LESSON 12 Flashcards
Toxicant
a poison or a poisonous agent.
Poison
a chemical that has a lethal dose of 50 milligrams or less of chemical per kilogram of body weight.
Toxicity
the intrinsic or inherent capacity of a substance to damage a biological system (produce injury) when tested by itself.
Hazard
A thing or action that can cause adverse health effects in animals (including fish), plants or humans. The capacity to produce injury under the circumstances of exposure.
threshold
The dose at which a substance begins to have an undesirable effect, that is, the upper limit of its “no effect” dose
Constituents
are chemical entities that are part of the normal composition of a food material - they are not the result of some external organism or activity.
Contaminants
are present because of the presence of moulds or bacteria, or because the plant or animal was grown in a condition which permitted the toxicant to become part of the food.
Glycoalkaloid-Cholinesterase Inhibitors
The name “cholinesterase inhibitors” refers to a variety of chemicals which are able to inhibit the activity of the enzyme cholinesterase.
This enzyme is found in nerve tissues and plays an important role in the transmission of nerve impulses. When its function is inhibited, nerve function is affected.
Cyanogenic Glycosides
Cyanogenic glycosides yield hydrogen cyanide (HCN) upon treatment with acid or particular hydrolytic enzymes.
They are found widely in higher plants, and also occur in ferns, moths and insects. Among the plants used as food which contain one or more of these toxicants are: cassava, sweet potato, yam, maize, bamboo, sugar cane, peas, lima beans, almonds, lime, apple, pear, cherry, apricot and plum.
Cyanide is very rapidly absorbed from the gastrointestinal tract and produces recognizable symptoms at both fatal and non-fatal levels.
Nitrates
Widely found constituents of plant materials, especially green leafy plants.
Nitrates themselves are not very toxic; however, bacteria can reduce them to nitrites.
A primary concern about nitrites is their ability to interact chemically with hemoglobin, interfering with the blood’s ability to transport the required oxygen to the body’s cells. By a rather complex series of reactions, not only bacteria but also metabolic pathways within the digestive system of humans can utilize nitrate/nitrite as a precursor for the formation of nitrosamines, potent carcinogens.
Protease inhibitors
Proteinaceous compounds found in many of the legume species.
have the ability to complex to, and thereby interfere with, certain proteolytic enzymes.
Proteins need to be hydrolyzed into their constituent amino acids by digestive enzymes such as trypsin and chymotrypsin. If these enzymes are rendered inactive by complexing inhibitors, the body cannot fully hydrolyze the proteins, thereby creating the possibility of amino acid deficiencies.
Mycotoxins
Mycotoxins are substances produced by moulds, which may be toxic. Mycotoxins may occur by direct contamination (due to mould growth on the food) or by indirect contamination (by using a food ingredient that was contaminated). Mycotoxins can be highly toxic to the body, some have been known to cause cancer in animal tests, others are mutagenic and able to cause mutation, and others are teratogenic and capable of causing deformities in embryos. Mycotoxins are invisible to the eye, are often unchanged by heat and can potentially spread throughout a product. As a result, any sign of visible mould could indicate that the product contains mycotoxins and should be thrown away.
Of the many known mycotoxins (aflatoxins, sterigmatocystin, ochratoxin A, citrinin and patulin), the ___ are of greatest concern because they are ____ in all animals in which they have been tested and carcinogens in some species.
aflatoxins, potent liver toxins
Scombroid poisoning
due to an allergic-type reaction to high levels of histamine or a histamine-like substance. Histidine, a naturally occurring amino acid which is particularly high in scombroid fish, is converted to histamine by bacterial action on the dead flesh of the fish. Histamine has strong vaso-active properties and in sufficient quantities will cause blood pressure changes resulting in symptoms as indicated above. It should be noted that toxic amounts of histamine may be formed before the fish starts to smell or taste bad (“spoil”). Histamine formation is dependent on the holding time and temperature of the fish during transportation and storage.
Saxitoxin
Saxitoxin and a group of 18-24 marine biotoxins derived from saxitoxin are thought to be responsible for the condition known as paralytic shellfish poisoning (PSP). This condition is the result of consuming shellfish, such as mussels, oysters, and clams, containing the toxin. The toxins can also accumulate in the liver of crustaceans such as crabs and lobsters.
Domoic Acid
Domoic acid is (an analog of the amino acid glutamic acid), is found in some marine algae (dinoflagellate Nitschia), which can accumulate in filter feeding shellfish such as clams, mussels, scallops and oysters. Consumption of shellfish with this naturally occurring marine biotoxin can lead to amnesic shellfish poisoning (ASP).
Tetrodotoxin
This toxin is the chemical of interest in puffer-fish or fugu poisoning. In Asian countries this hazard has been known for thousands of years. Although pufferfish have been known to be poisonous, many deaths still occur from eating these fish. Tetrodotoxin is found mainly in the ovaries, liver, intestine, skin and spawn of the various species of pufferfish. Although tetrodotoxin (TTX) was discovered in these fish, it is thought to be synthesized by a bacterial species such as Pseudoalteromonas tetraodonis associated with the puffer fish.
Microbiological agents
are responsible for the majority of foodborne disease outbreaks.
Parasitic agents
refer to parasites such as Trichinella spiralis, Anisakis simplex, tapeworm, and so forth, that are acquired from consumption of infested foods:
Trichinella spiralis, associated with consumption of undercooked pork, contaminated water or produce.
Anisakiasis caused by Anisakis simplex. Anisakiasis is associated with eating raw fish (sushi, sashimi, lomi lomi, ceviche, sunomono, Dutch green herring, marinated fish and cold-smoked fish) or undercooked fish.
Outbreak - definition
an incident in which two or more people experience a similar illness after ingestion of the same food and where epidemiological evidence implicates the food as the source of the illness.
food intoxications VS foodborne infections.
foodborne intoxications = toxic substances are produced in the foods as by-products of the microorganisms prior to consumption, and cause the symptoms of foodborne illness upon ingestion.
Foodborne infections = result from the ingestion of viable microorganisms in the food at the time of consumption; these pathogenic microorganisms multiply and grow in the host, causing the symptoms of foodborne illness
Clostridium botulinum - prevention
Commercially sterile after processing must receive a “botulinum cook” (12 D)
Use sodium nitrite for cured meats
Properly refrigerate vegetable/fruit juice.
Honey, corn syrup and molasses must not be fed to infants < 1 year of age. Pasteurization of honey does not inactivate the spores.
Escherichia coli O157:H7(Shiga toxin) - prevention
Practice good food sanitation and hand washing.
Properly handle and cook foods.E. coli is killed by normal cooking and pasteurization, as well as ionizing radiation, but is able to survive in acidic conditions (e.g. apple juice). It does not grow well at temperatures below 8°C.
Listeria monocytogenes - prevention
The bacteria is capable of growing slowly on foods during storage in the refrigerator, and appears to be fairly tolerant to salt. It is easily killed by proper cooking and pasteurization techniques. Refrigerate raw materials and high-risk foods below 4°C.
Temperature Danger Zone”
4°C to 60°C (40-140°F)
The HACCP System: Seven steps to food safety
Identify Hazards
Determine the critical control points (CCPs)
Establish control measures (critical limits or thresholds)
Establish procedures to monitor CCPs
Establish corrective actions
Keep records
Verify procedures
