Role of polysaccharides in food, digestion, and health

Abstract

Polysaccharides derived from plant foods are major components of the human diet, with limited contributions of related components from fungal and algal sources. In particular, starch and other storage carbohydrates are the major sources of energy in all diets, while cell wall polysaccharides are the major components of dietary fiber. We review the role of these components in the human diet, including their structure and distribution, their modification during food processing and effects on functional properties, their behavior in the gastrointestinal tract, and their contribution to healthy diets.

Keywords: Starch; dietary fiber; food processing; health benefits; nonstarch polysaccharides.

Figure 1.

A schematic illustration of the organization of starch in a native granule. (A) Structure of a native starch granule showing alternating regions of amorphous and semicrystalline growth rings. (B) A semicrystalline growth ring showing the repeated layers of amorphous and crystalline regions. (C) Lamellar microstructure of the starch granule displaying the amylose chains in amorphous regions and the amylopectin helices in crystalline regions. Adapted from (Buléon et al., 1998).

Figure 2.

Effects of processing on starch granules. (A) Intact native starch granule. (B) Heat treatment in excess water under high shear conditions results in granular swelling. (C) Granule disruption occurs during starch gelatinization with linear amylose chains leaching out of the granule. (D) Upon cooling, amylose chains aggregate together to form an ordered gel network. (E) Recrystallization of amylopectin and amylose chains occurs upon storage of gelatinized starch. Schematic representation adapted from (Goesaert et al., 2005).

Figure 3.

Food processes targeting starch digestibility. (HHP: high hydrostatic pressure).

Figure 4.

Schematic diagram of carbohydrate digestion through the digestive tract. It is recognized that transit times are not very reliable and we have therefore quoted average times. Some foods reside in the stomach for longer or shorter periods of time. In ileostomy subjects, the remaining part of the meal may reach the terminal ileum after more than four hours while the remaining parts of an almond meal came out of the stoma at 9–12 hours (Maurer et al., 2013).