Rye and Health

CHAPTER 1

Rye and Rye Bread— An Important Part of the North European Bread Basket Kaisa Poutanen VTT Technical Research Centre of Finland, VTT, Finland, and Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland

Production and Uses of Rye

Rye (Secale cereale L.) is to a large extent a European grain, as 90% of the world rye production (18.3 million tonnes) in 2009 was in Europe (according to FAOSTAT, the statistics platform of the Food and Agriculture Organization of the United Nations). Even though rye production was then only 0.8% of the total grain production, rye is, along with wheat, an important raw material of bread baking especially in Northern and Eastern Europe. The total production increased slightly, by 0.6 million tonnes, from 2004 to 2009. The trends in European agriculture toward sustainability may lead to increasing interest in rye cultivation (Altpeter and Korzun 2007). Rye is cold resistant and can be grown in soil with low fertility, so it can be cultivated in areas not very suitable for other cereal crops. Of the 16.5 million tonnes of European rye produced in 2009, about 30% was used for food, the majority of it in areas close to the Baltic Sea. As pointed out by SahlstrĂśm and Knutsen (2010), the major producers are in the same region. The Russian Federation, Germany, and Poland are the largest producers, with 12.3 million tonnes in

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2009, followed by Belarus and Ukraine (Table 1.1). These five countries made up 79% of world rye production and 88% of the rye production in Europe in 2009.

Rye is an important part of the cereal food culture in Germany and in the Nordic, Baltic, and Eastern European countries. The staple rye food, rye bread, is often made of whole-­grain flour using sourdough technology. This makes it a good source of dietary fiber, phenolic compounds, vitamins, and trace elements and minerals.

For example, in Finland, 90% of rye consumption (14 kg per capita per year) consists of whole-­grain flour (Finnish Bread Information 2012). Rye crisp bread, the dry form of rye bread, is probably the best-­known rye bread globally. Rye bread seems to have beneficial effects on glucose metabolism and postprandial satiety, as described later in this book. Expanding research data about the various components of rye grain beneficial to health have increased the interest in using rye for food and in the development of new products. Rye also has long been used as porridge and in breakfast cereals. Some traditional Finnish rye foods include Karelian pastries, made of a thin “skin” of rye dough filled with rice or barley porridge, and Kalakukko, fish and meat baked in a thick rye cover that provides a shelf-­stable complete meal in one loaf. Mämmi, the Finnish Easter pudding, is based on the action of rye malt enzymes on rye flour; after partial liquefaction of starch, the naturally sweetened pudding is baked in the oven for several hours to reach its typical dense texture and almost black color. In the Nordic countries, a widespread range of modern products containing rye is also available, including pasta, biscuits, rice substitutes, frozen dough, and snacks. Rye baking mixes, puddings, and flakes, as well as rye hamburgers, can also be found in Scandinavian markets.

Chemical Composition of Rye Grain

The overall chemical composition of rye is shown in Table 1.2. Rye grain is rich in dietary fiber, which is concentrated in the bran but is also present in the endosperm more than it is in wheat grain (Fig. 1.1). In the HEALTHGRAIN variety screen study, the content of dietary fiber in different rye varieties varied from 20.4 to 25.2%, whereas total arabinoxylan content was 12.1–14.8% and 3.1–4.3% in the bran and flour fractions, respectively (Nyström et al 2008, Shewry et al 2010). Rye also contains about 2% β-­glucan (Nyström et al 2008) and 4–7% fructan (Karppinen et al 2003). Rye fiber is further discussed in Chapters 3 and 4.

Rye contains 11.2–15.8% protein (Nyström et al 2008, Shewry et al 2010). Rye prolamins (secalins) behave quite differently from wheat prolamins in baking, as they are not able to create comparable amounts of polymeric proteins and form a

Importance of Rye and Rye Bread

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gluten-足t ype network as in wheat baking (Gellrich et al 2003). Thus, the structure of rye bread is very different from that of wheat bread, and the cell walls and their polysaccharides have an important role in whole-足meal rye bread baking (Parkkonen

Fig. 1.1. Micrographs of a cross section of rye grain (A) and rye bran (B). Cell walls (blue) have been stained with Calcofluor and protein (red) with acid fuchsin. (Courtesy Ulla Holopainen-Mantila, VTT Technical Research Centre of Finland)

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et al 1994, Autio et al 1997). In sourdough, rye proteins are partially hydrolyzed and probably influence the properties of bread in many ways (Tuukkanen et al 2005).

This may open interesting possibilities in terms of physiological responses.

Rye is also rich in phytochemicals, such as the phenolic compounds (Bondia-­ Pons et al 2009), vitamins, and minerals. These may contribute to the typical flavor of rye (Heiniö et al 2008). While phenolic acids are the phenolic compounds present in the highest quantities, rye also contains significant amounts of lignans, alk(en)ylresorcinols, and also benzoxazinoids. Rye also contains folate, tocols, and sterols, the content of the latter two correlating with arabinoxylan content (Nyström et al 2008). The genetic variation of five rye lines studied with respect to phytochemical components was very limited compared with the strong impact of environmental factors (Shewry et al 2010), and especially the content of phenolic acids was more dependent on environmental conditions during cultivation than on the genetic origin of the grain. The bioactive compounds, together with dietary fiber, are concentrated in the germ and outer layers of the rye kernel (Nilsson et al 1997, Liukkonen et al 2003).

Frolich et al (2013) pointed out that different whole grains and whole-­grain foods have distinct properties. Rye contains 19–22% dietary fiber, which is more than that in other cereal grains (Åman et al 2010), and it has a wide range of distinct bioactive compounds. As pointed out by Frolich et al (2013), the specific properties of each cereal type, as well as the processing methods, should be considered when evaluating the health properties of cereals. This is one of the aims of the current book regarding rye grain and foods.

Consumption and Nutritional Significance of Rye and Rye Bread

Rye has recently been pointed out, from a British perspective, to be “the overlooked cereal” (Buttriss 2006). Nevertheless, Poland and Belarus have a rye supply of more than 30 kg per person per year (Table 1.3). However, the consumption trend is decreasing (Sahlström and Knutsen 2010). In the Nordic and Baltic countries, the supply is in the range of 11.7–19.1 kg per capita per year. Whole-­grain bread, with rye bread as an important example, is one component in the healthy Nordic diet,

Importance of Rye and Rye Bread

5

with many demonstrated physiological benefits (Uusitupa et al 2013). In Finland, users of rye bread make up 85% of the population, and the consumption among the users is 124 g/day (men) and 78 g/day (women). This means that rye bread is the most important source of dietary fiber consumption in Finland, the total of which is 24 g/day for men and 21 g/day for women (Paturi et al 2008). Intake of dietary fiber, especially grain dietary fiber, has been shown to be protective toward many chronic diseases, especially cardiovascular disease and type 2 diabetes (Hauner et al 2012). Similar findings are repeatedly reported for intake of whole-­grain foods (Ye et al 2012). The traditional forms of rye bread often use the outer grain layers as well as the inner ones. Rye bread thus has an important role for public health.

The European Food Safety Authority has recently accepted a health claim about consumption of rye fiber and changes in bowel function (EFSA 2011).

The consumption of rye bread decreased in Finland as eating habits changed in the 1900s, but at the end of the century, the female population slightly increased its rye bread consumption (Prättälä et al 2001). The declining consumption of rye and increased use of white wheat bread during the 1900s pose challenges for the development of new food uses of rye grain but also for consumer communication about the importance of whole-­grain rye and rye bread in nutrition and health.

Studies about barriers to whole-­grain intake have shown that factors preventing individuals from consuming whole-­grain foods include taste preferences, lack of cooking skills, price, and lack of availability of whole-­grain foods (Kuznesof et al 2012). Encouraging increased consumption of local healthy diets is a joint challenge for scientists, food producers, and health professionals. Rye and rye bread have an established role in the diet of many countries, with much potential for increased use and public health benefits.

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