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Chapter 12

Chapter 12 Summary, Principles of Food Science

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Food Science
FOOD 2010
Massimo Marcone

FOOD*2010 Chapter 12: 329-354 Chapter Objectives: 1. List the three types of food toxicants, citing specific examples 2. Evaluate a dose-response curve 3. Explain the possibility of cyanide toxicity from eating certain vegetables 4. Describe the toxicity of domoic acid arising from shellfish consumption 5. Discuss the safety of herbal products 6. Explain the structure and mechanism of cholera toxin 7. Describe the problem of antibiotic resistance and how it relates to human health 8. Decide if growth promotants BST and DES are harmful and why 9. Explain how pesticides might be present in a fast food meal 10.Discuss the distinction between a food allergy and a food intolerance What is a Food Toxicant?  A toxicant is a chemical substance that can elicit a detrimental effect to ta biological system  Endogenous o Produced by tissue cells in plants and raw materials o Protect plant from pests o Transmission to people can occur through consumption of animal that has ingested the toxic plants  Naturally occurring o Produced by organisms that contaminate the food products o Microorganisms (fungi, bacteria, etc) can produce these  Synthetic o Synthetically produced which enter food supply via contaminated food processing environment o Can include drug residues in foods of animal origins Risk Assessment for Chemical Hazards  Dose-response assessment: determining the concentration of toxicant needed to cause unfavourable effect on biological system  Exposure assessment-determining the risk of exposure of a biological system to a toxicant  Acute effects: take place quickly  Chronic effects: appear slowly  Bioassays: animal studies used to predict the effects of toxicants on humans  Cell culture studies: observe the effects of toxicants on specific cells  Modes of action of toxicant: o Change certain body function (e.g. respiratory rate or heart rate) by increasing or decreasing speed o Inactivate enzyme activities o Can have wide spread effects or be localized to particular area or organ  Assessing dose response o Dose response: the relationship between a toxic reaction (the response) and the amount of toxicant received (the dose) o Threshold level: dose above which adverse effects are produced o Effective dose (ED )50an adverse effect seen in 50% of animals tested o Legal dose (LD ): will kill 50% of animals tested 50  Large LD 501000mg/kg  Small LD 50100ug/kg  Carcinogens: chemical toxicants which cause cancer Endogenous Toxicants  Flavonoids: organic molecules that impart colour and flavour o Include: flavones, flavonols, flavanonols, flavanones, leucoanthocyanins, anthocyanins, catechins o Found in plant tissues, secretions and cells o Can impart pigmentation to foods and can promote or inhibit plant growth o Some have antioxidant activity (ability to inactivate toxic oxygen radiation) o Absorbed in GI tract and excreted in bile or metabolized by liver  Goitrogens are responsible for producing goiter in humans and death in some farm animals o Found in cruciferour vegetables (broccoli, cauliflower, brussel sprouts) o Goiter is condition caused by the enlargement and atrophy of thyroid gland  Coumarins cause a pleasant citrus aroma o Found in peel of citrus fruit o Can cause dermatitis due to bergapten, psoralen, xanthotoxin and isopimpinellin which are photosensitizing agents which cause oversensitivity to light  Cyanide compounds contain cyanogenic glycosides which are converted hydrogen cyanide, a powerful toxicant, when ingested o Inhibit respiration of body cells o Cassava is vegetable crop containing linamarin, a cyanide based chemical  Is eaten daily by people in West Africa, who consume enough to have an average daily dose of ½ the dose required to kill a person each day  Herbal extracts are natural compounds often used as a substitute for synthetic medicines o Pyrrolizidine alkaloids are toxic compounds found in Indian herbal teas, tomatoes, potatoes, eggplants, etc  These inhibit the enzyme cholinesterase which breaks down acetylcholine which results in overstimulation of cells  Can also cause stomach pain, nausea, vomiting, difficulty breathing and death o Sassafras root contains 75% safrole which is a known carcinogen o Sage has been used as abortifacient to induce abortions (30% effective in women 2-6 days after drinking 1 quart of tea made from it)  Toxic Mushrooms: all mushrooms contain at least one toxicant (hydrazine) though in food mushrooms these levels are low enough to avoid health effects  Protoplasmic poisoning affects the liver and kidneys o Amantin poisoning:  Occurs after period of 6-15 hours  Symptoms of , persistent vomiting, and watery diarrhea, as well as thirst and lack of urine  Irreversible damage to liver, kidney, heart and muscle occurs, and death follows within a few days due to necrosis of liver and kidneys o Hydrazine:  Produced by all mushrooms  Toxicant called gyromitrin is produced by G. gigas and Gyromitra esculenta  Symptoms include feeling of fullness, as well as vomiting and headache  Central nervous system and liver are affected, but death rate is low o Orellanine poisoning:  Long period with no symptoms (3 days-2weeks) then nausea, headache, chills, muscle aches, and can case kidney failure  Neurotoxin Poisoning affects the central nervous system o Muscarine poisoning is caused by Inocybe genera  Profuse sweating, increased salivation and lacrimation, nausea, diarrhea, blurred vision and laboured breathing can occur  Psilocin and psilocybin toxins can produce symptoms that mimic drunkenness and hallucinations  Gastrointestinal poisoning causes GI irritation o Symptoms include nausea, diarrhea, and abdominal cramps Naturally Occurring Toxins  Marine toxins are often ingested via shellfish and finfish
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