Peter J. Wood, Agriculture and Agri-Food Canada, Guelph Food Research Centre, Guelph, ON Canada
OATS: Chemistry and Technology, Second Edition
Pages 219-254
DOI: https://doi.org/10.1094/9781891127649.011
ISBN: 978-1-891127-64-9
Abstract
The mixed-linkage polysaccharide, (1→3)(1→4)-β-D-glucan (β-glucan), of cereals possesses several functionalities and roles that make it unique as a plant cell wall component and as a dietary fiber. Oat β-glucan was first reported in oat kernels by Morris (1942). A similar polysaccharide in barley was recognized as having a significant role in malt and beer production, which stimulated a considerable amount of research into the barley (1→3)(1→4)-β-D-glucan, but, until the 1980s, there was no equivalent stimulus for similar research on oats. In the 1980s, clinical research indicated that inclusion of rolled oats and oat bran in the diet may lower serum cholesterol levels (Chapter 12), which has led to an explosion of interest in oat (and barley) β-glucan and the foods that contain them. Based on studies of the ability of viscous water-soluble polysaccharides, such as guar gum, to attenuate blood glucose and insulin levels and lower serum cholesterol, it was suggested that the physiological effects of oats were due to the β-glucan, which, like guar, is a water-soluble viscous polysaccharide. It is generally accepted that for every 1% lowering of serum low-density lipoprotein (LDL) cholesterol levels, the risk of development of coronary heart disease is lowered by 1–2% and that lowered insulin levels reduce the risk of developing insulin insensitivity and metabolic syndrome1. Diets with a low glycemic index and high dietary fiber are associated with reduced risk of development of type 2 diabetes and heart disease (Salmerón et al 1997, Ludwig et al 1999, Wolk et al 1999, Meyer et al 2000).
In this chapter, oat β-glucan is reviewed with respect to structure and physical properties, extraction, and analysis. Where data on other cereal β-glucans and the structurally similar lichenan (or lichenin) from the lichen Iceland moss are relevant, these also are reviewed. Aspects of biosynthesis that relate to structure are briefly discussed. Animal and clinical studies of physiological effects of isolates of oat β-glucan are also reviewed, with a focus on the role played by physicochemical characteristics.
