food spoilage and preservation Flashcards
what cause food spoilage on a product?
microorganisms
how do microorganisms cause food poisoning?
by producing toxins, waste products or poisons that contaminate the foods
what are the typical microorganisms?
bacteria, yeast, moulds
what the signs of food spoilage?
-a sour smell or taste
-areas of mould on food
-slimy feel to the surface of the food
-a loss of moisture leading to wrinkled food that can be discoloured
what are bacteria most likely to cause?
food poisoning
what are the conditions needed for bacteria growth?
-time (every 20 minutes- called binary fission)
-temperature- (24C=optimum temp + 5C->63C is the danger zone)
-Food- (hbv protein and moisture= ‘high risk food’)
-moisture
-pH(bacteria needs neutral conditions to grow)
-oxygen
what is binary fission?
where the bacteria multiplies every 20 minutes
what is the danger zone?
between 5->63C
what is the optimum temp for growth of bacteria?
24C
what is a ‘high risk food’?
a food that promotes the growth of bacteria and eventually causes food poisoning. a hbv protein with moisture
what does acid do to bacteria?
slows down growth
what are some high risk foods?
meat, eggs, fish, cheese, milk
how does food poisoning happen?
if harmful bacteria contaminate food and then have the correct conditions to grow
what are some causes of food spoilage?
insects, pets, cleaning products (bleach), dust
why may pathogenic bacteria cause death in young children, pregnant women and elderly?
as they have lowered immune systems and their stomach acid can’t fight all the bacteria
what are some examples of pathogenic bacteria?
salmonella and stapphylococcus aureus
what are the sources of salmonella?
raw poultry, eggs, raw meat, milk
what are some symptoms of salmonella?
onset diarrhoea, vomiting, fever
how should you prevent cross contamination?
-wash hands before and after handling food
-never wash raw chicken
-store all foods in the correct position in fridge
-cook meat, eggs and fish thoroughly
-wash fruit and veg
-keep animals away from food
- cover cuts, tie back hair
-use correct chopping boards
how stop/prevent bacterial growth?
chill (fridge)
freeze
cook-chill
cook-freeze
canning
bottling/UHT/pasteurisation + sterilisation
what temperature should a fridge be kept at?
between 1-4C
what should be kept on the top shelf of the fridge? and why?
dairy products, deli items
as the fridge temp cools as rises and they are ‘high risk foods’ so should be kept at the coldest part to prevent food spoilage