**3. Soybean phospholipids processing**

### **3.1 Preparation of concentrated soybean phospholipids**

Concentrated soybean phospholipids are products obtained by drying and dehydrating hydrated soybean crude oil foot. Industrial methods preparing concentrated soybean phospholipids include continuous and batch processings.

Phospholipids consist of fluidic and plastic phospholipids. Fluidic phospholipids have the flow property of Newtonian fluid and the fluidity of plastic phospholipids increases with the addition of fatty acids. The viscosity of phospholipids is affected by such factors as AI (acetone insoluble) content, moisture, mineral content, acid value (AV) and various additives for example plant-based surfactant. Generally, high AI or water content results in high viscosity while high AV results in low viscosity. Some bivalent minerals for example

N-hexane insolubles (HIs) make fluidic phospholipids turbid. The turbidness not only influence the appearance of the products, but also leads to precipitation in long-term storage. The phospholipids also get turbid when the water content is over 1% (Wu, 2001).

Phospholipids are very unstable when exposed to the air or the sunshine, and color deepening and oxidative rancidity easily happen. However, phospholipids are stable in oil without water. So the oil in concentrated phospholipids can prevent oxidative rancidity and is conductive to the phospholipids storage. Phospholipids are unstable at high temperature. In oil and phospholipids processing, the color of the oil get deeper at 150 degrees Celsius and the odor of phospholipids get worse. Phospholipids decompose at over 150 degrees

Hydrolysis of phospholipids occurs upon exposure to strong acid at high temperature. Saponification of phospholipids happens when heated in alkaline ethanol or water solution, and soaps are produced. The salts of phosphoglycerol and inositol phosphate are further heated to be hydrolyzed into glycerol, inositol and phosphoric acid. Free fatty acids and free substances of the above compound are produced after acid hydrolysis or high pressure

Phospholipids can be hydrolyzed by enzymes. At least four kinds of lipases can cleave ester bonds formed by carboxylic acid and phosphoric acid attached to the glycerol molecule and some of them can only cleave unsaturated fatty acids from phospholipids and can't act on saturated fatty acids. These actions result in production of so called lysophospholipids

Phospholipids may be modified under certain conditions. The modification reactions include hydroxylation, acetylation, hydrogenation, sulfonation, hydroxyl acetylation and enzymatic modification etc. Modified phospholipids vary in their properties and functions

Phospholipids are regarded as the synergist of antioxidant, and they can synergize or prolong the antioxidation functioin of tocopherol. The synergism of phospholipids differs due to the differences of oil and phospholipids. Mixtures of PE, mixed tocopherol and

Concentrated soybean phospholipids are products obtained by drying and dehydrating hydrated soybean crude oil foot. Industrial methods preparing concentrated soybean

synthetic antioxidant exhibit the highest antioxidant property (Wu, 2001).

Ca2+ affect viscosity too.

**2.3.2 Chemical properties** 

which have strong effect of hemolysis.

**3. Soybean phospholipids processing** 

**3.1 Preparation of concentrated soybean phospholipids** 

phospholipids include continuous and batch processings.

Celsius.

hydrolysis.

(Lu, 2004).

#### **3.1.1 Continuous processing**

The processing steps are as follows: The crude oil is heated to 80 degrees Celsius and then centrifuged and passed through the flowmeter followed by addition of 80 degrees Celsius water of 2% (w/w) of the oil.

Degumming oil and oil foot sediments are produced and they can be separated by centrifugation. The hydrated oil foot should be concentrated immediately to avoid microbial rancidity due to the high moisture and neutral oil content. Oil foot (or mixed with hydrogen peroxide or fluidity agent in advance) is pumped into the agitated film dryer. Phospholipids film is formed under gravity or centrifugal force and the pressure of incoming production materials and flow to the bottom of the vessel while moisture evaporates under high temperature and vacuum conditions. The motionless fluid product is dried at vacuum (726 mm Hg) and 100-110 degrees Celsius for 2 min and then cooled to obtain concentrated soybean phospholipids with less than 1% moisture content. The concentrating procedure should be operated under vacuum as phospholipids are thermosensitive (Ji & Li, 2005).
