2009_Book_FoodChemistry

182 3 Lipids
(3.40a)
(3.40b)
(3.41)
(3.42)
Phytosphingolipids are isolated from soya and
peanuts (cf. Formula 3.42).
3.4.2 Analysis
3.4.2.1 Extraction, Removal of Nonlipids
A solvent mixture of chloroform/methanol
(2 + 1v/v) is suitable for a quantitative extraction
of lipids. Addition of a small amount of
BHA (cf. 3.7.3.2.2) is recommended for the
stabilization of lipids against autoxidation.
Nonlipid impurities were earlier removed by
shaking the extracts with a special salt solution
under rather demanding conditions. An improved
procedure, by which emulsion formation is
avoided, is based on column chromatography
with dextran gels.
3.4.2.2 Separation and Identification
of Classes of Components
Isolated and purified lipids can be separated
into classes by thin layer chromatography using
developing solvents of different polarity. Figure
3.12 shows an example of the separation of
neutral and polar lipids. Identification of polar
lipids is based on using spraying reagents which
react on the plates with the polar moiety of
the lipid molecules. For example, phosphoric
acid is identified by the molybdenum-blue
reaction, monosaccharides by orcinol-FeCl 3 ,
choline by bismuth iodide (Dragendorff reagent),
ethanolamine and serine by the ninhydrin reaction,
and sphingosine by a chlorine-benzidine
reagent.
When sufficient material is available, it is advisable
to perform a preliminary separation of lipids
by column chromatography on magnesium sili-