Food Spoilage - Enzyme Action Flashcards
What are enzymes?
Protein catalysts that speed up chemical reactions without being destroyed or changed
Name one place where enzymes are naturally present?
Food
What do enzymes in food bring about?
Ripening of food
Browning of food/enzymic browning
Enzymic deterioration
What is spoilage caused by enzymes called?
Enzymic spoilage
What happens to the taste of fruit or veg as enzymes bring about their ripening?
Sweetness improves as the high starch content converts into sugars such as fructose
What happens to the colour of fruit or veg as enzymes bring about their ripening?
A colour change takes place such as tomatoes changing from green to red
What happens to the texture of fruit or veg as enzymes bring about their ripening?
A texture change takes place such as bananas changing from hard to soft and easily digestible
When do enzymes stop ripening fruit and veg?
Enzymes will continue to work even after the food has ripened
What happens when enzymes continue to work after a fruit or veg has ripened?
The enzymes will bring about the overripening of the food and will bring about the decay and decomposition of food
What happens to some fruit and vegetables when they are cut?
They will turn brown
Why do fruits such as apples turn brown when cut?
An enzyme called oxidase is released from their cell walls which oxidises
What happens to fruits and veg when their enzyme oxidase has oxidised?
They will turn brown and will eventually spoil
The oxidisation of oxidase does what to the quantity of Vitamin C in fruits and veg?
Reduces the amount of Vitamin C available
The oxidisation of oxidase reduces the quantity of what vitamin in fruit and veg?
Vitamin C
What do fish naturally contain which speeds up the spoilage and deterioration of their flesh even at low temperatures?
Enzymes
What do the enzymes naturally present in fish do even at low temperatures
They bring about the spoilage and deterioration of the fish’s flesh
What is released when a fish’s flesh deteriorates by enzymes?
A putrid odour
What five factors can control enzymic spoilage?
Acids Heat Additives (Preservatives) Cold Temperatures Blanching
How do acids control enzymic spoilage?
Acids lower pH levels which inactivates enzymes which work best at neutral pHs
How does heat control enzymic spoilage?
Enzymes are sensitive to high temperatures and are inactivated by cooking
How do additives/preservatives control enzymic spoilage?
Sulfur dioxide is a preservative which inactivates enzymes and is used commercially to prevent enzymic spoilage
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 does blanching control enzymic 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
