The development history of oil fractionation technology
The main component of oil is fatty acid triglyceride. The carbon chain length of fatty acid in triglyceride is different, and the degree of unsaturation is also different. This makes the oil contains a considerable amount of triglyceride with low melting point and high melting point , low melting point triglyceride in liquid form is referred to as the "oils", while the high melting point triglyceride in solid or semi-solid form, usually called "fats." The fractionation process is oil and fat processing method that divides the triglyceride into low-melting liquid phase (olein) and high melting point solid fat (stearin) by controlling the cooling and crystallization process, and separates "olein" from "stearin".
Ⅰ.Early history of the fractionation process
油脂分提工艺已经应用了近150年。油脂分提技术的发明归功于法国人希伯利特•麦加•莫利哀 Hippolyte Mège-Mouriès，希伯利特是他母亲的娘家姓。麦加•莫利哀(1817-1880)，出生于法国南部的德拉吉尼昂。1867年麦加•莫利哀正忙于在巴黎附近帝国农场从事乳品研究，他发现瘦小的奶牛尽管减少了牛奶的产出, 仍然在牛奶中产生脂肪。因此, 他开创了一个工艺以人工方法生产奶油，因此成为生物技术的先驱, 这给他带来了持久的名声, 即人造黄油的发明。
The oil fractionation process has been used for nearly 150 years. The invention of oil fractionation technology is attributed to the French Hippolyte Mège-Mouriès, Hippolyte is his mother's maiden name. Mège-Mouriès(1817-1880), born in Draguignan, southern France. Mège-Mouriès was busy doing dairy research on the imperial farm near Paris in 1867,he found that even though thin cows reduced milk production, they still produced fat in milk.Therefore, he created a process to produce butter by artificial methods, and thus became a pioneer in biotechnology, which gave him lasting reputation, namely the invention of margarine.
1869年7月15日, 法国农业和贸易部授予麦加•莫利哀 15 年的专利，用于加工和生产某些动物来源油脂，该专利1873年也在英国获得注册。到 1873年麦加•莫利哀获得美国专利 (146012; 1-1-1873)专利名为 "动物脂肪的改性"，不久后他的美国专利由纽约市的美国乳品公司获得，用于生产人造奶油。
On July 15, 1869, the French Ministry of Agriculture and Trade granted Mecca Molière with 15-year patent for processing and producing some animal fats,the patent was also registered in the United Kingdom in 1873. In 1873, Mecca Molière received U.S. patent (146012; 1-1-1873) entitled "Modification of Animal Fat". Soon after this, his US patent was obtained by the American Dairy Company in New York City for the production of margarine.
The fat in the patented method came from animal fat, tallow and mutton fat, after moderate cooling, the liquid components are separated from ordinary tallow. However, only the temperature difference is the driving force, and the step-by-step crystallization of fat is a completely natural phenomenon. Therefore, it was also observed that palm (kernel) oil harvested in tropical regions was transported to cold Western Europe in wooden barrels, and the crystals formed after cooling were suspended in the wooden barrels. These small amounts of dense solids eventually settled, and such components can effectively replace the hardened fat in margarine.Therefore, we can consider these wooden oil barrels as the first oil fractionation crystallizer, and the waves provided the necessary stirring for mixed suspension. In addition, palm oil naturally crystallizes in winter, which is an economical way of oil fractionation.
II. The development of fractionation technology
直到二十世纪六十年代, 分提技术才得以蓬勃发展, 当时东南亚棕榈油的生产大量增加, 加工棕榈油的出口税也减少了。然而, 当时的技术边界主要是由相分离来决定的。在分提技术的早期阶段, 油与脂仅依靠重力力量导致较重的固相和较轻的液相之间的分离, 固相包含大量液体油夹带，几乎超过 75% 。在过去的几十年中, 从真空带过滤到离心机和膜压力过滤器等分离技术的不断发展, 使分提成为一种通用的经济改性技术。虽然一些特定的技术依赖表面活性剂适用于非常特殊的生产, 实际上只有两个主要的分提技术是在第二十一世纪的食用油工业中使用:干法分提和溶剂分提。
The technology of fractionation did not take off until the 1960s, when palm oil production in Southeast Asia surged and export taxes on processed palm oil were reduced. However, the technical boundary at that time was mainly determined by the phase separation.In the early stages of the fractionation technology, oil and fat rely solely on gravitational forces to cause the separation between the heavier solid phase and the lighter liquid phase, which contains a large amount of liquid oil, almost over 75%. In the past few decades, the continuous development of separation technology from vacuum filtration to centrifuge and membrane filter press makes fractionation become a general economic modification technology. Although some specific technologies rely on surfactants for very specific production, actually there are only two kinds of main fractionation technology used in the 21st century edible oil industry: dry fractionation and solvent fractionation.
III Factors affecting fractionation
The factors affecting the palm oil crystallization process include the oil grease composition, homogeneous polycrystals and cooling conditions.
Palm oil contains 4% to 8% triglycerides, which will form eutectic mixture with triglycerides, thereby reducing the solid content and slowing down the crystallization rate of oils. The content of monoglycerides in palm oil is less than 1%, so it has no obvious effect on the crystallization process of palm oil.
（2） 同质多晶体 棕榈油的甘油三酯存在同质多晶现象，故其有不同形式的结晶形态，即α型、β’型和β型晶体。这些晶型的稳定性及熔点依次递增，在将棕榈油冷却时，首先得到的是α型晶体，然后依次转化为β’型和β型晶体。为了能得到良好的分离效果，结晶过程中希望能得到β’和β型晶体，因为β’型晶体具有晶体大而且硬的特点，有利于后续的过滤分离。
The triglycerides of palm oil have homogeneity and polymorphism, so they have different forms of crystals, namely α-type, β'-type and β-type crystals. The stability and melting point of these crystal forms gradually increase. When palm oil is cooled, α-type crystals are obtained first, and then they are converted into β'-type and β-type crystals in turn. In order to obtain a good separation effect, it is desirable to obtain β'and β-type crystals during the crystallization process, because β'-type crystals have characteristics of large and hard crystals, beneficial to subsequent filtration and separation.
The cooling rate will affect the formation of crystal nucleus and crystal growth. When the temperature is low enough (32~36℃), saturated glycerides will crystallize. These crystals become crystal nucleus for further crystallization of low-melting glycerides, and then form large crystals. Slow cooling rate and proper stirring rate are necessary conditions for obtaining ideal crystals.
IV The application and development of oil fractionation technology
棕榈油干法分提的*步是在10℃以下的结晶。液体组分被用作油炸、烹调和沙拉油中的替代品, 或进一步分提。随着单级棕榈油分提技术的进一步发展,有一种增加的倾向, 执行双重或三重组份的棕榈油, 以产生具有特定特征的组份，如高碘价超级油酸 (iv > 65) 和超硬棕榈硬脂以及中间组分。
The first step of dry fractionation of palm oil is crystallization below 10°C. The liquid component is used in frying, cooking and as a substitute of salad oils, or is being further separated. With the further development of single-stage palm oil fractionation technology, there is a tendency to increase, perform double or triple components of palm oil to produce components with specific characteristics, such as high iodine number super oleic acid (iv> 65) and super hard palm stearin and intermediate components.
中间组分可以用作生产典型的可可脂 (CBE) 的原料, 它们在物理和化学性质上与可可脂相似, 是非月桂脂。
Intermediate components can be used as raw materials for the production of typical cocoa butter (CBE), which are similar in physical and chemical properties to cocoa butter and are non-laurel butter.
Another technical field is the use of plug flow reactor (Plug Flow Reactor, PFR), which allows continuous step crystallization, thereby greatly reducing operating costs (such as steam usage and cooling power). In fact, just like other edible oil processing technologies, we constantly pursue economic and process optimization. The heat recovery system, feed crystal device, optimized mixing procedure and elegant plant layout help to maximize the capacity and cost of the dry fractionation device.
The fractionation process produces two products, so the sum of two components should always exceed the processing cost and raw material cost. This is why the feasibility of multi-stage fractionation is not only a question of technical know-how, but also a question there is market for all "by-products".