2.6. Analytical methods
The concentration of soluble solids (Bx) was determined with a
portable refractometer (Cole–Palmer). The reducing sugars were
analyzed by the DNS method (Miller, 1959). This colorimetric
method tests for the presence of free carbonyl group (C@O) on
the carbohydrate molecule. This involves the oxidation of the aldehyde
or ketone functional group and the 3,5-dinitrosalicylic acid
(DNS) is reduced to 3-amino,5-nitrosalicylic acid under alkaline