Peanut oil processing technology

Description of peanut oil processing technology:

1. Cleaning: the same equipment used for ordinary secondary peanut oil squeezing

2. Classification: Use a grading screen to separate the immature, moldy, and broken peanuts from the peanuts. This part can be used to produce secondary pressed peanut oil and sold separately.

3. Drying/cooling: The drying equipment can be equipped with a hot air flow dryer. The moisture content of peanuts after drying is controlled at 5%~6%. Then quickly use cold air to reduce the temperature of the oil particles to below 40°C.

4. Crushing/Peeling: The crusher can be a toothed roller crusher, the purpose is to remove the infrared coat of peanuts, after crushing, the infrared coat is sucked out with a wind separator or a suction flat screen, and the separated peanuts can be used For pharmaceutical and chemical raw materials.

5. Hot-air roasting: 25%-30% of the total amount of peanuts is sent to the coal-fired hot-air roasting furnace, where the oil is heated to 180℃~200℃. The roasting temperature is the key factor for the aroma of aromatic peanut oil. If the temperature is too low, the aroma will be weak; if the temperature is too high, the oil will easily gelatinize.

6. Cooling and rolling grits: In order to prevent oil gelatinization and spontaneous combustion, heat dissipation and temperature reduction should be rapid after roasting, and then use a toothed roller crusher to crush it into granules after cooling.

7. Steaming and frying: Use a five-layer vertical steaming and frying pan to steam and fry the green body. Layers 1~2 should be full for steaming; Layers 3~5 should be shallow to remove moisture; discharge temperature 108℃~112℃, moisture content 5%~7%, To ensure that the peanut oil has a strong fragrance, the indirect steam pressure of the steaming boiler should not be less than 0.6mpa.

8. Oil pressing: This process uses a 200-type screw oil press. Taking into account the peculiarities of the peanut oil production process, the spindle speed of the oil press is adjusted appropriately, and the spindle speed is increased from the original 8rpm to 10rpm. The thickness of the thick cake is generally controlled at about 10mm. The squeezing temperature is 135℃, the squeezing water is 1.5%-2%, and the residual oil of the machine-pressed cake is 9%-10%.

The crude oil obtained after precipitation is filtered by a vertical leaf filter and sent to the refining workshop.


Specific operation method of peanut oil refining:

(1) Fast delivery of peanut oil: Before the filtered crude oil is pumped into the refining tank, check whether the pipeline valve is normal. After each tank has completed the delivery of oil, the oil inlet valve should be closed immediately. The crude peanut oil to be refined in the oil tank must first be cleaned of foam on the oil surface to smooth the oil surface, and let it stand for an appropriate period of time (not less than 15 minutes) so that there is no foam in the oil. Adjust the crude oil temperature to 25-35°C.

(2) Preparation of lye: Weigh out the prescribed amount of NaOH (purity must be identified first), mix it with appropriate amount of water, start the alkali pump, and circulate the lye to completely melt the NaOH. Reduce the temperature of the lye to 25-30°C, let it stand for 20 minutes, measure the Baume degree of the lye with a Baume meter, and adjust it to 10–12°C.

(3) Alkali mixing: When the oil surface of the crude oil is smooth and the temperature is stable at 25-35℃, turn on the agitator to start stirring, firstly turn slowly (20r/min) and stir for 1min, then change to fast turn (40r/min), and stir. At the same time, open the valve of the alkali tank and put in the alkali solution. The time for adding the lye is generally about 15 minutes. After the lye is put in, continue to stir quickly until the oil and soap particles are clearly separated. The stirring time is about 3-3.5h. When the oil and soap feet are clearly separated, change to slow stirring, open the heating steam door (vapor pressure 1.4kgf/C㎡), and increase the temperature of the oil to 60℃ (the increase in oil temperature should be maintained at 1℃/min, the highest (The temperature should not exceed 65℃). Stop stirring immediately, close the steam valve and let it cool and precipitate by itself (precipitation time is about 8h). After checking that the oil delivery valve pipeline is normal, pump the oil into the washing tank. When pumping to the interface between the oil and the precipitated soap feet, you must be very careful not to pump the soap feet out, and at the same time you must pump the oil out.

(4) Water washing: Heat the oil pumped into the washing tank to increase the temperature, and at the same time start the stirrer to add 75-80℃ hot water to keep the oil temperature at 80-85℃ (the temperature must not exceed 85℃). When the water is added (the amount of water added is 15%-20% of the oil, the time of adding water is 38-40min), stop heating and continue stirring for 15 minutes, that is, stop stirring, settling for 2h (first time), and wash the bottom of the tank with water Open the drain valve and let go of about 3/4 of the washing water (first put the oil in the pipeline into the oil-water separation tank before letting go of the washing water). Then close the drain valve, open the valve leading to the oil-water separation tank, and slowly put in the remaining oil-water mixture. For the first washing, you must put all the viscous material in the middle layer of oil and water into the separation tank until you see good oil, and then close the valve.

The separation of oil and water must be controlled by a special person. When separating in the separation tank, the heating coil in the tank must be turned on, the temperature must be increased (not allowed to exceed 80℃), and the water will be released after separation to recover the residual oil.

Follow the above method to continue washing the oil machine with water until the washing water is completely clear. The sedimentation time of the second washing is 1.5h.


(5) Dehydration: Check whether the relevant pipeline valves are normal before delivery, and then pump the water-washed oil into the vacuum dehydration tank, open the steam valve at the same time, turn on the vacuum pump and agitator, adjust the cooling water of the condenser, and turn on the circulating oil pump Speed up the oil circulation in the vacuum dehydration tank. The vacuum degree of the vacuum dehydration tank is kept above 0.0867MPa. The dehydration time is about 3 hours, counting from the oil delivery in the dehydration tank, and the dehydrated oil should be sampled and inspected by the quality inspector. When it is found that the dehydration is insufficient, the dehydration must be continued. The dehydration temperature is maintained at about 70°C.

After dehydration is complete, stop the vacuum pump, open the air valve, and slowly add air. Check whether the pipeline valve is normal, and then the conveyed oil is cooled to 25–30℃ through the cooling pipe and flows into the sedimentation tank for pressure filtration.

(6) Filter press: Check whether the valve of the filter press pipeline is normal. Check that the oil temperature must be below 30°C. After the oil is filtered, stop the oil filter pump to close the valve, gently open the filter plate to allow the internal oil to flow into the oil pan, and then remove the filter residue on the filter cloth. Check the usage of the filter cloth and prepare to be replaced or washed. The residual oil of the filter cloth should be separated and recovered by a centrifuge.

(7) Residual oil recovery: Use the oil-water separation tank to separate the recovered oil and re-refine it. The filter cloth with residual oil is folded neatly and evenly, put into the centrifuge, and after separation, the residual oil is recovered for refining. When operating the centrifuge, you must strictly control the speed of the centrifuge, and gradually increase from slow to fast when starting. If it is necessary to stop in the middle of the rotation, the motor should be stopped, but when the centrifuge is not completely stationary, it is absolutely not allowed to close and continue to start.

The amount of caustic soda added and the concentration of the lye are determined by the acid value and impurity content of the filtered crude peanut oil. If the acid value is high, the amount of alkali needed to neutralize the free fatty acid should be more, the concentration should be higher, the acid value should be low, the amount of alkali should be less, and the concentration should be lower. When there are a lot of impurities, the amount of super-alkali will be more. According to the impurity content of peanut oil, the amount of super alkali added is generally 0.1%-0.2%. However, the ingredients collected in crude oil are complex. For example, the acid value and impurities determine the amount of alkali used and the concentration of lye. Sometimes it may not necessarily achieve good results. Therefore, it is best to do a small cup test before refining. The temperature of alkali addition must not be too high. After adding alkali to neutralize the oil, the temperature of the oil is increased to destroy its emulsified state and completely separate soap particles from the oil. The stirring speed should be fast when adding alkali to neutralize. The purpose is to make the lye and the oil fully contact, so that the free fatty acids in the oil can be quickly neutralized. After the free fatty acids are completely neutralized, the stirring should be slow during the heating period to prevent formation The soap noodles are broken into small ones that are difficult to sink. Then wash with water to remove trace soap particles and free alkali dissolved in the oil. After peanut oil has been washed with water, it has a high water content (0.3%), and it is easy to change the quality during storage, so it must be dehydrated. The last process of refining is cold-cold filter press to remove waxy substances contained in the oil.