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Food Science 210 > Thermal Processing > Flashcards

Flashcards in Thermal Processing Deck (69)
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1
Q
types of thermal processing?
A
cooking, blanching, pasteurization, sterilization
2
Q
most widely applied unit op in food processing?
A
thermal processing
3
Q
three basic mechs of heat transfer?
A
conduction, convection, radiation
4
Q
conduction is heating of ___, convection is heating of ___
A
solids; fluids
5
Q
examples of radiation?
A
infrared, microwave, dielectric
6
Q
primary objective of cooking?
A
increase palatability
7
Q
baking and roasting happen at _____degrees, frying happen at ____ degrees
A
150-200; 175-225
8
Q
cooking inactivates ____ factors like ___ in pulses
A
anti-nutritional factors; lectins
9
Q
___ bioavailability reduced by ___ browning
A
lysine; Maillard (non enzymatic)
10
Q
these vitamins decrease in bioavailability but not concentration with cooking
A
vitamin A and D
11
Q
these vits decreases in both [ ] and availability
A
thiamine, niacin, folate
12
Q
primary purpose of blanching?
A
inactivate deteriorative enzymes, kill spoilage bacteria
13
Q
blanching usually done on __ foods, prior to ____
A
solid; freezing/canning
14
Q
blanching reduces ___ by removing tissue gases
A
volume
15
Q
blanching of fruits before ___ allows surface ___
A
drying; pasteurization
16
Q
blanching inactivates these deteriorative enzymes
A
LOX (lipoxygenase), polyphenol oxidase (PPO), pectinase
17
Q
pectinase ___ plant tissues
A
softens
18
Q
blanching is referred to as :
A
hot break process
19
Q
loss of nutrients during blanching is mainly due to;
A
leaching (loss of ascorbic), thermal destruction, oxidation
20
Q
what is observed as indicator of severity of blanching?
A
loss of ascorbic acid
21
Q
A heat treatment which kills part of the microbial population present in food
A
pasteurization
22
Q
target pathogens in pasteurization in milk?
A
tuberculosis (old), coxiella burnetti (new)
23
Q
What are the two processes in pasteurization?
A
LTH, HTST
24
Q
LTH is at __ degrees for ___ minutes; HTST is at ___ degrees for ___ seconds
A
63; 30; 72; 15
25
Q
Is LTH or HTST more detrimental to nutritional/sensory properties?
A
LTH
26
Q
2 processes in pasteurization?
A
batch (small), continuous (large)
27
Q
equipment used in continuous process?
A
PHE (plate heat exchanger)-->high production rate, no overheating
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