Lecture
The problem of food safety is complex, difficult,
and requires efforts on the part of scientists and food producers.
The relevance of the food safety problem grows with each
year, as it is decisive in preserving people's health.
Food safety is understood as the absence of danger to
human health when food products are consumed. Food products can be considered
safe if they do not exert harmful, adverse effects on the health of
present and future generations. This danger may arise as a result
of a negative impact on the human body in cases of food poisoning and
infections. A danger is also posed by the long-term consequences of
exposure to contaminants – carcinogenic, mutagenic, teratogenic
effects. A carcinogenic effect leads to the development of cancerous
tumors. A mutagenic effect leads to qualitative and quantitative
changes in the genetic apparatus of cells. A teratogenic effect leads to
abnormalities in fetal development.
Food products are complex multicomponent
systems consisting of a large number of compounds of diverse chemical nature.
These compounds can be divided into three groups:
Compounds necessary for humans (having alimentary significance). This
group includes proteins, lipids, carbohydrates, vitamins, minerals.
Substances involved in the formation of taste, aroma, color,
precursors and breakdown products of nutrients, biologically active
substances.
Foreign, potentially hazardous substances of anthropogenic or
natural origin. These substances are called xenobiotics,
foreign chemical substances. They may be of inorganic and
organic nature, or of microbiological origin. The sources and pathways
by which these substances enter food raw materials and food products
are diverse.
Toxic elements (for example, heavy metals) constitute a group of substances that is dangerous in
toxicological terms.
Contamination of the environment and food products with toxic metals
occurs through:
- industrial emissions (for example, from the coal, metallurgical, chemical
industries);
- motor vehicle emissions (automobile exhaust gases contain
lead);
- the use of low-quality metal containers in the canning industry;
- contact of raw materials and finished products with the metal parts of equipment.
Among heavy metals, the greatest danger is posed by mercury, lead,
cadmium.
Mercury – one of the most dangerous and highly toxic elements, possessing
the ability to accumulate in plants and in the bodies of animals and humans. Mercury
alters the properties of, or inactivates, a number of vital enzymes. Mercury
compounds disrupt the metabolism of ascorbic acid (vitamin C), pyridoxine (vitamin
B6), tocopherols (vitamin E), proteins, cysteine, calcium, copper, zinc, selenium, iron,
manganese. Mercury enters the human body mainly with fish products. Fish
flesh is distinguished by the highest concentration of mercury and its compounds, as it extracts
them from water and feed. Mercury may also be present in other types of products: meat,
liver, kidneys, milk, butter, eggs, vegetables, fruits, legumes, cereals, and in
cap mushrooms.
Lead. At present the range of areas of its application is very broad:
the production of batteries, electrical cables, chemical machinery construction,
the nuclear industry, the production of enamels, varnishes, crystal, pyrotechnic
products, etc. The main source of atmospheric lead contamination is the
exhaust gases of motor vehicles and the burning of coal. Many plants
accumulate lead, which is then found in the meat and milk of animals.
Lead inactivates enzymes, affects the hematopoietic, nervous and
digestive systems, and the kidneys. Lead poisoning leads to headaches,
dizziness, increased fatigue, irritability, worsening of sleep,
paralysis, mental retardation.
Cadmium is widely used in various branches of industry. Cadmium enters
the environment through the burning of fuel, from the gaseous emissions of
enterprises, and with mineral fertilizers. Cadmium salts are used in veterinary medicine as
a means of controlling parasites. It has been proven that cadmium enters the human body with
food, from the atmosphere and through smoking. Cadmium damages the kidneys and disrupts the metabolism of iron and
calcium. It causes hypertension, anemia, ischemic heart
disease, renal failure.
Radioactive isotopes can get into food products. Natural
sources include radioactive substances found in the earth's crust. They can
enter food products through the use of mineral fertilizers produced from
phosphate rocks with a high content of these radionuclides.
A significantly more dangerous source is the contamination of the environment
as a result of the construction and operation of nuclear reactors and the use of
radioactive isotopes in other branches of industry, as well as due to the burial of
solid and liquid waste from such production. Accidents at nuclear power plants and other enterprises of the
nuclear industry are one of the main sources of contamination of the
environment with radionuclides. The accident at the Chernobyl nuclear power plant sharply intensified
the exposure of a huge number of people to radiation. The same result was caused by the recent
accident at the nuclear power plant located in the city of Fukushima (Japan). Such accidents
provoke the development of various diseases.
The most dangerous for humans and animals are strontium-90 and cesium-137.
Strontium has a number of radioactive isotopes formed during the fission of uranium in
nuclear reactors, as well as during the explosions of atomic bombs. Being an analog of calcium,
strontium is incorporated into mineral metabolism in the body. In the body, strontium-90
is well absorbed in the gastrointestinal tract, and significant amounts of it
are deposited in the skeleton. This leads to irradiation of the bones, bone marrow,
and other tissues. Strontium poses a great danger to children; it enters their bodies
with milk and accumulates in bone tissue. With prolonged
intake of strontium into the body, even in relatively small amounts,
the continuous irradiation of bone tissue can lead to the development of leukemia and
bone cancer.
Cesium. It is contained in radioactive fallout, radioactive waste, and is
sorbed by soil. Cesium accumulates in the muscles, heart, liver, kidneys,
skin, blood, and adipose tissue. With prolonged intake of cesium-137, there is a
constant increase in its total content in the body, after which a
state of equilibrium sets in, when the daily intake is balanced by
excretion. Cesium causes disruption of the functions of the endocrine, hematopoietic,
cardiovascular, immune, nervous, reproductive, respiratory and other systems, with the
development of severe pathological processes (leukemia, malignant
neoplasms, dystrophy, obesity, etc.).
9.4 Polycyclic aromatic hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are strong
carcinogens. Among the most active carcinogens are 3,4-benzopyrene, which
is the carcinogenic component of soot and tar, as well as dibenzopyrene.
PAHs form during the combustion of petroleum products, coal, wood, refuse,
food, tobacco. Conditions of heat treatment significantly increase the content of
benzopyrene. Polymer packaging materials can play a role in the contamination of
food products with PAHs; for example, milk fat extracts benzopyrene from
paraffin-paper bags or cups. The concentration of benzopyrene is high in
tobacco smoke and in the smoke intended for smoky smoking. From this point of
view, smokeless smoking is safer. But at the same time smokeless smoking cannot be considered
completely safe. Benzopyrene has been found in bread, vegetables,
fruits, margarine, vegetable oils, roasted coffee beans, smoked products,
and fried meat products.
9.5 Dioxins
Dioxins are byproducts of the production of plastics, pesticides,
paper, defoliants (chemical substances that cause the leaves of
plants to fall). Dioxins have been found in the waste of the metallurgical, pulp-and-paper
and woodworking industries. They form during the burning of refuse at
municipal landfills, of gasoline, at thermal power plants running on solid
fuel, during the combustion of synthetic coatings and oil, i.e. everywhere where chlorine or
bromine ions interact with active carbon in an acidic medium.
Dioxins accumulate intensively in soil and bodies of water, and actively move
along food chains. Dioxins enter the human body mainly with food.
Among the main products that pose a danger due to the possible presence of
dioxins are animal fats, meat, dairy products, fish, root vegetables.
These substances exert a toxic effect at any concentration.
Dioxins possess a broad spectrum of biological action on humans and
animals. In small doses they cause a mutagenic effect, are distinguished by the ability to
accumulate, and by an inhibiting or inducing action on various
enzyme systems of the body. Dioxins cause various diseases, including
oncological ones. Their danger is very great, and therefore dioxins and
dioxin-like compounds are classified in the group of superecotoxicants.
Agricultural chemicals are present in almost all types of
food products. These include pesticides (bactericides, fungicides,
insecticides, herbicides, etc.), fertilizers, plant growth regulators, anti-sprouting
agents, and agents that accelerate fruit ripening.
Pesticides – substances used in agriculture to protect
cultivated plants from weeds, pests and diseases. The most widespread are
organochlorine, organophosphorus, organomercury, and copper-containing
pesticides.
Violations of the conditions of storage, transportation and application of pesticides, and
improper handling of them, lead to their accumulation in feed,
food raw materials and food products. At present an
increase is observed in the total content of pesticides in products of plant and animal
origin. This particularly concerns potatoes, onions, cabbage, tomatoes, cucumbers,
carrots, beets, apples, cereal crops, fish raised in ponds, and milk. Since
at present it is impossible to abandon the use of pesticides, control
over the production and application of pesticides is important.
Nitrates, nitrites, nitrosamines. Nitrates are normal
metabolic products of any living organism. But an excessive amount of nitrates
leads to their reduction to nitrites. In the body, nitrites interact with
blood hemoglobin, forming methemoglobin, which is incapable of binding and
transporting oxygen. From nitrites, nitrosamines can form, some
of which possess carcinogenic, mutagenic, and teratogenic action.
Chronic exposure to nitrites leads to a decrease in the content in the
body of vitamins A (retinol), E (tocopherol), C (ascorbic acid), B1
(thiamine), B6 (pyridoxine), and this causes a decrease in the body's resistance to
oncogenic factors. The main sources of intake of nitrates and nitrites into the
human body are plant products. Meat products,
sausages, fish, and cheeses can also contain nitrates and nitrites. They are added to these
products as preservatives or color-regulating substances.
Plant growth regulators (PGRs) – are compounds that exert an influence on the
processes of growth and development of plants and are used in agriculture to
increase yield, improve the quality of crop products, facilitate
harvesting, and extend the storage life of plant products. This group
can also include some herbicides which, depending on concentration,
may also exhibit a stimulating action. Plant growth regulators are divided into two
groups: natural and synthetic.
Natural PGRs – are the natural components of plant organisms,
which perform the function of phytohormones: auxins, gibberellins, cytokinins,
endogenous ethylene, etc. In the process of evolution, appropriate
defense mechanisms against these substances have developed in the human body, and therefore natural PGRs do not
pose a danger to humans.
Synthetic PGRs – are compounds that are analogs of endogenous
phytohormones and are able to influence the hormonal status of plants. For example,
preparations that are derivatives of sulfonylurea are used.
Synthetic PGRs exert a negative influence on the body. However, the degree of
danger of most PGRs has not been fully studied.
9.7 Contamination by substances used in animal husbandry
For the purpose of increasing the productivity of farm animals,
preventing and treating diseases, and preserving feed quality, various
medicinal and chemical preparations are used in animal husbandry. These are antibiotics,
hormones, tranquilizers, antioxidants. Regular consumption of food
products contaminated with these substances is a cause of various deviations in
human health (for example, dysbacterioses).
Antibiotics. Antibiotics present in food products may have
various origins:
- natural antibiotics – are the natural components of certain food
products; for example, egg white, milk, honey, onion, garlic, fruits, and spices contain
natural antibiotics;
- those forming as a result of food production – these are substances
that appear during the carrying out of technological processes; for example, during
the fermentation of certain kinds of cheeses;
- those getting into food products as a result of the treatment of animals;
- those getting into food products when they are used as
biostimulants, which are added to feed to improve its digestibility and
stimulate growth; antibiotics eliminate factors that hinder the growth of the
animal, for example, they suppress bacteria that interfere with the assimilation of feed;
- those used as preservative substances – antibiotics are added to
food products in order to prevent microbiological spoilage.
Sulfonamides. The antimicrobial action of sulfonamides is less effective
than the action of antibiotics, but they are cheaper and more accessible for combating
infectious diseases of animals. Sulfonamides are able to accumulate
in the bodies of animals and poultry and to contaminate livestock products: meat,
milk, eggs.
Hormones. Hormonal preparations are used in veterinary medicine and animal husbandry
to improve feed digestibility, stimulate the growth of animals, and accelerate sexual
maturation. A consequence of the use of hormones in animal husbandry is the problem of
their contamination of food raw materials and food products. At present,
synthetic hormones have been created which, in their anabolic action,
are significantly more effective than natural hormones. They accumulate in the bodies of
animals in large quantities and are transmitted along food chains.
Tranquilizers. Sedatives are used for the purpose of
preventing stress states in animals, for example during transportation
or before slaughter. Their use must be carried out under strict control, since
they are able to exert a negative effect on the human body. In order for the
meat not to contain residues of these preparations, they may be applied no later
than 6 days before the slaughter of the animal.
Antioxidants. These are food additives introduced into animal feed to protect
oxidizable components (mainly lipids). Butylated hydroxyanisole,
butylated hydroxytoluene, and propyl gallates are used.
Mycotoxins – are the products of the vital activity of mold fungi, possessing
toxic properties. These are particularly dangerous toxic substances that contaminate
feed and food products. The danger of mycotoxins lies in the fact that they
exert a toxic effect in very insignificant amounts and are able to
actively penetrate into the depths of a product.
Aflatoxins. They disrupt the permeability of plasma membranes and block
the synthesis of DNA and protein, which ultimately leads to the death of the cell. Aflatoxins
are found in peanuts, corn, and cottonseed; they accumulate in nuts,
oilseed crops, wheat, barley, and cocoa and coffee beans. Aflatoxins are also found in feed for
farm animals, and therefore they
occur in products of animal origin. To remove aflatoxins,
the separation of contaminated raw material, autoclaving, ultraviolet
irradiation and ozonation, and treatment of the material with strong oxidizers are used.
Ochratoxins possess a teratogenic effect. The producers are
microscopic fungi of the genera Aspergillus and Penicillium. Ochratoxins damage the kidneys,
liver, lymphoid tissues, and the gastrointestinal tract. Ochratoxins
are found in corn, wheat, and barley. Therefore they may be present in
livestock products.
Zearalenone and its derivatives are produced by microscopic fungi of the genus
Fusarium. Zearalenone possesses pronounced hormone-like properties and
possesses a teratogenic action. Zearalenone is most often found in
corn, mixed feed, as well as in wheat and barley, and oats. Among food products,
this toxin has been found in corn flour, flakes and corn beer. Heat
treatment in a neutral or acidic medium does not destroy zearalenone, but in an alkaline
medium partial destruction occurs.
Patulin possesses carcinogenic and mutagenic properties. The producers of
patulin are microscopic fungi of the genus Penicillium. Patulin has been found in
apples, pears, apricots, peaches, cherries, grapes, bananas, strawberries,
blueberries, cowberries, sea buckthorn, quince, tomatoes. In high concentrations it is also
found in the products of processing of fruits and vegetables: juices, compotes, purees and
jams.
Antialimentary nutritional factors – substances of natural origin,
not possessing toxicity, but able to worsen or block the assimilation of
nutrients.
Inhibitors of digestive enzymes. They block the activity of
digestive enzymes. Protein inhibitors have been found in the seeds of legume
crops, cereals, potatoes, and egg white. The consumption of seeds of legume crops
is possible only after appropriate heat treatment.
Cyanogenic glycosides – are glycosides which upon hydrolysis release
hydrocyanic acid. Hydrocyanic acid causes damage to the nervous system.
Representatives of cyanogenic glycosides are limarin, contained in white
beans, and amygdalin, found in the pits of almonds, peaches, plums, apricots.
Alkaloids (lysergic acid diethylamide (LSD)), morphine, caffeine,
solanines).
Antivitamins. Antivitamins are divided into two groups of compounds:
- compounds that are chemical analogs of vitamins;
- compounds that inactivate vitamins.
Antivitamins include:
- leucine - disrupts the metabolism of tryptophan, as a result of which the formation
of niacin (vitamin PP) from tryptophan is blocked;
- indoleacetic acid and acetylpyridine are antivitamins with respect
to niacin; they are contained in corn; excessive consumption of products
containing the above-mentioned compounds may intensify the development of pellagra,
caused by a deficiency of niacin;
- ascorbate oxidase and some other oxidative enzymes exhibit
antivitamin activity with respect to ascorbic acid (vitamin C);
ascorbate oxidase is most active in cucumbers and squash, and least active in carrots, beets,
tomatoes;
- thiaminase – an antivitamin factor for thiamine (vitamin B1); the highest
content of this enzyme has been noted in freshwater and marine fish;
- hydrogenated fats – are factors that reduce the preservation of
retinol (vitamin A).
Factors that reduce the assimilation of minerals – oxalic acid and
oxalates, phytin and tannins.
Oxalic acid disrupts salt metabolism and binds calcium ions, and therefore
promotes the formation of stones in the kidneys. It is contained in spinach, sorrel, red
beet.
Phytin forms poorly soluble complexes with calcium ions. A fairly
large amount of phytin is contained in cereal and legume crops (wheat,
pea).
Tannic substances (tannins) are also factors that reduce the
assimilation of minerals.
Alcohol – is a product that has only energy value (7 kcal/g),
while not being a source of nutrients.
During the course of a day the human body is able to synthesize 1-9 g of ethanol.
Endogenous alcohol is a natural product of metabolic processes, and the
body easily oxidizes it for energy purposes. When large
amounts of alcohol enter the body, the enzymes cannot cope, and there occurs an accumulation of
ethyl alcohol and acetaldehyde, which causes symptoms of extensive
intoxication (headache, nausea, cardiac arrhythmia). This gives
grounds to consider alcohol an antialimentary nutritional factor, since
metabolism is disrupted. Regular consumption of alcohol leads to
avitaminoses, disruption of carbohydrate, fat and protein metabolism and ends with
the destruction of the body.
Food additives have become an integral part of most food
products. Each food additive, before registration and the assignment of an E-code,
undergoes research. The presence of an E-code means that:
- the given substance has been tested for safety;
- the substance may be used on the condition that, in its application,
the consumer will not be misled regarding the type and composition of the food
product into which it is introduced;
- for the given substance, purity criteria have been established that are necessary for
achieving a certain level of quality of food products.
It cannot be said that they are absolutely harmless, otherwise how to explain the fact
that from time to time one or another food additive is banned either in an individual
country or in a whole series of countries. For example, at present in the food
industry the use of the following additives is prohibited:
- citrus red (E121) – a synthetic red dye;
- amaranth (E123) – a synthetic red dye;
- erythrosine (E127) – a synthetic brown dye;
- brown FK (E154) – a synthetic brown dye;
- lithol rubine BK (E180) – a synthetic red dye;
- hexamethylenetetramine (urotropine) (E239) – a preservative;
- guaiac resin (E314) – a natural antioxidant.
Review questions
1. What effect is called carcinogenic?
2. What effect is called mutagenic?
3. What effect is called teratogenic?
4. List the heavy metals most dangerous to the human body.
5. Why is mercury dangerous to the body?
6. Why is lead dangerous to the body?
7. Why is cadmium dangerous to the body?
8. What is the danger of the radioactive isotope strontium-90?
9. What is the danger of the radioactive isotope cesium-137?
10. In the course of what processes do polycyclic aromatic
hydrocarbons form? Give examples of polycyclic aromatic hydrocarbons.
11. Why are dioxins dangerous to the body?
12. What substances used in crop farming can become a cause of
contamination of food raw materials and food products? Why are they dangerous?
13. What substances used in animal husbandry can become a cause of
contamination of food raw materials and food products? Why are they dangerous?
14. Why are mycotoxins dangerous to the body? Name them.
15. What are antialimentary nutritional factors? List them.
16. What is the danger of antialimentary nutritional factors?
17. Why are some food additives regarded as substances that contaminate
food raw materials and food products?
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