2.3.6. Diastase activity
Honey diastase activity was determined according to AOAC
method 958.09, by placing 5 g of honey into a 20 ml beaker and
diluting with 10 ml distilled water and 2.5 ml of acetate buffer
(1.59 M, pH 5.3). It was transferred to a 25 ml volumetric flask containing
1.5 ml of 0.5 M NaCl solution. Ten ml of honey solution
were incubated in a thermostatic bath at 40 C along with a second
flask containing 100 ml of 1% (w/v) starch solution. After 5 min,5 ml of starch solution was added to the honey solution. After
5 min 1 ml of the mixture was mixed with 10 ml of 0.0007 M
diluted iodine solution, and measured at 660 nm in a spectrophotometer
(Shimadzu UV-1601 UV/VIS, Japan), compared with a
water blank. A plot of absorbance against time was used to determine
the time at which the specified absorbance of 0.235 was
reached.
Diastase is the enzyme responsible for converting starch to dextrins
and sugars. It is added to ripening honey by the bees. The
diastase number expresses the diastase activity as the number of
ml of a 1% starch solution hydrolyzed by the enzyme in 1 g of
honey in 1 h at 40 C. The results are expressed in Gothe degrees.
The use of diastase as a honey quality indicator has been questioned
(White, 1994).