A Detailed Guide to the Harvesting and Processing Methods of Camellia Oil

I. Harvesting: There are many varieties of camellia oleifera, and the fruit ripening period is generally from October to early November. Ripe fruit has the following characteristics: the camellia fruit is bright in color, red or yellow, with a glossy sheen; the fuzz on the fruit skin has fallen off completely; the hairs at the base of the fruit are hard and coarse; the fruit shell is slightly split; the seed shell turns black and shiny; and the kernel shows oil. Camellia fruit should be harvested promptly once ripe. For different varieties, harvest early-ripening fruit first and late-ripening fruit later, picking as they ripen; for ripe fruit of the same variety, harvesting should also be completed within about 7 days. The harvested camellia fruit should be piled indoors for 6 to 7 days to allow the seeds to undergo after-ripening and increase their oil content. Then, as soon as there is fine weather, spread them out and turn them to dry in the sun. After 3 to 4 days of drying, the camellia fruit cracks open naturally, and the seeds of most fruits can be separated; those not separated should be removed by hand. Then sift and winnow them clean and continue drying them intermittently; generally 12 days of sun-drying are needed for the starch, soluble sugars and other organic matter to be fully converted into oil. For drying camellia seeds, an earthen yard or bamboo mat is better than a concrete drying yard, as it can increase the oil yield and improve the quality of the camellia oil. If continuous rainy weather makes timely sun-drying impossible, spread the camellia seeds on a dry, well-ventilated floor slab at a thickness of about 20 cm, turn them 1 to 2 times a day to prevent heating, molding or sprouting, and spread them out to dry in the sun as soon as fine weather returns. After the camellia seeds are sun-dried, the weight ratio of seeds to fruit shells is 1:2. The well-dried camellia seeds should be stored in a ventilated, dry place. After 1 to 2 months, when the oil content of the seeds reaches its highest level, sun-dry them again for 1 to 2 days; in this way the oil yield is high and the oil quality is good as well.

II. Oil pressing: At present, camellia oil is basically extracted from camellia seeds by pressing. The traditional oil-pressing tool in China's rural areas is the wooden press, which is labor-intensive and yields little oil. It will gradually be replaced by hydraulic presses and screw presses. Before pressing, the seeds need to be crushed and then steamed and roasted: (1) Crushing: Remove the shells from the camellia seeds. To avoid difficulty in shelling and excessive breakage of the kernels, the moisture content of the camellia seeds must be controlled within 5% to 6%. After shelling, process them into powder with a crusher. If a stone mill is used, the material must be sifted several times during rolling so that it is ground finely and evenly, with no coarse particles, thereby achieving a higher oil yield. (2) Steaming and roasting: The purpose of steaming and roasting is to turn the raw material into cooked material, deepen the color of the material cake, and bring it into the state most suitable for oil separation; it is a key step before pressing. Traditional steaming and roasting uses a wooden steamer for steaming and an iron wok for roasting. If the raw material is first moistened with steam or sprinkled water and then roasted, it is called "wet steaming and roasting"; if it is roasted without moistening, it is called "dry steaming and roasting." Generally, "wet steaming and roasting" is preferable. The moisture and temperature during steaming and roasting vary with the type of machinery used. With a hydraulic press and a wooden press, the roasting temperature of the material is generally 110 to 120°C, and the moisture content after steaming and roasting is 7% to 8%. With a screw press, the roasting temperature of the material is generally 130 to 140°C, and the moisture content after steaming and roasting is 3% to 4%.