Phenolic compounds in cereal grains and effects of processing on their composition and bioactivities: a review

Abstract

Cereals are a staple food in the diets of many populations globally. Besides their nutritive function in food, they are also rich in various groups of bioactive compounds, especially polyphenols. Wheat, rice, barley, rye, oat, maize, millet, sorghum, and other cereal grains present a great variety of phenolic acids, flavonoids, proanthocyanidins, alkylresorcinols, and lignans, which can be affected in many ways by the post-harvest treatments and further processing of these feedstocks. This review discusses up-to-date studies about the effects of common cereal processing techniques on their phenolic composition, biological activities, and bioefficiency. Generally, mild thermal and high-pressure treatments enhance cereals’ phenolic composition by releasing the insoluble-bound fraction, which increases their bioaccessibility. On the other hand, processes involving extreme temperature conditions and removal of the grains’ outer layers may drastically reduce the phenolic content. Therefore, it is imperative to optimize the processing conditions of cereals, so their health-promoting benefits are preserved.

Diversity of the Peruvian Andean maize (Zea mays L.) race Cabanita: Polyphenols, carotenoids, in vitro antioxidant capacity, and physical characteristics

“…The storage time have shown to decrease the phenolic concentrations in sorghum grain and flour ( 61 ). Other factors related to the cultivation and harvesting practices also influence the phenolic contents in cereal grains and might also explain observed differences ( 62 ). The TPC range obtained in this study was comparable to that reported by De la Parra et al ( 63 ) (243.8–320.1 mg GAE/100 g DW, samples from the United States) and higher than results found in maize landraces with variable pigmentations from Chile (132.2–262.5 mg GAE/100 g DW) ( 47 ), Mexico (77.3–123.6 mg GAE/100 g DW) ( 64 ) and India (102.3–206.4 mg GAE/100 g DW) ( 65 ).…”

Advances in the novel and green-assisted techniques for extraction of bioactive compounds from millets: A comprehensive review

“…Foxtail millet is another rich source of phenolics [ 50 , 51 ] and moderate amounts of flavonoids [ 51 ], bioactive peptides, carotenoids, and tocols. The major phenolic acids are ferulic acid, vanillic acid, and soluble forms of caffeic and sinapic acids [ 53 ]. Zeaxanthin and lutein are the most common carotenoids in foxtail.…”

Effect of processing on the preservation of bioactive compounds in traditional and exotic fruits: a review

“…Phenolic compounds are secondary plant metabolites and their basic structures consist of a benzene ring to which one or more hydroxyl groups are attached. Depending on their structural features, phenolics can be broken down into several subgroups, including phenolic acids, flavonoids, tannins (hydrolysable and condensed), stilbenoids, lignans, coumarins, and tyrosol (Shahidi et al, 2021).…”

“…In food matrices, phenolics may exist in the soluble (free or esterified/etherified to fatty acids, carbohydrates, and soluble proteins) and insoluble-bound forms (covalently bound to cell wall molecules, such as fiber, cellulose, and structural protein) (Shahidi et al, 2021;Schefer et al, 2021). Flavonoids, the main phenolic class, are present in high amounts in fruits (Pan et al, 2009); their seeds may possess flavonoid glycosides (attached to a sugar molecule) or aglycones (Fang et al, 2005).…”

“…The latter is predominantly found in dark-colored fruits, such as blueberries, grapes, strawberries, blackberries, and blackcurrants, among others. Anthocyanins are water-soluble pigments, and structural changes caused by pH variations alter their color, ranging from red to purple and blue (Shahidi et al, 2021).…”