Soy bean oil; degumming and refining process
Soy bean oil refining refers to the process of using oil refining equipment to remove impurities from crude oil, extract essence, and purify it. The impurities contained in unrefined soybean oil mainly include cake crumbs, peptized impurities, free fatty acids, pigments, and odor substances. The reason for refining soy bean oil is to reasonably filter out the cake crumbs, peptic impurities, free fatty acids, pigments and odor substances contained in the pressed or leached crude oil. Therefore, it is more suitable for edible and storage, and enhances the edible value and market value of soybean oil.
The presence of impurities in crude soy bean oil not only affects the edible value and safe storage of the oil, but also brings difficulties to the deep processing of soybean oil. The purpose of refining is not to remove all the impurities in the oil, but to remove the harmful and unhelpful impurities such as gossypol, protein, phospholipids, mucus, moisture, etc., and beneficial “impurities” , Such as tocopherols, etc. should be retained.
CRUDE SOY BEAN OIL REFINING PROCESS
The process of refining crude soy bean oil involves series of steps from degumming, neutralizing, bleaching to deodorizing.
DEGUMMING OF SOY BEAN OIL
Crude soy bean oil contains two kinds of phospholipids: hydratable and non-hydratable. Degumming involves adding of food grade acid(phosphpric acid, citric acid) into the oil, which transforms non-hydratable phospholipids into hydratable. All hydratable phospholipids are then removed by the addition of water (hydration), which causes agglomeration of the phospholipids into flakes, which are subsequently centrifuge separated. Phospholipid removal is always the first step of vegetable oil processing. It can be done together with free fatty acid (FFA) removal, which carries out the process of neutralization, which is an optional feature of the degumming technology. Hydratable gums can be removed from the oil by water-degumming and non-hydratable gums are removed by addition of phosphoric acid.
NEUTRALIZATION AND WASHING OF SOY BEAN OIL
The process of neutralization f soy bean oil involves breaking of bonds in free fatty acids using caustic soda (NaHO) and making the oil free from moisture, hexane, sludge e.t.c. after the washing process.
Process of Neutralization
The quantity of NaHO to be used is calculated and dissolved in water depending on the percentage of FFA in the oil.
Steam is sent through the steam line to the neutralizer which already contains the desired quantity of oil to be neutralized
Heat the oil to 40-45 degree celcius
At 68-70 degree celcius stop heating but keep stirring the oil
Add NaHO (calculated quantity)
The oil is now neutralized
Stop stirring
Allow oil to settle for 5 minutes
Wash down process
Add hot water and allow to settle for 3 hours
Drain the soap
Washing process
Heat oil t 85 degree celcius with stirrer on
Stop stirring and heating
Allow to settle for 5minutes
Add hot water and allow to settle for 45minutes
Drain
Repeat the process three times at higher temperatures until the oil stops foaming and is well washed.
phenolptaleine indicator is used in drops, slight pink color shows the oil is well neutralized and colourless shows the oil is well washed.
BLEACHING OF SOY BEAN OIL
Oil bleaching is a step in the process of crude oil refining. In the bleaching technology, bleaching earth is applied to crude oil, minimizing its content of pigments (e.g., carotenes and chlorophylls), heavy metals, and the phosphorus remaining after degumming. This improves the appearance and taste of the oil.
Bleaching process
Vacuum is created to -760mmHg in the bleacher
Oil is sent from the neutralizer to the bleacher
Heat the oil to 110-115 degree celcuis while stirring and build up the vacuum back to -760mmHg
Stop heating but keep stirring
Add the bleaching earth (tonsil) and keep stirring for 20minutes
Break the vacuum and release pressure
Send the oil to the Pressure Leaf Filter (PLF) which separates the oil from the spent earth which is steam dried and discarded
Then send the oil to the polish filter which removes any remains of bleaching earth
DEODOURIZING OF SOY BEAN OIL
Vacuum is built in the deodourizer to -760mmHg
Bleached oil is sent to the deodorizer
The thermopac is started which heats the oil to 120-125 degree celcius
Steam is then sent t keep heating the oil to 250-300 degree celcius
The booster is started and the steam valves are opened and direct steam is sent to the deodorizer which evaporates along side the aldehydes, ketones and poisonous gases hence the oil is heated above boiling point of water
The oil is allowed to rest for 5minutes
If the oil is well deodorized,
Break the vacuum and open the outlet valves to send the oil to the cooler
Cool the oil to room temperature to avoid reverse of colour
Send the oil to the polished filter t remove remaining impurities
Send the polished and deodorized oil the deodorized oil tank
Add vitamin A
Finally send the oil to the refined oil tank
The oil is now well refined and ready for packaging and distribution or storage.
