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Flashcards in Food Analysis Deck (78)
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1
Q

Which type of HPLC analysis involves the use of a polar stationary phase and a non-polar mobile phase?

A

Normal phase HPLC

2
Q

What types of carrier gases are used to carry samples in a gas chromatograph?

A

Helium and Nitrogen

3
Q

What test is used to detect adulteration of milk with water?

A

Freezing point analysis

4
Q

What symbol is used to express the O/R potential of a system?

A

The symbol Eh

5
Q

What statistic is equal to the square root of the sample variance?

A

Standard deviation

6
Q

What property is the Westphal balance used to measure?

A

Specific gravity

7
Q

What property does a piezometer measure?

A

Pressure

8
Q

What phenomenon occurs when a compound absorbs light and then immediately re-emits energy as light of a longer wavelength?

A

Fluourescence

9
Q

What law describes the relationship between absorbance and concentration?

A

Beer’s law

10
Q

What is the unit of expression of transmittance in spectrophotometry?

A

%T

11
Q

What is the standard method for determining total nitrogen in food?

A

Kjeldahl Nitrogen Determination

12
Q

What is the specific gravity of sulfuric acid used in the Babcock Test for milk?

A

1.82-1.83

13
Q

What is the scale to measure percent sugar?

A

Brix

14
Q

What is the principle of Atomic Absorption Spectroscopy?

A

Determination of elements based on absorption of radiation by the free atoms

15
Q

What is the official method for determining sulfites in foods?

A

Modified Monier-Williams Procedure

16
Q

What is the most commonly used test for the detection of improperly pasteurized milk?

A

Alkaline Phosphatase test

17
Q

What is the most accurate and sensitive method for quantitative determination of metals and metalloids?

A

Atomic Absorption Spectroscopy

18
Q

What is the Michaelis Menten equation?

A

Vo = Vmax[S] / Km + [S]

19
Q

What is the Henderson Hasselbach equation?

A

pH=pKa + log [base]/[acid]

20
Q

What is the denominator of a t-test?

A

Standard error of the mean

21
Q

What is the common term used to describe -log(H+)?

A

pH

22
Q

What is provitamin A?

A

β-carotene

23
Q

What is an Operating Characteristic or OC curve?

A

A plot of the probability of acceptance of a lot of material at various levels of defects in the lot at a given AQL (acceptable quality level).

24
Q

What is a type II error?

A

Falsely accepting a null hypotheses

25
Q

What is a Mojonnier test used for?

A

Percentage milk fat

26
Q

What instrument is used to determine Brix?

A

Hydrometer or refractometer

27
Q

What instrument is used for measuring optical activity of compounds?

A

Polarimeter - Dextrorotatory (+), Levorotatory (-)

28
Q

What does the Schaal Oven test measure?

A

Susceptibility of fat to undergo lipid oxidation

29
Q

What does the phenol sulfuric acid assay measure?

A

Reducing sugars

30
Q

What does the ninhydrin assay measure?

A

primary amines; amino acids

31
Q

What does the Karl Fisher test measure?

A

Water concentration

32
Q

What does the Fiske-Subbarow assay measure?

A

Phosphate

33
Q

What does AOAC stand for?

A

Association of Official Analytical Chemists

34
Q

What does ANOVA stand for?

A

Analysis of Variance

35
Q

What color is produced by the addition of iodine to amylose?

A

Blue

36
Q

What color is produced by the addition of iodine to amylopectin?

A

Red-violet

37
Q

What color is phenolphathalein under acidic conditions?

A

Colorless

38
Q

What can the Peroxide Value tell you about your product?

A

Extent of lipid oxidation

39
Q

What AOAC method is used to measure Vitamin C in juices?

A

Dichloroindophenol titration method

40
Q

The thiobarbituric acid (TBA) test measure what secondary product of lipid oxidation?

A

Malonaldehyde

41
Q

The term used to describe the relative masses of equal volumes of a material being measured and water at a stated temperature is what?

A

Specific gravity - the ratio of the density of a food (or other substance) to that of water

42
Q

The number of grams of Iodine absorbed by a 100 gram sample of fat is called what? What does this measure?

A

Iodine Value; unsaturation

43
Q

The extensigraph, mixograph, and farinograph are empirical rheological devices most commonly used for assessment of what product?

A

Dough

44
Q

The difference between adsorption and desorption curves on an isotherm is called what?

A

Sorption hysteresis

45
Q

The Carr-Price method determines the content of which vitamin in foods?

A

Vitamin A

46
Q

The Bostwick viscometer was invented for use with what types of products?

A

Ketchup/tomato sauce

47
Q

The AOAC method for the determination of thiamin requires the formation of a flourescent compound which is an oxidation product of thiamin. Name the flourescent compound?

A

Thiochrome

48
Q

Neutron scattering is a technique that could be used to study the structure and functionality of molecular food components in real time. What is a common type of elastic neutron scattering?

A

Small-angle neutron scattering (SANS) OR spin echo small-angle neutron scattering (SESANS)

49
Q

Name a reagent used to determine the amount of reducing sugar present in food:

A

Benedict’s reagent (reacts with aldolases, but not ketones)

50
Q

In which type of absorption chromatography are interactions between solute and stationary phase primarily electrostatic in nature?

A

Ion-exchange chromatography

51
Q

In the phosphatase test for proper pasteurization of milk, raw milk would appear would appear what color?

A

Blue

52
Q

In signal detection theory, what term is defined as the number assigned to the threshold level?

A

Criterion

53
Q

In gas chromatography, what are the two phases?

A

Liquid & gas

54
Q

How many times more acidic is something with a pH of 2 than a substance with a pH of 5?

A

1000 times more acidic

55
Q

How many radians are in 360 degrees?

A

2 pi (about 6.28)

56
Q

How is the variance of a data set related to the standard deviation of the data set?

A

Variance is the square of the standard deviation. s2 = variance, s =standard deviation

57
Q

How is O-R potential measured?

A

With a platinum redox electrode attached to a pH meter

58
Q

For whom is the GAB Model for sorption isotherms named?

A

Guggenheim, Andersen, and de Boer

59
Q

For whom is the BET Model for adsorption isotherms named?

A

Brunauer, Emmett, and Teller

60
Q

For what part of a proximate analysis is the Soxhlet apparatus used for?

A

Crude fat determination

61
Q

Determination of the water or moisture, fat, protein, minerals and carbohydrates in a food sample is known as what?

A

Proximate analysis

62
Q

BET and GAB are equations to determine what?

A

Isotherms

63
Q

Attributes data is a function of what type of distribution?

A

Binomial distribution

64
Q

At what pH does phenolphthalein change color?

A

8.3 (colorless-red)

65
Q

An ion-exchange material that binds or removes positive ions is called what?

A

Cation

66
Q

A plot of 1/initial velocity vs. 1/[substrate] is called what?

A

Lineweaver Burk Plot (double reciprocal plot)

67
Q

A bomb calorimeter measures: a. physiological fuel; b. kcalories a person derives from food; c. energy available from foods;d. heat a person releases from basal metabolism

A

c. energy available from foods

68
Q

What is the difference between pH and titratable acidity?

A

Titratable acidity is a measure of the amount of acid present in food; pH is the negative of the base 10 logarithm of the hydronium ion concentration.

69
Q

What is a PERT chart and how do food companies use them?

A

PERT-Program Evaluation Review Technique. Used as an organization tool for food product development.

70
Q

What does MALDI-TOF stand for? What is it a form of?

A

Matrix-assisted Laser Desorptions/Ionization Time of Flight; Mass Spectrometry

71
Q

What are the three main steps of the original Kjeldahl Method for measuring protein content?

A

Digestion, neutralization/distillation, titration

72
Q

Name two tests used to track lipid oxidation.

A

Peroxide value, thiobarbituric acid test, activated oxygen method, GLC, total volatiles, total carbonyls

73
Q

Name three assays used to measure antioxidant capacity of a food

A

ORAC (Oxygen Radical Absorbance Capacity); FRAP (Ferric Reducing Antioxidant Power OR ferric reducing ability of plasma); TEAC (Trolox Equivalent Antioxidant Capacity); TRAP (Total Radical Trapping Parameter); TOSC (Total Oxygen Scavenging Capacity); DMPD (N,N-dimethyl-p-phenylenediamine); DPPH (2,2-diphenyl-1-pierylhydrazyl)

74
Q

Name 2 wet methods to determine fat content in milk.

A

Babcock, Gerber, Mojonnier

75
Q

Give the equation for Beer’s Law and explain what each variable

A

A=εbc; A=absorbance value measured, ε=extinction coefficient (which is the slope of the standard curve), b=path-length (usually 1 cm), c=concentration.

76
Q

Determine the number of carbon, hydrogen and oxygen atoms in a trisaccharide of glucose molecules.

A

C18 H32 O16 (3 x C6 H12 O6 = C18 H36 O18; C18 H36 O18 - H4 O2 = C18 H32 O16)

77
Q

Define accuracy and precision

A

Accuracy refers to how close a particular measure is to the true or correct value. Precision is a measure of how reproducible or how close replicate measurements become.

78
Q

Calculate the milliliters of 20% acid required to neutralize 12 ml of 5% base.

A

C1V1 = C2V2; 20(X) = 5(12); X = 3 ml