccharides to mechanical properties of materials.