3.1.1 Micro-organisms and Enzymes Flashcards
What are micro-organisms?
tiny organisms found in many places that can spoil foods. also known as microbes. yeast, moulds and bacteria are types of this
How is food spoilt?
contamination of yeasts, moulds or bacteria and contaminates with their waste products (toxins they produce)
enzymic activity can spoil food + ripen fruit and veg
What conditions do micro-organisms need for growth?
yeast, moulds and bacteria require:
food, moisture, warmth, time and correct pH
Why is food a condition for micro-organism growth?
nutrients are needed for growth
How can you prevent growth and multiplication of micro-organisms in food?
prevent contact with food and keep it covered
Why is moisture a condition for the growth of micro-organisms?
water is needed for all biological processes. if water is removed they cannot grow/multiply
How and why might you remove moisture from a food?
drying: adding high concentrations of sugar/salt - the water from cells are removed by osmosis
in order to prevent micro-organisms to grow/multiply
Why is warmth a condition for the growth of micro-organisms?
if too hot the micro-organisms will be destroyed, if too cold their multiplication slows down until it stops (become dormant)
the ideal temp is 37 degrees celcius
How to control micro-organism growth/multiplication by temperature?
cook food thoroughly at high enough temperature. cook at least to 75 degrees celcius to kill most microbes.
don’t leave food out in warm places. cool cooked and left over food must be refrigerated quickly and not left out. refrigerate between 0-5 degrees celcius or freeze -18 degrees celsius or below.
Why is time a condition for the growth of micro-organisms?
bacteria multiply every 10-12 minutes in the right conditions by binary fission
How to control the growth/multiplication of micro-organisms through time?
cook and cool foods thoroughly and use within “use by date”/ expiry date
Why is pH level a condition for the growth of micro-organisms?
right amount of acidity/alkalinity (pH) needed. if too much of one they cannot grow.
How can you prevent the growth of micro-organisms through pH level?
preserving food in vinegar is a method of preventing multiplication
vinegar is pH 2-3 (strongly acidic)
What are yeasts?
single celled fungi that reproduce by “budding”
What is ‘budding’?
the yeast cells grows a bud that becomes bigger, until it it breaks off and becomes a new yeast cell
How can yeasts grow?
with oxygen (aerobic yeast) or without oxygen (anaerobic yeasts)
in high concentrations of sugar + salt (jam, honey, chutney)
grown best in warm conditions (25-29 degrees)
can grow at refrigerator temps (0- below 5 degrees)