Modified starch, also called starch derivatives, are prepared by physically,
enzymatically, or chemically treating native starch to change its properties.
Modified starches are used in practically all starch applications,
such as in food products as a thickening agent, stabilizer or emulsifier; in
pharmaceuticals as a disintegrant; as binder in coated paper. They are also
used in many other applications. Starches are modified to enhance their
performance in different applications. Starches may be modified to increase
their stability against excessive heat, acid, shear, time, cooling, or freezing;
to change their texture; to decrease or increase their viscosity; to lengthen or
shorten gelatinization time; or to increase their visco-stability.
Modification methods Acid-treated starch, also called thin
boiling starch, is prepared by treating starch or starch granules with inorganic
acids, e.g. hydrochloric acid breaking down the starch molecule and thus
reducing the viscosity. Other treatments producing modified
starch are: dextrin, roasted starch with
hydrochloric acid alkaline-modified starch with sodium
hydroxide or potassium hydroxide bleached starch with hydrogen peroxide
oxidized starch with sodium hypochlorite, breaking down viscosity
enzyme-treated starch, maltodextrin, cyclodextrin
monostarch phosphate with phosphorous acid or the salts sodium phosphate,
potassium phosphate, or sodium triphosphate to reduce retrogradation
distarch phosphate by esterification with for example sodium
trimetaphosphate, crosslinked starch modifying the rheology, the texture
acetylated starch esterification with acetic anhydride
hydroxypropylated starch, starch ether, with propylene oxide, increasing
viscosity stability hydroxyethyl starch, with ethylene oxide
starch sodium octenyl succinate starch used as emulsifier adding hydrophobicity
starch aluminium octenyl Succinate cationic starch, adding positive
electrical charge to starch carboxymethylated starch with
monochloroacetic acid adding negative charge
and combined modifications such as phosphated distarch phosphate
acetylated distarch phosphate acetylated distarch adipate,
hydroxypropyl distarch phosphate, acetylated oxidized starch.
Modified starch may also be a cold-water-soluble, pregelatinized or
instant starch which thickens and gels without heat, or a cook-up starch which
must be cooked like regular starch. Drying methods to make starches
cold-water-soluble are extrusion, drum drying, spray drying or dextrinization.
Other starch derivatives, the starch sugars, like glucose, high fructose
syrup, glucose syrups, maltodextrins, starch degraded with amylase enzyme are
mainly sold as liquid syrup to make a sweetener.
Examples of use and functionality of modified starch
Pre-gelatinized starch is used to thicken instant desserts, allowing the
food to thicken with the addition of cold water or milk. Similarly, cheese
sauce granules or gravy granules may be thickened with boiling water without the
product going lumpy. Commercial pizza toppings containing modified starch will
thicken when heated in the oven, keeping them on top of the pizza, and then
become runny when cooled. A suitably modified starch is used as a
fat substitute for low-fat versions of traditionally fatty foods, e.g.,
reduced-fat hard salami having about 1/3 the usual fat content. For such uses, it
is an alternative to the product Olestra.
Modified starch is added to frozen products to prevent them from dripping
when defrosted. Modified starch, bonded with phosphate, allows the starch to
absorb more water and keeps the ingredients together. Modified starch
acts as an emulsifier for French dressing by enveloping oil droplets and
suspending them in the water. Acid-treated starch forms the shell of
jelly beans. Oxidized starch increases the stickiness of batter.
Carboxymethylated starches are used as a wallpaper adhesive, as textile printing
thickener, as tablet disintegrants and excipients in the pharmaceutical
industry. Cationic starch is used as wet end
sizing agent in paper manufacturing. Genetically modified starch
Modified starch should not be confused with genetically modified starch, which
refers to starch from genetically engineered plants, such as those that
have been genetically modified to produce novel fatty acids or
carbohydrates which might not occur in the plant species being harvested. In
the United States the term can also refer to foods that have been created by
traditional cross-breeding rather than gene splicing. In Europe the term
"Genetically Modified Organism" is used solely where "the genetic material has
been altered in a way that does not occur naturally through fertilisation
and/or natural recombination". The modification in "genetically modified"
refers to the genetic engineering of the plant DNA, whereas in the term "Modified
Starch" seen on mandatory ingredient labels it refers to the later processing
or treatment of the starch or starch granules.
Genetically modified starch is of interest in the manufacture of
biodegradable polymers and noncellulose feedstock in the paper industry, as well
as the creation of new food additives. For example, researchers aim to alter
the enzymes within living plants to create starches with desirable modified
properties, and thus eliminate the need for enzymatic processing after starch is
extracted from the plant. See also
Acceptable daily intake Retrogradation
Starch gelatinization Resistant starch
References GCSE Food Technology for OCR, Jenny
Ridgwell. 2001. ISBN 978-0-435-41951-6 Revise for OCR GCSE Food Technology,
Alison Winson. 2003. Degradable Polymers, Recycling, and
Plastics Waste Management. S Huang, Ann-Christine Albertsson. 1995.
Modified Starch, Jenny Ridgwell, Ridgwell Press, 2001, ISBN
978-1-901151-07-7