Put the fresh citrus peel into the press, and use pressure to crush the oil sac cells on the citrus exocarp to make the essential oil seep out, and spray it with water, then separate and refine to obtain the cold-pressed essential oil. The process is as follows:
(1) Selection and crushing of citrus peels
For the cold pressing method, fresh and mildew-free citrus peels should be selected, and the sediment and sundries should be removed first, and then washed with water. Because the essential oils of different types of citrus peels are different, they can be classified according to citrus peel, orange peel, orange peel, and pomelo peel. If possible, the mesocarp (white layer) of orange peel and pomelo peel should be removed as much as possible to prevent it from absorbing the extracted essential oil. Crush the cleaned citrus peels into 4-5mm pieces with a crushing machine for later use.
Pressing is preferably carried out in a screw press. After the material is put into the press from the feeding port, under the push and extrusion of the screw propulsion rod, the oil sac cells on the exocarp are squeezed and crushed, and the essential oil seeps out from it, and is sprayed with an appropriate amount of water from the press. flow out. The amount of spray water should not be too much, too much water will increase the burden of subsequent treatment; it should not be too little, too little, and the squeezed essential oil cannot be completely flushed out of the press. The operation should be mastered according to the actual situation. The pomace from the press is retained for subsequent extraction of other ingredients.
The peel juice from the squeezer can be filtered immediately into the filter to remove the residue from the peel juice. The filtered peel juice is placed in a settling tank for oil-water separation, and the filter residue is combined with the pressed residue for subsequent extraction of other components.
(4) Oil-water separation
Settling tanks can be continuous or intermittent. Continuous settling tank. The filtered peel juice liquid enters the settling tank from the middle of the settling tank, and the essential oil and water are gradually separated in the settling tank to form an oil layer and a water layer. The clarified essential oil overflows from the upper part of the settling tank, and the water is drawn from the lower part of the settling tank. By adjusting the height of the water outlet of the water outlet pipe, the height of the oil-water interface in the settling tank can be adjusted.
If an intermittent settling tank is used, fill the settling tank for each concentration and let it stand for a period of time to slowly release the oil and water.
(5) Stand still
Since the crude essential oil obtained by oil-water separation is also entrained with a small amount of water and possible peel wax, it needs further standing treatment. The most commonly used simple method is to stand the crude essential oil at a low temperature of 5-8°C for 5-6 days, most of the residual water will settle out, and the peel wax in the essential oil will also crystallize at low temperature. The water and wax precipitated at the bottom are released, and the upper essential oil flows through a column filled with anhydrous calcium chloride to further remove possible residual moisture to obtain the Citrus Essential Oil product.
Put the freshly crushed citrus peels into the distiller and strip them with steam at 100 ℃. The oil sac cells on the citrus exocarp are broken under the action of high temperature, and the essential oil seeps out and distills out with the water vapor. After condensation, separation and refining Get distilled essential oils. Distillation can be divided into batch distillation, continuous distillation and water distillation according to the distillation form. Its technological process is as follows:
(l) Selection and crushing of citrus peels
The citrus peels used in the distillation method can be fresh peels or dried peels. It is required to be free from mildew and rot, and the sediment and sundries should be removed and cleaned. The crushing particle size is preferably 5-10mm, if it is too small, the stripping resistance is high, and it is easy to form stalling; if it is too large, it is not conducive to the diffusion of essential oil.
(2) Batch distillation
Batch distillation equipment is relatively simple, its equipment structure and processing flow. Batch stills generally use an open-cover still pot with a built-in charging frame. The broken citrus peels are placed in the charging frame fluffy, the top cover is tightly closed, and 100 ° C steam is used for distillation. The temperature of the water vapor should not be too high, otherwise it will destroy the essential oil components, resulting in a decline in quality. The distillation time is affected by the amount of feed and steam conditions, and should be mastered according to the actual operating conditions. Usually, it can be judged by observing the oil content of the condensed steam. After the distillation is completed, turn off the steam, open the top cover and take out the charging box, pour out the distilled citrus peels (reserved for subsequent extraction of other components), and replace with new materials. After draining the water at the bottom of the pot, put the charging frame into the still pot for the next round of distillation. The distilled steam from the distiller is condensed with cooling water through the condenser, and then enters the oil-water separator to separate the essential oil from water to obtain crude essential oil. Crude essential oils are refined in the same way as cold-pressed oils.
(3) Continuous distillation
The process flow of continuous distillation is the same except that the still operation is different from that of batch distillation. The structure of the continuous distiller is more complicated than that of the batch distiller, and the equipment investment is relatively high, but the production efficiency is much higher than that of the batch distiller. The structure of a continuous still. During operation, the crushed citrus peels are fed from the hopper and sent into the column through the screw conveying rod. While the material is descending, it is distilled in contact with the steam from the steam nozzle. In order to ensure that the material is fully distilled in the still, the height of the continuous still is usually in the range of 8 to 10m. The accumulated material in the tower should not be too much higher than the steam nozzle, so as to avoid excessive steam rising resistance and cause steam to leak down. The bottom material after distillation is discharged from the discharge port through the screw at the bottom of the tower.
(4) Distillation in water
Distillation in water is actually a batch distillation. Unlike the batch distillation described above, the broken citrus peels are heated in water with a water-to-solid ratio of about 2:1. Citrus Essential Oil is brought out with the steam generated by the boiling water. Still pot. The structure of the distillation pot is similar to that of the steam distillation pot, only the steam pipe is replaced with a heating type or heated by other methods.