Food Additives: Safety and Limits of Use
Jasper K. Imungi, PhD
Professor of Food Chemistry
Department of Food Science, Nutrition and Technology
University of Nairobi
Paper presented in the Food Additives and Safety Workshop, 24th June, 2014
Intercontinental Hotel, Nairobi
• All over the World food additives are perceived to be evil
chemicals that will cause ill health in humans. They are
referred to as “chemicals”
• The tropical and subtropical countries can not afford to do
without some additives like preservatives
• The additives allowed for use in food have been subjected
to scientific testing and have been found to be safe for
use, nevertheless some with caution
• There is no chemical that will fail to cause allergic
reaction to all peoples of the World – remember the many
people who are allergic to some of the foods we eat
Introduction cont’d
Categorized in two ways:
• The manner in which they get into food: 1) Intentional
additives - considered ingredients in food
processing/preparation; 2)Unintentional or inadvertent
additives - from the environment of the food – contaminants
• The manner in which they are used: 1) Generally recognized
as safe (have been in safe use for long) – require no testing
before allowed for use, use can be regulated by consumer;
Regulated food additives – maximum levels are given beyond
which they might cause ill health
• The list of grass currently stands at aboutb800 chemicals and
is slowly growing
Introduction cont’d
The additives dealt with in this paper are the regulated that
are in common usage, but are sometimes controversial. They
• Preservatives including - benzoic acid, sulfur dioxide,
nitrites, and antioxidants
• Flavor potentiators - monosodium glutamate (MSG)
• nonnutritive sweeteners – cyclamates, saccharin,
glycyrrhizic acid, aspartame
The presentation will be limited to the safety and limits of
use of these chemicals
Preservatives - antimicrobials
Benzoic acid
• Occurs naturally in cranberries, prunes, cinnamon and cloves and in
smaller amounts in the seeds of many fruits
• Undissociated acid is the form with antimicrobial activity, optimum
activity at pH 2.5 – 5.0
• Suited for use in acid products such as fruit juices, carbonated
beverages, pickled products and fermented products
• Used at the level of 0.05 – 0.1% by weight, ADI = 0.5mg/kg body
• Most active against yeasts and bacteria and least active against molds
• eliminated from the body after conjugation with glycine (amino acid)
to form hippuric acid (benzoyl glycine), precludes accumulation in
the body
• Caution: Persons with asthma, or who have recurrent urticaria
(skin rashes) may be sensitive to benzoic acid
Sulfur dioxide
• Has long been used as a general food preservative
• Forms used include sulfur dioxide gas, sodium or potassium salts of sulfite,
bisulfite and metabisulfite
• Forms sulfurous acid and bisulfite ion in solution
• Undissociated acid dominant below pH 3 and inhibits yeasts and bacteria, but not
always to the same extent
• Bisulfite ion dominant at pH 4.5 and inhibits bacteria but not against yeasts
• Levels of use to maximum 300ppm, but levels up to 2000ppm found in dehydrated
fruits and vegetables. Levels beyond 500 ppm cause disagreeable flavor. ADI =
0.07mg/kg body weight
• Suitable for acidic products like in benzoic acid
• Also used against enzymic and non enzymic discoloration during handling,
processing or storage
• Cleared from the body by oxidation to sulfates – out with urine with no pathology
• Caution: No use in infant foods, by asthmatic, kidney and liver impaired. Can
cause allergic response in some people (looking like nettle rash, eczema)
• Initially potassium and sodium salts of nitrates and nitrites to develop
and fix pink color
• Later found to generate carcinogenic nitrosamines, but then found to
inhibit clostridium botulinum, organism that produces one of the
most lethal toxins known to man (6 mcg kills man)
• Accumulation in the liver can cause chronic toxicity (cancer)
• Choice of continued use is a choice of the bigger risk, acute botulism
or cancer
• Maximum levels of use 150 – 200 ppm. ADI = 0 – 0.15mg/kg body
• Nitrites can also bind the HB to impair blood transport in the body
(detrimental specially to small children.
• Nitrates wide spread in our vegetables such as spinach and carrots
esp. those grown with high levels of fertilizer (Be aware of carrot
juice esp. on children)
• Many antioxidants existing in nature include polyphenol compounds,
carotenoids and tocopherols, also ascorbic acid. These mediate against
• Important here are synthetic antioxidants that are used for preservation of
fats and fatty foods against oxidation of fats to cause off-flavors
• Some of the oxidation intermediate products have been known to be
• The common antioxidants include Butylated hydroxy anisole (BHA),
Butylated hydroxy toluine (BHT), Propyl gallate (PG) and Tert-butyl
hydroquinone (TBHQ)
• Recommended maximum use 0.01% for single or similar amount of each if
more than one are used. If with a synagist 0.028, but antioxidant same level.
• All polyphenol compounds are implicated in carcinogenesis
• The ADI: Propyl gallate 0 – 0.5mg, BHA 0 – 0.5mg, BHT 0.05, but ascorbic
acid 300mg/kg body weight
Common antioxidants
Flavor potentiators – Monosodium glutamate (MSG)
• Flavor potentiators – substances with little or no flavour but enhance
desirable flavors or depress undesirable flavors in food
• Commonly used flavour potentiators are MSG and some 5’-nucleotides
• MSG is a derivative of the amino acid glutamic acid by neutralization of
one carboxyl group only. Abudant in many foods esp. wheat and maize
gluten, soybean protein and casein
• Used in levels of 2 – 5g/kg of food. Taste threshold 300mg/liter
• Manufactured by fermentation, chemical process or extraction from plant
or animal tissues, mainly by AJINOMOTO in Japan. Known by the name
in the Kenyan markets.
• Local products containing it include aromat, cooking mixes, beef and
chicken cubes and soups and sauces
• Judicious use causes Chinese restaurant syndrome (CRS) – characterized
by headaches, facial pressure, chest pains, gastric distress, and burning
sensations over various parts of the body.
• Clearance from the body is the normal way of glutamic acid
Non-nutritive sweeteners
Broad group of substances that have been found to evoke a sweet taste or
enhance the perception of sweet taste. They do not yield calories on
metabolism. Their use is regulated by the consumer taste. Include:
• Sodium cyclamate (sodium cyclohexane sulfamate): also available as
calcium cyclamate. Burned for use in many countries including Kenya.
Metabolizes into cyclohexylamine which is a known carcinogen. Exposes
the bladder to cancer.
• Sodium saccharin (sodium ortho-benzosulfimide): Most commonly
available sweetener, sold simply as saccharin, 300 times sweeter than
sucrose. Allowed in Kenya only for dietetic products (Is it so? – sold freely).
Many imported products contain saccharin – evidence of use in
manufacturing in the country.
• Glycyrrhizic acid: Natural sweet-tasting substance found in the licorice
root as calcium and sodium salts of glycyrrhizic acid . 50 times as sweet as
sucrose. mainly used in tobacco.
Non-nutritive sweeteners cont’d
• Substances structurally related to glycyrrhizic acid have
recently been discovered. The most important is stevioside,
found in the leaves of Stevia rebaudiana Bertoni. It is 300
times as sweet as sucrose. Stevioside is available in the
market in this country under the name Stevia
• Aspartame (aspartylphenylalanine methyl ester): A dipeptide
and therefore not to be categorized as non-nutritive. About
200 times sweeter than sucrose. Use may be limited because
it lacks stability in food systems especially during storage. The
amide-linked amino acids and the methyl ester are potentially
labile to both chemicals and microbiological attack
In conclusion
• Many products local or imported contain food additives. It is
difficult to validate good manufacturing use of additives in this
• Food additives are a necessary evil and in the tropical and
subtropical countries we have to learn to live utilizing them
• In consuming/or preparation of food with specific additives, know
yourself and members of your family
• Consume foods processed with food additives in moderation (this
applies more to the children)
• Read the label of a processed food before purchase, it could contain
a chemical that you or your family member could be sensitive to.
• Eat from a variety of foods, both fresh an processed
You are what you eat

Food Additives: Safety and Limits of Use