Studies on improvement of plant efficiency and quality control in cassava starch manufacturing by controlling of sulphur dioxide treatment
1998
Sittichoke Wanlapatit
Sulphur dioxide (SO2) obtained from burning of sulphur solid has been used in most of cassava starch factories in Thailand for bleaching and disinfection purposes. In this study, 3 factories; A, B and C were chosen as models. The production process treated with SO2 at the levels of 0, 252.5 and 317.8 kg/day, which is equivalent to 0, 1.0 and 1.7 g/kg starch in respect factories. Consequently, the high residual of SO2 contaminated at the level of 0 ppm (0 percent), 153 ppm (13.3 percent) and 190 ppm (10.4 percent) contributed to lowering of starch qualities like swelling power, solubility and peak viscosity of starch. It was too difficult to quantify SO2 from burning of sulphur solid, therefore sodium metabisulphite were introduced instead. In laboratory scale, starch extraction treated with water soluble of sodium metabisulphite at the level of 0.4 to 1.6 g/kg of starch gave lower SO2 residual at 16 to 55 ppm (equivalent to 5 to 6 percent), improved of whiteness and starch qualities were still acceptable after 4 months storage. The sodium metabisulphite treatments were also practiced in factory C at several levels of 0.5, 0.6, 0.8 and 1.0 g/kg starch which released SO2 at 0.3, 0.4, 0.6 and 0.7 g/kg starch. The SO2 residuals were 22.7 ppm (2.0 percent), 30 ppm (2.0 percent), 34 ppm (1.8 percent) and 43 ppm (1.9 percent), respectively. When the SO2 residue and disinfection in starch were compromised, the SO2 levels of 0.6 to 0.7 g/kg starch were recommended. The SO2 residue, total plate count, whiteness, peak viscosity would be 34 to 43 ppm, 10*[5) to 10*[6) CFU/g, 94 to 98 and 64 to 727 BU, respectively were acceptable.
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