2.4.2. Non- enzymatic browning index (NEBI) and total phenols
The method of Meydav, Saguy, and Kopelman (1977) was used
to determine the NEBI of the juice pre- and post-processing. The total
phenolic content was determined by the Folin–Ciocalteu colorimetric
method (Singleton & Rossi, 1965). The juice was centrifuged
for 20 min at 8700g (Model No. J2-HS, Beckman Instruments Inc.
Palo Alto, CA, USA) to remove any remaining pulp and 1 ml of supernatant
was mixed to 5 ml of 0.2 N Folin Ciocalteu reagent (Sigma–
Aldrich) and 4 ml of 7.5% sodium carbonate (Sigma–Aldrich). The
solution was allowed to stand for 2 h at room temperature and
away from strong light. The absorbance was measured at 765 nm
using a UV–Vis spectrophotometer (Model No. UV Mini 1240,
Shimadzu, Japan) and results were expressed as gallic acid equivalents
(GAE, mg/l).