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Raw & Refined Sugar Quality

Quality of raw sugar plays very important role in manufacturing of refined sugar and as such the quality of raw sugar should be normally specified for price negotiations. The following criteria will represent the desired quality of raw sugar:-

Polarisation (Pol )

Safety factor

Moisture Content

Raw sugar with a high moisture content cannot be stored because it is susceptible to microbial activity and sugar hardening during storage. The sugar-refi ning industry uses the ratio of water content (W) to nonsugars (NS) to calculate the safety factor (SF):

SF = W X 100 / NS = W X 100 / (100 ( S + W ) )

Here, the S (sucrose content) refers to sucrose measurement by polarimetry, called polarimetric sugar or pol.

 

Total impurities

Affinability

Concentration of specific impurity group

Colour value of whole crystals

Colour distribution within the crystals

Average crystal size

A suitable raw sugar has uniform crystals from 0.6 to 1.0 mm, preferably 0.8 mm. The grain size is determined by screening washed sugar through a 28 mesh screen.

Uniformity in crystal size

Crystal shape and Conglomerates

Filterability

Wax, Gums and Starch Contents

The raw sugar is mainly divided into three types having following specifications. The proposed refinery will use VHP quality raw sugar as its raw material

Based on the quality of the raw sugar, you can calculate a theoretical (expected) recovery (yield). The recovery (R) is the percentage (on mass base) of the refined sugar produced per raw sugar processed. Sucrose (S), invert-sugar (I), and ash (A) content are used to judge the recovery of raw sugar. Different countries use different formulas for recovery estimation, as below table

 

In almost all countries, the price of raw cane sugar is calculated based on 96% sucrose content (polarimetric sucrose, PS). Raw sugar above the base level gets credit, and sugar below the limit is penalized. In the United States, the refi ners pay a premium up to 98.8% and deduct for sugars that contain less than 96% sucrose. In addition to the sugar content, moisture, ash, crystal size, dextran content, and color are included in the premium (or penalty). The adjustments are different according to the country.