Robert Witkowicz

Identification of polyphenolic compounds and determination of antioxidant activity in extracts and infusions of buckwheat leaves

The objective of this study was to determine the chemical composition in the dried leaves and the content of bioactive compounds, antioxidant activity as well as the identification of polyphenolic compounds not only in extracts but also in infusions prepared from leaves of selected strains of buckwheat. To the best of our knowledge, it is the first comprehensive and in-depth study, which focuses on identification and quantitative determination of individual polyphenolic compounds of buckwheat leaves. Furthermore, the aim of presented research is to analyse the new, unknown strains of buckwheat. A statistically significant effect of strain on the content of individual components was observed. The extracts contained more polyphenols and were characterized by higher antioxidant activity than infusions. Strains DW15 and DWO Karzel were characterized by one of the highest contents of polyphenols, dietary fibre, protein, ash and antioxidant activity. Phenolic acids (3,5-diCQA, ferulic acid, sinapinic acid, p-coumaric acid), flavanones (hesperidin), flavonoids (isorhamnetin) as well as flavanols (catechin) and flavonols (rutin, quercetin) in the extracts and infusions, were found. Both extracts and infusions were the richest in ferulic acid. These studies indicate that the buckwheat leaves can be used for preparation of various types of tea and can also be introduced for consumers as the source of bioactive compounds.

Quinoa Tempe as a Value-Added Food: Sensory, Nutritional, and Bioactive Parameters of Products from White, Red, and Black Seeds

This experiment was aimed at comparing the sensory, nutritional, and bioactive parameters of tempe-type products obtained from quinoa seeds by means of solid-state fermentation with Rhizopus oligosporus. Quinoa tempe was compact and nonsporulating, of 61–65% moisture content. The products were favorably assessed by a sensory panel. Tempe from colored and white quinoa differed according to descriptive profiling of texture and flavor. As compared with the substrates, tempe had more protein (15–20%), free amino acids (5.5-fold to ninefold), and fiber (on average 48%, with increased share of soluble fraction), higher antiradical activity (160%), and higher reducing power. Quinoa tempe contained on average 160 g/kg dry matter (DM) of protein, 759 g/kg DM of carbohydrates, and 56 g/kg DM of fat. Black quinoa tempe was the richest in total fiber (180 g/kg DM) and insoluble fiber (155 g/kg DM). Products differed according to antioxidant parameters: white quinoa tempe had the highest phenols level (6.8 mg/g DM), A...