General Description
White solid with a mild odor. Floats on water.
Reactivity Profile
STEARIC ACID(57-11-4) is incompatible with strong oxidizers and strong bases. STEARIC ACID(57-11-4) is also incompatible with reducing agents.
Air & Water Reactions
Slightly soluble in water.
Health Hazard
Compound is generally considered nontoxic. Inhalation of dust irritates nose and throat. Dust causes mild irritation of eyes.
Fire Hazard
This chemical is combustible. This chemical can heat spontaneously.
Occurrence
Stearic acid is naturally present in the glycerides of animal fats and most vegetable oils. Reported found in fresh apple, banana, Vitis vinifera L., melon, tomato, ginger, blue cheeses, cheddar cheese, Swiss cheese, feta cheese, buttermilk, raw fatty fish, raw lean fish, raw shrimp, grapefruit juice, guava, papaya, cucumber, saffron, pork and lamb liver, pork fat, hop oil, beer, cognac, rum, whiskies, sherry, tea, peanut oil, soybean, roast coconut, coconut milk, avocado, passion fruit, rose apple, mushroom, starfruit, fenugreek, mango, cardamom, cooked rice, prickly pear, dill seed, buckwheat, malt, wort, cassava, loquat, shrimp, crab, cape gooseberry and Chinese quince.
Definition
A solid
carboxylic acid present in fats and oils as
the glyceride.
Definition
ChEBI: A C18 straight-chain saturated fatty acid component of many animal and vegetable lipids. As well as in the diet, it is used in hardening soaps, softening plastics and in making cosmetics, candles and plastics.
Preparation
Commercially it is produced by the hydrogenation of the unsaturated 18-carbon fatty acids of soybean, cottonseed or other vegetable oils. When obtained from animal fats by hydrolysis and fractional crystallization, commercial stearic acid is a mixture of solid organic acids, chiefly palmitic and stearic acids. Commercial products containing about 90% stearic acid are produced by hydrolysis and crystallization of a completely hydrogenated vegetable oil or by fractional distillation of fatty acid mixtures obtained from tallow
Production Methods
Stearic acid is manufactured by hydrolysis of fat by continuous
exposure to a countercurrent stream of high-temperature water and
fat in a high-pressure chamber. The resultant mixture is purified by
vacuum steam distillation and the distillates are then separated
using selective solvents.
Stearic acid may also be manufactured by the hydrogenation of
cottonseed and other vegetable oils; by the hydrogenation and
subsequent saponification of olein followed by recrystallization
from alcohol; and from edible fats and oils by boiling with sodium
hydroxide, separating any glycerin, and decomposing the resulting
soap with sulfuric or hydrochloric acid. The stearic acid is then
subsequently separated from any oleic acid by cold expression.
Stearic acid is derived from edible fat sources unless it is intended
for external use, in which case nonedible fat sources may be used.
The USP32–NF27 states that stearic acid labeled solely for external
use is exempt from the requirement that it be prepared from edible
sources. Stearic acid may contain a suitable antioxidant such as
0.005% w/w butylated hydroxytoluene.
Production Methods
Stearic Acid occurs in many animal and vegetable fats and oils, but it is more abundant in animal fat (up to 30 %) than vegetable fat (typically < 5 % ) . The important exceptions are cocoa butter and shea butter where the stearic acid content (as a triglyceride) is 28 – 45 %.
Stearic acid is prepared by treating these fats and oils with water at a high pressure and temperature (above 200 °C), leading to the hydrolysis of triglycerides. The resulting mixture is then distilled. Commercial stearic acid is often a mixture of stearic and palmitic acids, although purified stearic acid is available.
In terms of its biosynthesis, stearic acid is produced from carbohydrates via the fatty acid synthesis machinery via acetyl-CoA .
Brand name
Hystrene 5016 (Witco).
Aroma threshold values
Detection: 20 ppm
Pharmaceutical Applications
Stearic acid is widely used in oral and topical pharmaceutical
formulations. It is mainly used in oral formulations as a tablet and
capsule lubricant, although it may also be used as a
binder or in combination with shellac as a tablet coating. It has
also been suggested that stearic acid may be used in enteric tablet
coatings and as a sustained-release drug carrier.
In topical formulations, stearic acid is used as an emulsifying and
solubilizing agent. When partially neutralized with alkalis or
triethanolamine, stearic acid is used in the preparation of
creams. The partially neutralized stearic acid forms a creamy
base when mixed with 5–15 times its own weight of aqueous liquid,
the appearance and plasticity of the cream being determined by the
proportion of alkali used.
Stearic acid is used as the hardening agent in glycerin
suppositories.
Stearic acid is also widely used in cosmetics and food products.
Biochem/physiol Actions
β-Oxidation of stearic acid yields eight FADH2 (flavin adenine dinucleotide) and NADH2 (nicotinamide adenine dinucleotide) molecules and nine acetyl-CoA molecules.
Safety
Stearic acid is widely used in oral and topical pharmaceutical
formulations; it is also used in cosmetics and food products. Stearic
acid is generally regarded as a nontoxic and nonirritant material.
However, consumption of excessive amounts may be harmful.
LD50 (mouse, IV): 23 mg/kg
LD50 (rat, IV): 21.5 mg/kg
Carcinogenicity
Stearic acid was administered
subcutaneously to several groups of Swiss–Webster mice
at doses of 0.05 or 0.5mg once weekly for 25 weeks (total
dose of 1.3–130 mg), 1.0 mg thrice a week for a total of
10 injections or 1.0 mg twice weekly for a total of 82
injections. No neoplasms were reported in these studies
. In 3 groups of 10–15 BALB/c mice administered
0.05 mg or 0.5 mg stearic acid (twice weekly for 52 or
57 weeks), one pulmonary neoplasm was detected in each
group after 19–21 months.Afewsubcutaneous sarcomas and
one adrenal carcinoma were also reported.No injection
site sarcomas or other carcinogenic effects were reported
by the same authors in a later study of mice injected with
0.05–0.5 mg weekly for 26 weeks. Rats given subcutaneous
injections of 0.05 or 0.5 mg stearic acid weekly for
26 weeks did not develop sarcomas at the site of injection.
When rat fibroblast cells were transfected with an activated
human c-H-ras oncogene and the cells subsequently grown
in a medium supplemented with stearic acid (20–80 mM),
there was a marked increase in the number of transformed
foci. Stearic acid inhibited the colony-forming ability
of four out of five rat and two human tumor continuous cell
lines in vitro. Using rats pretreated with nitrosomethyl urea as
a model for mammary carcinoma, Habib et al. demonstrated
that subcutaneous injection of stearic acid at weekly
intervals prevented tumor development. Increasing levels of
stearate in the diet resulted in decreased mammary tumor
incidence and increased time to tumor in mice.
Metabolism
An isotope labeling study in humans concluded that the fraction of dietary stearic acid oxidatively desaturated to oleic acid was 2.4 times higher than the fraction of palmitic acid analogously converted to palmitoleic acid. Also, stearic acid was less likely to be incorporated into cholesterol esters. In epidemiologic and clinical studies stearic acid was associated with lowered LDL cholesterol in comparison with other saturated fatty acids. These findings may indicate that stearic acid is healthier than other saturated fatty acids.
storage
Stearic acid is a stable material; an antioxidant may also be added to
it. The bulk material should be stored in a wellclosed
container in a cool, dry place.
Purification Methods
Crystallise stearic acid from acetone, acetonitrile, EtOH (5 times), aqueous MeOH, ethyl methyl ketone or pet ether (b 60-90o), or by fractional precipitation by dissolving in hot 95% EtOH and pouring into distilled water, with stirring. The precipitate, after washing with distilled water, is dried under vacuum over P2O5. It has also been purified by zone melting and partial freezing. [Tamai et al. J Phys Chem 91 541 1987, Beilstein 2 IV 1206.]
Incompatibilities
Stearic acid is incompatible with most metal hydroxides and may be
incompatible with bases, reducing agents, and oxidizing agents.
Ointment bases made with stearic acid may show evidence of
drying out or lumpiness due to such a reaction when compounded
with zinc or calcium salts.
A number of differential scanning calorimetry studies have
investigated the compatibility of stearic acid with drugs. Although
such laboratory studies have suggested incompatibilities, e.g. with
naproxen, they may not necessarily be applicable to formulated
products.
Stearic acid has been reported to cause pitting in the film coating
of tablets applied using an aqueous film-coating technique; the
pitting was found to be a function of the melting point of the stearic
acid.
Regulatory Status
GRAS listed. Accepted as a food additive in Europe (fatty acids).
Included in the FDA Inactive Ingredients Database (sublingual
tablets; oral capsules, solutions, suspensions, and tablets; topical
and vaginal preparations). Included in nonparenteral medicines
licensed in the UK. Included in the Canadian List of Acceptable
Non-medicinal Ingredients.
