Juice concentration
The concentrated juice was obtained by putting the extract in an open kettle which was heated by electric heater. Enough amounts of refined white sugar and 0.3-0.5% citric acid were added to the open kettle; mixing and heating was started gradually up to 80ºC. The concentration was stopped when the mixture reached 56% of total soluble solids measured by refractometer (Bellinghan and Stanley Ltd., Tunbridge Wells, UK) (FAO, 1995). High temperatures and long concentration times were avoided in order to reduce or eliminate damage. Thickening and burn-on of product to the kettle wall was also avoided as these gradually lower the efficiency of heat transfer and slow the concentration process. The procedure and formula used are similar to that used in commercial product. The obtained concentrated juice was kept in dry clean plastic jars and stored at -3ºC.