Cassava starch processing at small scale in North Vietnam.

摘要

In Northern Vietnam, small-scale cassava starch processing is conducted in densely populated craft villages, where processors face difficulties to expand their activities. 3 different processing systems were studied among a cluster of 3 communes in the Red River Delta, producing up to 430 tonnes of starch (at 55% DM) per day. The first system, type A, is a cylindrical rasper and a manual sieve, the second, type B, is a cylindrical rasper and stirring-filtering machine and the third, type C, used equipment for both the rasping and filtering stages. Moisture, starch, crude fibers and ash content analysis were carried out on samples collected from the A-B-C manufacturing processes to establish the mass balance of starch. Production capacity, water consumption, electrical requirements and capital-labour costs per tonne of starch (12% moisture) were also reported. A-B-C manufacturing processes enabled 75% recovery of the starch present in fresh roots. No significant change was observed in the composition of starch. Upgrading from system A to B and subsequently to C resulted in an increase in extraction capacity (up to 0.9 tonnes of peeled roots per h), extraction efficiency during the extraction stage (by up to 93%), and water consumption and electrical power (up to 21 m3 and 55 kWh per tonne of starch, respectively). Highest amounts of total solids carried in the waste-water were obtained with type C (up to 17% of the dry wt. of fresh roots, compared to 10 and 13% for type A and B, respectively). This may lead to a higher chemical O2 demand (COD) and biological O2 demand (BOD) in waste-water, which could result in more polluted waste-water than with type A and B technologies. Upgrading the rasping-extraction technologies also resulted in higher profits and reduction of labour per tonne of starch (up to USD 18 US and 26 man-h respectively).