Moisture was determined by weighing 5–10 g of the
sample in a metal dish and drying for 6 h at 70±1°C under
pressure of ≤100 mm Hg (13.3 Kpa). Titratable acidity was
determined by titrating known quantity of sample against
0.1 N NaOH and expressed as %citric acid. Reducing and
total sugars were determined by inversion method. Ascorbic
acid was determined by 2,6-dichlorophenol indophenol
titration based on the reduction of ascorbic acid by the dye
in the pH range of 1 to 3.5. Tannin content was determined
by spectrophotometric (Model – GBC-10 Cintra, USA)
method based on the measurement of blue colour formed
by the reduction of phosphotungstomolybdic acid by tannin
like compounds in alkaline solution (AOAC 2000).
Five g of litchi juice concentrate were soaked in 100 ml
of 65% ethanol (v/v) overnight and the extract was fi ltered
through Whatman Nr 41 fi lter paper. The optical density of
the fi ltrate was measured at 420 nm in a spectrophotometer
and expressed as absorbance to determine non-enzymatic
browning (NEB) (Askar and Treptow 1993).