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Food Science 210 > Thermal Processing > Flashcards

Thermal Processing Flashcards

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
Is LTH or HTST more detrimental to nutritional/sensory properties?
LTH
26
2 processes in pasteurization?
batch (small), continuous (large)
27
equipment used in continuous process?
PHE (plate heat exchanger)-->high production rate, no overheating
28
why is PHE corrugated?
for more surface area-->more points of contact
29
foods that are pasteurized?
milk, beer, juices, eggs
30
process used in canning, retorting, and ultra high temp processing
sterilization (appertization)
31
how is sterilization diff from pasteurization?
much higher temp used in sterilization
32
4 types of microorg destruction processes?
sanitation, pasteurization, commercial sterilization, sterilization
33
how is sterilization diff from commercial sterilization?
sterilization means no living orgs present-->only possible with autoclaving; commercial uses heat sufficient destroy all microorg able grow under conditions of storage
34
low acid food is pH ___, acid is ____, high acid is ___
>4.5; 3.7-4.5;
35
most severe process is needed for canning ____ acid foods; need to process at ____ degrees C for ___ min.
low; 121; 15
36
how to get water boil at 121 degrees instead of 100?
high pressure boiling
37
food processing industry uses ____ chamber to create temp >100 degrees inside cans for low acid foods
retort
38
examples of acid foods?
fruit jams, fruit cocktail, tomatoes, peaches, veg juice
39
primary target when canning acid foods?
facultative anaerobes (bacillus sp.)
40
temp for canning acid foods?
100 degrees C
41
examples of high acid foods?
apple juice, cider, berries, citric juices, picles, sauerkraut
42
targets for high acid foods?
yeasts, molds
43
for high acid foods, can ____ containers at ___ degrees C
hot fill; 90
44
milk sterilized this way is a shelf-stable product that needs no fridge
UHT (140 degrees C for 2 seconds)
45
UHT products are ____ packaged
aseptically
46
severity of thermal process required to produce commercial sterility depends on:
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
what is conductivity?
conduction through can wall and solid foods
48
what is specific heat?
convection through liquid foods
49
cold point in conduction is ___, convection is ___
centre; below centre
50
units used in thermal conductivity
Watt/m/K
51
most foods have conductivity ____
52
copper has ___ conductivity, glass has ___ conductivity
high; low
53
Units used in specific heat capacity (Cp)
J/kg/K
54
If heat food containing oil and water (like milk), which part of food will be more hot?
oil
55
survivor curve of microbes becomes ____ with time
asymptotic
56
time needed to achieve 90% kill at given temp
D value (decimal reduction time)
57
Calculation of D value?
D= (T1-T2)/logD2-logD1
58
often assume there are _____ microorganisms present
10^12
59
temperature increase needed to cause a 1 log reduction in D value
Z value
60
number of min required kill known population of specific microorganism in given food under specific condition
F value
61
how to calculate F value?
=D value * (log starting pop-log ending pop)
62
factors affecting D value before processing?
types of microorg, growth temp, medium and phase
63
factors affect D val during processing?
type of food, pH, water activity, salt [ ], [ ] of microorg, rate of heating
64
factors affect D val after processing?
recovery medium, temp, presence of O2, background microflora
65
where does cooked flavour come from?
reaction of S from amino acid "cysteine"
66
which is more heat resistant: bacteria or vitamins?
vitamins
67
4 thermal process techniques?
batch process, continuous process, indirect heating, direct heating
68
example of indirect heating?
can, pouch, pot on stove
69
example of direct heating?
steam injection in UHT

Food Science 210 (23 decks)

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