Food Chemistry

3.7 Changes in Acyl Lipids of Food 187

The role of waxes is to protect the surface of
plant leaves, stems and seeds from dehydration
and infections by microorganisms. Waxes are re-
moved together with oils by solvent extraction of
nondehulled seeds. Waxes are oil-soluble at ele-
vated temperatures but crystallize at room tem-
perature, causing undesired oil turbidity. Ceryl
cerotate (ceryl alcohol esterified with cerotic acid,
C 25 H 51 COOH)

(3.47)

is removed from seed hulls during extraction
of sunflower oil. Waxes are removed by an oil
refining winterization step during the production
of clear edible oil.
Waxes are also components of the mass used to
cover fruit to protect it from drying out.
Waxes are present in fish oils, especially in sperm
whale blubber and whale head oil, which contain
a “reservoir” of spermaceti wax.

3.6.2.2 Alkoxy Lipids

The higher alcohols, 16:0, 18:0 and 18:1 (9), form
mono- and diethers with glycerol. Such alkoxy-
lipids are widely distributed in small amounts
in mammals and sea animals. Examples of con-
firmed structures are shown in Formula 3.48.
The elucidation of ether lipid structure is usually
accomplished by cleavage by concentrated HI at
elevated temperatures.

(3.48)

Common names of some deacylated alkoxy lipids
(1-O-alkylglycerol) are the following:

Chimyl alcohol (3.49)

Batyl alcohol (3.50)

Selachyl alcohol (3.51)

3.6.3 Cutin..................................................

Plant epidermal cells are protected by a suberized

or waxy cuticle. An additional layer of epicuticu-

lar waxes is deposited above the cuticle in many

plants. The waxy cuticle consists of cutin. This

is a complex, high molecular weight polyester

which is readily solubilized in alkali. The struc-

tural units of the polymer are hydroxy fatty acids.

The latter are similar in structure to the com-

pounds given in 3.7.2.4.1. A segment of the pos-

tulated structure of cutin is presented in Fig. 3.16.

3.7 ChangesinAcylLipidsofFood

3.7.1 EnzymaticHydrolysis

Hydrolases, which cleave acyl lipids, are present

in food and microorganisms. The release of

short-chain fatty acids (<C 14 ), e. g., in the

hydrolysis of milk fat, has a direct effect on food

aroma. Lipolysis is undesirable in fresh milk

Fig. 3.16.A structural segment of cutin (according to

HitchcockandNichols, 1971)