Color formation in wheat starch based glucose syrups and use of commercially available and laboratory-prepared agricultural waste-based activated carbons for decolorization

Glucose syrups were produced from wheat starch using alpha-amylase at 97 degrees C for 45-90 min liquefaction times, followed by saccharification with amyloglucosidase at 60 degrees C for 18 h to study the color formation. This was followed by decolorization studies using 0.25 to 1.00 g activated carbon per g of syrup of the commercially available NORIT and several activated carbons prepared from apricot stones and hazelnut shells and husks on laboratory scale. Increase in liquefaction time resulted in higher extents of hydrolysis in both maltodextrins and glucose syrups. In maltodextrins, 9-21% and in glucose syrups 72-98% of the linkages were hydrolyzed at 45-90 min liquefaction times. Color levels of glucose syrups increased with increased liquefaction time. The color levels were between 657-1424 ICUMSA units for glucose syrups obtained at 45-90 min liquefaction times. The dosage of activated carbon necessary to decolorize the syrups to the color level lower than 100 ICUMSA units, however, became lower and lower as the liquefaction time (and the level of starting color), was increased; and this behavior was the same for all types of activated carbon studied. Decolorization performances of NORIT, apricot stone (AS), hazelnut husk (HH) and hazelnut shell (HS) based activated carbons were compared by adjusting the activated carbon dosage to be the same as that of NORIT required for 100 ICUMSA residual color. HH was the best giving practically same residual color as NORIT for the decolorization of 90 min liquefied glucose syrups. The HS and AS had similar performances, reducing the color to less than 180 ICUMSA units for syrups liquefied for 45 and 90 min