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food science 210 > Thermal Processing > Flashcards

Thermal Processing Flashcards

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1
Q

types of thermal processing?

A

cooking, blanching, pasteurization, sterilization

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2
Q

most widely applied unit op in food processing?

A

thermal processing

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3
Q

three basic mechs of heat transfer?

A

conduction, convection, radiation

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4
Q

conduction is heating of ___, convection is heating of ___

A

solids; fluids

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5
Q

examples of radiation?

A

infrared, microwave, dielectric

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6
Q

primary objective of cooking?

A

increase palatability

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7
Q

baking and roasting happen at _____degrees, frying happen at ____ degrees

A

150-200; 175-225

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8
Q

cooking inactivates ____ factors like ___ in pulses

A

anti-nutritional factors; lectins

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9
Q

___ bioavailability reduced by ___ browning

A

lysine; Maillard (non enzymatic)

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10
Q

these vitamins decrease in bioavailability but not concentration with cooking

A

vitamin A and D

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11
Q

these vits decreases in both [ ] and availability

A

thiamine, niacin, folate

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12
Q

primary purpose of blanching?

A

inactivate deteriorative enzymes, kill spoilage bacteria

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13
Q

blanching usually done on __ foods, prior to ____

A

solid; freezing/canning

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14
Q

blanching reduces ___ by removing tissue gases

A

volume

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15
Q

blanching of fruits before ___ allows surface ___

A

drying; pasteurization

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16
Q

blanching inactivates these deteriorative enzymes

A

LOX (lipoxygenase), polyphenol oxidase (PPO), pectinase

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17
Q

pectinase ___ plant tissues

A

softens

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18
Q

blanching is referred to as :

A

hot break process

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19
Q

loss of nutrients during blanching is mainly due to;

A

leaching (loss of ascorbic), thermal destruction, oxidation

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20
Q

what is observed as indicator of severity of blanching?

A

loss of ascorbic acid

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21
Q

A heat treatment which kills part of the microbial population present in food

A

pasteurization

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22
Q

target pathogens in pasteurization in milk?

A

tuberculosis (old), coxiella burnetti (new)

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23
Q

What are the two processes in pasteurization?

A

LTH, HTST

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24
Q

LTH is at __ degrees for ___ minutes; HTST is at ___ degrees for ___ seconds

A

63; 30; 72; 15

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25
Q

Is LTH or HTST more detrimental to nutritional/sensory properties?

A

LTH

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26
Q

2 processes in pasteurization?

A

batch (small), continuous (large)

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27
Q

equipment used in continuous process?

A

PHE (plate heat exchanger)–>high production rate, no overheating

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28
Q

why is PHE corrugated?

A

for more surface area–>more points of contact

29
Q

foods that are pasteurized?

A

milk, beer, juices, eggs

30
Q

process used in canning, retorting, and ultra high temp processing

A

sterilization (appertization)

31
Q

how is sterilization diff from pasteurization?

A

much higher temp used in sterilization

32
Q

4 types of microorg destruction processes?

A

sanitation, pasteurization, commercial sterilization, sterilization

33
Q

how is sterilization diff from commercial sterilization?

A

sterilization means no living orgs present–>only possible with autoclaving; commercial uses heat sufficient destroy all microorg able grow under conditions of storage

34
Q

low acid food is pH ___, acid is ____, high acid is ___

A

> 4.5; 3.7-4.5;

35
Q

most severe process is needed for canning ____ acid foods; need to process at ____ degrees C for ___ min.

A

low; 121; 15

36
Q

how to get water boil at 121 degrees instead of 100?

A

high pressure boiling

37
Q

food processing industry uses ____ chamber to create temp >100 degrees inside cans for low acid foods

A

retort

38
Q

examples of acid foods?

A

fruit jams, fruit cocktail, tomatoes, peaches, veg juice

39
Q

primary target when canning acid foods?

A

facultative anaerobes (bacillus sp.)

40
Q

temp for canning acid foods?

A

100 degrees C

41
Q

examples of high acid foods?

A

apple juice, cider, berries, citric juices, picles, sauerkraut

42
Q

targets for high acid foods?

A

yeasts, molds

43
Q

for high acid foods, can ____ containers at ___ degrees C

A

hot fill; 90

44
Q

milk sterilized this way is a shelf-stable product that needs no fridge

A

UHT (140 degrees C for 2 seconds)

45
Q

UHT products are ____ packaged

A

aseptically

46
Q

severity of thermal process required to produce commercial sterility depends on:

A

nature/heat resistance of microbes, initial microbe load, nature of food, heat transfer characteristics of food/container, conditions of storage, characteristic of canning equipment

47
Q

what is conductivity?

A

conduction through can wall and solid foods

48
Q

what is specific heat?

A

convection through liquid foods

49
Q

cold point in conduction is ___, convection is ___

A

centre; below centre

50
Q

units used in thermal conductivity

A

Watt/m/K

51
Q

most foods have conductivity ____

A
52
Q

copper has ___ conductivity, glass has ___ conductivity

A

high; low

53
Q

Units used in specific heat capacity (Cp)

A

J/kg/K

54
Q

If heat food containing oil and water (like milk), which part of food will be more hot?

A

oil

55
Q

survivor curve of microbes becomes ____ with time

A

asymptotic

56
Q

time needed to achieve 90% kill at given temp

A

D value (decimal reduction time)

57
Q

Calculation of D value?

A

D= (T1-T2)/logD2-logD1

58
Q

often assume there are _____ microorganisms present

A

10^12

59
Q

temperature increase needed to cause a 1 log reduction in D value

A

Z value

60
Q

number of min required kill known population of specific microorganism in given food under specific condition

A

F value

61
Q

how to calculate F value?

A

=D value * (log starting pop-log ending pop)

62
Q

factors affecting D value before processing?

A

types of microorg, growth temp, medium and phase

63
Q

factors affect D val during processing?

A

type of food, pH, water activity, salt [ ], [ ] of microorg, rate of heating

64
Q

factors affect D val after processing?

A

recovery medium, temp, presence of O2, background microflora

65
Q

where does cooked flavour come from?

A

reaction of S from amino acid “cysteine”

66
Q

which is more heat resistant: bacteria or vitamins?

A

vitamins

67
Q

4 thermal process techniques?

A

batch process, continuous process, indirect heating, direct heating

68
Q

example of indirect heating?

A

can, pouch, pot on stove

69
Q

example of direct heating?

A

steam injection in UHT

food science 210 (23 decks)

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