Refining process of edible oil
(1) Processing and utilization of rapeseed oil in China.
A. The process flow of pre pressed vegetable oil refining secondary edible oil is as follows: crude oil → filtration → hydration dephosphorization → vacuum drying → product oil.
B. The technological process of secondary edible oil refining from extracted rapeseed oil is as follows: extracting rapeseed oil → hydration (or alkali refining) → desolvation → product oil.
C. The process flow of pre pressed vegetable oil refining primary edible oil is as follows: crude oil filtration → alkali refining → water washing → decolorization → deodorization → product oil.
D. The technological process of refined rapeseed oil (salad oil) is as follows: crude oil extraction → hydration → alkali refining → water washing → decolorization → deodorization → filtration → product oil.
(2) Processing and utilization of Canadian low erucic acid rapeseed oil.
A. Salad oil production process:
Deacidification: through steam or hot water, the oil is hydrated, and then the impurities are removed, that is, the steam is introduced into the oil, and the free fatty acids are distilled with the steam and removed after condensation; Or let hot water and oil mixed emulsification, clarification after centrifugation to remove phospholipids, free fatty acids and plant mucus and other substances. After vacuum drying, the product is called crude oil.
Alkali refining: through alkali refining, most free fatty acids, phospholipids, pigments, iron and copper ions and some sulfur compounds can be further removed. First, add 0.02% ～ 0.5% phosphoric acid in a cylindrical iron pot, treat it at 60 ～ 90 ℃ for 15 ～ 30 minutes, then add 1% ～ 3% 8% ～ 12% sodium hydroxide (caustic soda) and saponify it for 10 ～ 30 minutes. Due to the large specific gravity of the saponified substance, it sinks into the bottom of the pot and is called soap foot after it is released; Then, wash twice with water or dilute acid at 65 ℃, remove the water, heat at 114 ℃ to remove the water, and store in the oil tank after drying.
Hydrogenation: when using selective hydrogenation (temperature 200 ℃, pressure 41.37 kPa) or non selective hydrogenation (temperature 135 ℃, pressure 413.69 kPa), 0.01% ～ 0.2% nickel formate or nickel carbonate is added into the snake tube hydrogenation pot to promote the hydrogenation of unsaturated fatty acids in oil to form saturated fatty acids, so as to change cis fatty acids into trans isomers, To increase the degree of hardening and antioxidant capacity of oil, and improve the flavor of oil. If a hydrogenation device called Kaufman is used, it can be carried out at a temperature lower than 100 ℃, adding 40% miscella (an oil solvent mixture), and the oil continuously passes through the catalyst (nickel), the hydrogenation process can also be completed. There is only a small amount of oleic acid in the oil, which can improve the quality of the oil.
Esterification: this process is heated at 95-135 ℃ for about 2 hours, and can also be carried out at low temperature (32-38 ℃) in the presence of catalyst (0.1% - 0.5% sodium methoxide or sodium ethoxide, or potassium sodium alloy); The catalyst is removed by washing with water, and six different triglycerides are formed by esterification of triglyceride and triglyceride inside and outside the oil molecules, so as to increase the plasticity of the oil, and the low melting point oil is changed into high melting point oil, which is convenient for manufacturing solidified margarine.
Deodorization: in order to remove odorous yellow substances, such as free fatty acids, aldehydes, ketones and sulfur compounds decomposed by glucosinolates, distillation should be carried out in a real tank under high temperature (240-270 ℃) and pressure (5.07 kPa absolute pressure), and 0.005% - 0.01% citric acid should be added after cooling to prevent oxidation.
B. The main process of shortening is quick freezing, that is, using salad oil as raw material, freezing the oil at 2 ~ 5 ℃ in a gas filled device, a large number of triglycerides will form crystals, filtered and removed, and then adding a small amount of preservatives and anti foaming agent, a semi-solid milky white and plastic shortening will be made. Generally, shortening is not hard and brittle at 10-16 ℃ and not soft and liquefied at 33-34 ℃. It is the raw material for making cakes, bread and margarine; Generally, 1.2kg of rapeseed oil is needed to refine the shortening per 1kg.
C. The preparation process of margarine: 80% shortening and 20% other auxiliary materials, such as fermented de esterified milk, dairy products and a small amount of emulsifiers, salt, spices, pigments, preservatives and other additives, are used to make margarine. The oil soluble ingredients are added to the oil and the water-soluble ingredients are added to the milk, and then they are sent to the cooler according to the specified proportion, so that the materials can be quickly cooled and crystallized, and the finished products can be obtained through cutting and packaging. Compared with animal oil, it has low cholesterol and low price. Margarine is an important raw material for making cakes and cold drinks.
D. Preparation process of blending oil: several different edible oils are mixed in a certain proportion, without chemical reaction process, and its fatty acid composition is more reasonable. From the perspective of food nutrition, the nutritional value of any kind of vegetable oil is not perfect. The proportion of palmitic acid, oleic acid and linoleic acid should be close to 1:1:1 in the more reasonable fat composition of oil. Only blended oil can meet this requirement, so it is also called healthy oil. If the ratio of rapeseed oil to rice bran oil or safflower oil is 1:1, the linoleic acid content will increase 2-3 times and the erucic acid content will decrease 50%. In Japan, 70% rice bran oil and 30% safflower oil were used as blending oil, and the cholesterol was reduced by 26%; The blended oil made of 85% rice bran oil and 15% safflower oil can reduce cholesterol by 19%. This can improve the nutritional value of rapeseed oil and expand the utilization range of rapeseed oil.
