14 Toxic Substances in Food Flashcards
Chemicals substances that can be harmful when it enters the body
Poison
Poison of biological origin (synthesized by microbe, animal or plant)
Toxin
Name of toxic compounds intentionally added to food
adulterant
Name of toxic compounds unintentionally present in food
- pollutant (fossil fuels, industrial emissions)
- components of packaging materials, processing utensils, processing aids
- toxic metabolites of microbes
- toxic compounds present in raw materials (toxins in plants, residue of plant protective agents, residue of livestock and poultry husbandry)
- formed during processing (rxn between food components/ingredients/additibes, rxn occuring due to thermal processing)
Sources of arsenic (As)
element in the earth’s crust,
thus present in water, air, soil from arsenic containing rocks, volcanic eruptions, contamination from mining, As containing pesticides
Which type of arsenic is more toxic
inorganic
Characteristics of organoarsenic and their source
compounds containing chemical bonds between arsenic and carbon (e.g. triphenyl arsine)
found in seafood
Characteristics of inorganic arsenic and their source
compounds containing arsenic and at least one other element, but not carbon
e.g. arsenic(V) acid in drinking water
What food type has high arsenic accumulation
Rice
Effects of long term ingestion of inorganic arsenic
skin lesions
cancer
developmental toxicity
neurotoxicity
cardiovascular diseases
abnormal glucose metabolism
diabetes
WHO recommended limit of arsenic in drinking water and in rice
10 microgram/L in water
100 ppb in rice
Prevention and control of arsenic
Substitute high arsenic sources (eg groundwater) with low arsenic, microbiologically safe sources (eg rainwater and treated surface water)
Mercury (Hg) poisoning caused by food intake is derived from?
Organomercury compounds
- dimethyl mercury (CH3-Hg-CH3)
- methyl mercury salts (CH3-Hg-X; X = Cl/P)
- phenyl mercury salts (C5H6-Hg-X; X = Cl/acetate)
Properties of mercury
highly toxic
lipid soluble
readily absorbed and accumulate in erythrocytes and the central nervous system
Tolerable mercury dosage for adults (70kg)
0.35 mg Hg/week
Example of a mercury poisoning case
Minamata disease
Contamination of large quantities of fish and shellfish with methylmercury, causing neurological symptoms and the death of 900 people in Minamata bay
Contamination source of lead (Pb)
- vehicle emission
Tetraethyllead (C2H5)4Pb is an additive used to increase octane value of gasoline converted to PbO, PbCl2, etc by combustion -> contaminates air, soil, plants - in tin cookware and soldered metal cans (has lead containing enamels, especially in contact with sour foods)
Tolerable dose of lead (Pb)
1.75mg/week
Toxicity symptoms of lead
abdominal pain
fatigue
high blood pressure
kidney abnormalities
memory loss
aggressive behavior
Usage of cadmium (Cd)
TV screens, lasers, batteries, paint pigments, water pipelines
Contamination sources of cadmium
crustaceans, meats, leafy vegs (readily absorbed by plants and distributed uniformly; cant be removed by removal of outer leaves), rice, water (polluted from old Zn/Cd sealed pipes or industrial pollution)
cigarette smoking
Symptoms of cadmium poisoning
cancer
insulin resistance
kidney abnormalities
Tolerable dose of cadmium
0.49 mg/week
What is radionuclide
Unstable form of chemical elements that raadioactively decays, resulting in emission of nuclear radiation
also called radioisotope
Contamination sources of radionuclide
Contaminates air, food water
Rapidly increasing levels of radioactive fallout in the environment and food due to extensive testing of nuclear weapons
Which radioisotopes present the most significant internal radioation hazard?
Ba-140
Cs-137
Sr-89
Sr-90 (most dangerous; induces leukemia and bond cancer)
examples of mycotoxins
aflatoxins
ochratoxins
patulin
fumonisin, zearalenone, tricorechene
Aflatoxins are produced by what fungi
Aspergillus flavus and Aspergillus parasiticus
(warm and humid environment)
One of the most powerful toxins known
aflatoxins; highly carcinogenic
Examples of aflatoxins
B1, B2, G1, G2 (there are 8 in total)
B1 is a very powerful liver carcinogen
Mycotoxin that gives blue and green fluorescence under UV
aflatoxin
Lowest limit of aflatoxins
None in which no side effect can be observed
How to control aflatoxins
- roasting of peanuts reduces levels (150C for 30 mins reduces aflatoxin B1 by 80%)
- reduction of water, low aw during storage
- detoxification with NH3, CaOH, or a combination of formaldehyde and CaOH treatment
Aflatoxins are found in what commodity
cottonseed meal, rice, sweet potatoes, beans, nuts, wheat, milk , meat
Source and development of aflatoxins in food
improper drying and storage
development depends on temperature and moisture
Ochratoxins are produced by what fungi
Aspergillus and Penicilium
Best known species: A. ochraceus
Grows in moderate temp and high aw, significant source of orchatoxin A in cereals
How many members of ochratoxins are there
3; A, B, C
Most abundant and most toxic ochratoxin
orchatoxin A, affects the kidney
What commodity is ochratoxin A found in
cereal and cereal products, coffee, spices dried fruits, grape juice
Patulin is produced by what fungi
Aspergilus sp., Penicilium sp., Byssolamys sp.
Patulin is found in what food commodity
fruit, grains, cheese, apple juice, apples and pears with brown rot
How to control and prevent patulin
- destroyed by fermentation
- thermal processing causes MODERATE reduction (can still survive pasteurization)
- removal of rotten part of fruit before processing
Fusarium sp. produces what mycotoxin
Fumonisin, zearalenone, tricotechenes
Symptoms caused by mycotoxins produced by fusarium sp.
anorexia
depression
inhibition on immune system funtion
heametoxicity
infertility
Stability of fumonisin
Unstable under roasting conditions
Stable during canning and baking of corn-based foods
Stability of tricotechenes
Stable to heating
Not degraded during normal food processing or autoclaving
Stable at neutral and acidic pH (not hydrolyzed in stomach after digestion)
Stability of zearalenone
Stable during storage and milling
Stable during processing/cooking at high temp
Toxin production favored by high humidity and low temp
Zearalenone is found in what commodity
especially in corn
also found in oats, barley, wheat, sorghum
Exotoxins are found in what microbe
gram positive
Exotoxins consist of mostly …
proteins
Exotoxin symptoms
vomiting, diarrhea, stomachache
Example of exotoxin
Botulin toxin by Clostridium botulinum
Exotoxins are found in whar commodity
meat and meat products, poultry, cheese, potato salad, pastry
Endotoxins are produced by what microbe
Gram negative bacteria
Composition of endotoxins
protein, polysaccharide, lipids
Stability of endotoxins
heat stable
Symptoms of endotoxin
typhoid and parathyphoid fever, salmonellosis, bacterial dysentery
Sources (commodity) of endotoxin infection
egg products, frozen poultry, ground or minced beef, confectionery products, cocoa
Direct contamination of plant protective agents through …
treatment of crop before storage and distribution (eg fruits and vegs with fungicides, cereals with insecticides)
Indirect contamination of plant protective agents through
Uptake from soil of resudual PPA by subsequent crop, atmosphere, drifting from neighboring fields, storage space pretreated with PPA
Food contamination source of plant protective agents
animal origin; feed containing PPA
Most likely contaminant: insecticides (chlorinated hydrocarbon and organophosphorus)
Stability and chemical properties of plant protective agents
Very stable > persistent in the environment
Soluble in fat, results in deposition and accumulation in fatty tissues
Purpose of veterinary and feed additive
Maintain health, prevent spread of diseases, economic reasons (shorten animal growth or feeding tiem)
Dangers of veterinary and feed additive
Vet prep residues in food are ingested by humans in low amounts but continuously
Toxic substances from thermal processing
- polycyclic aromatic hydrocarbon
- heterocyclic aromatic amines
- furan
- acrylamide
- polychlorinated dibenzodioxin (PCDD)
- dibenzofuran (PCDF)
- 3-monochloropropane-1,2-diol (3-MCPD)
polycyclic aromatic hydrocarbons (PAH) formation mechanism
burning of organic materials (wood/coal/fuel oil) causes pyrolysis of hydrocarbons at 500-800C) in flame zones with insufficient O2. This causes the formation of PAH with more than three linearly/angularly fused benzene rings
they are carcinogenic
Properties of polycyclic aromatic hydrocarbons (PAH)
highly lipophilic (accumulates in fatty tissue)
Polycyclic aromatic hydrocarbon contamination in food
- fall out from atmosphere (contaminates fruits and leafy veg in industrial districts)
- smoking or roasting food (bbq, charcoal broiling, smoking of sausage/ham/fish, roasting of coffee)
Example of polycyclic aromatic hydrocarbon (PAH)
- benzo[a]pyrene (Bap): most common, most toxic
- anthracene
- naphtacene
Source of heterocyclic aromatic amines
heating of proteinaceous food products (eg meat)
examples of heterocyclic aromatic amines
animoimidazoazaarene (AIA)
potent mutagens
examples of heterocyclic aromatic amines
animoimidazoazaarene (AIA)
potent mutagens
Sources of heterocyclic aromatic amines
- 2-aminoimidazo part from naturally occuring creatine in muscles
- quinoline and quinoxaline from Maillard rxn products, especially precursors of pyrazines/pyridines and aldehydes
Mechanism of heterocyclic aromatic amines from Maillard rxn
- reducing sugar + amino acids -> reactive dicarbonyl compound (eg pyruvaldehyde)
- Strecker degradation between dicarbonyl compound and amino acid -> reactive dihydropyrazine molecule
- condensation among dihydropyrazine, creatinine and acetaldehyde -> 4,8-DiMelQx formation
Dangers of furan
carcinogen
Formation of furan
- amino acids which yield acetaldehyde and hlycoaldehyde on thermal degradation (steps: aldol condensation, cyclization and elimination of water)
- from carbohydrates, polyunsaturated fatty acids, carotenoids
- thermolysis of ascorbic acid
Formation of acrylamide
reaction of amino acid aspargine with reductive carbohydrates (or their degradation products)
dangers of acrylamide
carcinogenic on chronic exposure animal tests
How to avoid acrylamide
- enzymatic degradation of aspragine with asparginase
- lowering pH
- reduce heating temp
PCDD and PCDF are also called…
dioxins
Formation of PDCC and PDCF
in thermal processes (200-600C) in the presence of chlorine or other halogen in organic/inorganic form
non-volatile and lipophilic
Sources of PCDD and PCDF
side product of paint, pesticide, paper bleaching, steel industries, fuel combustion
food exposure: animal based food (eg meat, milk)
most toxic dioxin
2,3,7,8-TCDD
Dangers of 3-MCPD
Human carcinogen with tolerable daily intake (TDI) 2 microgram/kg b.w.
Mechanism of 3-MCPD formation
Reaction product of triacylglycerols/phospholipids/glycerol and HCl with heat in fat based foods
Occurence of 3-MCPD
Depends on type of food:
- as free substance
- in the form of ester with fatty acids
- both
What are the uses of nitrite and nitrate in meat products
Preservative that inhibits c. botulinum growth and fat oxidation
How are nitrosamines formed
Reaction of nitrite with secondary amines
How to avoid nitrosamine formation
- ascorbic acid (500 ppm) together with nitrites 9100-200 ppm) to reduce use of nitrites up to 90%
- adjust dose of nitrites used in curing so it inhibits C botulinum growth but insufficient to be converted to nitrosamines
Examples of natural plant toxicants
- lectines
- pyrrolizidine alkaloids
- cyanogenic glycosides
- biogenic amines
Source of lectines
legumes and cereals
Adverse effects of lectine
- cause blood coagulation (thats why its also called hemaglutinine)
- interfere with nutrient absorption when bound to intestinal mucosal cells
molecular structure of lectine
glycoprotein
How to avoid lectine
heating above 176C for at least 10 minutes
heating should be BOILING with WATER (lectine levels will decrease 200x)
Example of lectine
Ricin from castor bean; highly toxic and can cause death in children
Structure of ricin
Ricin A chain (RTA)
- N-glycoside hydrolase composed of 267 amino acids
- Has three structural domains with 50% of polypeptides arranged to alpha helices and beta sheets
- The three domains form a pronounced cleft that is the active site
Ricin B chain (RTB)
- Composed of 262 amino acids
- able to bind terminal galactose residues on cell
Structure of pyrrolizine alkaloids (PA)
- naturally occuring alkaloid vased on the structure of pyrrolizidine
- consist of amino alcohol referred to as necine/necine base and an acid part called necic acid
How are pyrrolizine alkaloids formed
Produced by plants as a defence mechanism against insect herbivores
Danger of pyrrolizine alkaloids
exhibit hepatotoxicity
Food that contain pyrrolizine alkaloids
honey, milk, organ meats, eggs, cereals
Spread of pyrrolizine alkaloids are facilitated by what
insects (bees, butterflies) and livestock
Structure of cyanogenic glycoside
cyanide bound to sugar group
Source and release mechanism of cyanogenic glycoside
Released with the aid for hydrolyrtic enzymes present naturally in foodstudds
Sources: cassava, fava bean, peaches
Source and release mechanism of cyanogenic glycoside
Released with the aid for hydrolyrtic enzymes present naturally in foodstudds
Sources: cassava, fava bean, peaches
Cyanide content of raw and rotten cassava
Raw: 1- 60 mg per 100g
Rotten: 245 g per 100 g
How to remove cyanide
its volatile so can be removed by stripping, washing with running water, cooking and fermentation
Biogenic amine formation
Enzymatic decarboxylation of amino acids
Where are biogenic amines found
fermented meat, sauerkraut, fish, red wine, cheese, dairy products
Examples of biogenic amines
histamine, tyramine, cadaverine, putrescine, spermidine
Where is tyramine (a biogenic amine) found, and symptoms caused
old cheese,
causes migraine and hypertension
What is scrombrotoxicosis
histamine intoxication after scromboid fish consumption (tuna, mackarel, saury, bonito)
