FREEZING

Question 2

at temperatures below _______ there is a significant reduction in growth rates for microorganisms and in the corresponding deterioration of the product due to microbial activity

Answer 2

0C

Question 3

the _______________ and _________________ lower the water activity of the food and hence less water is available to support deteriorative reactions

Answer 3

immobilization of water as ice, resulting concentration of dissolved solutes

Question 4

when correct _______, ________ and ______ procedures are followed, there are only small changes to the nutritional value and sensory quality of food

Answer 4

freezing, storage and thawing

Question 5

_____________, temperature abuse during frozen storage and thawing can each damage the quality of food

Answer 5

slow freezing

Question 6

the water inside the food migrates to the ____________________ and forms ice crystals that evaporate that leaves dry, grayish spots on meats, vegetables crusty and tough, and forms thick frozen slimy film on top of ice cream

Answer 6

coldest places/top surface

Question 7

_____________ molecules can combine with other molecules from other foods and come back into food again, making food taste off or unpleasant

Answer 7

evaporated

Question 8

the product and refrigerant are separated by a barrier throughout the freezing process

Answer 8

indirect contact system

Question 9

include any system without direct contact, including those where the package material becomes the barrier

Answer 9

indirect contact systems

Question 10

product is frozen while being held between two refrigerated plates

Answer 10

plate freezers

Question 11

the barrier between product and refrigerant in plate freezers will include both _______________ and _______________

Answer 11

plate and packaging material

Question 12

the plate freezing process consists of plates with refrigerant flowing through them: ____________, ___________, ______, and __________ depending on compressor

Answer 12

ammonia, freon, CO2, and brine

Question 13

the product is placed on the plates for a specified residence time before being removes

Answer 13

batch system plate freezer

Question 14

the ______________ is the residence time and represents the total time required to reduce the product from the initial temperature to some desired final temperature

Answer 14

freezing time (batch type plate freezer)

Question 15

operates by moving the plates holding the product through and enclosure

Answer 15

continuous system plate freezer

Question 16

the _______________ is the total time required for the product to move from the entrance to exit

Answer 16

freezing time (continuous system plate freezer)

Question 17

the package film is the barrier for the indirect freezing, with cold air being the source of refrigeration

Answer 17

air-blast freezer

Question 18

in air blast freezer, refrigerated air is circulated over food at between _______ and _________ at a velocity of _____ to ________

Answer 18

-30C to-50C; 3 to 18 m/s

Question 19

in stationary (naturally circulating) air at between -20C and -30C; not used for commercial freezing owing to low freezing times (3 to 73 hr)

Answer 19

chest freezer

Question 20

in __________________, food is stacked on trays in rooms or cabinets

Answer 20

batch equipment (air blast freezer)

Question 21

the product is placed in the room and the low temperature air is allowed to circulate around the product for the desired residence of freezing time

Answer 21

refrigerated room (air blast freezer)

Question 22

the refrigerated room (air blast freezer) may act as ___________ in addition to the freezing compartment

Answer 22

storage space

Question 24

in most cases, freezing time in refrigerated room will be _________ because of _________ air speeds over the product, _______ to achieve intimate contact between product and cold air, and the ________ temperature gradients between product and air

Answer 24

long; lower; inability; smaller

Question 25

_____________ has trolleys stacked with trays of food that are moved through an insulated tunnel or on conveyor belts

Answer 25

continuous equipment (air blast freezer)

Question 26

the ___________ and _________ of the conveyor (air blast freezer) establish the residence of freezing time

Answer 26

length and speed

Question 27

variation of continuous air blast freezer

Answer 27

belt freezer

Question 28

have a flexible stainless steel mesh, passing through an insulated tunnel, in which foods are frozen by air

Answer 28

belt freezer (air blast freezer)

Question 29

mesh belt is stacked into spiral tiers that carry food up through a blast freezing chamber

Answer 29

spiral freezer (air blast freezer)

Question 30

there are no barriers to heat transfer between the refrigerant and the product

Answer 30

direct contact systems

Question 31

refrigerants used in direct contact systems may be ____________ or ___________ while in contact with product surface

Answer 31

low temperature air at high speed or liquid refrigerants with phase change

Question 32

combination of low temperature air, high convective heat transfer coefficient (high air speed), and small product shape

Answer 32

air blast individual quick freezing (direct contact system)

Question 33

the product is moved through a high speed air region on a conveyor in a manner that controls the residence time

Answer 33

air blast individual quick freezing (direct contact system)

Question 34

limited to products that have the appropriate geometries and that require rapid freezing for maximum quality

Answer 34

air blast individual quick freezing (direct contact system)

Question 35

the high speed air is directed vertically upward through the mesh conveyor carrying product through the system

Answer 35

fluidized bed individual quick freezing (direct contact system)

Question 36

in fluidized bed individual quick freezing (direct contact system), the ___________ is adjusted in relation to the product size to lift the product from the conveyor surface and remains suspended in low temperature air

Answer 36

air speed

Question 37

in fluidized bed individual quick freezing, the air flow is not sufficient to maintain the product in suspension at all times but the fluidized action results in the highest possible __________________ for the freezing process

Answer 37

convective heat transfer coefficients

Question 38

immersion of food product in liquid refrigerant

Answer 38

immersion (direct contact system)

Question 39

for immersion of typical products, the freezing time is ___________ than for the air blast or fluidized bed system

Answer 39

shorter

Question 40

the product is carried into a bath of liquid refrigerant and is conveyed through the liquid while the refrigerant changes from liquid to vapor and absorbs heat from product

Answer 40

immersion (direct contact system)

Question 41

most common refrigerants for immersion (direct contact system)

Answer 41

nitrogen and carbon dioxide

Question 42

selection factor of freezing equipment

Answer 42

-rate of freezing required -size, shape and packaging requirements of food -batch or continuous operation -scale of production -types of products to be processed -capital and operating cost

Question 43

temperature of food is reduced to between -1C and 8C

Answer 43

chilling

Question 44

reduces the rate of biochemical and microbiological changes and hence extends the shelf life of fresh and processed foods

Answer 44

chilling

Question 45

often used in combination with other unit operations (ex. fermentation, minimal processing methods, pasteurization and modified atmosphere packaging)

Answer 45

chilling

Question 46

causes minimal changes to sensory characteristics and nutritional quality of food

Answer 46

chilling

Question 47

strict conditions of ___________ and precise ____________ are essential at all stages in the cold chain to avoid the risk of food spoilage or food poisoning

Answer 47

hygiene; temperature control

Question 48

___________ chilled food are susceptible to contamination of pathogenic bacteria (ex. fresh and precooked meats, unfermented dairy products, pizzas and unbaked dough)

Answer 48

low acid

Question 49

e.g. fresh fish, meats, sausages and ground meats, smoked meats and breaded fish

Answer 49

-1C to 1C

Question 50

e.g. milk, cream, yoghurt, prepared salads, sandwiches, fresh pasta, soups and sauces, baked goods, pizzas, pastries and unbaked dough

Answer 50

0C to 5C

Question 51

e.g. fully cooked meat, fish and vegetable pies, cooked or uncooked cured meats, butter, margarine, cheese, cooked rice, fruit juices and soft fruits

Answer 51

0C to 8C