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FST 131 > FREEZING > Flashcards

FREEZING Flashcards

1
Q
A
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2
Q

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

A

0C

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3
Q

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

A

immobilization of water as ice, resulting concentration of dissolved solutes

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4
Q

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

A

freezing, storage and thawing

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5
Q

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

A

slow freezing

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6
Q

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

A

coldest places/top surface

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7
Q

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

A

evaporated

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8
Q

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

A

indirect contact system

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9
Q

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

A

indirect contact systems

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10
Q

product is frozen while being held between two refrigerated plates

A

plate freezers

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11
Q

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

A

plate and packaging material

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12
Q

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

A

ammonia, freon, CO2, and brine

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13
Q

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

A

batch system plate freezer

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14
Q

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

A

freezing time (batch type plate freezer)

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15
Q

operates by moving the plates holding the product through and enclosure

A

continuous system plate freezer

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16
Q

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

A

freezing time (continuous system plate freezer)

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17
Q

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

A

air-blast freezer

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18
Q

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

A

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

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19
Q

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

A

chest freezer

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20
Q

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

A

batch equipment (air blast freezer)

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21
Q

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

A

refrigerated room (air blast freezer)

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22
Q

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

A

storage space

23
Q
A
23
Q
A
24
Q
A
24
Q

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

A

long; lower; inability; smaller

25
Q

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

A

continuous equipment (air blast freezer)

26
Q

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

A

length and speed

27
Q

variation of continuous air blast freezer

A

belt freezer

28
Q

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

A

belt freezer (air blast freezer)

29
Q

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

A

spiral freezer (air blast freezer)

30
Q

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

A

direct contact systems

31
Q

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

A

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

32
Q

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

A

air blast individual quick freezing (direct contact system)

33
Q

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

A

air blast individual quick freezing (direct contact system)

34
Q

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

A

air blast individual quick freezing (direct contact system)

35
Q

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

A

fluidized bed individual quick freezing (direct contact system)

36
Q

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

A

air speed

37
Q

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

A

convective heat transfer coefficients

38
Q

immersion of food product in liquid refrigerant

A

immersion (direct contact system)

39
Q

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

A

shorter

40
Q

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

A

immersion (direct contact system)

41
Q

most common refrigerants for immersion (direct contact system)

A

nitrogen and carbon dioxide

42
Q

selection factor of freezing equipment

A

-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

43
Q

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

A

chilling

44
Q

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

A

chilling

45
Q

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

A

chilling

46
Q

causes minimal changes to sensory characteristics and nutritional quality of food

A

chilling

47
Q

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

A

hygiene; temperature control

48
Q

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

A

low acid

49
Q

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

A

-1C to 1C

50
Q

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

A

0C to 5C

51
Q

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

A

0C to 8C

52
Q
A

FST 131 (1 decks)

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