Alteration of phenolic profiles and antioxidant capacities of common buckwheat and tartary buckwheat produced in China upon thermal processing

Abstract

BACKGROUND: Buckwheat products are receiving increasing attention because of their high nutritive values and significant health-promoting properties. In the present study, 15 buckwheat products grown in different parts of China were investigated. Representative common or tartary buckwheat samples were further subjected to soaking, roasting, microwave cooking, boiling and steaming treatments. Colorimetric analyses and high-performance liquid chromatography (HPLC) analyses were performed to determine the phenolic profiles and antioxidant capacities of the raw and thermally processed buckwheat samples, respectively. RESULTS: Tartary buckwheat exhibited a remarkably higher total phenolic content (TPC), total flavonoid content (TFC), 2-diphenyl-1-picryhydrazyl (DPPH) free radical scavenging activity and ferric reducing antioxidant power (FRAP) compared to common buckwheat, although there were no significant differences between their 2,2 ′ -azino-di-(3-ethylbenzthiazoline sulfonic acid) (ABTS) free radical scavenging capacity. All thermal treatments, particularly microwave cooking, contributed to the greatest losses of phenolics and antioxidant capacities in the common buckwheat samples, whereas boiling and steaming usually resulted in the lowest losses. For the tartary buckwheat samples, all thermal treatments (except roasting), especially boiling and steaming, led to significant increases in TPC, TFC, DPPH free radical scavenging activity, FRAP and ABTS free radical scavenging capacity. However, HPLC analyses indicated that all thermal treatments, especially microwave cooking, gave rise to the greatest losses of the total content of 14 phenolic acids and three flavonoids, whereas boiling led to the lowest losses. CONCLUSION: Both steaming and boiling treatments are recommended when preparing common or tartary buckwheat food products because they can minimize thermal degradation or promote their phenolic compounds and antioxidant capacities to the greatest extent.

Use of Sieving as a Valuable Technology to Produce Enriched Buckwheat Flours: A Preliminary Study

“…Kalinová et al (2019) [13] reported the phenolic content in different parts of common buckwheat, in which the content of catechin, epicatechin, and rutin (20.87, 56.51 and 52.48 mg kg −1 d.w.) in groat was in the same order of magnitude as that obtained for whole buckwheat flour in our work [13]. Liu et al (2019) [27] reported the phenolic profiles and antioxidant capacities of common buckwheat and Tartary buckwheat, in which the content of rutin in common buckwheat was 62.19 mg kg −1 d.w. and this value was similar to that obtained in whole buckwheat in the present study (87.33 mg kg −1 d.w.) [27]. Hence, our results are in accordance with the previous studies.…”

Free and Bound Phenolics of Buckwheat Varieties: HPLC Characterization, Antioxidant Activity, and Inhibitory Potency towards α-Glucosidase with Molecular Docking Analysis

“…Owing to the genotypes and growth-influencing environmental factors of buckwheat varieties, significant differences were seen in TPC/TFC. Many studies have confirmed that phytochemical compositions of cereal crops mainly depend qualitatively and quantitatively on its genotypes and environmental factors that influence growth [30,31]. Different lowercase letters (a-e) mean statistically significant differences following different samples at the same fractions (p < 0.05).…”

“…Qin et al (2010) reported that the FP contents (25.3 mg GAE/g DW) were higher than the BP contents (1.8 mg GAE/g DW) in tartary buckwheat bran [15]. Liu et al (2019) confirmed that the highest phenolic content of 15 buckwheat varieties from China was only 7.32 mg GAE/g DW, which was lower than that of samples from Shanxi (13.74 mg GAE/g DW) [30]. In this work, we found that the average TPC and TFC of tartary buckwheat samples (TPC: 9.97 mg GAE/g DW; TFC: 19.26 mg RE/g DW) were significantly higher than those of the common buckwheat samples (TPC: 6.47 mg GAE/g DW; TFC: 10.87 mg RE/g DW) (p < 0.001).…”

Distribution of Free and Bound Phenolic Compounds in Buckwheat Milling Fractions

“…These values were lower than those obtained in bran meal, light flour, and de-hulled grain meal, and also, the content of rutin in seed coat (54.23 mg/kg d.w.) represents a quart of the phenolic bran meal (214.99 mg/kg d.w.) obtained in our study. This could be due to the different cultivar and/or the different methodology of determination of phenolic compounds (by MS detection a higher number of compounds are determined).In addition, Liu et al (2019) [22] reported the concentration of rutin in common buckwheat (62.19 mg/kg d.w.) that was in the same order as that obtained in de-hulled grain meal (87.33 mg/kg d.w.). According to the results obtained in these previous works, it has shown that rutin in the free form is concentrated in the outer layers, which is in concordance with our results.…”