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161 > Lab 1 > Flashcards

Lab 1 Flashcards

0
Q

Quantifies nutritive value

A

Food composition analysis

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1
Q

Determine levels of diff. Nutrients in food

A

Food Composition analysis

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2
Q

Role of food composition analysis in assessment and maintenance of food quality

A

Detects gross adulteration

Check if processed food are produced within limits prescribed manufacturing standards, legal specifications, etc

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3
Q

Food composition analysis studies additives and contaminants?

A

True

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4
Q

Proximate vs. Ultimate food composition analysis

A

Proximate - main: moisture, CFP, ash

Ultimate - particular: iron calcium niacin ascorbic acid

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5
Q

Physical FCA method (1)

A

Drying

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6
Q

Chemical FCA methods (6)

A

Extraction, colorimetry, fluorimetry, chromatography, titration, atomic absorption

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7
Q

Instrumental FCA methods (4)

A

Electric resistance
Nuclear magnetic resonance
Near infrared reflectance
Microwaves

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8
Q

Measures physical or physiochemical principles in FCA

A

Instrumental methods

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9
Q

Four types of FCA methods

A

Physical
Chemical
Instrumental
Biological assay using microorganisms or animals

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10
Q

Factors that affect value in chemical FCA (3)

A

How well prepared the sample is
How representative of the lot or batch
Kind of chemical info needed

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11
Q

How to homogenize liquids and pulverized

A

Pour from one container to another

Stirring

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12
Q

How to homogenize wet animal and plant tissue

A

Chopping or blending

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13
Q

How to homogenize fats and oils

A

Warming and mixing

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14
Q

How to homogenize cheese and chocolate

A

Grating and hand mixing

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15
Q

How to homogenize butter and margarine

A

Reemulsify by shaking after melting at 35c

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16
Q

How to homogenize dry food

A

Use grinder or mortar and pestle, mix wit spoon

Do rapidly to reduce moisture loss

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17
Q

Temperature of storage until FCA

A

20C

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18
Q

Most abundant and always present component of food

A

Moisture

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19
Q

Three types of water and explain

A

Bound - chemically bonded (crystallization or Hydrates)
Adsorbed - physically bound as surface monolayer
Free - separate, easily lost by evaporation

20
Q

Four methods of moisture deteremination

A

Drying/ oven/ indirect distillation
Immiscible solvent distillation
Chemical
Instrumental

21
Q

Measures weight lost from FS due to evaporation in thermostatically controlled oven, not always true measure

A

Oven method

22
Q

May be lost at drying temperature

A

Volatile oils

23
Q

Factors that influence the oven method (4)

A

Particle size
Sample weight
Type of dish
Oven temp variation

24
Q

Higher rate if drying seen in _____

A

Ovens mechanically ventilated by internal fan

25
Q

Alternative method for drying food with appreciable amount of sugar

A

Dried with vacuum oven at 70C

Decompose at 100C

26
Q

Alternative oven method for heat sensitive food

A

Vacuum desiccator with h2so4

27
Q

Method for food that contains volatile compounds other than water

A

Immiscible solvent distillation method

28
Q

immiscible solvents used for distillation

A

toluene, heptane, xylene

29
Q

low results common with which method of moisture analysis

A

immiscible solvent method

30
Q

based on nonstoichiometric rxn of water and iodine and sulfur dioxide in pyridine methanol solution

A

Karl Fischer titration method

31
Q

best for moisture determination in low moisture food such as chocolate, sugar, molasses

A

chemical or Karl Fischer method

32
Q

method that considers physical or physiochemical principles in moisture analysis

A

instrumental methods

33
Q

method used for rapid results with large samples in moisture determination

A

instrumental method

34
Q

desiccator contents

A

phosphorus pentoxide, calcium chloride, silica gel

35
Q

apparatus used for immiscible distillation

A

Liebig condenser in reflux position

with Bidwell and Sterling receiver

36
Q

chemical methods in protein determination (4)

A

Kjeldahl procedure
formal titration
colorimetric methods using biuret rxn
sulfonated acid dye rxn

37
Q

physical methods in protein determination (3)

A

neutron and proton activation analysis

infrared methods

38
Q

how to methods in protein analysis work

A

based on presence of functional groups in protein molecule: amino group, peptide bond, amino acids: asparagines and glutamine

40
Q

Winkler modification has three stages:

A

digestion with acid
distillation to release ammonia
titration with sulfuric acid

41
Q

Used to calibrate physical and auto methods in protein determination

A

Kjeldahl procedure for determining amt or organic nitrogen

42
Q

chemical formula for digestion in acid in winkler modification

A

organic compound + H2SO4 –> CO2 + H2O + (NH4)2 SO4 + SO2

43
Q

reduces nitrogen to NH3

A

SO2

44
Q

NH3 + H2SO4

A

ammonium sulfate (NH4)2 SO4 with a high boiling point

45
Q

catalysts in digestion with acid stage in winkler

A

copper, mercury, selenium

46
Q

reduces time to digest protein

A

potassium or sodium sulfate

47
Q

alkali used to liberate NH3

A

NaOH

48
Q

weak acid used to trap NH3

A

boric acid

49
Q

ammonium borate

A

NH4B4O7, 3H2O

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