Marjatta Salmenkallio-Marttila, Raija-Liisa Heiniö, Anu Kaukovirta-Norja, and Kaisa Poutanen, VTT Technical Research Centre of Finland, Espoo, Finland
OATS: Chemistry and Technology, Second Edition
Pages 333-346
DOI: https://doi.org/10.1094/9781891127649.016
ISBN: 978-1-891127-64-9
Abstract
Northern countries like Finland, Canada, and Scotland have a long tradition of using oats in a variety of foods. Even in these countries, however, the consumption of oats is low in comparison with that of other cereals. Processing of oats is required to provide edible products that are stable in storage and have good sensory properties. “Grandmother's” cookbooks contain a variety of oat recipes that form the traditional foods that are the basis of current food uses, namely, porridge, bread, fermented oat custard, and flour made of boiled, lightly smoked oats. Traditionally, oats are used as whole grains. The development of new ingredients, such as various milling fractions (i.e., bran, flour, and hulls) and enriched fractions (i.e., starch, protein, and β-glucan), started in the 1980s in response to accumulating evidence of the health benefits of oat dietary fiber. New functional oat foods conferring specific health benefits are needed to make the most of these nutritionally based assets of oats.
Oats' distinguishing features, in comparison with other cereal grains, are their high lipid and β-glucan concentrations and lower starch concentration. These features give rise to special challenges: lipid oxidation during storage and processing can cause rancid flavors, and the high viscosity of water-solubilized β-glucan—i.e., mixed-linkage (1→3)(1→4)-β-D-glucan—impacts texture and sensory characteristics. Oat starch is special in comparison with other cereal starches. It contains more lipids and has a lower gelatinization temperature and slower rate of retrogradation than cereal starches in general. Oat grain also contains dietary fibers other than β-glucan, as well as vitamins, minerals, phenolic antioxidants, sterols, and proteins high in lysine (Lásztity 1998, South et al 1999). Special properties of oat lipids (Chapter 9), β-glucan (Chapter 11), and starch (Chapter 7) are reviewed in their own chapters.
Appearance, odor, texture, and flavor are key attributes in determining the overall sensory characteristics of a food. Since sensory quality is a crucial criterion in consumer food choice, control of sensory attributes is important to the attractiveness of new oat foods. Oats are considered by most people to make a tasty cereal, and they have a positive health image. However, a tendency to develop rancidity and bitter off-flavors may limit their use. Control of texture is a challenge in products with high levels of dietary fiber, especially soluble β-glucan; sliminess is an undesirable texture associated with oat-containing foods of high water content.
The flavor of native oat grain is mild. The familiar oat flavor is, to a large extent, formed during traditional heat processing and arises from a combination of volatile and nonvolatile compounds, including or produced from phenolics, amino acids and peptides, sugars, and fatty acids. The flavor perceived depends upon the relative amounts of all of these components, some of which have greater influence than others. To some extent, flavor formation can be controlled by careful selection of raw material combinations and processing steps (Heiniö 2003). Knowledge of the chemistry and structure-function relationships of raw materials and products is needed to produce specific qualities that meet consumer expectations.
The usage of oats in various food products (Ranhotra and Gelroth 1995, Welch 1995, Welch and McConnell 2001) as well as the flavor of oats (Heydanek and McGorrin 1986) have been reviewed in the past. Flavor, texture, and color are the salient sensory attributes of cereal foods, and each product has a characteristic sensory profile. For example, crispiness is a characteristic texture attribute of dry cereal products, and roasted flavor is an especially important attribute in thermally processed foods such as bread and other bakery products. An understanding of the influence of different processing systems on oat components, of the role of these components in the flavor and texture of the products, and of consumer preferences and differences should allow sensory quality to be adjusted in the desired direction. There are, for example, large differences between individual perceptions of mouthfeel. Understanding the physiochemical factors involved in mouthfeel requires correlation of instrumental measurements with sensory testing data (Bourne 1994, Meullenet and Gross 1999, Lillford 2001, Autio et al 2003). This chapter reviews literature about recent developments in factors affecting the sensory quality of oat foods and discusses the challenges of combining high sensory quality with health benefits.
