Consumers: Food and Nutrition Contamination

1.2 HOW DO CONTAMINANTS AFFECT THE FOOD PEOPLE EAT AND

CONSEQUENTLY THEIR HEALTH?

Consumers: Food and Nutrition

Contamination

Food Poisoning

‘Food poisoning comes from eating foods that contain germs like bad bacteria or toxins, which are poisonous substances.’ (Kid’s Health 2012)

Pathogenic Bacteria are disease causing bacteria that lead to food poisoning and death.

Non-Pathogenic Bacteria are not harmful to health and are used in food processing. For example, yeast in bread and beer making and cultures in yoghurt and cheese.

Has food poisoning increased?

About 5.4 million Australians contract food poisoning each year and most cases can be prevented. (NSW Food Authority 2011)

This results, on average: in 120 deaths, 1.2 million visits to doctors, 300,000 prescriptions for antibiotics, and 2.1 million days of lost work. (NSW Food Authority 2011)

The estimated annual cost of food poisoning in Australia is $1.25 billion. NSW and the public health system bear roughly one-third of these costs. (NSW Food Authority 2011)

Food Poisoning - Symptoms

It’s not always the last thing you’ve eaten that causes the symptoms of food poisoning. For example, vomiting can occur shortly after eating contaminated food, but it’s not always an indication of the food responsible for the illness.

Symptoms include: Stomach pains, Headache Vomiting, Diarrhoea and, General fatigue

Urgent medical attention is required if: Symptoms last more than 3 days, Symptoms are severe: blood or mucus in diarrhoea

Food Poisoning

Three classes of food poisoning: Microbial contamination Biological contamination Chemical contamination

The source or cause of the illness determines the type of food poisoning

Microbial Contamination

Micro-organisms occur naturally in our environment.

Less than 1% of all micro-organisms are harmful to humans.

Micro-organisms are classified into the following groups: Protozoa, Algae, Viruses, Bacteria, Yeast and Moulds

Microbiological Contamination

Bacteria, yeasts and moulds are the groups containing organisms, which have the most relevance to food handling and food poisoning.

Micro-organisms require specific conditions to live in, as most respire using oxygen and food to produce energy and survive.

Microbial Contamination

Conditions required by micro-organisms are: Temperature in the range 5-60oC

Below 5oC the micro-organisms are less active Microbes multiply in warmer temperatures Temperatures above 60oC slow microbial growth and most microbes are

destroyed above 80oC pH

pH of 7 needed for optimal growth of bacteria Yeast prefer a more acidic environment with a pH of 4.5

Moisture Low water activity will not support micro-organism growth. Bacteria require more than yeast which require more than moulds

Oxygen Aerobes require oxygen for growth while an Anaerobe requires no oxygen Moulds are aerobic

The pH values of common foods, fluids and cleaning substances (Burnett-Fell et al 2009)

Temperature in various typical food handling

situations (Burnett-Fell et al 2009)

Bacteria

Classified according to their shape (round, spiral, comma, rod) and generally about 3 μm in size.

Reproduce very quickly (approximately every 20 minutes)

Some bacteria have a thick protective covering and can lie dormant when conditions are not favourable. (Spore)

Bacteria

Some bacteria release toxins, which are not easily destroyed by heat. These toxins are not usually detected by taste which increases the chance of them affecting the consumer.

Are responsible for most cases of dangerous food poisoning.

Doctors must report ‘notifiable’ pathogen outbreaks to the Department of Health

Types of Bacteria – Listeria

Listeria are bacteria that can cause a serious illness called listeriosis in some people. (Food Standards Australia New Zealand n.d.)

Listeriosis is usually caused by eating food contaminated by certain types of Listeria bacteria. Typically found in untreated water and milk, dairy products, raw meat and seafood.

Storing contaminated foods, even in the refrigerator, may allow the Listeria bacteria to grow. (Food Standards Australia New Zealand n.d.)

The bacteria may be present in raw foods or may contaminate food after it has been cooked or processed. (Food Standards Australia New Zealand n.d.)

Listeriosis– Who is at risk? and Symptoms

People at higher risk of listeriosis include: Pregnant women, their unborn and newborn children; Older people (generally considered to be persons over 65-70 years); People of all ages whose immune systems have been weakened by disease

or illness; Anyone on medication that can suppress the immune system.

Symptoms include: Fever, Headache, Tiredness, aches and pains. Less common symptoms are diarrhoea, nausea and abdominal cramps.

However, Symptoms may progress to more serious forms of the illness, such as meningitis and septicaemia.

Symptoms in pregnant women may be mild, but can result in miscarriage, premature birth or, in rare cases, stillbirth.

Types of Bacteria - Salmonella

‘Salmonellosis is caused by infection with bacteria called Salmonella.’

Spread when contaminated food is eaten raw or uncooked. Also when cooked food comes in to contact with contaminated raw food or when an infected person prepares food.

Can be prevented by: Separating raw food from cooked food Thoroughly cooking meat, chicken and eggs Avoid leaving food for over two hours at room temperature Refrigerate below 5 degrees

Symptoms

Onset 6-48 hours after eating

Symptoms include: Vomiting Diarrhoea Nausea Abdominal cramps

Can be fatal in infants and the elderly

Type of Bacteria – Botulism

The bacterium found in soil, sediments, raw foods and honey.Common in low acid foods canned improperly at home.Presence of this bacteria can be signalled by clear liquids

turning milky, cracked jars, loose or dented lids, swollen or dented cans or an ‘off’ odour.

Symptoms start 4-7 hours after eating and include nervous system disturbance including: Double vision Droopy eyelids Trouble speaking Swallowing or breathing

To prevent carefully examine canned goods; cook and reheat food thoroughly

Recap

Q1. True or false? All micro-organisms found in food cause disease.

Q2 Why are dry foods not susceptible to the growth of micro-organisms compare to foods such as fresh fruit?

Q3. Why does keeping food above 60 degrees or cold below 5 degrees help prevent bacteria in food.

Q4. What temperature do bacteria become less active?

Yeast

Small single celled plant organisms

Used in the production of some foods but can be responsible for infrequent cases of food poisoning

Can cause slime to form on fruit juices and vinegar products

Foods affected by yeast can have a slightly acidic flavour (cause tongue to tingle)

Yeast

Grows best between 20-40oC and can be destroyed in most cases by heating to 60oC for 15 minutes.

Occur on the outsides of fruit (eg skin of grapes) and will travel in the air.

Consequently post processing contamination is a major issue

Moulds

Enjoy warm, moist nutrient rich conditions where they grow rapidly.

Visible to naked eyeMay be white, coloured or

furryForm spores which are

difficult to destroy.Most moulds can be

destroyed by heating above 60oC for 10 minutes

Cross Contamination

Raw foods (especially meat and other animal products) contain micro-organisms which will transfer easily to preparation surfaces, equipment and hands.

Most of the microbes are killed when the food is cooked.

Provided the food is stored correctly and eaten within an acceptable time period, food poisoning is rare

Cross Contamination

Cross contamination occurs when cooked foods come into contact with surfaces, hands and equipment with the active microbes on them.

This causes the food to become re-contaminated and the warm conditions cause the microbes to flourish.

Cooked foods may also come in contact with raw foods in refrigerators

Biological Contamination

Caused by ingesting foods that naturally contain toxic or hazardous compounds

Sunday Mail 6/08/06

Chemical Contamination

Caused by the presence of toxic chemicals in foods, which do not naturally occur in the food.

The source of these chemicals may be industrial, agricultural or from the food processing itself.

The chance of the chemical levels reaching dangerous amounts is generally low assuming a normal varied diet is consumed.

Industrial Origin Food likely to be affected

Mercury FishLead All foods, waterCadmium Fish, shellfish, kidneyPolychlorinated biphenyls Fish, poultry, milk, eggsAgriculturalPesticides All foodsAntibiotics MilkHormones Some poultry

Food ProcessingOrigin Food likely to be affected

•Cleaning agents •Any processed food•Lubricants•Packing materials•Solvent residues•Extraneous substances (rodent excreta, hair, insects etc)

Sunday Mail 6/08/06

Food Spoilage

Differs from food poisoning because food spoilage is usually easy to identify visually.

The food is obviously inedible because of changes to the expected colour, texture, smell and flavour.

Foods naturally spoil and decompose as a result of being harvested and enzymes reactions from normal aging

Food Spoilage

Obviously inedible because of changes in colour, texture, smell and flavour.

Food spoilage can be unintentionally hastened by: Mishandling of food. Bruising and damage to

the surface of the food. Poor storage conditions. Temperature and

humidity not correct for food. Exposure to oxygen. Oils and fats go rancid,

mould grows on bread, jam and citrus fruit Absorbing odours of other foods nearby.

Cream cakes spoil if stored near onions or garlic.

Exposure to light. Milk loses B2 (Riboflavin)

Homework Task

Q1. Explain the difference between food poisoning and food spoilage?

Q2. Identify 3 factors that contribute to food spoilage.

Q3. For each factor identified, give one example of food spoilage.

Q4. Using two examples explain how food spoilage affects nutritional value of some foods. For each example, identify the nutrients affected.