Whatman glass microfibre filters

Soil microbial C, N, and P were measured using the chloroform fumigation extraction method (Beck et al., 1997; (link)Brookes et al., 1985) (link) with 20 g of moist soil for each of the fumigated and non-fumigated treatments. The fumigated and non-fumigated soils were extracted with 75 mL 500 mM K 2 S0 4 , placed for one hour on a shaker, and filtered onto precombusted Whatman glass microfibre filters (GF/F). The extracts were then frozen until analysis. Organic C and N in the extracts were measured using a Hach-Lange IL-550 analyzer (Hach-Lange, Germany), while P was measured using a FIA star 5000 analyzer (FOSS Tecator, Höganäs, Sweden). Microbial biomass was calculated as follows: biomass C = E C /k EC , where E C is (organic C extracted from fumigated soil) -(organic C extracted from non-fumigated soil), and k EC is 0.45 for C (Beck et al., 1997) (link). The same formula was used to calculate biomass N and P with k EN = 0.54 (Brookes et al., 1985) (link), and k EP = 0.40 (Brookes et al., 1982; (link)Turner et al., 2001) (link). All biomasses were expressed in mg per kg soil.

Chlorogenic acid and caffeic acid (Sigma-Aldrich, Saint Louis, MO. USA) standard solutions were prepared (0.00-0.06 mg/ml) in HPLC water. Sample solutions of doughs or cookies (0.3 g in 10 ml of HPLC water) were homogenized at 0.68 x 10 3 g for 45 s and centrifuged at 3.3*10 3 g for 30 min (AccuSpin 1R-75003449, Thermo Fisher Scientific, Inc. CA.
USA) at 4 °C. The solutions were filtered, using Whatman ® glass microfibre filters (Grade GF/A circles, diam. 90 mm), and then filtered, with a 0.45 µm nylon syringe filter. The CGA of the supernatant was quantified, as decribed by Liang and Were (2018b) . Chlorogenic acid-lysine standard solutions were prepared according to our previous study (Liang & Were, 2018b) and
TBA was quantified at 680 nm, considering that all the CGA was reacted with lysine in the standard solutions. The results were expressed as mmol TBA/g cookies.