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Food Science 210 > Thermal Processing > Flashcards

Flashcards in Thermal Processing Deck (69):
1

types of thermal processing?

cooking, blanching, pasteurization, sterilization

2

most widely applied unit op in food processing?

thermal processing

3

three basic mechs of heat transfer?

conduction, convection, radiation

4

conduction is heating of ___, convection is heating of ___

solids; fluids

5

examples of radiation?

infrared, microwave, dielectric

6

primary objective of cooking?

increase palatability

7

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

150-200; 175-225

8

cooking inactivates ____ factors like ___ in pulses

anti-nutritional factors; lectins

9

___ bioavailability reduced by ___ browning

lysine; Maillard (non enzymatic)

10

these vitamins decrease in bioavailability but not concentration with cooking

vitamin A and D

11

these vits decreases in both [ ] and availability

thiamine, niacin, folate

12

primary purpose of blanching?

inactivate deteriorative enzymes, kill spoilage bacteria

13

blanching usually done on __ foods, prior to ____

solid; freezing/canning

14

blanching reduces ___ by removing tissue gases

volume

15

blanching of fruits before ___ allows surface ___

drying; pasteurization

16

blanching inactivates these deteriorative enzymes

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

17

pectinase ___ plant tissues

softens

18

blanching is referred to as :

hot break process

19

loss of nutrients during blanching is mainly due to;

leaching (loss of ascorbic), thermal destruction, oxidation

20

what is observed as indicator of severity of blanching?

loss of ascorbic acid

21

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

pasteurization

22

target pathogens in pasteurization in milk?

tuberculosis (old), coxiella burnetti (new)

23

What are the two processes in pasteurization?

LTH, HTST

24

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

63; 30; 72; 15

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