New brunswick innova 2300

The antioxidant capacity was measured by the change of colour of 1,1-diphenyl-2-picrylhydrazyl (DPPH) solution after the addition of germinated brown rice flour supernatant (17 (link), 18 (link)). The antioxidant activity of the sample was demonstrated by the change of the DPPH purple colour to the yellow colour of the final solution. Approx. 2 g of flour and 20 mL of 80% (V/V) ethanol were poured into a 50-mL centrifuge tube. The sample was extracted for 30 min at 30 °C, and shaken at 150 rpm (New Brunswick™ Innova® 2300; Eppendorf AG). The supernatant was obtained through centrifugation (centrifuge Z 366 K; Hermle-Labortechnik, Wehingen, Germany) at 4032×g and 4 °C for 30 min. Furthermore, 0.2 mL of the supernatant was mixed with 3.8 mL of 0.1 mM DPPH (in methanol). The mixture was incubated for 30 min in a dark room before analysis at a wavelength of 517 nm using UV-Vis spectrophotometer Genesys™ 150 (Thermo Fisher Scientific). Ascorbic acid was used to construct the linear regression (R²=0.996), and the antioxidant capacity was expressed in mg ascorbic acid (AA) per 100 g sample (19 (link)).

The determination of available phosphorus (Ps) in soil was determined following a method previously described [26 (link)]. Briefly, the soil sample (1 g) was dissolved in a Bray II solution containing 0.03 N ammonium fluoride and 0.1 N concentrated hydrochloric acid (10 mL). The mixture was shaken in a New Brunswick Innova 2300, 51 mm shaker (Eppendorf, Hamburg, Germany) for 1 min and filtered through a Whatman No. 5 filter paper (Whatman International Ltd., Kent, UK). The filtrate was then mixed with a sulfuric-molybdate-tartrate solution containing ascorbic acid in a ratio of 1:16. The mixture was left for 30 min, and the extracted Ps was monitored using a lambda 35 UV-vis spectrophotometer (Perkin Elmer, Waltham, MA, USA) at a wavelength of 882 nm. Blank and standard solutions (0, 2, 4, 6, 8, 10, and 15 mg/L) were run in parallel. The Ps were calculated using Equation (4) as follows: $$\mathrm{Available} \mathrm{phosphorus} (\mathrm{mg}/\mathrm{kg})=\frac{\mathrm{B} \times \mathrm{df} \left(\mathrm{Sample}\right) \times \mathrm{R}}{\mathrm{A} \times \mathrm{df} \left(\mathrm{Standard}\right)},$$
where A is the weight of the soil sample (g); B is the volume of the Bray II extract solution (mL); df is the dilution factor, and R is the readout value when compared with the standard set.