preservation processes

Question 1

list the different types of preservation

Answer 1

• canning
• pasteurisation
• refrigeration
• fermentation
• dehydrating
• chemicals methods

Question 2

canning

canning

Answer 2

a preservation method where the food is processed and sealed on an air tight can.

Question 3

canning

what two principles of preservation does canning involve?

Answer 3

1. exclusion of air
   - the vacuum created inside the sealed can prevent microorganisms from entering
2. control of temperature
   - heating the food inside to destroy all possible microorganisms at a high temperature

Question 4

canning

traditional canning

Answer 4

• 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

Question 5

canning

aseptic canning

Answer 5

• food inside is heated to the correct temperature to kill microorganisms before being put in a sterile can

Question 6

canning

what could have occurred if the can end is buldging?

Answer 6

• 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.

Question 7

pasteurisation

pasteurisation

Answer 7

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)

Question 8

pasteurisation

list the different types of pasteurisation

Answer 8

• holder process method
• high temperature, short time (HTST)
• ultra high temperature (UHT)

Question 9

pasateurisation

describe the holder process method

Answer 9

the food is quickly heated to 65℃ and held at this temperature for 3 minutes before being quickly cooled.

Question 10

pasteurisation

describe the HTST method

Answer 10

• 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.

Question 11

pasteurisation

describe the UHT method

Answer 11

• stands for ultra high temperature
• allows the food to not require refrigeration until opened
• food is heated up to 140℃ for a couple seconds

Question 12

refrigeration

refrigeration

Answer 12

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.

Question 13

refrigeration

list the different types of refrigeration

Answer 13

• chilling
• freezing
• blanching

Question 14

refrigeration

chilling

Answer 14

• 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

Question 15

refrigeration

freezing

Answer 15

• foods are kept in storage well below -18℃
• enzyme acitivty is significantly reduce to extreme low temperatures
• microorganism numbers are reduced by freezing them

Question 16

refrigeration

blanching

Answer 16

• food products are cooked between 95-100℃ before being put in the freezer
• blanching inactivates the enzymes present on the food product

Question 17

drying

dehydration

Answer 17

The preservation method of the water content in foods evaporating (i.e. drying)

Question 18

drying

freeze drying

Answer 18

When a food is frozen, then out in a vaccum environment and slight heat, evaporating the ice crystals and leaving the dehydrated particles.

Question 19

fermentation

fermentation

Answer 19

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.

Question 20

fermentation

binding of water

Answer 20

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.

Question 21

chemical methods

additives

Answer 21

chemicals which are either directly added to the foods or are present in foods as a result of pre-processing treatments, processing or storage.

Question 22

chemical methods

smoking

Answer 22

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

Question 23

chemical methods

curing and salting

Answer 23

a process in which nitrite, nitrates and salt are added to meats (e.g. bacon and salami).