food preservation
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What are the common causes of food spoilage?
Bacteria, mould, yeast
2) What is the earliest form of long-term food preservation?
dehydration
What is the range of the temperature danger zone for food? Why is it called this?
5°C-60°C is the temperature range where most microorganism growth occurs
Why does removing water inhibit microorganism growth?
The cells can no longer function, because nutrient cannot move around without water.
What are the requirements for bacterial growth?
food, optimal pH, warm/optimal temp., time to grow, Oxygen, humid (FATTOM)
How does our body help protect us from infection?
Skin, saliva, tears, mucus, stomach acid
What is food preservation?
Action of treating foods such that they can be stored for a while and eaten later.
What are the 3 goals of food preservation?
Preventing spoilage, avoiding food borne illness, maintaining freshness and nutritional content, denaturing enzymes which cause ripening.
What do bacteria produce when they ferment ethanol?
Acetic acid
What does yeast produce when it ferments glucose?
Ethanol and carbon dioxide (CO 2 )
What do bacteria produce when they ferment glucose?
Lactic acid
What are the downsides of canning?
Heating decreasing nutritional content, alter taste and texture, chance of botulism
How do jar lids let you know the food is safe to eat?
They pop when opened. This sound indicates the seal has never been broken since the food was sealed in the sterile container, so little chance of food borne illness.
Why are cracked jars or badly dented cans associated with botulism?
Botulism spores can survive the canning process. A crack or dent allows air in causing the botulism to multiply and increases the chance of causing food poisoning.
What type of food preservation make the food take up less space?
Dehydration
What happens to food when it is frozen?
The water in the food turns to ice. This stops microbe growth.
Why are freezers kept at -18°C when the freezing point of water is 0°C?
The water in foods usually has other things dissolved in it (salt/sugar) and this lowers its freezing point. A low temperature ensures the food is frozen solid (no liquid water which would promote microbe growth).
Why would thawed tomatoes be better for cooking in a sauce than for slicing fresh in a salad?
Tomatoes have a high water content, so when frozen the ice crystals break open the cells. Later when they are thawed most of the water will not be in the fruit so better for making a sauce than eating whole.
Can frozen food be kept indefinitely? Explain.
Yes. However, over time the ice in the food will sublime (slowly change to water vapour) leaving it dehydrated. This is freezer burn, the food is still edible but can have an off taste and/or very tough dry patches. It will not cause illness, but probably won’t be enjoyable to eat.
Why do foods generally lose more nutritional value during cooking and canning than from dehydration?
Dehydration happens at lower temperatures. The high temperatures can decompose vitamins and phytochemicals reducing nutritional content.
Are most fermentation reactions aerobic or anaerobic? What does that mean?
Anaerobic, meaning they happen without oxygen.
What type of acid is produced by cabbage when combined with salt to make sauerkraut?
Lactic acid
How would you slice apples to dry them most effectively?
Thinly to maximise the contact with air so the water can evaporate quicker.
Since drying temperatures are not high enough to kill bacteria, why does dehydration work to preserve food?
Bacteria need water to survive, if there is no water in the cells, they cannot function or reproduce.