Гречишные травяные чайные напитки: сырье, способы получения и оценка биологической активности

Abstract

Introduction. Buckwheat grain has long been used in food technology. However, its aboveground part remains understudied even though it is richer in biologically active substances than grain. The research objective was to evaluate the potential of buckwheat grass as a raw material for functional tea beverages.
 Study objects and methods. The research featured the lower and upper parts of the stem, leaves, and flowers of common buckwheat, as well as buckwheat tea beverages. The content of polyphenol compounds was determined by the Folin-Ciocalteu method, while the amount of rutin was measured by HPLC analysis. Sensory properties were analyzed by standard methods and quality score, and antioxidant activity – by DPPH radical scavenging method.
 Results and discussion. The sensory analyses proved that the best tea beverages were made from the upper part of the plant: the samples had a strong smell of meadow grass and honey. The taste of the samples was pleasant, sweetish, with a honey and light floral aftertaste. As the total score (maximum score – 20) increased, the tea samples were arranged in the following order: lower stem (14.3) > upper stem (16.8) > leaves, (18.5) > blend – mix of leaves, flowers, and upper stem (18.6) > flowers (19.3). Polyphenol compounds were found in all parts of the plant: flowers – 6.67%, leaves – 5.71%, blend – 5.45%, upper and lower stem – 1.92 and 1.32%, respectively. Only 30–40% of buckwheat grass polyphenol compounds were found in tea beverages. Most of them were in the samples prepared from leaves and flowers – 1.78 %. Rutin made up most of the polyphenol compounds found in the leaves (5.05%), but its content was lower in other parts of the plant: 3.43% in the blend, 3.03% in the flowers, 1.08 and 0.76% in the upper and lower stem. Except for the lower stem samples, the tea contained from 15 to 75% of the daily rutin intake. All the tea samples showed antioxidant activity: flowers – 66.7%, leaves – 62.3%, and blend – 52.5%. In terms of ascorbic acid, it was 69, 64, and 52 μmol/g dry matter, respectfully. The same samples demonstrated antiradical activity.
 Conclusion. Common buckwheat grass can serve as a raw material for tea beverages. Buckwheat tea is a natural functional food product with zero caffeine. They have a pleasant taste and aroma. They owe their high biological activity to the high content of rutin and other polyphenol compounds.