Barley

A healthy diversity of gut microbiota is associated with numerous health benefits. To see how processing grains relates to the microbiome in animals, researchers analyzed the gut microbiota of pigs after feeding them whole grain barley and oats, or extruded whole grain barley and extruded oats. Extrusion is a process used to make pasta, cereal, croutons, and other grain products, by sending a flour and water mixture through a die to get uniform shapes. The gut microbiota of pigs eating the extruded grains showed less diversity and less presence of the microbes associated with health. The researchers concluded that “cereal extrusion affects the microbiota composition and diversity towards a state generally thought to be less beneficial for health.”
Food & Function. 2016 Feb;7(2):1024-32. (Moen B et al.)

While fruits and vegetables are known as sources of healthy antioxidants and phenolic compounds, research increasingly shows that whole grains contain them too. In this review, researchers analyzed the total phenolic contents, phenolic acid profile and antioxidant activity of several whole grains, including wheat, corn, rice, barley, sorghum, rye, oat and millet. The review shows that whole grains contain a number of phytochemicals (including antioxidants) and significantly exhibit antioxidant activity. Researchers conclude that the consumption of whole grains is considered to have significant health benefits including prevention of chronic diseases such as cardiovascular disease, diabetes, and cancer because of the contribution of phenolic compounds. 
Critical Reviews in Food Science and Nutrition. 2014 July 30. [epub ahead of print] (Van Hung P et al.)

A food’s nutritional quality is influenced not only by its ingredient list, but also by how it is processed. To see how processing grains affects the bioaccessibility of nutrients in animals, researchers measured the free and bound phenolic acids in pigs after feeding them whole grain barley and oats, or extruded whole grain barley and extruded oats. Extrusion is a process used to make pasta, cereal, croutons, and other grain products, by sending a flour and water mixture through a die to get uniform shapes. The researchers found that the phenolic acids (healthy phytochemicals found in plant foods) were 29% and 14% more bioaccessible in extruded barley and extruded oats, respectively, compared to their non-extruded counterparts. While this is just an animal study, it indicates that different processing methods might make different nutrients more readily available.
Journal of Agricultural and Food Chemistry. 2013 Mar 20;61(11):2739-47. (Hole AS et al.)