palm oil It is extracted from the palm fruit on the oil palm tree. The palm tree originated in West Africa, spread to Malaysia at the end of the 18th century, and was gradually widely planted in Southeast Asia. At present, palm trees are planted in many countries in Southeast Asia, South America and Africa. After the palm fruit is boiled, crushed, and extracted, crude palm oil is obtained. After the crude palm oil is refined, free fatty acids, natural pigments, and odor are removed, refined palm oil (RBD PO) and palm salad oil (RBD PKO) are obtained. According to different needs, palm oil with different melting points such as 24 degrees, 33 degrees, and 44 degrees can be obtained by fractionation. Palm oil is rich in nutrients and antioxidant, and is widely used in food industry and chemical industry. The hydrolysis of lipase or fatty acid catalase in palm fruit makes the quality of palm oil unstable, so it is necessary to fill nitrogen in the storage tank to ensure its quality.

（1） Development history of palm oil

Palm oil is extracted from the palm fruit (Elaeis Guineensis) on the oil palm tree. It has been used as a natural food for more than 5000 years. Oil palm is a kind of crop that blooms and bears fruit all the year round. Commercial production of oil palm

It can last for 25 years. Oil palm is the most efficient oil producing plant in the world. Palm trees usually begin to bear fruit in 2-3 years, enter the peak production period in 8-15 years, and age and yield decline after 18-20 years

It usually needs to be cut down and replanted. The palm fruit grows on the big fruit clusters of the palm tree, and each fruit cluster has more than 2000 palm fruits. Palm oil is native to West Africa. In 1870, palm trees were introduced into Malaysia

As a decorative plant. It was not until 1917 that the first commercial planting was carried out. In the 1960s, in order to reduce rubber Trade dependence with coffee started to increase palm oil production on a large scale. Now the improved palm products have been widely planted in tropical Africa, Latin America and Southeast Asia. The palm oil production is highly concentrated in Malaysia and Indonesia.

（2） Production process of palm oil

Crude palm oil (CPO) and palm meal (PE) can be obtained from palm pulp through boiling, crushing and extracting; At the same time, in the process of crushing, the palm kernel (i.e. palm kernel) is separated, and then crushed and the shell is removed. The remaining kernel is squeezed to obtain crude palm kernel oil (CPKO) and palm kernel meal (PKE). The fruit of oil palm contains two kinds of different oils, and palm oil is obtained from the pulp; Palm kernel oil is obtained from palm seed (kernel), of which the former is more important. All of these products have been effectively used in food, chemical, agriculture and other fields. It can be said that palm is a good economic plant.

After the above primary stage of extraction, the crude palm oil and crude palm kernel oil are sent to the refinery for refining. After the removal of free fatty acids, natural pigments and odors, they become salad grade oils - refined palm oil (RBD PO) and palm oil salad oil (RBD PKO). The refined palm oil is nearly colorless and transparent in liquid state and nearly white in solid state. In addition, according to the needs of different users, palm oil can also be further fractionated and treated to form palmitic acid (PFAD), palm liquid oil (OLEAN for short), palm stearin (STEARINE or ST for short). The oil palm fruit contains more lipase, so the harvested fruit must be processed or treated with yeast killing in time. The crude palm oil is easy to hydrolyze itself to generate more free fatty acids, and the acid value increases rapidly, so it should be refined or extracted in time.

Specifications	free fatty acids	Water impurity	Iodine value	color and lustre	melting point
Crude palm oil	Less than 5.0%	Less than 5.0%	---	---	---
Refined palm oil	Less than 0.1%	Less than 0.1%	50-55	Red 3 or less than 6	33-39
Crude palm oil	Less than 5.0%	Below 0.25%	Over 56	---	Below 24
Refined palm liquid oil	Less than 0.1%	Less than 0.1%	Over 56	Red 3 or less than 6	Below 24
Crude palm stearin	Less than 5.0%	Below 0.25%	Below 48	---	Above 44
Refined palm stearin	Below 0.2%	Below 0.15%	Below 48	Red 3 or less than 6	Above 44

Table 1: Palm oil quality indicators

Palm oil is rich in carotene (0.05% - 0.2%), which is dark orange red. This pigment cannot be effectively removed by alkali refining. The oil color can be generally light yellow by oxidation. Under the action of sunlight and air, palm oil will also gradually decolorize. Palm oil is slightly sweet and has a pleasant violet fragrance. It is semi-solid at room temperature, and its consistency and melting point depend largely on the content of free fatty acids. In the international market, palm oil with low free fatty acid content is called soft oil, and palm oil with high free fatty acid content is called hard oil.

Relative density (40 ℃/20 ℃ water)	0.9170-0.9440
Refractive index (40 ℃)	1.4560-0.4590
Freezing point (℃)	27-30
Iodine value (gI2/100g)	52-58
Saponification value (mgKOH/g)	196-210
Total fatty acid content (%)	94.2-98.7
Unsaponifiable matter (%)	About 0.3

Table 2: Characteristic indicators of palm oil

Myristic acid	About 0.73
Brown acid	thirty-seven point nine four
stearic acid	four point five one
oleic acid	thirty-nine point five six
linoleic acid	seventeen point two six

Table 3: Fatty acid composition of palm oil (%)

（3） Nutritional composition of palm oil

Palm oil is also called saturated fat because it contains 50% saturated fat. Oil is a mixture of saturated fat, monounsaturated fat and polyunsaturated fat. The human body's digestion and absorption rate of palm oil exceeds 97%. Like all other vegetable edible oils, palm oil itself does not contain cholesterol.

As a kind of oil with high saturation, palm oil was once speculated to increase the cholesterol content in human serum. However, after further experimental demonstration by many experts, it was found that the consumption of palm oil would not increase the cholesterol in the serum, but would tend to reduce it. The reason is that a large number of research data show that different saturated fatty acids have different effects on blood lipids. Palm oil is rich in neutral fatty acids, and the content of substances that promote cholesterol increase in palm oil is very small (1%), The palm oil is rich in natural vitamin E, tocopherols (600-1000mg/kg), carotenoids (500-700mg/kg) and linoleic acid (10%), which are very beneficial to human health. Some researchers have studied different races (Europe, America, Asia), and the results show that palm oil is an edible vegetable oil that fully meets the needs of human health.

（4） Main uses of palm oil

Palm oil has two major characteristics. One is that it contains more saturated fatty acids, has good stability, and is not prone to oxidative deterioration. Second, palm oil is rich in vitamin A (500-700ppm) and vitamin E (500-800ppm). The palm oil is fractionated to separate the solid fat from the liquid oil. The solid fat can be used to replace the expensive cocoa butter as chocolate; Liquid oil is used for cold dressing, cooking or frying, and its taste is light and refreshing. A large amount of unrefined palm oil is used in the soap industry. Soaps produced with palm oil can have durable foam and strong decontamination ability. Palm oil can also be used for tin plating of tinplate and rolling of aluminum foil. Therefore, palm oil is widely used in catering industry, food manufacturing industry and oleochemical industry in the world.

1. Application of palm oil in catering industry

History shows that palm oil has been used for catering for more than 5000 years. Compared with other edible oils, palm oil products show greater advantages in frying and grilling food, which is mainly due to the following three reasons:

(1) Unique and good antioxidant property (frying resistance): This is mainly because palm oil is moderately unsaturated and does not contain linolenic acid. The rich natural vitamin E and tocopherols are natural and efficient antioxidants, which makes palm oil more suitable for frying and barbecue food than other oils.

(2) It is composed of nutritious fatty acids: palm oil has 50% unsaturated fatty acids, no trans acids, and is not easy to polymerize with acids.

(3) Economy: The cost of oil has always been an important consideration for the catering industry to choose oil for frying and barbecue. Oil palm is a high-yielding perennial oil plant, which can be harvested for about 20 years after one planting. Moreover, the annual oil production per unit area is far higher than that of other plant oils, and the yield is relatively stable. All these have made palm oil the most affordable edible vegetable oil in the world. Oil palm is the most productive oil crop. One hectare of land produces 3.5 tons of palm oil and 0.4 tons of palm kernel oil annually on average. Its production efficiency is much higher than that of similar vegetable oils, which also means that the output of palm oil per hectare is soybean 9-10 times.

In China, the main index of edible refined palm oil at present is that its melting point does not exceed 24 ℃ - 33 ℃. It is used for cooking and frying food (bread, biscuits, etc.), and its annual demand accounts for the vast majority of imports.

2. Use of palm oil in food industry

Palm oil is generally processed into shortening, margarine, hydrogenated palm oil, frying oil and special oil in the application of food industry. Like other edible oils, palm oil is easy to digest, absorb and promote health. Palm oil is an important component of fat. With mild properties, it is a good material for making food. From the composition of palm oil, its high solid glycerol content allows food to avoid hydrogenation and remain stable, and effectively resist oxidation. It is also suitable for hot weather as a good seasoning for pastry and bakery products. Because of these characteristics, palm oil is deeply loved by the food manufacturing industry.

(1) Shortening: Shortening is different from margarine, which is 80% grease and 20% water, while shortening is 100% pure grease. There are many kinds of shortening. Strictly speaking, each kind of food manufacturing needs to use special shortening, but there are also general types of shortening suitable for a variety of foods, usually used for frying and baking food, such as chips, cakes, biscuits, sandwiches and bread. Generally, the production and use of shortening need to be matched with different ingredients to be suitable for different products, such as ice cream, biscuits with different flavors, etc.

(2) Margarine: Margarine is an emulsion composed of water and oil. At first, it was developed to imitate butter, but now it has formed a variety of products, among which palm liquid oil is suitable for making liquid margarine, and palm stearin is more suitable for making solid margarine.

(3) Hydrogenated palm oil: Hydrogenated palm oil has a wide market in India, Pakistan and the Middle East countries, and these markets usually use it as a casein product.

(4) Frying oil: This is one of the most extensive uses of palm oil in the food industry. The main reason is that it has good antioxidant properties (its rich tocopherols are natural and efficient antioxidants), is not easy to polymerize with acids, and is composed of healthy fatty acids (50% unsaturated and fatty acids, no trans acids). In the production of instant noodles in most countries, including China, palm products are mostly used for frying pancakes, while in the Chinese market, some fried foods with local characteristics (such as fried breakfast, fried snacks, etc.) have also begun to use palm products for production.

(5) Special oils: Palm oil and palm kernel oil are ideal raw materials for producing special oils. Special oils are mainly used in the production of candy, especially chocolate food. Among them, brown kernel stearin is also called cocoa butter substitute because its physical properties are very close to cocoa butter.

Palm oil is increasingly widely used in the food industry, mainly because it has good natural antioxidant properties, unique physical properties, nutrient composition suitable for human health and obvious economy. With the continuous efforts of oil research institutions, palm oil will be more widely used in various fields of the food industry.

3. Industrial use of palm products

In recent years, the industrial use of palm oil has developed rapidly. In developed countries, a large number of palm oil has been used for industrial purposes. In China, palm industrial products are known as industrial monosodium glutamate, which shows that they are widely used. Refined palm oil for industrial use is required to have a melting point of no less than 44 ℃. It is mainly used to manufacture soap, stearic acid and glycerin. The annual demand is basically more than 100000 tons. In recent years, with the rise of crude oil prices, the theme of biofuel has been explored again. Palm oil as a biofuel has been found to be a new growth point of palm oil use in the future.

Palm oil can be directly obtained from palm products, such as soap, epoxy palm oil and its polyols, polyurethane and polyacrylate products. The other is oil chemical products, such as fatty acids, esters, fatty alcohols, nitrogen-containing compounds and glycerol. On the basis of these products, various derivatives can also be produced by different chemical methods. The main raw materials of oil chemical industry are oils rich in C12-C14 and C16-C18 carbon chain length, among which palm kernel oil, palm stearin and palmitic acid are the main raw materials.

category	purpose	characteristic
soap	Make soap	Good economy and lasting fragrance
Epoxy palm oil	Plastic plasticizers and stabilizers	Good economy
Polyol	Plastic manufacturing	Good hydrophobicity
polyurethane	Manufacturing foam plastics	There is no need to use the foaming agent harmful to the environment in the manufacturing process
Polyacrylate	coating
fatty acid	Production of rubber, candles and cosmetics	Light color and high purity
Fatty acids for soaps	High grade soap	Easy to produce, flexible formula
Fatty acids for metal soaps	Metallic soap
Fatty acid ester	Industrial synthetic lubricants	Good lubricity, low temperature fluidity and oxidation resistance
Fatty acid ester for soap	High quality white soap
Sulfonate methyl ester	Washing products	Simple production process, good decontamination effect, environmental protection and economy
fatty alcohol	surface active agent
glycerol	Medicine, industry, military, daily chemical, etc

Table 4: Main uses of palm industrial products

（5） Storage mode of palm oil

In palm oil, acid formation is caused by hydrolysis of either lipase or fatty acid catalase in palm fruit. The free fatty acid is very low in the unbroken fruit, but once the cells are damaged, the fruit lipase is activated, and the free fatty acid will rise sharply at the initial stage; Then, the rise of free fatty acids slowed down until the lipase activity was inactivated. The content of free fatty acids in palm oil actually depends on three factors: the degree of immaturity of the fruit (too mature fruit is vulnerable to damage); The degree of ear pretreatment (yeast killing); And the delay time between harvesting and lipase inactivation.

Iron is removed when making oil, which can indirectly control oxidation. At the same time, attention should be paid to controlling all environmental conditions that promote oil oxidation. The conveyor and elevator shall be cleaned regularly; Prevent soil and debris from planting areas from polluting oil. Do not use copper, brass, or bronze fittings to prevent contact between copper and oil. The reason is that copper is a strong oxidant. Keep the temperature as low as possible without prejudice to oil extraction. At the same time, try to make the oil less exposed to the air.

During storage, a refrigerator can be installed behind the vacuum drying section of the factory to reduce the temperature of oil to 45-50 ℃ before entering the storage tank. After the oil is filled into the tank, fill the tank with inert gas (carbon dioxide, nitrogen). Antioxidants can also be added to the oil to passivate trace metals to eliminate oxidation during oil storage. In addition, when large containers are used to store oil, oxidation can also be controlled, and oil splash during loading and unloading can also be reduced.

Precautions during transportation and unloading: First, the tank is coated with epoxy resin, and the tank cleaning shall be checked before oil loading. Second, spray and cover with inert gas. Third, the oil shall not be spilled. Fourth, the oil temperature shall be kept at 32-40 ℃ during shipping. Before loading, heat the oil to raise its temperature at a rate not exceeding 5 ℃ every 24 hours. Fifth, the shipment temperature of oil shall not exceed 55 ℃. Sixth, when deodorized palm oil arrives at the destination, it is loaded into an oil tank coated with epoxy resin and filled with nitrogen.