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Food Chemistry > 14 Toxic Substances in Food > Flashcards

14 Toxic Substances in Food Flashcards

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1
Q

Chemicals substances that can be harmful when it enters the body

A

Poison

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1
Q

Poison of biological origin (synthesized by microbe, animal or plant)

A

Toxin

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2
Q

Name of toxic compounds intentionally added to food

A

adulterant

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3
Q

Name of toxic compounds unintentionally present in food

A
  • 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)
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4
Q

Sources of arsenic (As)

A

element in the earth’s crust,

thus present in water, air, soil from arsenic containing rocks, volcanic eruptions, contamination from mining, As containing pesticides

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5
Q

Which type of arsenic is more toxic

A

inorganic

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6
Q

Characteristics of organoarsenic and their source

A

compounds containing chemical bonds between arsenic and carbon (e.g. triphenyl arsine)

found in seafood

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7
Q

Characteristics of inorganic arsenic and their source

A

compounds containing arsenic and at least one other element, but not carbon

e.g. arsenic(V) acid in drinking water

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8
Q

What food type has high arsenic accumulation

A

Rice

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9
Q

Effects of long term ingestion of inorganic arsenic

A

skin lesions
cancer
developmental toxicity
neurotoxicity
cardiovascular diseases
abnormal glucose metabolism
diabetes

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10
Q

WHO recommended limit of arsenic in drinking water and in rice

A

10 microgram/L in water
100 ppb in rice

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11
Q

Prevention and control of arsenic

A

Substitute high arsenic sources (eg groundwater) with low arsenic, microbiologically safe sources (eg rainwater and treated surface water)

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12
Q

Mercury (Hg) poisoning caused by food intake is derived from?

A

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)
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13
Q

Properties of mercury

A

highly toxic
lipid soluble
readily absorbed and accumulate in erythrocytes and the central nervous system

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14
Q

Tolerable mercury dosage for adults (70kg)

A

0.35 mg Hg/week

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15
Q

Example of a mercury poisoning case

A

Minamata disease

Contamination of large quantities of fish and shellfish with methylmercury, causing neurological symptoms and the death of 900 people in Minamata bay

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16
Q

Contamination source of lead (Pb)

A
  • 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)
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17
Q

Tolerable dose of lead (Pb)

A

1.75mg/week

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18
Q

Toxicity symptoms of lead

A

abdominal pain
fatigue
high blood pressure
kidney abnormalities
memory loss
aggressive behavior

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19
Q

Usage of cadmium (Cd)

A

TV screens, lasers, batteries, paint pigments, water pipelines

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20
Q

Contamination sources of cadmium

A

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

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21
Q

Symptoms of cadmium poisoning

A

cancer
insulin resistance
kidney abnormalities

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22
Q

Tolerable dose of cadmium

A

0.49 mg/week

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23
Q

What is radionuclide

A

Unstable form of chemical elements that raadioactively decays, resulting in emission of nuclear radiation

also called radioisotope

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24
Q

Contamination sources of radionuclide

A

Contaminates air, food water

Rapidly increasing levels of radioactive fallout in the environment and food due to extensive testing of nuclear weapons

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25
Q

Which radioisotopes present the most significant internal radioation hazard?

A

Ba-140
Cs-137
Sr-89
Sr-90 (most dangerous; induces leukemia and bond cancer)

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26
Q

examples of mycotoxins

A

aflatoxins
ochratoxins
patulin
fumonisin, zearalenone, tricorechene

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27
Q

Aflatoxins are produced by what fungi

A

Aspergillus flavus and Aspergillus parasiticus
(warm and humid environment)

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28
Q

One of the most powerful toxins known

A

aflatoxins; highly carcinogenic

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29
Q

Examples of aflatoxins

A

B1, B2, G1, G2 (there are 8 in total)

B1 is a very powerful liver carcinogen

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30
Q

Mycotoxin that gives blue and green fluorescence under UV

A

aflatoxin

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31
Q

Lowest limit of aflatoxins

A

None in which no side effect can be observed

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32
Q

How to control aflatoxins

A
  • 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
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33
Q

Aflatoxins are found in what commodity

A

cottonseed meal, rice, sweet potatoes, beans, nuts, wheat, milk , meat

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34
Q

Source and development of aflatoxins in food

A

improper drying and storage

development depends on temperature and moisture

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35
Q

Ochratoxins are produced by what fungi

A

Aspergillus and Penicilium

Best known species: A. ochraceus
Grows in moderate temp and high aw, significant source of orchatoxin A in cereals

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36
Q

How many members of ochratoxins are there

A

3; A, B, C

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37
Q

Most abundant and most toxic ochratoxin

A

orchatoxin A, affects the kidney

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38
Q

What commodity is ochratoxin A found in

A

cereal and cereal products, coffee, spices dried fruits, grape juice

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39
Q

Patulin is produced by what fungi

A

Aspergilus sp., Penicilium sp., Byssolamys sp.

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40
Q

Patulin is found in what food commodity

A

fruit, grains, cheese, apple juice, apples and pears with brown rot

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41
Q

How to control and prevent patulin

A
  • destroyed by fermentation
  • thermal processing causes MODERATE reduction (can still survive pasteurization)
  • removal of rotten part of fruit before processing
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41
Q

Fusarium sp. produces what mycotoxin

A

Fumonisin, zearalenone, tricotechenes

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42
Q

Symptoms caused by mycotoxins produced by fusarium sp.

A

anorexia
depression
inhibition on immune system funtion
heametoxicity
infertility

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43
Q

Stability of fumonisin

A

Unstable under roasting conditions

Stable during canning and baking of corn-based foods

44
Q

Stability of tricotechenes

A

Stable to heating

Not degraded during normal food processing or autoclaving

Stable at neutral and acidic pH (not hydrolyzed in stomach after digestion)

45
Q

Stability of zearalenone

A

Stable during storage and milling

Stable during processing/cooking at high temp

Toxin production favored by high humidity and low temp

46
Q

Zearalenone is found in what commodity

A

especially in corn
also found in oats, barley, wheat, sorghum

47
Q

Exotoxins are found in what microbe

A

gram positive

48
Q

Exotoxins consist of mostly …

A

proteins

49
Q

Exotoxin symptoms

A

vomiting, diarrhea, stomachache

50
Q

Example of exotoxin

A

Botulin toxin by Clostridium botulinum

51
Q

Exotoxins are found in whar commodity

A

meat and meat products, poultry, cheese, potato salad, pastry

52
Q

Endotoxins are produced by what microbe

A

Gram negative bacteria

53
Q

Composition of endotoxins

A

protein, polysaccharide, lipids

54
Q

Stability of endotoxins

A

heat stable

55
Q

Symptoms of endotoxin

A

typhoid and parathyphoid fever, salmonellosis, bacterial dysentery

56
Q

Sources (commodity) of endotoxin infection

A

egg products, frozen poultry, ground or minced beef, confectionery products, cocoa

57
Q

Direct contamination of plant protective agents through …

A

treatment of crop before storage and distribution (eg fruits and vegs with fungicides, cereals with insecticides)

58
Q

Indirect contamination of plant protective agents through

A

Uptake from soil of resudual PPA by subsequent crop, atmosphere, drifting from neighboring fields, storage space pretreated with PPA

59
Q

Food contamination source of plant protective agents

A

animal origin; feed containing PPA

Most likely contaminant: insecticides (chlorinated hydrocarbon and organophosphorus)

60
Q

Stability and chemical properties of plant protective agents

A

Very stable > persistent in the environment

Soluble in fat, results in deposition and accumulation in fatty tissues

61
Q

Purpose of veterinary and feed additive

A

Maintain health, prevent spread of diseases, economic reasons (shorten animal growth or feeding tiem)

62
Q

Dangers of veterinary and feed additive

A

Vet prep residues in food are ingested by humans in low amounts but continuously

63
Q

Toxic substances from thermal processing

A
  • polycyclic aromatic hydrocarbon
  • heterocyclic aromatic amines
  • furan
  • acrylamide
  • polychlorinated dibenzodioxin (PCDD)
  • dibenzofuran (PCDF)
  • 3-monochloropropane-1,2-diol (3-MCPD)
64
Q

polycyclic aromatic hydrocarbons (PAH) formation mechanism

A

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

65
Q

Properties of polycyclic aromatic hydrocarbons (PAH)

A

highly lipophilic (accumulates in fatty tissue)

66
Q

Polycyclic aromatic hydrocarbon contamination in food

A
  • 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)
67
Q

Example of polycyclic aromatic hydrocarbon (PAH)

A
  • benzo[a]pyrene (Bap): most common, most toxic
  • anthracene
  • naphtacene
68
Q

Source of heterocyclic aromatic amines

A

heating of proteinaceous food products (eg meat)

69
Q

examples of heterocyclic aromatic amines

A

animoimidazoazaarene (AIA)

potent mutagens

70
Q

examples of heterocyclic aromatic amines

A

animoimidazoazaarene (AIA)

potent mutagens

71
Q

Sources of heterocyclic aromatic amines

A
  • 2-aminoimidazo part from naturally occuring creatine in muscles
  • quinoline and quinoxaline from Maillard rxn products, especially precursors of pyrazines/pyridines and aldehydes
72
Q

Mechanism of heterocyclic aromatic amines from Maillard rxn

A
  1. reducing sugar + amino acids -> reactive dicarbonyl compound (eg pyruvaldehyde)
  2. Strecker degradation between dicarbonyl compound and amino acid -> reactive dihydropyrazine molecule
  3. condensation among dihydropyrazine, creatinine and acetaldehyde -> 4,8-DiMelQx formation
73
Q

Dangers of furan

A

carcinogen

74
Q

Formation of furan

A
  • 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
75
Q

Formation of acrylamide

A

reaction of amino acid aspargine with reductive carbohydrates (or their degradation products)

76
Q

dangers of acrylamide

A

carcinogenic on chronic exposure animal tests

77
Q

How to avoid acrylamide

A
  • enzymatic degradation of aspragine with asparginase
  • lowering pH
  • reduce heating temp
78
Q

PCDD and PCDF are also called…

A

dioxins

79
Q

Formation of PDCC and PDCF

A

in thermal processes (200-600C) in the presence of chlorine or other halogen in organic/inorganic form

non-volatile and lipophilic

80
Q

Sources of PCDD and PCDF

A

side product of paint, pesticide, paper bleaching, steel industries, fuel combustion

food exposure: animal based food (eg meat, milk)

81
Q

most toxic dioxin

A

2,3,7,8-TCDD

82
Q

Dangers of 3-MCPD

A

Human carcinogen with tolerable daily intake (TDI) 2 microgram/kg b.w.

83
Q

Mechanism of 3-MCPD formation

A

Reaction product of triacylglycerols/phospholipids/glycerol and HCl with heat in fat based foods

84
Q

Occurence of 3-MCPD

A

Depends on type of food:

  • as free substance
  • in the form of ester with fatty acids
  • both
85
Q

What are the uses of nitrite and nitrate in meat products

A

Preservative that inhibits c. botulinum growth and fat oxidation

86
Q

How are nitrosamines formed

A

Reaction of nitrite with secondary amines

87
Q

How to avoid nitrosamine formation

A
  • 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
88
Q

Examples of natural plant toxicants

A
  1. lectines
  2. pyrrolizidine alkaloids
  3. cyanogenic glycosides
  4. biogenic amines
89
Q

Source of lectines

A

legumes and cereals

90
Q

Adverse effects of lectine

A
  • cause blood coagulation (thats why its also called hemaglutinine)
  • interfere with nutrient absorption when bound to intestinal mucosal cells
91
Q

molecular structure of lectine

A

glycoprotein

92
Q

How to avoid lectine

A

heating above 176C for at least 10 minutes
heating should be BOILING with WATER (lectine levels will decrease 200x)

93
Q

Example of lectine

A

Ricin from castor bean; highly toxic and can cause death in children

94
Q

Structure of ricin

A

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

95
Q

Structure of pyrrolizine alkaloids (PA)

A
  • 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
96
Q

How are pyrrolizine alkaloids formed

A

Produced by plants as a defence mechanism against insect herbivores

97
Q

Danger of pyrrolizine alkaloids

A

exhibit hepatotoxicity

98
Q

Food that contain pyrrolizine alkaloids

A

honey, milk, organ meats, eggs, cereals

99
Q

Spread of pyrrolizine alkaloids are facilitated by what

A

insects (bees, butterflies) and livestock

100
Q

Structure of cyanogenic glycoside

A

cyanide bound to sugar group

101
Q

Source and release mechanism of cyanogenic glycoside

A

Released with the aid for hydrolyrtic enzymes present naturally in foodstudds

Sources: cassava, fava bean, peaches

101
Q

Source and release mechanism of cyanogenic glycoside

A

Released with the aid for hydrolyrtic enzymes present naturally in foodstudds

Sources: cassava, fava bean, peaches

102
Q

Cyanide content of raw and rotten cassava

A

Raw: 1- 60 mg per 100g
Rotten: 245 g per 100 g

103
Q

How to remove cyanide

A

its volatile so can be removed by stripping, washing with running water, cooking and fermentation

104
Q

Biogenic amine formation

A

Enzymatic decarboxylation of amino acids

105
Q

Where are biogenic amines found

A

fermented meat, sauerkraut, fish, red wine, cheese, dairy products

106
Q

Examples of biogenic amines

A

histamine, tyramine, cadaverine, putrescine, spermidine

107
Q

Where is tyramine (a biogenic amine) found, and symptoms caused

A

old cheese,
causes migraine and hypertension

108
Q

What is scrombrotoxicosis

A

histamine intoxication after scromboid fish consumption (tuna, mackarel, saury, bonito)

Food Chemistry (5 decks)

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