Polyphenols Extraction from Freeze-Dried Fruit

TN were collected in June 2019 at the orchards of “Giaccio Frutta” society (Vitulazio, Caserta, Italy, 41°10′ N–14°13′ E), at 20–25 days after full bloom, coinciding with the fruit thinning stage. The whole fruits were frozen at −80 °C, freeze-dried and ground to obtain a uniform powder that represented the production batch used for the analysis. For TN polyphenols extraction, 1 g of homogenized sample was suspended in 5 mL of 80% aqueous methanol containing 1% formic acid for 10 min, mixed on a vortex mixer for 1 min, sonicated (Branson Fisher Scientific 150E Sonic Dismembrator) for 10 min, and centrifuged for 10 min at 9000× g. The supernatant was decanted, and the pellet was re-extracted with 5 mL of the previous solution. Finally, the combined supernatants were filtered with a 0.22 μm nylon filter (CellTreat, Shirley, MA, USA) and stored at −20 °C until analysis [14 (link)].