investigating materials
DESCRIPTION
Year 6 - Sc NoteTRANSCRIPT
FOOD SPOILAGE
FOOD SPOILAGEAll food turns bad or spoilt after a certain
period of time.Characteristics of spoilt food:1.Unpleasant smell2.Unpleasant taste3.Change colour4.Change texture5.Mouldy
FOOD SPOILAGE
FOOD CHARACTERISTIC
Bread and cakes •Turns mouldy with black, green or white dots or hairy patches•Has unpleasant smell and taste•Become slimy
Vegetables •Turn yellowish•Become soft and withered•Become slimy and watery
Fruits •Become bruised•Turns mouldy•Has unpleasant smell and taste
FOOD SPOILAGE
FOOD CHARCTERISTIC
Fish and meat •Has unpleasant smell•Flesh becomes sunken when pressed•Has pale gills and sunken eyes in fish
Milk •Smells and taste sour•Becomes curdled and foamy•Its has swells (bulges)
Canned food •Tin can swells (bulges)•Food in it smells bad
FOOD SPOILAGEFood become rotten or decayed foodWhy? Due to the microorganism mainly bacteria
and fungiMicroorganism live and feed on the food. It
breaks the food down into simpler substances. This process called decaying.
When the food is decaying, it will smell and taste unpleasant and cause food poisoning when we eat.
Microorganism need air, water, nutrients (food), moderate temperature and suitable acidity to grow.
FOOD PRESERVATION
FOOD PRESERVATIONInvolves treating food so it can be stored
without spoiling for along time.Prevents or slow down the growth of
microorganism on food.Killing the microorganism or making the
condition unsuitable for them to growth and survival.
WASTE
TYPES OF WASTESome waste can be decayed and some cannot be
decayedThe waste can be decayed by the microorganism is
called biodegradable waste.The waste cannot be decayed by he microorganism is
called non biodegradable wasteMostly biodegradable waste originated from living thing.
For examples:1.Discarded food, sewage, animal waste, paper and wood2.Certain types of plastics known as biodegradable plastics
and detergents known as biodegradable detergent.3.Effluent from factory that produce food or processes
agricultural product such as palm oil and rubber
Biodegradable WasteDecaying and decomposition is a process of
breaking a material down into simpler substances by microorganism.
The biodegradable waste changes like the following:
1.Change in appearance : It may change colour, become softer, become liquid or gas.
2.Reduction in size and volume : For example, a huge heap of dried leaves will be come small heap
It can also be useful. The biodegradable waste can be used to make compost, nutrient-rich substance used as fertilisers.
Advantages and disadvantages of waste decayAdvantagesAllows nutrient in waste to be returned to the
soil and be reused.Helps to reduce the volume of waste.DisadvantagesContribute to global warmingMethane is produced by the global warming.
Methane is a flammable gas. It will cause the landfill catch the fire easily especially during the hot and dry season.
Rubbish and sewage treatment plants give out the bad smell.
Non Biodegradable WasteNon biodegradable waste remain in the
environment for a very long time.It cannot be decayed easily.For example : The plastic bag takes about
10 to 20 years to decay.We should reduce the waste by reused and
recycle them.