S.S. Miller, Agriculture and Agri-Food Canada, Eastern Cereal and Oilseed Research Centre, Ottawa, Ontario, Canada; R. G. Fulcher, Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada
OATS: Chemistry and Technology, Second Edition
Pages 77-94
DOI: https://doi.org/10.1094/9781891127649.005
ISBN: 978-1-891127-64-9
Abstract
In our quest for sources of food, feed, and industrial raw materials, we sometimes forget that the primary purpose of a mature, viable seed is to produce a new plant. To accomplish this, a seed must include in its organization 1) quiescent vegetative tissue (the embryo) that will generate new shoots and roots during germination; 2) the nutrients necessary for the first few days of growth while young leaves and roots establish photosynthetic and absorptive function; 3) mechanisms to release these nutrients from their storage state and transport them as small, soluble molecules to the germinating embryo; and 4) protection from adverse environmental conditions and potential pathogens. In oats, as in all cereals, each of these functions is the mandate of separate and distinct tissues, leading to an impressive degree of structural and chemical compartmentalization.
Inside the protective hull, the groat (or caryopsis) can be divided into three main components: the bran, germ, and starchy endosperm. These terms are traditional descriptions of commercial milling fractions, however, and do not reflect the genetic, chemical, or functional characteristics of each fraction. A diagram showing the anatomy of a groat (enclosed within the hull) in longitudinal (left) and cross section (lower right) is presented in Figure 5.1. Approximations of the three major industrial fractions are shown within the figure as bran (A), starchy endosperm (B), and part of the germ adjacent to the starchy endosperm (C).
In addition to morphological similarities, oats share many developmental features with other common cereals. Bonnett (1961) published a detailed study of the development of the oat, and a comparison of the similarities and differences in the development of many of the common cereals was reviewed by Evers and Millar (2002).
Both the structure and chemistry of the kernel have impacts on different aspects of oat quality. For the purposes of this chapter, quality can be defined in three ways. After harvest, the oats go to the mill, and the hullability, or ease of dehulling, is an important milling quality parameter, which affects the efficiency and economics of the milling process (Ganssmann and Vorwerck 1995). The architecture of the hull is a major determinant of hullability in oats. Nutritional quality, of course, is extremely important, and oats have long been recognized as having superior quality among cereals with respect to protein and lipid composition, as well as soluble dietary fiber. Several of the chapters in this book are devoted to aspects of oat nutritional quality. Functional quality affects the processing attributes of the grain; that is, how a grain is processed and how it responds to that processing may affect consumer acceptance of the final product. Functionality is also covered in greater detail elsewhere in this book. In this chapter, we look at the structure and chemical composition of the mature oat, using conventional microscopy as well as some newer technologies.
