Food Emulsifiers and Stabilizers - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 217

TABLE 7.4
Specifications of Commercial and Industrial Grades of Soybean Lecithins

Grade

Fluid
Unbleached
Lecithin

Fluid
Bleached
Lecithin

Fluid
Double-Bleached
Lecithin Analysis

Acetone insoluble, min. 62% 62% 62%

Moisture, max. 1% 1% 1%

Hexane insoluble, max. 0.3% 0.3% 0.3%

Acid value, max. 32 32 32

Color, gardner, max. a 18 14 12

Viscosity, centiPoise, @77°F, max. b 15,000 15,000 15,000

Acetone insoluble, min. 65% 65% 65%

Moisture, max. 1% 1% 1%

Hexane insoluble, max. 0.3% 0.3% 0.3%

Acid value, max. 30 30 30

Color, gardner, max. a 18 14 12

Penetration, max. 22 mm 22 mm 22 mm

a Undiluted basis.
b By any appropriate conventional viscometer, or by AOCS Bubble Time Method Tg 1A-64, assuming
density to be unity. Fluid lecithin having a viscosity less than 7,500 centipoises may be considered
a premium grade.

By Karl-Fischer Titration (AOCS Method Tb 2-64).
Using Precision cone 73525, Penetrometer 73510; sample conditioned 24 hours at 77°F. Yearbook
and Trading rules, National Soybean Processors Association (1986-87).

component is a complex mixture of inositol phosphatides (PI) present at levels of
approximately 12%. 50 Miscellaneous low level constituents include water, phospha-
tidic acid, pigments, galactosyl glycerides, various glycolipids, phosphatidylserine,
carbohydrates, sterols, and tocopherols. The moisture content in commercial crude
lecithin is usually 1% or less. The multifunctional properties and its “natural” status
of lecithin makes it an ideal food ingredient. The major functional properties of
lecithin are summarized in Table 7.5 . Lecithins exhibit many beneficial properties
and are used in many commercial applications, including nutrition and health.
However, the main function of the phosphatides is their emulsifying ability for fats
and oils.
The long-chain fatty acid moieties contribute hydrophobic properties; those
properties are counterbalanced by the polar or hydrophilic character of the phosphate
moiety. In an oil-in-water system, the phospholipid components concentrate at the
oil/water interface. The polar, hydrophilic parts of the molecules are directed towards
the aqueous phase and the nonpolar hydrophobic parts are directed towards the oil
phase. Concentration of phosphatides at the oil/water interface lowers the surface
tension and makes it possible for emulsions to form. Once the emulsion is formed,