Background
Oat (Avena sativa L.) is an important crop, with annual global production of about 22 million tons. It is the seventh most abundant cereal produced in the world. It contains many health-promoting ingredients such as dietary fiber, protein, and minerals (Sibakov, J., 2014). Dietary fiber is closely related to the prevention and treatment of various features of metabolic syndrome (El Khoury et al., 2012). Compared with insoluble fibers, soluble fibers are more effective in decreasing the presence of metabolic syndrome components in humans (El Khoury et al., 2012). Among soluble fibers, 𝛽-glucan is the most frequently consumed. It is associated with reduced presence of insulin resistance, hypertension, and obesity (El Khoury et al., 2012). Also, oat β-glucan has a positive effect on the feeling of satiety (Rebello et al., 2016). However, it may be challenging for the consumers to obtain the recommended intake of β-glucan (at least 3 g/day). For example, a regular portion of oat porridge, which contains 1 dl of oatmeal, provides about 1.5 g of β-glucan (El Khoury et al., 2012). Therefore, technologies for the enrichment of β-glucan ingredients are needed to achieve the recommended daily intake.
β-glucan-rich fractions are easily obtained from grains by dry milling followed by sieving and air classification, or by wet milling followed by sieving and solvent extractions. (Lazaridou & Biliaderis, 2007). Compared to wet extraction, dry fractionation methods exhibit lower energy and water consumption and retain the original structure and functionality of the components (Schutyser & Van der Goot, 2011). It is clear that a more energy-efficient dry fractionation process is the future. However, these techniques are not yet suitable to produce high-purity isolates (Assatory et al., 2019). Increases in product concentration have been achieved by linking different separation technologies together, such as air classification followed by sieve separation. Recent patents show a trend toward technological developments that integrate elements of grinding, sieving, and air classification (Assatory et al., 2019).
In today’s food market, the demand for protein-rich products is increasing. Due to our growing understanding of the issue of animal protein sustainability, there is an increasing demand for plants as a source of protein (Mäkinen et al., 2017). Challa et al. (2010) found that using a combination of sieving and air classification can increase the protein and fiber in soybean meal, cottonseed meal, and wheat middling. There is a desire for increased protein and energy content, so the combination of sieving and air classification could be useful for preparing protein and β-glucan rich fractions with potential for food applications (Challa et al., 2010).
Compared to wet extraction, dry fractionation methods exhibit lower energy and water consumption and retain the original structure and functionality of the components (Schutyser & Van der Goot, 2011). It is clear that a more energy-efficient dry fractionation process is the future. However, these techniques are not yet suitable to produce high-purity isolates (Assatory et al., 2019). Increases in product concentration have been achieved by linking different separation technologies together, such as air classification followed by sieve separation. Recent patents show a trend toward technological developments that integrate elements of grinding, sieving, and air classification (Assatory et al., 2019).
β-glucan-rich fractions are easily obtained from grains by dry milling followed by sieving and air classification, or by wet milling followed by sieving and solvent extractions. (Lazaridou & Biliaderis, 2007). Compared to wet extraction, dry fractionation methods exhibit lower energy and water consumption and retain the original structure and functionality of the components (Schutyser & Van der Goot, 2011). It is clear that a more energy-efficient dry fractionation process is the future. However, these techniques are not yet suitable to produce high-purity isolates (Assatory et al., 2019). Increases in product concentration have been achieved by linking different separation technologies together, such as air classification followed by sieve separation. Recent patents show a trend toward technological developments that integrate elements of grinding, sieving, and air classification (Assatory et al., 2019).
In today’s food market, the demand for protein-rich products is increasing. Due to our growing understanding of the issue of animal protein sustainability, there is an increasing demand for plants as a source of protein (Mäkinen et al., 2017). Challa et al. (2010) found that using a combination of sieving and air classification can increase the protein and fiber in soybean meal, cottonseed meal, and wheat middling. There is a desire for increased protein and energy content, so the combination of sieving and air classification could be useful for preparing protein and β-glucan rich fractions with potential for food applications (Challa et al., 2010).
Compared to wet extraction, dry fractionation methods exhibit lower energy and water consumption and retain the original structure and functionality of the components (Schutyser & Van der Goot, 2011). It is clear that a more energy-efficient dry fractionation process is the future. However, these techniques are not yet suitable to produce high-purity isolates (Assatory et al., 2019). Increases in product concentration have been achieved by linking different separation technologies together, such as air classification followed by sieve separation. Recent patents show a trend toward technological developments that integrate elements of grinding, sieving, and air classification (Assatory et al., 2019).
Oat tissuesThe oat grain is a complex matrix containing a protective hull the groat. The latter consists of bran, germ and starchy endosperm. The bran is an outer layer rich in minerals, vitamins and cell wall polysaccharides, mainly cellulose, arabinoxylan and β-glucan. The endosperm cells have a thinner cell wall and are rich in β-glucan. The concentration of oat protein and lipids increases from the interior to the periphery of the grits, while the concentration of starch increases from the sub-grain region to the center of the endosperm (Mille & Fulcher, 2011).
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Figure 4. Structural representation of the oat grain presenting different oat tissues and the nutrient distribution/organization within these tissues.
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