Food Spoilage and Preservation Flashcards
Food spoilage definition
Change in colour or texture of food and and off putting odour or unpleasant taste.
Results in food waste and can lead to food poisoning.
Causes of food spoilage
Moisture loss
Enzyme action
Microbial contamination
Moisture loss
Mainly affects fruit and vegetables
After harvesting, can’t absorb water from soil.
Moisture loss through skins and leaves results in shrinkage, wrinkling of skin and limp appearance
Enzyme action includes
Ripening
Browning/ enzymic browning
Enzyme deterioration
Enzyme action: ripening
Certain enzymes in fruit and veg are responsible for ripening
During ripening process, starch in under ripe fruit is converted to sugars
There’s also a colour change eg: green to yellow in bananas
Texture change hard to soft and easier to digest
Enzymes continue to work after ripening, resulting in over ripe fruit eg: black bananas at which stage food spoilage has occurrd
Enzyme action: Browning/ Enzymic browning
When fruit or veg are cut during food preparation, enzyme oxidase is released and exposed to air
This causes apples to turn brown
Enzyme action: Enzyme deterioration
Enzymes naturally present in fish cause deterioration even at low temperatures
Fish must be consumed or processed quickly to avoid spoilage
Controlling enzymic spoilage of food
Enzymes are inactivated by heat, browning can be stopped by cooking food
Cold temps slow down enzymic action, low temp lengthen shelf life
Blanching veg before freezing prevents enzymic spoilage of frozen foods
Addition of acids inactivates enzymes eg: lemon juice in apple prep
Preservative sulphur dioxide used in dry fruit, veg and fruit juices to control enzymic spoilage of food
Microbial contamination
Food is an ideal medium for microbial growth, provides nutrients, pH, oxygen, optimum temp if not stored correctly
Role of microorganisms in food spoilage:
Fungal
Fungi favour acidic pH so they can grow on and spoil foods such as cheese, fruit and preserves eg: jam
Foods spoiled by yeast generally have an off odour of flavour and texture changed
Moulds mai sky spoil exterior of foods, usually visible and therefore the food is seldom consumed
Some moulds produce mycotoxins which can be a health risk
Fungal spoilage is rarely responsible for food poisoning as it’s visible
Role of microorganisms in food spoilage:
Bacterial
They grow rapidly in food when conditions are suitable eg: food in danger zone for a prolonged period.
Souring bacteria spoil milk, cream and yogurt.
Pathogenic bacteria produce toxins which aren’t visible in food
Bacterial spoilage can result in food poisoning when these bacteria and or their toxins are consumed in food
Danger zone!!!
5-63°C
Preventing food spoilage by mo’s
Removing favourable growth conditions such as oxygen, moisture, temperature, pH
Preventing food spoilage by Fungi
Store perishables in clean fridge and use rotation according to expiry dates
Ensure storage areas are clean and dry and quickly remove any spoiled foods
Preserving foods by drying, canning or putting in chemicals such a vinegar
Cooking food
High sugar content in preserves inhibits growth
Preventing food spoilage by bacteria
Observe strict personal hygiene when prep
Ensure structure and maintenance of kitchen facilities good food hygiene
Observe hood hygiene practices in safe storage, preparation and cooking of food
