Food Spoilage Flashcards
Causes of food spoilage
Enzyme action
Moisture loss
Microbial contamination
What are enzymes
Protein catalyst that are naturally found in food that speed up chemical reactions without being destroyed
3 things enzymes do in food
Ripen food
Brown food
Deteriorate food
What does ripening do
Improve taste - get sweeter as start getting turns to sugar
Colour change
Texture change eg banana
Why do enzymes cause cut food to become brown
The enzyme named oxidase from the cell wall reacts with the oxygen in the air (a process called oxidation) and causes browning
Examples of enzymic denaturation
Fish - naturally present enzymes speed up spoilage
Veg - naturally present enzymes causes deterioration
Ways of preventing enzymic spoilage
Acids - lowers ph eg lemon juice
Heat - inactivates enzymes eg stewing apples
Additives - sulfur dioxide eg in dried fruit
Cold temperatures - slows down eg fish
Blanching
Why would veg and fruit lose moisture
Once harvested they no longer absorb moisture from soil via roots
Dehydrated fruit and veg
Shrink/shrivel
Wrinkle
Limp
Are yeast and mould visible
Yes
Are mycotoxins carcinogenic
Yes
What are mycotoxins
Toxins produced by mould
Why don’t mould and yeast call food poisoninh
People see them and don’t eat them
Why is bacteria food poisoning more common
Not visible on exterior of the food so people eat them
Types of food poisoning
Chemical
Biological
Bacterial
Examples of chemical food poisoning
Lead
Pesticides / herbicides
Examples of biological food poisoning
Solanine in green potatoes
Haemagglutin in raw red kidney beans
Two types of bacterial food poisoning
Infectious
Toxic
Infectious food poisoning
Pathogenic bacteria that produces endotoxins (made inside pathogenic cell)
Released when cell dies
Destroyed by normal cooking temp
Incubation period ; over 12 hours
Examples of infectious poisoning
Salmonella
Listeria
E. coli
Toxic food poisoning
Food containing pathogenic bacteria that produces exotoxins (secreted by cell wall as they grow)
Produced before or after food is eaten
Difficult to destroy - boil 30 min
Incubation period - 2 hours
Examples of toxic poisoninh
Staphylococcus
Clostridium botulinum
What is the incubation period
The time it takes for symptoms to appear
Describe salmonella
Infectious Contagious Facultative Neutral ph Op temp = 37
Sources of salmonella and high risk foods
Human and animal faeces Unwashed hands Rodents and pests Raw/undercooked eggs, fish, meat, poultry Unpasteurised milk and cheese
Symptoms of salmonella
Nausea Vomiting Abdominal pain Diarrhoea Fever
Incubation period and duration of food poisoning for salmonella
12-36h
Lasts 1-7 days (up to a week)
Describe clostridium botulinum
Toxic Not contagious Anaerobic Slightly acidic Optimum temp = 30-37
Sources of clostridium botulinum and high risk foods
Soils Vegetables Pig intestines Unpasteurised cheese Canned food Vacuum packed food
Symptoms of clostridium botulinum
Diarrhoea
Slurred speech
Dizziness
Double vision
Incubation period and duration of poisoning for clostridium botulinum
12-36h
Lasts 1-8days
