Lecithins moisture content

Commercial cmde lecithin is a brown to light yeUow fatty substance with a Hquid to plastic consistency. Its density is 0.97 g/mL (Uquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or filtered. Its consistency is deterrnined chiefly by its oil, free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aflphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aflphatic alcohols (Table 5). Pure phosphatidylcholine is soluble in ethanol. 

Liquefaction of the rolled product with more cocoa butter and lecithin occurs at 60°C (Fig. 14.28, right). This works mainly with pre-treated raw materials, such as crumb powder, where the flavor has already been formed and the moisture content has already decreased to less than 1%, providing a free-flowing mixture that allows for easy for pouring. This process saves several days of batch conching. 

Commercial lecithin is produced by water degumming (precipitation from oil with ion-exchange treated water), separation by stacked disk centrifuge, and vacuum drying to less than 1 percent moisture content. Crude lecithins contain 70-72 percent acetone insolubles (AI) and are standardized to 62-64 percent and an acid value of 30 by addition of oil and fatty acids before sale. Crude lecithins may be treated with acetone to obtain free-flowing powders with 95-98 percent AI. Lecithin can be additionally purified, bleached, fractionated, hydrogenated, hydrox-ylated, acetylated, sulfonated, and halo-genated.104 One domestic company makes 13 kinds of lecithin for food uses alone. 

Moisture. The water content of lecithin products is usually less than 1.0%. As a consequence of lecithin s essentially moisture-free state, lecithin products have very low water activity and do not adversely contribute to the microbiological profile of most food systems. Most lecithin products are preserved well in storage. Higher moisture levels usually indicate a greater potential for spoilage or chemical degradation. Moisture is determined by AOCS Official Method Ja 2b-87 (77). A less accurate moisture level can also be determined by azeotropic toluene distillation (AOCS Official Method Ja 2-46) (77). One cannot determine lecithin moisture by vacuum oven methods. These methods are known to degrade lecithin products and yield false moisture levels. 

Consistency. Lecithins are available in both fluid and plastic (solid) forms. Fluid lecithins generally follow Newtonian flow characteristics. The viscosity profile of lecithins is a complex function of acetone-insoluble content, moisture, mineral content, acid value, and the combined effects of assorted additives such as vegetable oils and surfactants. Generally, higher AI and/or moisture content yields higher viscosity, whereas an increased AV often decreases viscosity. Certain divalent minerals, such as calcium and others, can also adjust the viscosity level. 

Dry lecithin is highly viscous, and the viscosity increases drastically and then falls off as the moisture content increases. Comparative conditions used for drying lecithin in the two types of drying apparatus are given in Table 24 (59, 130). 

Soybean oil contains 1.5-3.0% phospholipids (71). Crude soybean lecithin has an oil content of about 30%. PC is present at a level of about 16%., PE about 14%, and inositol phospholipids about 12% (7). As can be seen in Table 18 (8), the fatty acid compositions of soybean phospholipids are rich in polyunsaturated fatty acids. Miscellaneous low-level constituents include water, phosphatidic acid, pigments, galactosyl glycerides, various glycolipids, phosphatidylserine, carbohydrates, sterols, and tocopherols. Phosphorus content of crude soybean oil extracted from flours can vary depending on extraction temperature and flour moisture (72). 

Clarity. In some soy processing plants, high levels of HI may partition with the lecithin gums on separation from the oil. This lipid-insoluble material can cause haziness in fluid lecithins. With modem miscella and oil filtration techniques, lecithins with very low HI contents can be produced. Consequently, modern lecithins are clear. Additionally, moisture can also contribute to lack of clarity. Generally, moisture levels over 1% can cause haziness. Besides being an aesthetic problem, if haziness is caused by HI material, it can result in sediment over time solid particles may appear on the bottom of an otherwise clear liquid product containing lecithin. 

Plastic lecithins are available in several forms and are typified by high AI, low AV, high moisture, or their content of certain minerals. One, or a combination of these, can produce a plastic lecithin. Oil-free lecithins are plastic, because of the removal of their nascent oil, i.e., residual soybean oil. They are generally powdered or granular in form. 

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