A mixture of 0.050 0.002 g of dried tomatowas extracted with
1 mL of methanol and vortexed for 30 min, after which the extract was filtered through cotton wool. The concentration of total polyphenols
in the extracts was quantified using the FolineCiocalteu
reagent method adapted for a BioTek ELx808 microplate reader
equipment. A reaction mixture was prepared with 60 mL of extract,
720 mL of deionized water and 60 mL of the FolineCiocalteu reagent.
This mixture was vortexed for 6 min at medium speed, followed by
the addition of 600 mL of a 70 g L1 Na2CO3 aqueous solution. After
the reaction was started, nitrogen was injected to displace oxygen
and the mixture was vortexed for 5 min. When the reaction was
completed, a 120 mL aliquot of the mixture was pipetted into
a microplate well and incubated for 30 min at 40 C. Subsequently,
the absorbance was read using a 630 nm filter. Standards and
samples were sheltered from light during the assays. TPP contents
in the tomato samples were determined with a gallic acid calibration
curve, and expressed as milligrams of gallic acid equivalents
(GAE) per 100 g DM.