Ascorbic acid (vitamin C) is used extensively in
the food industry, not only for its nutritional value
but for its many functional contributions to
Acting as an antioxidant, ascorbic acid can
improve the color and palatability of many kinds of
food products. By removing oxygen from its
surroundings, ascorbic acid in its reduced form
becomes the oxidized form, dehydroascorbic
the available oxygen in its immediate
environment, making ascorbic acid an
Ascorbic acid addition is common in the
manufacture of beverages, especially those
made from fruit juices. Ascorbic acid not
only restores nutritional value lost during
processing, but also contributes to the
products’ appearance and palatability.
Fruits can be divided into two categories: those
that do not. Fruits such as apples, bananas and
peaches belong to the first group, while oranges,
lemons, and other fruits that contain a large
amount of ascorbic acid belong to the second.
Besides variety, natural vitamin C content in fruit
varies (Table 1) with growing region, climate, and
time of harvest.
In the manufacture of fruit juices or purees from
fruits such as apples and peaches, ascorbic acid may
be added during the crushing, straining, or press-
ing processes to prevent enzymatic browning of the
raw fruits. Browning takes place when enzymes
called polyphenolases, which occur naturally in
fruit tissue, catalyze the oxidation of phenols, also
naturally present in the fruit, to form compounds
called quinones. The quinones can then polymerize
to form melanins, which cause the brown pigments
Ascorbic acid can inhibit browning reactions by
reducing the quinones back to the original phenol
compounds. In the presence of oxygen or metal
ions, the phenols can readily convert to quinones.
ascorbic acid can make each compound unavail-
able for reacting with the phenols (Figure 2).
Also, because polyphenolases are most active in a
pH range between 6.0 and 7.0, combinations of
ascorbic acid and citric or malic acids are some-
times used to diminish enzyme activity by
lowering the pH of the juice or fruit puree. Heat
treatment or pasteurization during processing will
also inactivate the enzymes and prevent any
further enzymatic browning in the final juice
Other benefits of
ascorbic acid addition
When secondary processed products such as
juices or purees, additional ascorbic acid is
often added during the mixing process to
restore nutrient losses that might have oc-
curred during processing.
Ascorbic acid is added to soft drinks and fruit
beverages to prevent oxidative flavor deteriora-
Adding extra ascorbic acid to bottled and
canned beverages reduces the oxygen in the
head spaces of the containers to prevent future
oxidation of the product. Usually 3.3 mg of
ascorbic acid will remove the oxygen in 1cc of
Stability of ascorbic acid
when added as a nutrient
If ascorbic acid is added as a nutrient to
beverages, either to replace processing losses or as
fortification, the stability of the ascorbic acid over
the shelf-life of the product becomes important.
There have been many studies on the stability of
ascorbic acid in different beverages, different
containers, and under exposure to different types
of light. Marcy and coworkers observed a 40%
loss of ascorbic acid in an aseptically packaged
orange drink containing 10% orange juice after
six months at storage temperatures of 4°and 15°C
and up to a 75% loss at 22° and 30°C. Sattar and
coworkers observed the greatest losses of ascorbic
acid in a HTST pasteurized orange drink pack-
tetraPak and amber glass
had lower losses when
exposed to fluorescent light
over a 30 day storage
period at temperatures
between 25-30ºC. Similar
findings were observed by
Sattar and coworkers using
the same packaging and
but exposed to incandes-
cent light. Ahmed and
coworkers observed greater
ascorbic acid losses in
orange juices and drinks stored in plastic and
paperboard containers held at 5-7°C than in
glass containers held at similar temperatures.
industry for its antioxidant properties. In cured
meats, ascorbic acid can: (1) accelerate color
development, (2) inhibit nitrosamine formation,
(3) prevent oxidation, and (4) prevent color
fading. Ascorbic acid is also used in fresh meat
to prevent oxidation and color fading during
When ascorbic acid is added to cured meats,
it oxidizes to become dehydroascorbic acid. It is
this oxidation that accelerates the reduction of
nitrosomet-myoglobin to nitrosomyoglobin
(Figure 3), which imparts to cured meats their
Ascorbic acid can prevent nitrosamine
formation in cured meats by reducing nitrate to
nitrogen oxide, which will not be able to react
with the amines to form nitrosamines (Figure 4).
Ascorbic acid also prevents the oxidation of
lipids and fats in both raw and cured meat prod-
ucts. Lipid oxidation causes the release of many
lower-weight molecules, which can impart off-
flavors and rancid notes to the meat. By reducing
the oxygen in the environment, less oxygen is
available to breakdown the lipids. The color of
both fresh and cured meats is sensitive to decompo-
sition caused by oxidation of the myoglobin in the
tissues. Ascorbic acid’s antioxidant action preventsthe myoglobin from oxidizing to metmyoglobin,
which has a brown color.
Oils and Fats
The unsaturated long-chain fatty acids present
in fats and oils readily oxidize when exposed to
heat, light, and air. As in meats, lower molecular
weight compounds are formed and impart rancid
odors and flavors. Because ascorbic acid is a water
soluble compound, it can control these reactions
only to a certain extent. The antioxidant effects of
ascorbic acid are more apparent in an oil system if
ascorbic acid is used in combination with other
antioxidants such as tocopherols, BHT, and BHA.
In fat systems the use of fat soluble esters of
ascorbic acid, such as ascorbyl stearate or ascorbyl
palmitate are recommended.
Ascorbic acid’s ability to improve bread dough
has been known since the 1930s. In dough sys-
tems, adding ascorbic acid to the flour improves
both bread texture and loaf volume. The ascorbic
acid is first oxidized to dehydroascorbic acid. Then
the reduction of dehydroascorbic acid back to
ascorbic acid drives the reaction of sulfhydryl
compounds in the gluten to form intermolecular
disulfide bonds (Figure 4). It is the network of
disulfide bonds formed in the gluten structure that
enables the dough to retain carbon dioxide pro-
duced by the yeast, which in turn allows for
maximum volume and improved texture.
As a nutrient
In addition to its benefits as a processing aid and
preservative, ascorbic acid has nutritional value in
Fruits, vegetables and juices are primary sources
of vitamin C in the diet (Table 2), but during
processing and storage, vitamin C losses may occur.
Many processors add ascorbic acid to their products
to make up for processing losses.
Vitamin C may also be added for caloric density
fortification, which is the addition of nutrients to a
food based on the caloric content, and for stan-
dardization. Differences in crops and in processing
conditions may affect final vitamin content, and
standardization insures that all food products in the
same category have the same amount of a particu-
lar nutrient per serving.
Several studies have shown that airtight and
non-light penetrating (brown, amber, opaque)
containers are best used to protect vitamin C from
degradation. Overages of vitamin C above the label
claim are usually necessary to insure label claim
compliance after processing and storage.
Processing with Ascorbic Acid
Ascorbic acid has many applications in the food
industry. It is used to reduce browning in fruits and
vegetables; as a processing aid and to reduce
nitrosamine formation in cured and raw meat
products; to reduce the oxidation of fats and lipids;
and as a dough conditioner.
Ascorbic acid stability is greatly influenced by
temperature, oxygen, and metal ion content.
Precautions should be used when adding ascorbic
acid as a nutrient to processed fruit products:
(1) Use stainless steel or plastic manufacturing
(2) Remove as much oxygen as possible from
equipment and containers.
(3) Use flash heat sterilization and/or add the
ascorbic acid as close to the end of thermal
processing as possible.
Ascorbic acid will not upgrade poor raw materi-
als or cover poor processing techniques, and it
should be used in connection with good manufac-
turing practices. Standards of identity regulating
the amount of vitamin C addition vary for each
product must be individually checked.
TAKEDA U.S.A., INC.
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USDA Handbook No. 8, U.S. Department of