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

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. © 2019 Society of Chemical Industry.

[Studied on Colored Dissolved Organic Matter of Spring in North Yellow Sea with Three-Dimensional Fluorescence Spectroscopy Combined with Parallel Factor Analysis].

This paper conducted fluorescent spectra of dissolved organic matter of Spring China North Yellow Sea by using three-dimensional fluorescence spectroscopy (EEMs) combined with parallel factors analysis (PARAFAC). The results showed that the fluorescent dissolved organic matter (FDOM) in colored dissolved organic matter (CDOM) of North Yellow Sea could be resolved to four components. Two components, c1 (260,315/425) and c2 (295,355/490) were identified as humic-like fluorescence components while c3 (275/310) and c4 (230,290/345) were protein-like components. The different linear correlations showed different degrees of similarities in the source or the chemical constitution, the relationship of the humic-like fluorescence components were most closely, followed by protein-like components. Four fluorescent components and total fluorescence intensity (TFI) in the horizontal and vertical directions had a higher intensity in coastal area than that of the area far away from the coast. Additionally, besides terrestrial input, the seawater mass movement also affects the distribution of CDOM in North Yellow Sea. Cluster analysis not only further illustrated the TFI characteristics of different areas of the North Yellow Sea, but also reflects the overall uniformity of the CDOM. Fluorescence Index (FI), Humification Index (HIX) and Biological Index (BIX) at some extent indicated the source of North Yellow Sea CDOM and the conclusion was that the near shore side gets greater influence from terrigenous sources while the sea side is more impacted by biological activity, which matched with the prior distribution patterns of fluorescence components.