list the different types of preservation
- canning
- pasteurisation
- refrigeration
- fermentation
- dehydrating
- chemicals methods
canning
canning
a preservation method where the food is processed and sealed on an air tight can.
canning
what two principles of preservation does canning involve?
- exclusion of air
- the vacuum created inside the sealed can prevent microorganisms from entering - control of temperature
- heating the food inside to destroy all possible microorganisms at a high temperature
canning
traditional canning
- the can is filled with the food product and a liquid is added to force air out of the container. the air above is removed using either a steam or a vacuum chamber
- the lid is placed and sealed before being heated to destroy all possible microorganisms
- the can is then quickly cooled
canning
aseptic canning
- food inside is heated to the correct temperature to kill microorganisms before being put in a sterile can
canning
what could have occurred if the can end is buldging?
- microbial growth: bacteria could be present due to the can not being properly sealed
- physical action: over filling the can at a low temperature causes permanent buldging of the can aftering heating.
- chemical action: acidic foods can corrode containers and cause a chemical reaction which produces hydrogen gas. cans used for high acid foods have lacquered insides to stop this reaction from occuring.
pasteurisation
pasteurisation
a preservation method which uses a heat treatment to either kill all specific heat sensitive microorganisms or reduce the number present to an acceptable level.
(e.g. milk, yoghurt)
pasteurisation
list the different types of pasteurisation
- holder process method
- high temperature, short time (HTST)
- ultra high temperature (UHT)
pasateurisation
describe the holder process method
the food is quickly heated to 65℃ and held at this temperature for 3 minutes before being quickly cooled.
pasteurisation
describe the HTST method
- stands for high temperature, short time
- using a heat exchanger, the food is quickly heated up to 72℃ and held at this temperature for 15 seconds.
pasteurisation
describe the UHT method
- stands for ultra high temperature
- allows the food to not require refrigeration until opened
- food is heated up to 140℃ for a couple seconds
refrigeration
refrigeration
a preservation method where the food product is kept well below room temperature and maintained at that temperature constantly to slow down the growth of microorganisms.
refrigeration
list the different types of refrigeration
- chilling
- freezing
- blanching
refrigeration
chilling
- foods are kept in storage i.e. a fridge, inbetween 0-5℃
- slows the growth and activity of enzymes
- common preservation method for perishable foods
refrigeration
freezing
- foods are kept in storage well below -18℃
- enzyme acitivty is significantly reduce to extreme low temperatures
- microorganism numbers are reduced by freezing them
refrigeration
blanching
- food products are cooked between 95-100℃ before being put in the freezer
- blanching inactivates the enzymes present on the food product
drying
dehydration
The preservation method of the water content in foods evaporating (i.e. drying)
drying
freeze drying
When a food is frozen, then out in a vaccum environment and slight heat, evaporating the ice crystals and leaving the dehydrated particles.
fermentation
fermentation
when carbohydrates are converted to acids or alcohol through the action of microorganisms.
the pH of the food lowers, the flavour sours and thus the environment becomes unfavourable for the growth of microorganisms.
fermentation
binding of water
when the amount of free water avaliable to microorganisms for food spoilage is reduced by adding soluble materials (e.g. sugar or salt) to absorb the moisture.
chemical methods
additives
chemicals which are either directly added to the foods or are present in foods as a result of pre-processing treatments, processing or storage.
chemical methods
smoking
process originally done to destroy bacteria in meat products (e.g. sausages) through a combination of heat and antibacterial agents.
the smoke inhibits enzyme activity in fresh meats
chemical methods
curing and salting
a process in which nitrite, nitrates and salt are added to meats (e.g. bacon and salami).
