Past Exam Questions Flashcards
Discuss the main causes of food spoilage
(Enzyme action)
(3 headings)
(4, 3, 3)
Enzyme action:
- Ripening
- Sweetness improves as the high starch content converts into sugars such as fructose
- A colour change takes place such as tomatoes changing from green to red
- A texture change takes place such as bananas changing from hard to soft and easily digestible
- The enzymes will bring about the overripening of the food and will bring about the decay and decomposition of food - Enzymic Browning
- When some fruit or veg is cut an enzyme called oxidase is released with their cell walls
- Oxidase reacts with oxygen in the air and turns the food brown and eventually causes food spoilage
- Oxidation of oxidase reduces vitamin C - Enzymic deterioration
- fish naturally contain enzymes which speeds up the spoilage and deterioration of their flesh even at low temperatures
- these enzymes bring about the spoilage and deterioration of the fish’s flesh
- the deterioration of the flesh produces a putrid smell
Discuss the main causes of food spoilage
(Moisture loss)
(6 main points)
Moisture loss begins once the fruit or veg is harvested as they lose their ability to absorb water from the soil through their roots
Moisture loss causes fruit or veg to become dehydrated
Shrinkage can occur e.g. mushrooms shrivel
Wrinkling can occur e.g. apple or pepper skins wrinkle
Limp appearance in asparagus and celery
The surfaces of high protein foods such as cheese become hard
Discuss the main causes of food spoilage
(bacteria)
(2 main points)
Cause both internal and external food poisoning
They produce endotoxins and exotoxins which are not visible
Discuss the main causes of food spoilage
(moulds)
(3 main points)
Moulds produce visible food spoilage but rarely cause food poisoning as people tend to avoid visibly spoiled food
Moulds produce mycotoxins which are carcinogenic
The toxin aflatoxin is produced by the mould Aspergillus flavus
Name two food poisoning bacteria
Salmonella
Clostridium Botulinum
Describe salmonella
Rod-shaped Reproduces asexually by binary fission Contagious Facultative Mesophilic Causes infectious food poisoning Gram negative - cell wall with 2 thin layers - has flagella - no spore production - high resistance to antibiotics
Describe clostridium botulinum
Rod-shaped Reproduces asexually by binary fission Not contagious Anaerobic Mesophilic Causes toxic food poisoning Gram positive - cell wall is 1 thick layer - does not have flagella - produces endospores - low resistance to antibiotics
Describe the habitat for salmonella
Intestines of animals and humans
Human and animal waste
Unwashed hands
Describe the habitat for clostridium botulinum
Soil
Decaying matter
Vegetables
Pig intestines
What conditions are necessary for the growth of clostridium botulinum
Anaerobic - does not require oxygen for growth Mesophilic - Optimum pH between 30 and 37 degrees Celsius pH - slightly acidic environment (4.6)
How does clostridium botulinum reproduce?
Reproduces asexually by binary fission
- bacterial cell elongates
- its nuclear material (DNA) duplicates
- a cell wall and membrane forms between the duplicated DNA and the original to create two separate identical bacteria
What are high risk foods associated with clostridium botulinum?
Unpasteurised cheese
Canned food
Vacuum-packed food
Explain how blanching assists in controlling enzymic food spoilage
Blanching involves immersing vegetables in boiling water for five minutes and to destroy enzymes and then plunging them in ice cold water before freezing to prevent cooking
How do cold temperatures control enzymic spoilage?
Low temperatures slow down enzyme activity in food, reducing the rate of spoilage and lengthening shelf life
How do acids control enzymic spoilage?
Acids lower pH levels which inactivates enzymes which work best at neutral pHs