Effect of thermal treatments on anti-nutritional factors and antioxidant capabilities in yellow soybeans and green-cotyledon small black soybeans.

BACKGROUND: The effects of different thermal processes on the anti-nutritional factors (tannins, phytic acids and trypsin inhibitors) and antioxidant capacity of yellow soybeans (YS) and green-cotyledon small black soybeans (GCSBS) were investigated. The soybean samples were subjected to roasting, microwaving and boiling as the thermal treatments. RESULTS: Sixty-minute boiling was most effective for eliminating the tannins in both YS and GCSBS, and also resulted in the maximal reduction of phytic acids. Trypsin inhibitors were most effectively reduced (76.92-97.91%) by microwaving, and boiling was least favourable for retaining total phenolic content. The total flavonoid content was significantly (P < 0.05) decreased by all thermal processes, and particularly by employing 60-min boiling. The total anthocyanin content of GCSBS was higher than that of YS, but significantly declined upon boiling (P < 0.05). Roasting did not significantly affect the DPPH free radical scavenging activity of GCSBS (P > 0.05). Microwaving increased the FRAP (ferric reducing antioxidant power) of GCSBS up to 6.07%. CONCLUSION: Our raw GCSBS possesses much better antioxidant capacity than raw YS. Microwaving resulted in a substantial reduction of the trypsin inhibitors of our soybean samples. Dry thermal treatments caused slight increase of FRAP in GCSBS.

Influence of preheating on antioxidant activity of the water extract from black soybean and color and sensory properties of black soybean decoction.

BACKGROUND: Our previous study indicated that black soybean (BS) tea (BST) made from preheated BS showed a significant protective effect against CCl4 -induced liver damage in Sprague Dawley rats due to BS's antioxidant activity. In this study, we investigated three different preheating methods on the antioxidant activity of water extract from BS (WBS) (Glycine max (L.) Merrill), as well as on the color and sensory properties of BST. RESULTS: WBS baked at 130 °C for 5 min showed high total phenol, flavonoid and anthocyanin contents among three preheating methods, as well as high DPPH radical-scavenging activity, ferrous ion chelating ability and reducing power. BST baked at 130 °C for 5 min had higher polyphenol oxidase activity and L*, a* and b* values but lower peroxidase activity then BST made from unheated BS. Sensory evaluation indicated that BST made from baked BS produced better aroma and flavor than the tea made from unheated BS or a commercial preheated BS. CONCLUSION: An appropriate preheating process improved the amount of extractable antioxidant and the antioxidant activity in WBS. BST baked at 130 °C for 5 min had good flavor properties, as well as high amount of antioxidant.

Structures and electronic properties of the SiAu(n) (n = 17-20) clusters.

The structures and electronic properties of the SiAu(n) (n = 17-20) clusters are systematically investigated using DFT calculations. The result shows that doping with silicon would significantly change the structures of the gold clusters. For the SiAu(n) (n = 17-20) clusters, the lowest-energy structures exhibit shell-like cage configuration in which the dopant Si atom binds to the cage surface and one Au atom skips to the top of the Si atom forming a SiAu5 or SiAu6 subunit except SiAu19, which is a tetrahedron-like structure with a protruding Au atom. The Au atoms of the SiAu(n) (n = 17-20) clusters carry different partial charges due to their different locations.