L7 Food Toxicology – the study of poisons

Question 1

What is toxicology?

Answer 1

Food toxicology is the study of the nature, properties, effects and detection of toxic substances in food and their disease manifestation in human.

Question 2

What is a food toxicant?

Answer 2

A toxicant is any chemical or physical substance that can elicit a detrimental effect in a biological system.

Question 3

What are the 3 types of toxicants?

Answer 3

Endogenous: produced by the tissue cells in plants or other biological raw materials.
Naturally occurring: produced by the organisms that contaminate the food
Synthetic: synthetically produced and enter the food supply

Question 4

What are the 3 factors that affect adverse effects?

Answer 4

Dosage
Exposure Conditions
Response of Host

Question 5

Explain dose?

Answer 5

The dose is the amount of a substance administered at one time..

Other factors to consider:

Frequency of dosage
Number of doses
Duration of treatment

Question 6

What is a dose response graph?

Answer 6

Based on the principle that there is a relationship between a toxic reaction (the response) and the amount of toxicant received (the dose)

Dose rose relationship correlates exposures and the spectrum of induced effects with dose. Generally, the higher the dose, the more severe the
response.

The dose-response curve normally takes the form of a sigmoid curve
For most effects, small doses are not toxic.

Question 7

What is threshold level, LD50, ED 50?

Answer 7

The point at which toxicity first appears is known as the threshold dose level.

Threshold level – dose above which adverse effects are produced
LD50 lethal dose – dose required to kill 50% of animals tested
ED50 – effective dose – dose required to cause an adverse effect in 50% of animals

Question 8

How does slope predict toxicity in curve?

Answer 8

Homogeneous population: Most of the population react in a similar way; the curve is steeper

Heterogeneous: when some members of the population are more sensitive than the others, the curve is flatter

Heterogenous has lower threshold level than Homogenous.

Question 9

What is aldicarb?

Answer 9

Aldicarb is the most potent pesticide in the market and has a LD50of 1 mg/kg. In the US in 1985 they experienced the largest food outbreak of food borne pesticide illness, watermelons were contaminated by illegal or accidental use of aldicarb total 1376 illness within cali.

Question 10

What are some endogenous toxicants?

Answer 10

Goitrogens
Cyanogenic glycosides
Flavonoids*
Mushroom toxins

Question 11

What are some synthetic toxicants?

Answer 11

From animal farms
- Growth promoters
Drugs e.g. antibiotics
From crop pesticides, weed-killers
From packaging materials

Question 12

What are some naturally occurring toxins?

Answer 12

Marine algal toxins e.g.
Ciguatera
Paralytic shellfish poisoning (PSP)*
Neurotoxic shellfish poisoning (NSP)
Diarrhetic shellfish poisoning (DSP)*
Amnesic shellfish poisoning

Bacterial toxins e.g.
Staphylococcal endotoxins
Cholera enterotoxins
Verocytotoxins
Botulism

Fungal toxins e.g.
ergot alkaloids
Aflatoxins*

Question 13

What are cyanogenic glycosides?

Answer 13

Cyanogenic glycosides are chemical compounds that occur naturally in many
plants, including species of wild cherry, elderberry, cassava, flax, bamboo and sorghum and keluak

These compounds are potentially toxic as they are readily broken down by enzymic hydrolysis to liberate hydrogen cyanide when the plant suffers physical damage.

Upon consumption of the food, the enzyme beta-glycosidase will be released and hydrolysis of the cyanogenic glycoside will commence, resulting in hydrogen cyanide formation. Certain gut microflora also produce b-glycosidases, which can contribute to the breakdown of cyanogenic glycosides to hydrogen cyanide.

Adequate processing or preparation is required to ensure that detoxification of the food is complete before consumption.

However, if the processing or preparation is insufficient to ensure detoxification, the potential hydrogen cyanide concentration released during consumption can be high.

Question 14

What are the symptoms and dosages of cyanogenic glycoside posioning?

Answer 14

The symptoms of acute cyanide poisoning include:
rapid breathing
drop in blood pressure
raised pulse rate
dizziness, headache, stomach pains, vomiting,
diarrhoea, confusion, twitching and convulsions.
In extreme cases, death may occur.

The minimum lethal dose of hydrogen cyanide taken orally is approximately
0.5–3.5 mg/kg bodyweight, or 35–245mg for a person weighing 75 kg.

Question 15

How is cyanogenic glycosides controlled?

Answer 15

Heat processing and fermentation are proved to be effective in removing cyanogenic glycosides.

For flax seeds, wet autoclaving and solvent extraction using acid is also used to remove cyanogenic gylcosides

Question 16

Give example of cyanogenic glycoside poisioning?

Answer 16

Found in bitter apricot kernels.
Sold in UK as health food
cyanide content of 1450mg/kg (approximately 0.5 mg/kernel). While swallowing of apricot kernels whole may not release much cyanide, grinding or chewing them significantly increases its release.
There are case reports of children being poisoned after consumption of wild apricot kernels and where the kernels were made into sweets without proper processing.

Question 17

What is PSP?

Answer 17

Paralytic shellfish poisoning (PSP) is a foodborne intoxication associated with the consumption of contaminated marine shellfish harvested from waters affected by a sudden and rapid growth of certain types of toxic algae.
PSP is caused by the ingestion of toxins that accumulate in certain types of shellfish that have been feeding on the algae that produce the toxins.
PSP can cause a variety of neurological symptoms and severe cases can prove fatal within hours.

mussels and clams, but also oysters and scallops.
When the algae are digested PSP toxins are released into the animal’s digestive tissue.

Mussels accumulate toxins much more quickly and at higher concentrations than oysters, but they also detoxify much more quickly.

For these reasons, potential levels of PSP toxin in affected shellfish are almost impossible to predict.

Question 18

What are symptoms and dosage of PSP?

Answer 18

Symptoms:
numbness, or tingling around the mouth, which normally appears within 30 min. This then spreads to the head and neck.
numbness or tingling and weakness in arms and legs
incoherent speech and dizziness
In very severe cases, muscle and respiratory paralysis can develop leading to death within 2 to 24 h of ingestion of toxin

120 to 180 mg of PSP toxin is sufficient to produce symptoms in humans, 400 to 1060 mg may prove fatal and levels above 2000 mg are most likely to cause death.

Question 19

What are controls of PSP toxin?

Answer 19

PSP toxins are relatively heat stable
Cooking processes reduce toxin levels, but do not eliminate the risk of toxicity.
Even retorting processes cannot be relied upon to eliminate toxin
The only effective control available currently is the monitoring of waters where molluscs are harvested or produced by aquaculture
PSP toxins are relatively heat stable, especially at acid pH, but are easily oxidized under alkaline pH conditions.
Their effectiveness depends on the initial toxin concentration and only very severe processes (1201C for 60 min) have been shown to give complete detoxification.

Question 20

What are antibiotic residues?

Answer 20

The term ‘‘antibiotics’’ is now used to describe a broad and diverse range of chemical compounds that destroy, or limit, the growth of micro-organisms.
Antibiotics may have activity against bacteria, fungi, or protozoa
Used widely as veterinary drugs in food animals by the farming industry

Question 21

What are 2 reasons for antibiotics in farm animals?

Answer 21

Reason 1: at relatively high doses, as therapeutic agents to treat clinical infections

Reason 2: at low doses as ‘‘growth promoters’’

The use of antibiotic growth promoters in intensive livestock farming has been shown to be an effective means of increasing the growth rate of food animals and improving the quality of meat by raising the protein content. It is not entirely clear how this effect is achieved, but it seems likely that antibiotic growth promoters in animal feed suppress some of the bacteria in the gut and allow more of the energy in the feed to be diverted to the growth of the animal

Question 22

What are the ill effects of antibiotics?

Answer 22

The use of antibiotic growth promoters is widely thought to have contributed to reported increases in the prevalence of antibiotic resistance.

Most of the antibiotics manufactured goes as growth promoter in animal farming industry.
Some antibiotics and their metabolites may be toxic to
humans, or may cause serious reactions in sensitive individuals (e.g. penicillins). Therefore antibiotic and antibiotic metabolite residues in meat, milk
and other animal products may be a direct risk to human.

Question 23

What are ways to control antibiotic?

Answer 23

Variable results for different antibiotics
Penicillin and Tetracyclines are known to be heat sensitive
The degradation products is unknown in most cases.
The only control can be strict regulations on usage of these antibiotics in farming industry.

Question 24

What is botulism?

Answer 24

Botulinum is a gram-positive, spore-forming bacterium that produces neurotoxins. It is these toxins (the most potent natural toxins known) that cause the severe illness known as botulism.

Two types of botulism:

1. Classic botulism – an intoxication caused by the ingestion of pre-formed toxins in food.
2. Infant botulism: a condition arising from toxin produced when Cl. botulinum grows in the intestines of unweaned infants.

The presence of live organisms is unnecessary for ‘‘classic’’ foodborne botulism to occur and very small concentrations of pre-formed toxin (possibly as low as a
few nanograms) in food can cause illness. The ingestion of viable Cl. Botulinum spores, at levels as low as 10 to 100 spores, is required for infant botulism to
occur.

Question 25

What foods cause botulism?

Answer 25

fish, meat and honey
most low acid (pH > 4.6) foods stored in conditions that permit the growth of Cl. botulinum have the potential to be associated with botulism unless sufficient thermal processing to inactivate spores has been applied.

Question 26

What are the health effects of botulism?

Answer 26

Botulinum toxins are neurotoxins
Botulism is the most severe form of food poisoning
Mortality (35–40%)

Question 27

What are factors that affect (1)Protelytic,mesophillic botulinum and non (2)proteolytic,psychotropic bacteria.

Answer 27

(1) 
pH <4.6
aw <0.94
Temperature <10 degrees
121C 3min or equivalent

(2)
pH <5
aw<0.97
<3.3C
90C for 10min or equivalent