Evaluation of antioxidant capacity, structure, and surface morphology of ginger (Zingiber officinale) using different extraction methods

Valorisation of Zingiber officinale Roscoe postharvest residues as byproducts with antioxidant capacity

“…1 ) were washed, cut, oven-dried at 40 °C (UF160, Memmert, DUE), ground, and sieved with a 0.25-mm mesh. Phenolic compounds from the dried samples were extracted by refluxing (FA-46, MRC, ISR) at a loading of 3.125 mg/mL in methanol at 85 °C for 1 h [ 16 ]. At the end of the process, two fractions were obtained, a solid fraction (extracted mass), from which changes in surface and structural morphology were analyzed, and liquid fraction (extract), and their volumes were quantified.…”

“…For imaging, scanning electron microscopy (SEM; Q250 Analytical, Thermo Fisher Scientific, WI, USA) with an acceleration voltage of 20 kV and magnifications of 120 and 600 was used. For the analysis of the changes in the chemical structures of the samples, Fourier-transform infrared (FTIR) spectrophotometry (Nicolet iS10, Thermo Fisher Scientific, WI, USA) in a range of 700–4000 cm −1 was used [ 16 , 17 ].…”

“…The method to determine phenolic compounds is described in detail in our previous report [ 16 ]. The absorbance readings were carried out at 765 nm in an ultraviolet (UV)-visible spectrophotometer (Evolution 300, Thermo Fischer Scientific, WI, USA).…”

“…The standard curve was obtained with a 0.5–12.5 μg/mL solution of gallic acid in methanol ( Fig. 2 a), proceeding similarly to the sample described in detail in our previous report [ 16 ]. The TPC was expressed as mg gallic acid equivalent per gram of dry matter (mg GAE/g dm).…”

“…The quantification of 6-G and 6-S was performed using the method proposed by Vipin et al [ 19 ], described in detail in our previous report [ 16 ]. The absorbance reading was performed at 230 nm.…”