Whatman filters n 1

C. verum L. dried barks (batch number: C1900010, date: 16 January 2019) obtained by EPO s.r.l., was pulverized with an electric laboratory grinder. The method used for the preparation of cinnamon extracts has been described by De Giani et al., 2022 [14 (link)]. Briefly, 1 g of powder was extracted with hot water by 1 h incubation in a rotavapor (Strike-300, Steroglass Italia Srl, San Martino in Campo, Italy). At the end of the process, a centrifugation was carried out at 600 rpm for 15 min to recover the supernatant. Then, 75% ethanol was added in a 1:1 ratio to precipitate polysaccharides. To improve and accelerate the precipitation process, the mixture was stored 1 h at 4 °C. Then, the extract was filtered under vacuum using Whatman filters n.1. Finally, the solvent was evaporated with rotavapor and the dry fraction was resuspended in 5–10 mL of water. The samples were freeze-dried and stored at −20 °C.

Dried cinnamon bark (C. verum L., batch number: C1900010, date: 16 January 2019) was provided by EPO s.r.l. and powdered with an electric laboratory grinder. The cinnamon extraction method has been described by De Giani et al. (2022) [45 (link)]. After the extraction process from 1 g of powder with hot distilled water in a rotavapor and polysaccharide precipitation, the extract was filtered under vacuum using Whatman filters n.1. Finally, the dry fraction was resuspended in 5–10 mL of water. The samples were freeze-dried and stored at −20 °C. The gastrointestinal digestion simulation was carried out following the INFOGEST protocol described and used in Minekeus et al. (2014) [46 (link)]. The method was detailed in a previous paper [9 (link)]. Briefly, the gastrointestinal simulation was performed in 3 phases(oral, gastric, and intestinal)by preparing specific mixtures of salts and enzymes and adjusting the pH and temperature. The digestion product was subjected to acidification in order to precipitate the enzymes and preserve the polyphenols according to Pineda-Vadillo et al. (2016) [47 (link)]. Finally, protease inhibitors were added to conserve the samples.

Electrical conductivity (EC) values of the biochar sample extracts were determined following the EN European Standards (1999b) protocol for growing media and soil improvers.
Briefly, samples were treated as for the pH evaluation; after shaking, suspensions were filtered through Whatman filters (N°1, Whatman, Maidstone, United Kingdom) discarding the first 10 mL. The conductivities of the suspensions were measured, in triplicate, within an hour after extraction, using a Model S213 Seven Compact Duo meter (Mettler Toledo, Columbus, OH, United States), and expressed in mS cm^-1.