Transcript Flavoring agents

Flavoring agents
Flavoring agents
• Flavor has a profound influence on the
consumption of food
• three types of flavoring additives:
o flavorings
o flavor enhancers
o (non-nutritive) sweeteners
• More than 1500 substances are used as food
flavorings. The majority are of natural origin
or are nature-identical
• Only a few synthetic substances have been
approved as food flavoring.
• Examples are ethylvanillin, ethylmaltol, and
anisylacetone
• The most widely used flavor enhancer is salt
(sodium chloride, NaCl).
• It is also a preservative and a nutrient.
• Generally, it is primarily regarded as a food
additive.
• A well-known toxic effect of NaCl is high blood
pressure.
• Flavor enhancers intensify or modify the flavor
of food.
• They have no taste of their own.
• such as monosodium glutamate (MSG) and
various nucleotides.
• These substances are present in Japanese
seaweed (Laminaria japonica, traditionally
used for seasoning), mushrooms, tomatoes,
peas, meat, and cheese.
• They are often used in soups, sauces and
oriental food.
• No known adverse effects of flavor enhancers
have been reported, except for the case of
MSG.
MSG
• It is also a synthetic product.
• MSG is an excitatory neurotransmitter. It has
been shown to cause permanent lesions of
the hypothalamus in newborn rats and mice.
• Presumably, this is attributable to immaturity
of the blood-brain barrier.
• Further, in young mice and rats, lesions of the
retina have been reported after large doses of
glutamate.
• Humans have also been found to be sensitive to
food to which MSG has been added as a flavor
enhancer.
• The symptoms, known as “Chinese restaurant
syndrome,” include loss of feeling, general
weakness, and heart palpitations.
• Humans have been described to be sensitive to
food to which MSG had been added. The
symptoms include numbness, general weakness,
and heart palpitations
Sweeteners
• Sweeteners present the consumer with one of the
most important taste sensations.
• For nutritional and health reasons, however,
there is a growing need for sugar substitutes in
food that are non-nutritive, i.e., noncaloric, and
noncariogenic.
• Two important noncaloric synthetic sweeteners
are saccharin and aspartame.
SACCHARIN
• In 1912 it was prohibited in the US on the basis of
acute toxicity tests.
• Up to now, no mutagenicity has been found.
• However, long-term animal tests showed a higher
incidence of bladder cancer.
• Although it is difficult to extrapolate from
experimental animals to the human situation, the
present average level involves risks of cancer.
• Therefore, the use of saccharin in food is still
approved in the US and in Europe.
ASPARTAME
• Aspartame was discovered in the early 1960s
• Aspartame is a dipeptide, consisting of the
amino acids phenylalanine and aspartic acid.
• It is digested and absorbed by the body
• It is 200 times sweeter than saccharose and is
an excellent sweetener for dry products.
• At high temperature and low pH, aspartame is
gradually hydrolyzed, losing its sweetness.
• It is suitable as table top sweetener, in
chewing gum, in soft drinks, dairy products,
ice cream, and dessert mixes.
• Results from toxicity tests suggest that
aspartame has no adverse effects on humans
even when extreme amounts of 8 mg/kg body
weight are taken in. The ADI for aspartame is
40 mg/kg body weight.
Preservatives
• Preservatives keep food edible for long periods
of time by preventing the growth of
microorganisms such as bacteria and fungi.
• Although the public perceives preservatives in
particular as hazardous, they are not only
harmless at the levels ingested but in fact
beneficial in that they reduce or prevent the
risks due to bacterial and fungal contamination
Antimicrobial
• Common antimicrobial food additives are benzoic acid
and benzoates, sorbic acid and sorbates, short-chain
organic acids (acetic acid, lactic acid, propionic acid,
citric acid), parabens (alkyl esters of p-hydroxybenzoic
acid), sulfite, and nitrite.
• Most of these substances are believed to be safe for
application in food.
• They are easily excreted and metabolized by both
animal and man.
• An exception should be made for one of them, namely
nitrite. The intake of nitrite can lead to the formation
of nitrosamines, which are well-known carcinogens.
• Nitrates and nitrites are used to preserve meats.
• For example, they contribute to the prevention of
growth of Clostridium botulinum, the bacterium
that produces the well- known highly potent
botulinum toxin.
• The adverse effects after intake of nitrates and
nitrites are methemoglobinemia and carcinogenesis
(from the formation of nitrosamines)
Nitrite
• Nitrite oxidizes (ferrous) hemoglobin to
methemoglobin, which cannot bind oxygen.
• This may lead to a state of anoxia.
• The consumption of meat with high levels of nitrate
and nitrite as well as of other dietary nitrate
sources, such as drinking water and spinach, has
resulted in life-threatening methemoglobinemia,
especially in young children.
• Newborns are (transiently) deficient in NADHreductase, the major system responsible for
methemoglobin reduction.
• Nitrite (either ingested directly or indirectly
via the reduction of nitrate) also reacts with
secondary amines under the formation of a
variety of nitrosamines, e.g., dimethylnitrosamine, diethylnitrosamine, and Nnitrosopyrrolidine.
•
• Nitrosamine formation can take place in food and in
vivo.
• The acidic conditions in the stomach favor nitrosamine
formation.
• Nitrosamines are mutagens as well as carcinogens.
• They induce cancer in a variety of organs, including the
liver, respiratory tract, kidney, urinary bladder,
esophagus, stomach, lower gastrointestinal tract, and
pancreas.
• Nitrosamines need biotransformation for their
activation.
• The bioactivation of nitrosamines is mediated by
cytochrome P-450.
• It involves oxidative N-dealkylation, followed by a
sequence of rearrangements to yield the alkylating
alkylcarbonium ions
• It should be noted that a decrease in the
incidence of botulism may be accompanied by
an increase in the formation of carcinogenic
nitrosamines, as a result of an increase in the
nitrite level of the meat (products).
•
• From a food toxicological point of view, three
types of nitrosamines are of importance:
dialkyl nitrosamines, acylalkylnitrosamines,
and nitrosoguanidines.
• Cyclic nitrosamines are similar to the dialkyl
type. The nitrogen atom becomes part of the
heterocyclic ring.
• Nitrosoguanidines are a special class of highly
reactive nitrosamides.
• One of the most effective inhibitors of
nitrosation is ascorbic acid.
• This vitamin reacts rapidly with nitrite to form
nitric oxide and dehydroascorbic acid. In that
way, it can inhibit the formation of
dimethylnitrosamine by more than 90%.
• Other inhibitors of nitrosation are gallic acid,
sodium sulfite, cysteine, and tannins.
• Nitrosamine levels in food also depend on the
temperature at which food is prepared.
• Cooking can increase the nitrosamine level in
food.
• frying can increase the nitrosamine level in bacon
quite considerably.
• Up to 135° C, cooking or frying does not result in
detectable nitrosamine formation. Above 175°C,
however, the nitrosamine levels increase rapidly.
• Nitrite addition to fresh meat and food products is still
under discussion because of the toxicological hazards.
• Up to now, banning of this additive has been blocked
by the food industry.
• It is stressed that so far no other antimicrobial agent
has been found that can provide protection against
Clostridium botulinum as effectively as nitrite.
• In some EU countries (but not in Germany and the UK)
and the US, nitrite addition to fresh meat is allowed up
to a maximum of 200 ppm.
Antioxidants
• Antioxidants are used to protect oils, fats, and
shortening against oxidative rancidity and to
prevent the formation of toxic degradation
products and polymers.
• Many foods may undergo oxidation, but
particularly those containing fats are susceptible
to changes in color, odor, taste, and nutritional
value.
• Unsaturated fatty acids are readily peroxidized in
the presence of molecular oxygen.
• The peroxidation products may induce toxic
effects.
• Also, in biological systems peroxidation of lipids
may have severe adverse consequences.
• Peroxidation of polyunsaturated fatty acids is
believed to be involved in disturbing the integrity
of cellular membranes, the pathogenesis of
hemolytic anemia, and pulmonary and hepatic
injury.
• Secondary peroxidation products, e.g.,
hydroxynonenal, can form adducts with DNA.