Food Emulsifiers and Stabilizers - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 234

conditions. He also reported on a series of fatty acid esters of sorbitan (mixed
monoesters) that included lauric, palmitic, stearic, and oleic acids sold under the
trade name SPAN.
By modifying sorbitan's pattern of esterification with ethers of ethylene oxide,
products marketed under the trade name TWEENS are made. The industrial use of
these compounds depends on the nature of the fatty acid esterified to the alcohols,
the degree of esterification, and the formation of polyoxyalkylene derivatives. 127 When
such products are ethoxylated (with 20 moles of ethylene oxide), a hydrophilic range
of sorbitan esters called polysorbates is produced. 97 Consequently sorbitan esters can
form a wide range of HLB values, from 1.8 to 16.7, which can be used as W/O or
O/W emulsions for numerous applications. 134 Many polysorbates have been part of
feeding studies in animals and appear no more toxic than many other foodstuffs. 125
Sorbitan monostearate 136 is most often used in combination with polysorbates
in cakes, cake mixes, whipped toppings, cake icings, fillings, confectionery coatings,
and coffee whiteners. 123 Polyoxyethylene (20 EO) sorbitan monostearate 60
(Polysorbate 60) can be combined with lipophilic emulsifiers such as sorbitan
monostearate and glycerol monostearate to provide cakes with greater volume and
finer, more uniform grain, adding softness without acquiring fragility. In icings, these
combined emulsifiers increase lightness by improved emulsification of the fat and
hydrocolloidal phase to prevent oiling-off or sticking to the wrapper. Polysorbate
60 is also used in prepared dry mixes, whipped toppings, bread and yeast-raised
products, and coffee whiteners. 124 Polysorbate (20) sorbitan monooleate (polysorbate
80) is used in ice cream and frozen desserts for resistance to heat shock and to
improve texture and palatability. It is also used in non-standardized baked goods,
prepared mixes, fillings, icings, toppings, and very often as a solubilizing agent for
flavors. Polysorbate 65 (polyoxyethylene sorbitan tristearate) is also used in frozen
desserts, whipped toppings, cakes, cake mixes, and coffee whiteners. 124
Sorbitan esters of fatty acids are effective antiblooming agents (fat crystal mod-
ifiers) in confectionery products containing cocoa butter and cocoa butter substitutes.
In chocolate, an undesirable property called bloom is inhibited by the use of sorbitan
esters of fatty acids. Because of the complex composition of fat in cocoa, the product
tends to crystallize in stages characterized by a Solid Fat Index (SFI) curve which
quantifies the percentage of the solid phase content as a function of the temperature
of the cocoa butter. At least six crystalline structures (six different polymorphs) have
been isolated and characterized for cocoa butter. The different polymorphs differ in
melting points, heat capacity, refractive index, and X-ray diffraction pattern. The
polymorphs tend to transform from one to the other as the temperature is raised.
The organoleptic properties of the chocolate depend on the nature of the polymorphs
present in the product at any temperature and storage conditions. The polymorphic
transformations lead to “instability” in the sugar-cocoa solid matrix resulting occa-
sionally in the migration of one of the cocoa fat polymorphs from the interior, along
the cocoa fiber to the chocolate's surface. This phenomona is known as bloom and
is responsible for the dull-gray white appearance when chocolate has bloomed. In
the absence of blooming, the chocolate is bright and shiny with a rich appearance. 135-137
Sorbitan esters modify fat crystals by retarding/inhibiting the reversion of crystalline
fat to a more stable form.