Abstract
Nowadays, there is a growing interest for foods with a lower sugar content and rich in fiber and biologically active substances. The main purpose of this study was to prepare flakes from non-traditional pigmented cereals (Oryza sativa, Chenopodium quinoa, and Eragrostis tef) and to analyze their fibre, sugar, and in vitro digestibility values. Regarding phenolic antioxidants (soluble, soluble conjugated, and insoluble bound fractions), their content and antioxidant activity were measured using spectrophotometry and high performance liquid chromatography (HPLC) methods. Hydrothermally treated grains resulted in flakes with higher total dietary fibre contents (11.1–24.4%), quinoa and teff flakes were rich in maltose (up to 42.0 mg/g). Non-traditional flakes had lower in vitro digestibility, but conversely, they exhibited the highest phenolic contents corresponding with the highest antioxidant activity values (up to 2.33 mg Gallic acid equivalent/g of total phenolic content and 1.59 mg Trolox equivalent/g for 2,2-diphenyl-1-picrylhydrazyl (DPPH) in case of brown teff). Among free phenolics, the main contributors to an antioxidant activity were p-coumaric, o-coumaric, and gallic acids (r > 0.8186); among the soluble conjugated fractions, they were epigallocatechin, epicatechin, caffeic, and vanillic acids (r > 0.5935); while caffeic, protocatechuic, and ferulic acids (r > 0.5751) were the main contributors among the insoluble bound phenolics.
Highlights
Rice (Oryza sativa L.), quinoa (Chenopodium quinoa Willd.), and teff (Eragrostis tef ) belong to a group of gluten-free cereals or pseudocereals
Epidemiological studies have shown that a diet rich in whole grains with low sugar amount and high content of phenolics, exhibiting antioxidant activity, is able to decrease the risk of diverse chronic diseases, such as cardiovascular and neurodegenerative, type II diabetes, or some types of cancer
The results showed a positive linear correlation between antioxidant activity assays and total phenolic contents (TPC) contents in all fractions while applying ABTS (r = 0.6487–0.9861) and DPPH (r = 0.3795–0.9023) radicals
Summary
Rice (Oryza sativa L.), quinoa (Chenopodium quinoa Willd.), and teff (Eragrostis tef ) belong to a group of gluten-free cereals or pseudocereals. Quinoa, and teff grains are already widely used in diet around the world as a side dish or as a raw material for milling products which are processed into bakery products and breakfast cereals or flakes [1,2]. Since the society is looking for new sources of nutrients, especially ones with high antioxidant activity, we can see a lot of new products on the market. These may be flakes of wholegrain pigmented cereals and pseudocereals which are not widely used in European Union (EU), but it is known that they contain a high amount of minerals, vitamins, fibre, and other biological active compounds [3,4].
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