Detailed Guide to the Experiment and Production Process of Rose Essential Oil Extraction

With its brilliant colors and rich, pure fragrance, the rose has become a beloved aromatic plant. The extraction of rose essential oil originated in ancient times, initially by soaking fresh flowers in water to extract their active ingredients. With the development of science and technology, the technique of steam distillation of fresh roses to obtain essential oil emerged.

Rose Essential Oil Production Equipment

The distillation equipment for rose essential oil mainly includes: distillation vessel, re-distillation column, swan neck, condenser, and oil-water separator. It is best to make them all from stainless steel; the oil-water separator can also be made from aluminum. Boilers are generally used as heating equipment.

Process Flow

Put roses and water into the distillation vessel at a ratio of 1:4. First heat with indirect steam; when the temperature rises to 70-80°C, introduce direct steam and heat to boiling, taking about 30-40 minutes; continue distillation for 2.5-3 hours, controlling the volume of distillate to 1-2 times the weight of the flowers, with a distillation rate of 8-10% of the distillation vessel volume. Control the cooling water volume so that the temperature of the distillate is maintained at 28-35°C during the first half hour and at 40-45°C from half an hour onward until the end, generally not exceeding 50°C. The distillate passes through the oil-water separator to separate the rose oil from the rose oil-saturated distillate water. The rose oil is taken out, and the saturated distillate water flows from the oil-water separator under the effect of gravity difference into the re-distillation column, where it is heated and re-distilled under the action of the steam rising from the distillation vessel, then returns to the oil-water separator through the condenser. In this way, distillation and re-distillation are repeated

Key Technical Points

1. Picking: The picking time of roses has a great relationship with the content of rose essential oil. Generally, at 5-7 in the morning, the oil content is the highest, and the most suitable temperature is 15-23°C with a relative humidity of 55-70%. The oil content also varies with the degree of flower opening; when the flower has opened to a half-cup shape with yellow stamens, the oil content is the highest.

2. Transport: After picking, during transport, use well-ventilated containers, preferably flower baskets or burlap sacks. Fill them naturally without pressing, to avoid heat buildup and loss of oil.

3. Pre-processing before processing: (1) After picking, roses should generally be processed immediately, with storage time not exceeding 2 hours. Roses that cannot be processed in time can be temporarily stored by spreading them in a thin layer on a cement floor or on a mat-covered damp ground, and turning them frequently. (2) Preservation by soaking in salt water: soak the fresh flowers in a 20% salt water solution in a clean, seepage-proof pool. The salt water must completely submerge the flowers, and the pool should be sealed for storage.

4. Loading into the vessel: The amount of flowers loaded should be 2/3 of the distillation vessel.

5. Steam heating: At the beginning of distillation, direct steam should not be used, because the temperature inside the vessel is relatively low; using direct steam will undoubtedly increase the amount of water in the vessel, and at the same time direct steam causes the fresh flowers in the vessel to churn violently, and the steam flow carries flower residue and droplets severely. At this time, heat up slowly so that the flowers are fully moistened by the water. When the petals become soft from the heat and sink into the water, then appropriately speed up the heating process.

6. A thermometer should be installed at the outlet of the condenser to observe the temperature of the distillate.

7. Oil-water separation: Rose oil is a water-insoluble oil with a density less than that of water. When stationary, the oil is in the upper layer. Use a separator to separate it from the water and take out the rose oil.

8. Storage: Rose essential oil is a mixture of organic substances such as polyols, polyhydrocarbons, and polyenes. When exposed to light and air, it is prone to oxidation, affecting the aroma quality. Therefore, it is best to store it in brown glass bottles, sealed, in a dark place.