L7 Food Toxicology – the study of poisons Flashcards
What is toxicology?
Food toxicology is the study of the nature, properties, effects and detection of toxic substances in food and their disease manifestation in human.
What is a food toxicant?
A toxicant is any chemical or physical substance that can elicit a detrimental effect in a biological system.
What are the 3 types of toxicants?
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
What are the 3 factors that affect adverse effects?
Dosage
Exposure Conditions
Response of Host
Explain dose?
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
What is a dose response graph?
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.
What is threshold level, LD50, ED 50?
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
How does slope predict toxicity in curve?
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.
What is aldicarb?
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.
What are some endogenous toxicants?
Goitrogens
Cyanogenic glycosides
Flavonoids*
Mushroom toxins
What are some synthetic toxicants?
From animal farms - Growth promoters Drugs e.g. antibiotics From crop pesticides, weed-killers From packaging materials
What are some naturally occurring toxins?
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*
What are cyanogenic glycosides?
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.
What are the symptoms and dosages of cyanogenic glycoside posioning?
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.
How is cyanogenic glycosides controlled?
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