4.2. food processing- preservation by temperature control

Question 1

why is food preservation carried out?

Answer 1

to increase food choice and convenience for consumer and to add value for food producers

Question 2

how can the deterioration of food products be prevented using temperature control?

Answer 2

by processing foods at different temperatures to reduce the rate of microbial growth, thereby extending shelf life

Question 3

Temperature in sterilisation?

Answer 3

killing bacteria through thermal processing

Question 4

temperature in pastuerastion?

Answer 4

used for killing the majority of bacteria in a liquid

Question 5

what is canning

Answer 5

sealing a product in a metal tin

Question 6

temperature in chilling

Answer 6

process of keeping food between 1-5 C, to reduce the growth of bacteria

Question 7

temperature in freezing

Answer 7

process of storing food at -18c to prevent bacteria growth

Question 8

what are the 3 stages that thermal processing take place?

Answer 8

-container-when the actual packaging is sterilized at high temperatures, before a product is placed in it. Very important when using glass jars and bottles
-in-container-when product is sterilised inside the sealed packaging (canned foods)
aseptic- when the food is sterilised before being placed in a sterile container.(milk)

Question 9

what is pasteurisation?

Answer 9

the process of heat processing a liquid or a food to kill pathogenic bacteria to make the food safe to eat

Question 10

what are the 2 possible temperature treatments that can be used oil pasteurisation?

Answer 10

-High-Temperature-Short-Time Treatment (HTST)
—-uses higher heat for less time to kill pathogenic bacteria. For example, milk is pasteurized at 161°F (72°C) for 15 seconds.
-Low-Temperature-Long-Time Treatment (LTLT)
—–uses lower heat for a longer time to kill pathogenic bacteria. For example, milk is pasteurized at 145°F (63°C) for 30 minutes.

Question 11

what do the times and temperatures used in pasteurisation depend on?

Answer 11

-the type of food
-the final result one wants to achieve, such as retaining a food’s nutrients, color, texture, and flavor.

Question 12

what are the 2 thermal processes for the pasteurisation of food?

Answer 12

-flash pasteurisation
-steam pasteurisation

Question 13

what is flash pasteurisation?

Answer 13

-Involves a high-temperature, short-time treatment in which pourable products, such as juices, are heated for 3 to 15 seconds to a temperature that destroys harmful microorganisms. After heating, the product is cooled and packaged.

-Most drink boxes use this method as it allows extended unrefrigerated storage while providing a safe product.

Question 14

what is steam pasteurisation?

Answer 14

technology uses heat to control or reduce harmful microorganisms in beef.
-involves freshly-slaughtered beef carcasses passing through a chamber that exposes the beef to pressurized steam for approximately 6 to 8 seconds. The steam raises the surface temperature of the carcasses to 88° to 93°C
-carcasses are then cooled with a cold-water spray. This process has proven to be successful in reducing pathogenic bacteria

Question 15

what is there main objective of canning?

Answer 15

to preserve the food by the application of heat so that it can be safely eaten at a later time.
-food can either be made aseptic before being put into a sterile can and then sealed.
-Alternatively the cans are often heated once the product is inside and sealed

Question 16

what are important factors to consider when canning?

Answer 16

-Safety of the consumer should be considered
-achieve acceptable quality in the final product and to retain as much of the nutritive value of the food as possible.

Question 17

what are the 2 examples of cold processing?

Answer 17

chilling and freezing

Question 18

describe the process of chilling?

Answer 18

temperature of a fridge should be between 1˚C and 5˚C- the growth of pathogenic bacteria will be slowed.
-perishable foods should be chilled promptly and properly after purchasing
-hot foods should be cooled as quickly as possible- as hot food put in the fridge will increase the internal temperature and risk other foods being put in the danger zone.

Question 19

how can the chilling of foods be sped up ?

Answer 19

-spreading them out in shallow trays-increase the surface area
-placing pans in ice baths
-Blast chillers are also used in commercial/industrial setting, which blow cold air over food to chill the food quicker

Question 20

what are the 4 different freezing techniques?

Answer 20

-Horizontal plated freezing
-Vertical plated freezing
-Cryogenic freezing/Flash Freezing
-Fluidised bed freezing

Question 21

what is horizontal plated freezing?

Answer 21

• can be supplied with or without insulated enclosure freezers and are mostly used for freezing of more expensive fish products such as fish fillets, shrimp and surimi but also for meat fillets as poultry.
  -products are usually pre-packed in a carton or an aluminium tray

Question 22

what is Vertical plated freezing?

Answer 22

usually applied for freezing of large quantities of fish or meat. In general the coolant for the plates freezers is; Ammonia, CO2 or synthetic refrigerants.

Question 23

what is Cryogenic freezing/Flash Freezing?

Answer 23

-utilise either solid Carbon dioxide at -80Cor liquid nitrogen at - 196C. This the most rapid form of freezing and therefore creates smaller ice crystal and can improve quality and reduce weight loss of products when thawed.
-used for many types of pre-prepared products

Question 24

what is Fluidised bed freezing?

Answer 24

-where high speed air (liquid nitrogen) is sprayed vertically upward through a mesh conveyor belt.
-This type of freezing process results in rapid freezing of products such as fruit, vegetables, meat and fish.
-This is a form of cryogenic freezing

Question 25

what is the impact of temperature preservation on sensory qualities?

Answer 25

-Pasteurization can affect the nutrient composition and flavor of foods.
-Freezing can cause freezer burn
-chilling can cause low temperature damage and therefore affecting the aesthetics of a product.
-the addition of heat can alter a cell structure of different products. affecting texture eg.tinned fruits are much softer
-The taste can also be affected and the addition of additives are often used to used to counteract the negative impact of thermal processing

Question 26

what is the impact of temperature preservation on nutritional qualities ?

Answer 26

-Many vegetables begin to lose vitamins when harvested. Nearly half the vitamins may be lost within a few days unless the fresh produce is cooled or preserved.
-Within one to two weeks, even refrigerated produce may lose half of its vitamins. The heating process during canning destroys from 1/3 to 1/2 of vitamins A and C, thiamin, and riboflavin
-Once canned, additional losses of these sensitive vitamins are from 5 to 20 percent each year depending on storage conditions