What is safe food
- Food is not safe if it damaged, deteriorated or perished to an extent which it affects its intended use
- It is not safe if it comes from a diseased animal or an animal that has died other than by slaughter
- contaminated with biological, chemical or physical (BCP) matter or substance foreign to the nature of the food
Biological hazards in food
bacteria
viruses
fungi
protozoa
parasites
chemical hazards in food
pesticides
machine lubricants and inks
cleaners and sanitiser residues
antibiotics
heavy metals
physicals
glass
packaging materials
pieces of machinery
wood splinters
plastic
Shiga toxin-producing E.coli (STEC)
- E.coli is normal to have in gut of warm blooded animals
- Limit of 3-10 cfu/g
- Although pathogenic strains may cause illness
- STEC – main cause of haemolytic uraemic syndrome (HUS) which can be fatal - Strains characterised by O (somatic), H (flageller), K (capsular) antigens
- Meat may be contaminated if exposed to faecal matter during processing - Contaminated water for irrigation
May be asymptomatic or cause diarrhoea, vomiting, fever
Packages baby spinach outbreak
- Illness from E.coli cause kidney failure
- Attributed to uncooked spinach grown on land leased from an angus cattle ranch
- Investigators found presence of wild pigs and surface waterways exposed to faeces
from cattle and wildlife
Listeria spp.
- Gram positive, rod-shaped bacteria that grow with or without oxygen
- Grow best 30-37 C but also grow under refrigerated conditions and can tolerate high
salt - Can be found in:
- Water
- Soil
- Vegetation
- Wet area in food processing facilities - Raw milk
- Infection occurs through ingestion of contaminated food and water or mother to foetus
- Infective dose: 10^5-10^9 cfu in health people - Incubation period is long
- Symptoms
- Mild or severe
- Mild: fever, headache, muscle ache, diarrhoea, vomiting - Severe: septicaemia, meningitis, miscariage
- Small percentage of infected people develop disease
Melons outbreak
- Rock melon with listeria
- Contamination from the farms packing house because of dirty water on the floor and old, hard-to-clean equipment, trucks shuttling between beef ranch and horticultural operation
Salmonella spp.
- Bacteria which cause disease
- Two species, food-borne illness mostly related to salmonella enterica - Characterised by O and H antigens
- Grows 5.2-46.2 C, can survive freezing but generally killed above 60C - Susceptible to common food preservatives
- Limit of 0-25 cfu g allowed in food
- Salmonella
- Source of contamination wash tray in factory used for washing seeds
Salmonellosis
- Salmonella virulence varies with length and structure of surface lipopolysaccharide and ability to attach to epithelial cells – causes diarrhoea
- Multiple antibiotic resistant strains have emerged
- Most outbreaks associated with eggs
Hepatitis A
- Small virus
- Cannot grow in food but can persist under a range of environmental conditions
- Humans only source of HAv - transmitted via the faecal oral route
- Replicated in liver then via bile duct to small intestine and shed in faces - peak two
weeks before symptoms
Poisoning from fish
Histamine fish poisoning
- Certain types of fish kept above 16C - produce amino acid histidine - Natural bacteria convert histidine to histamine
- Not destroyed by cooking - stimulates an allergic reaction
Ciguatera
- Reef fish obtain ciguatoxin form toxic dinoflagellates - Causes gastrointestinal and neurological symptoms
Organic amendments
- Composting is a sustainable means of recycling nutrients
- May contain animal manures
- Composting process and times
- Exclusion period are required where animals have been grazed - Human waste should not be use
Sources of chemicals in food Extrinsic sources
- Chemicals applied during production or post harvest - Persistent chemicals in soil
- Accidental contamination
- Heavy metals
Sources of chemicals in food intrinsic sources
- Naturally Occuring toxins
- Allergens and chemicals causing intolerance - Mycotoxins
Chemical contaminants
- Pesticides
- Sanitisers
- Heavy metals
Pests, disease and weeds are responsible for enormous loose sin productivity where crop protection chemicals are importance for control and productivity
Types of pesticides
Organochlorines - highly stable, persist in environment, bioaccumulate, endocrine disruptors, heavily restricted
Organophosphates and carbmates: rapidly degrade, do not bioaccumulate, inhibit cholinesterase
herbicides: low toxicity in humans and animals: target plant metabolic pathways
fungicides: residues from post harvest use, low acute toxicity to humans
guidlines for agrichemicals
chemicals used in agriculture and veterinary medicine tightly controlled by APVMA in aus
Austrlian total diet survey
Samples selected on the basis of:
- Foods that are representative of current patterns of food and beverage consumption
in Australia
- Foods that are suspected or known to contribute significantly to the dietary exposure
for the chemical analysed
- Resource capabilities of the states and territories to collect samples
- Cost associated with the purchase, transport and analysis of samples
Heavy metals - cadmium
- Most concern to fresh produce
- Taken up by plants and accumulated in the food chain - Present in phosphate fertilisers, composts
- Can cause kidney disease
Heavy metals - Lead
- Risks have decreased
- Risks higher near smelter or heavy industry - Causes learning disabilities
Heavy metals - Arsenic
- Found in water, air, food and soil
- Can be naturally occurring or contamination from humans - Inorganic and og=rganic forms - inorganic more toxic
- Can be high levels ins seafood
Heavy metals - mercury
- Found naturally and introduced as a contaminant
- Affects nervous system
- Accumulates in aquatic food chain as methyl mercury - Can safely eat 2-3 serves a week
- Benefits of eating fish outweigh mercury posing
Cyanogenic glycosides in cassava
- Cassava tubers contain a varying quantity of cyanogenic glucosides - higher in bitter varieties
- Cyanogenic glucosides are components of plant defence
- Bitter taste and release of toxic hydrogen cyanide upon tissue distribution
Preparation - Should e soaked and dried for several days to release hydrogen cyanide before being eaten
- Acute poisoning causing konzo, irreversible paralysis of the legs
