Lecture 1: Introduction Flashcards Preview

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Flashcards in Lecture 1: Introduction Deck (56)
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1
Q

What is the primary objective of food processing?

A

preservation

2
Q

What are two main objectives of preservation?

A
  1. prevent undesirable changes (maintain wholesomeness, nutritive value, sensory qualities)
  2. control activities (chemical, biochemical, physiological, microbiological)
3
Q

What are other objectives of food processing besides preservation?

A
  1. product diversification
  2. value addition
  3. convenience foods
  4. marketing needs
  5. ingredients isolation and synthesis
  6. non-conventional foods
4
Q

what are fundamental unit operations of intermediate moisture foods?

A
heating
cooling
drying
mixing
blending
5
Q

what is considered primary processing?

and secondary processing?

A

primary: harvest/slaughter and post harvest processing
secondary: maufacturing of processing food products

6
Q

what technologies are involved in primary processing and secondary processing?

A

primary: post harvest storage technology and handling
secondary: food processing technologies

7
Q

what are food processing methods that use addition of heat?

A

pasteurization and sterilization

8
Q

what are food processing methods that use removal of heat

A

refridgeration and freezing

9
Q

what are food processing methods that use high pressure and pulse electric field

A

non thermal technologies

10
Q

what are food processing methods that use radiation and heat?

A

IR
MW
RF

11
Q

what are food processing methods that use radiation without heat generation?

A

UV

irradiation

12
Q

what are food processing methods that use control of environment

A

CA/MA storage and packaging (controls respiration rate to extend shelf life)

13
Q

what are food processing methods that use removal of liquid water

A

evaporation
concentration
membrane

14
Q

what are food processing methods that use concentration by extraction

A

SCFE: super critical fluid extraction

15
Q

describe SCFE

A

uses CO2 to bring food into a super critical state, where it will act like a liquid which is more powerful than gas in heat processing

16
Q

what are food processing methods that use separation of constituents?

A

extraction

17
Q

what are food processing methods that use composition control

A

dissolved oxygen
fermentation
salting
smoking

18
Q

what are food processing methods that use preparation

A

washing
grinding
mixing

19
Q

what are the 3 most widely used commercial processes of food preservation?

A
  1. thermal processing
  2. freezing
  3. dehydration
20
Q

what are fundamental dimensions?

A

dimensions used to characterize a physical quantity under consideration

21
Q

what are the two types of fundamental dimensions?

A
  1. absolute: mass, length, time, temp

2. gravitational systems: mass, length, time, temp, force

22
Q

what is a unit used to determine?

A

magnitude or size of a dimension

23
Q

what are 2 types of units?

A
  1. base units: dimensionally independent and used for one dimension (eg. mass and time)
  2. derived units: used for combinations of various dimensions (eg. velocity and flow rate)
24
Q

what is the metric system designated with?

A

c g s system

25
Q
what are the metric units for:
length
mass
time
temperature
force
A
length = cm
mass = g
time = s
temp = celcius or kelvin
force = dyne
26
Q

what are the british units?

A

lb, ft, hr, farenheit, poundal

used in US

27
Q

what is the MKS system

A

derived from the CGS system

28
Q

what does SI stand for? What is it?

A

system international

a revised version of MKS system

m, kg, s, celcius or kelvin, newton

29
Q

what are the units of force in metric and in SI?

A

metric: dyne
SI: newton

30
Q

what is the conversion of Fdegrees to C degrees?

A

C deg = (F-32) x 5/9

31
Q

what is the conversion of C to Kelvin?

A

K = C + 273

32
Q

what is the conversion of F to R?

A

R = F + 460

33
Q

100C is ____ F?

A

180

34
Q

what are the units of density?

A

M/L^3 or kg/m^3

35
Q

what is the equation of work (energy)?

what unit is work in?

A

F x distance

unit: joule

36
Q

what is one joule?

A

work done by 1N force resulting in a displacement of 1m

or one joule required to raise the temperature of 1kg of water by 1degC

37
Q

equation of potential and kinetic energy?

A

potential: mgh
kinetic: M*v^2 / 2

38
Q

what is sensible heat?

A

Qs = energy that results in a change in temperature

Q = mCp (T2-T1)

39
Q

what is latent heat

A

energy that results in a change of state at constant temp

Q = m * lambda

40
Q

what is the latent heat of ice?

A

heat required to melt 1kg of ice or freeze 1kg of water at 0degC

41
Q

what is the latent heat of steam?

A

heat required to boil 1kg of water or condense 1kg of steam at 100degC

42
Q

what is heat capacity?

A

Cp = heat required to change the temperature of au nit mass by a unit of temperature difference

Q = m * Cp * delta t

43
Q

what is the unit of heat capacity?

A

Kg/Kg - C
BTU/lb - F
cal/g - C

44
Q

what is specific heat?

what is the unit?

A

ratio of heat capacity of the substance to that of water

no unit because it is a ratio

45
Q

what is power? what are the units?

A

P = rate of producing energy

units: J/s or W or BTU/h

46
Q

what is thermal conductivity (k)?

what are the units?

what is the equation?

A

quantity of heat a given material of unit area of cross section can transfer under a unit temperature gradient in the direction of heat flow

units:
W/mC
BTU/hr
ftF
cal/s
cm*C

Q = (kAdelta t)/x

47
Q

what is the heat transfer coefficient of convection heat transfer?

what are the units?

what is the equation?

A

the quantity of heat transferred across an unit surface area to a fluid when a unit temperature gradient exists between the surface and the fluid

unit: Q/m^2 * C
equation: Q = h * A * delta t

48
Q

a higher heat transfer coefficient means a ____ heat transfer

(better or worse?)

A

better

49
Q

what is thermal diffusivity?

what does it describe?

A

ratio of the thermal conductivity divided by the specific heat and the density

it describes the ability of a material to respond to changes in temperature

50
Q

what is the equation of thermal diffusivity?

what is this the ratio of?

A

alpha = k / p * Cp

ratio of heat conducted to heat absorbed

51
Q

what is absolute pressure?

equation and units?

A

force per unit area

P = F/A

units: N/m^2 or Pa (pascal) or psia

52
Q

what is gauge pressure?

equation and units?

A

apparent pressure above the atmospheric pressure (aka the difference between absolute and atm pressure)

units: Pa(g) or psig
equation: gauge pressure = absolute pressure - atmospheric pressure

53
Q

what is vacuum pressure

A

the pressure below the atmospheric pressure and measured on a vacuum gauge

vacuum = atmospheric pressure - absolute pressure

54
Q

how much is atmospheric pressure usually?

A

101.3kPa or 760 mmHg

55
Q

what’s the difference with precision and accuracy?

A

accuracy: how close the measured value is to the real value
precision: how reproducible your experimental values are (implies how many significant digits there are)

56
Q

are the zeroes significant in:

  1. 100056
  2. 2.300
  3. 23000
  4. 0.00056
A
  1. yes
  2. yes
  3. yes
  4. no