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FDSC 300 > Lecture 4 - Moisture Analysis > Flashcards

Lecture 4 - Moisture Analysis Flashcards

1
Q

list the 5 main food components used in proximate analysis?

A
  • moisture
  • ash
  • protein
  • fiber
  • fat
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2
Q

how do you measure carbohydrate?

A

100-everything else

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3
Q

draw the proximate analysis tree

A

ok

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4
Q

what does water contribute to a food matrix?

A
  • structure
  • standard of identity
  • cheap filler
  • undesired in dry products
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5
Q

what does dry matter contribute to in a food matrix?

A
  • economic value
  • nutrition
  • easy transport
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6
Q

significance of moisture?

A
  • food safety
  • shelf-life/stability
  • food quality
  • economic consideration
  • govt regulation
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7
Q

what are the 3 common moisture levels in food?

A
  • high moisture
  • intermediate moisture
  • low moisture
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8
Q

what forms of water are there? (4)

A
  • free/bulk
  • capillary/trapped
  • physically bound
  • chemically bound
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9
Q

type of water in food free from any other constituents, surrounded only by other water molecules with the same physicochemical properties as pure water

A

free

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10
Q

type of water held in narrow channels formed by physical barriers by capillary forces; has similar properties to pure water

A
  • capillary/trapped water
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11
Q

type of water that is bound with other molecules; different physicochemical properties than pure water

A
  • physically bound water
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12
Q

type of water that is bound in the form of hydrates; different physicochemical properties than bulk water

A
  • chemically bound water
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13
Q

what types of methods are there for moisture determination?

A
  • drying
  • distillation
  • chemical methods
  • physical methods
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14
Q

describe dry methods of MD

A

remove water in the form of weight; lost weight is taken as the measure of moisture content

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15
Q

list some drying methods

A 
oven
- convection oven
- forced air oven
- microwave oven
- vacuum oven 
freeze, infrared
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16
Q

what happens to the boiling point as the food dries?

A

the BP continuously elevates as solute concentration increases

17
Q

list some relationships between moisture and temperature

A
  • higher temp leads to more moisture loss
  • after 185C decomp of proteins occur
  • CHO releases water at higher temps
  • oxidation of FA could increase weight of sample
18
Q

heating takes place in a chamber (105-110C for 22-24h); moisture remains in chamber

A

convection oven

19
Q

disadvantages of convection oven?

A
  • long time
  • loss of volatile components other than water
  • larger temp gradient
20
Q
  • air circulated by fan
  • T can be higher and time is shorter (135C for 4h)
  • temp differential not greater than 1C
  • no condensation of vapour due to fan
A
  • forced air oven
21
Q

disadvantages of forced air oven?

A
  • possibility of lipid oxidation
22
Q

chamber that has a built in balance to monitor weight as the sample is treated with specified microwave energy and time

A

microwave oven

23
Q

chamber that adjusts pressure surrounding liquid to equal the vapor pressure of the liquid; temp rang (95-102C or 60-70C for high sugar)

A

vacuum oven

24
Q

what are the 3 components of a vacuum oven?

A

vacuum oven, drying agents, vacuum pump

25
Q

list 4 common drying agents for vacuum oven

A
  • anhydrous CaCl2 (safest)
  • anhydrous SO3
  • phosphorus pentoxide P2O5
  • concentrated H2SO4 (most effective)
26
Q

advantages of vacuum oven?

A
  • reduction in lost volatiles
  • less effect on degradation
  • faster
27
Q

factors affecting oven drying methods:

A
  • temp
  • time
  • particle size
28
Q

describe IR drying

A
  • not approved by AOAC
  • IR rays dry sample
  • short drying time (10-25 min)
  • heat of lamp is 1730-2230C
29
Q

describe rapid moisture analyzer tech

A
  • uses halogen or ceramic heater
  • detects moisture levels from 50ppm to 99% using sample weights of 150mg-40mg
  • usual temp 25-275C
  • instrument equipped with digital abalance
30
Q

describe thermogravimetric analysis

A
  • mass continuously measured as heated at controlled rate/CA
  • N used to avoid oxidation and mass gain
  • can use higher temps so can measure decomposition, weight %ash

FDSC 300 (6 decks)

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