The DASA System
This is the first commercially available test for dextran that is both accurate and specific.
It can measure down to 200 ppm (parts per million) dextran in solution and easily copes with several thousand without dilution. The optional addition of a high accuracy Index Instruments refractometer allows the system to operate in the dextran and purity mode. The results can then be interpreted as dextran ppm on brix.
The enzyme employed is a highly specialised dextranase which hydrolyses the dextran into sugars of lesser optical rotation.
This decrease in optical rotation is stable after a few minutes depending on the size of the original dextrans present. The larger dextrans (i.e. +1 million Mr) take around 10 minutes to be hydrolysed.
The change in rotation between the enzyme treated and untreated samples is indicative of the original dextran concentration.
A specialised SacchAAr 880D NIR polarimeter, which is the basis of the measuring system, uses unique algorithms to automatically output the dextran reading. This takes away all possibilities of operator error.
The results obtained from the system have been shown to be unaffected by the dextran molecular weight.
Because a percentage solution of, say, a 9,000 molecular weight dextran is the same as, say, a 2,000,000 molecular weight dextran, the degree to which the dextran falsifies the polarimeter reading can be calculated.
A corrected polarimeter reading is displayed at the end of every test to assist with cane payment. The corrected reading is obtained by calculating the interference of the dextran present in terms of optical rotation, and subtracting this from the original control reading.
The Test Strip Technology
Each test requires an exact amount of the dextranase preparation. If this were to be added as a liquid, the sample would be diluted and the readings would need to be adjusted to account for this.
To assist the user and ensure accuracy, the dextranase is impregnated onto small strips. To avoid contamination, each test strip is supplied in a single-use sample vial.