Page 41 - FoodFocusThailand No.224 November 2024

SMART PRODUCTION

The cassava pulp obtained from the coarse extractor is
reprocessed to minimize the loss of starch that remains in
the wet pulp. The slurry from the fine extractor typically has
a starch concentration of 20-25% (10-17 Baume). This slurry
o
is then concentrated further to around 40% (20 Baume).
o
Next, the concentrated slurry is sent to a starch separation
unit, which uses a separator to centrifugally remove any
remaining cassava pulp and further thicken the starch
solution. A disc bowl centrifuge separates non-homogeneous
liquids from the starch, and a centrifuge clarifier divides the
liquid into three phases: a low-density phase, a denser phase,
and solids. The separator works by allowing the liquid to
enter from the top of the machine, where centrifugal force
pushes the solids against the discs, causing them to collect
and concentrate at the walls of the inverted cylindrical bowl.
The concentrated solids are then ejected through a nozzle
while the liquid flows out from the top of the machine. Once
the slurry is adequately concentrated, it is sent to a horizontal with protein content ranging from 0.25–7%. When the protein
centrifuge to further remove water, resulting in a starch cake is removed, the rice prepared in this way provides high-quality,
with a moisture content of 30-40%. If a centrifuge is not used, flavorful protein suitable for use in the food industry. Wet milling
a high-pressure filter may be employed to separate the starch yields finely ground starch with minimal impurities. Aside from
from the water instead. wet milling, dry milling is another method where impurities and
In cassava starch production, a high-speed horizontal dust are removed, and the rice is then ground. However, this
centrifuge or decanter may be used, though it is often not method produces the lowest quality starch, which is prone to
essential. This is because cassava contains relatively low rancidity and contains higher impurities.
levels of protein and impurities compared to potato starch
production. The decanter is used to separate waste liquids Corn Starch Preparation
containing starch, fat, protein, and cyanide. After this, the Corn kernels often contain impurities from harvesting, such as
high-moisture starch cake is transferred to a pneumatic cob fragments, corn silk, sand, and weed seeds. To clean the
conveying dryer, also known as a flash dryer, to reduce the kernels, they are first passed through a reciprocating or
moisture content to below 12% before packaging. During vibrating screen, which removes about 50% of the smaller
the drying process, starch dust is carried away with the hot debris. The next step is aspiration, where a fan is used to blow
air, but it is captured by a cyclone dust collector and a filter away dust and straw. After this, the corn passes through a
bag before exiting the factory. This ensures a cleaner magnetic separator to capture any metal fragments that could
production process and prevents dust from escaping into potentially damage the corn milling equipment.
the environment. Generally, the corn kernels are soaked in water before
milling at a temperature of 48-52°C for 24-40 hours. During
Rice Starch Preparation soaking, the balance of several factors must be carefully
Rice starch is made from broken or damaged rice grains to controlled: water flow rate, temperature, sulfur dioxide
increase its value. In some countries, rice starch production concentration, and pH levels. By the end of the soaking process,
may use an alkaline process to extract glutelin, which the corn kernels should absorb approximately 45% water
accounts for 80% of rice protein. This method can produce (calculated on a wet basis) and release about 6-6.5% of soluble
rice starch with less than 1% protein. The process begins solids into the soaking water. The kernels also absorb 0.2-0.4
by soaking broken rice in a 0.3-0.5% sodium hydroxide grams of sulfur dioxide per kilogram, which softens the corn
solution for 24 hours at room temperature or up to 50°C. The sufficiently for the kernels to be easily broken by hand. At this
soaking softens the rice and facilitates protein dissolution. stage, the germ (the corn embryo) separates easily from the
After soaking, the rice is wet-milled (known as wet grinding) endosperm and pericarp. When the endosperm is soaked in
with a sodium hydroxide solution. This process releases the water, gluten separates as a yellow suspended mass
starch into a thick starch slurry. The slurry is then held for (yellow floc), and starch separates as a white suspended mass
10-24 hours to allow the protein to dissolve completely. After (white floc).
that, the cell wall materials are filtered out, and the starch is Numerous methods exist for preparing raw materials to
thoroughly washed with water until the protein reaches a produce starch from various plants, and producers can study
neutral state, preparing the starch for drying. and adopt modern technologies to enhance the quality and
Another method involves mechanical separation, where yield of starch according to their specific requirements.
the proteins are physically separated from the starch
granules. After the starch granules and proteins are dislodged
from the endosperm through mechanical force, the starch
granules, which are approximately 10–20 microns in size, More Information Service Info C006
form clusters. This method results in rice starch products

NOV 2024 FOOD FOCUS THAILAND 41

22/10/2567 BE 08:19
37-41_Smart Production_����.indd 41 22/10/2567 BE 08:19
37-41_Smart Production_����.indd 41