Food Analysis Test 1

Front 1

Why is Food Analysis Important?

Back 1

Product development
New process evaluation
Quality assurance
Nutrition labeling
Identifying problems with complaint sample

Front 2

Food Analysis Applications

Back 2

Water Quality
USDA Nutrient Database
Detect small particles

Front 3

Steps in Analysis

Back 3

1. Select representative sample (Ch. 5)
2. Sample preparation (Ch. 5)
3. Perform the assay (entire text)
4. Calculate and interpret results

Front 4

CHOOSING A METHOD

Back 4

Multiple methods available
Compare new method to a standard method
Decision based on
1 Characteristics of the method
2 Objectives of the method
3 Composition of the sample

Front 5

Objective of the measurement

Back 5

Nutrition labeling
Process control samples
Moisture analysis – forced draft oven vs. moisture balance

Front 6

Food matrix = sample chemical composition

Back 6

Food matrix affects the method performance
High fat or high sugar foods can interfere
Digestion procedures and extraction steps often used
Can a single method be used for multiple foods?

Front 7

Method validity

Back 7

Method specificity, precision, accuracy, and sensitivity
Comparison with sensory data
Nature of samples, if they are representative and number of samples analyzed
Appropriate use of standardized equipment
Use of “standard reference materials” or “check samples”

Front 8

Examples of Official Methods

Back 8

AOAC International “Official Methods of Analysis”
American Association of Cereal Chemists (AACC)
American Oil Chemists’ Society (AOCS)
Standard Methods for the Examination of Dairy Products
Standard Methods for the Examination of Water and Wastewater

Front 9

Minerals:

Back 9

elements other than C,H,O, and N present in foods

Front 10

Nutritional value of food

Back 10

Enrichment, fortification increases content
Some processing methods decrease content
Which minerals are required on a Nutrition Facts label?
sodium, iron, calcium

Front 11

Toxicity

Back 11

Lead, mercury, cadmium, aluminum, fluoride, selenium

Front 12

Food quality

Back 12

Affect cloudiness in beverages
Textural properties of fruits and vegetables
Source of off-flavors (i.e. iron in milk)
Hardness of water

Front 13

Mineral analysis preparation
contamination

Back 13

ashing
Glassware
Acid wash
Water/reagents
Use purest reagents available, including water
Use a “reagent blank”

Front 14

reagent blank”

Back 14

Contains reagents but not the sample to be analyzed
Used as baseline
Result is subtracted from actual samples being analyzed

Front 15

Factors that interfere with mineral analyses:

Back 15

pH, sample matrix, temperature, other analytical conditions, and reagents

Front 16

Stop interfering factors of mineral analysis

Back 16

Isolate the sample mineral
Remove interfering minerals
Use a reagent blank
Use a “background matrix solution” to make the standard curve
Use a “spiked” standard curve

Front 17

Methods of Mineral Analysis

Back 17

Titration
Colorimetric Methods
Ion selective electrodes (ISE)
Atomic absorption spectroscopy (AAS) Lab 4
Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) Lab 4

Front 18

EDTA Complexometric Titration

Back 18

complexes are formed between EDTA and many mineral ions
pH dependent

Front 19

Precipitation Titration

Back 19

titration reaction has at least one product that is an insoluble precipitate.
Ag+ + Cl- → AgCl (white precipitate)
Mohr method
Volhard method

Front 20

Chloride Analyzer

Back 20

Titration
Relies on formation of AgCl
Silver ions generated by passing a constant current between donor electrodes
End point is detected by the use of sensing electrodes

Front 21

Colorimetric methods

Back 21

Minerals react with another chemical (a chromogen) to form a colored product
Quantified by absorption of light at a specified wavelength using spectrophotometer
Many methods exist

Front 22

Ion selective electrodes

Back 22

Direct measure of cations
Not affected by sample volume, turbidity, color, and viscosity
Simple (only requires electrodes and a pH meter)
Limit of detection is usually 2-3 ppm
Slow electrode response time at low concentration (below 10-4 M)
Some electrodes have short operating life

Front 23

Normality

Back 23

mequivalents/liter

Front 24

ppm

Back 24

part/wholeX1 million

Front 25

Titratable Acidity

Back 25

Equivalent to normality of the solution
Both ionized H+ and unionized H+; total potential H+.

Front 26

Brix/acid ratio

Back 26

Titratable acidity

Front 27

pKa is

Back 27

the pH where [HA] = [A-]

Front 28

Henderson-Hasselbalch Equation

Back 28

pH=pKa+log (A-/HA-)

Front 29

Standard acid:

Back 29

Potassium acid phthalate (KHP)

Front 30

Standard base:

Back 30

NaOH
Needs to be standardized because NaOH is hygroscopic and can have impurities present.

Front 31

% ACID

Back 31

(Ntitrant)(Vtitrant)(EqWt acid) X 100
---------------------------------------------------
(sample weight)(1000)

Front 32

A buffer is a solution of

Back 32

a weak acid and its salt

Front 33

FDA

Back 33

Food and Drug Administration

Front 34

(FSIS)

Back 34

Food Safety Inspection Service

Front 35

(NIST)

Back 35

National Institute of Standards and Technology

Front 36

(NOAA)

Back 36

National Oceanic and Atmospheric Administration

Front 37

(NMFS)

Back 37

National Marine Fisheries Service

Front 38

(ATF)

Back 38

Bureau of Alcohol, Tobacco, Firearms, and Explosives

Front 39

government regulations for food published

Back 39

Code of Federal Regulations (CFR

Front 40

Why is a standard of identity useful?

Back 40

Prevents adulteration
Makes quality more consistent

Front 41

FDA helps

Back 41

Inspects food processing facilities for compliance with GMP regulations and HACCP programs where required
Enforces nutrition labeling regulations
Enforces standards of identity, quality and fill
Works with other agencies regarding seafood safety (NMFS, EPA), imported products (CPB), interstate dairy industry (USDA
Enforces regulations on pesticide tolerance set by EPA
Responsible for food labeling

Front 42

GMP regulations FDA

Back 42

Goal to prevent adulterated food
Include requirements for acceptable sanitary operation in food plants:

Front 43

Standards of Identity

Back 43

Ingredients and levels contained in a food product

Front 44

Standards of Quality

Back 44

Minimum standards and specifications for some canned fruits and vegetables

Front 45

Standards of Fill

Back 45

How full a container must be to avoid consumer deception

Front 46

Hazard Analysis Critical Control Point

Back 46

HACCP

Front 47

HACCP

Back 47

Hazard Analysis Critical Control Point

Front 48

USDA mandatory inspection

Back 48

Meat and Poultry
Grains

Front 49

EPA

Back 49

Establishes allowable limits for pesticide residues in food
Establishes standards for drinking water safety
Establishes guidelines for effluent from food processing plants

Front 50

International Standards and Policies

Back 50

Codex Alimentarius
ISO Standards
JECFA Standards
Food Chemicals Codex (FCC)

Front 51

Spectroscopy:

Back 51

study of the interaction between electromagnetic radiation and matter

Front 52

light

Back 52

Particles of energy (photons) that move through space with wavelike properties

Front 53

Wavelike nature of light

Back 53

Explains light propagation
interference, diffraction and refraction

Front 54

Particle nature of light

Back 54

Explains interaction of light with matter
Absorption and emission

Front 55

Electronic
States of Matter

Back 55

Electron changing orbitals

Front 56

internal energy of a molecule

Back 56

depends on the electronic, vibrational, and rotational energies
Emolecule = Eelectronic + Evibrational + Erotational

Front 57

internal energy of an atom

Back 57

depends on its electronic energy.
Eatom = Eelectronic

Front 58

Accuracy

Back 58

How close a value is to the true or correct value

Front 59

Precision

Back 59

How reproducible, or how close replicate measurements become.

Front 60

Systematic error

Back 60

Results consistently deviate from the expected value in one direction or the other;
e.g., uncalibrated pipette, impure chemicals

Front 61

Random error

Back 61

Results fluctuate in a random fashion; unavoidable
e.g., judging endpoint in a titration, using a pipette

Front 62

Gross error (blunders)

Back 62

Results are scattered; easy to eliminate
e.g. missed adding reagent to one test tube

Front 63

Sensitivity

Back 63

Indicates how little change can be made in the amount of unknown material before we notice a difference on a readout

Front 64

Detection limit

Back 64

The lowest possible increment that we can detect with some degree of confidence

Front 65

Curve fitting

Back 65

describe the relationship and evaluation between two variables

Front 66

Correlation coefficient (r)

Back 66

Defines how well the data fit to a straight line

Front 67

Sampling

Back 67

Obtaining a portion, or sample from a population
Should be representative of the population

Front 68

Why Sample?

Back 68

Not usually feasible to test entire population
Makes analysis practical
Estimates population (if done properly)

Front 69

Sampling plan

Back 69

predetermined procedure for the selection, withdrawal, preservation, transportation, and preparation of the portions to be removed from a lot as samples

Front 70

Factors affecting the choice of a sampling plan

Back 70

Purpose of the inspection
Nature of the product
Nature of the test method
Nature of the population being investigated

Front 71

Attribute sampling

Back 71

Certain characteristic is present or absent
e.g., C. botulinum

Front 72

Variable sampling

Back 72

Quantitative amount on a continuous scale
e.g., percent fill of a container, or pH of a food sample

Front 73

Single sampling plans

Back 73

Test one sample of specified size
Accept/reject decision

Front 74

Double sampling plans

Back 74

Start with one sample
High or low quality = accept/reject decisions are made after one sample is evaluated
Intermediate quality = a second sample is taken and both samples are used to make the decision

Front 75

Multiple sampling plans

Back 75

Chart developed (see Fig 5-1)
Relates the cumulative number of defects to the number of samples taken from the lot
Sampling continues until the number of defects crosses the acceptance or the rejection line

Front 76

Risks Associated with Sampling

Back 76

Consumer risk

Vendor risk

Front 77

Consumer risk

Back 77

Probability of accepting a poor quality population

Front 78

Vendor risk

Back 78

Probability of rejecting an acceptable product

Front 79

Probability Sampling

Back 79

Statistically Sound
Recommended

Front 80

Nonprobability Sampling

Back 80

Use only with probability method is not feasible

Front 81

Problems in Sampling

Back 81

Sampling bias
Poor sample storage
Mislabeling or nonpermanent marker
Official or legal samples require sealing and chain of custody identified

Front 82

Preparation of Samples

Back 82

Size reduction
Grinding – to reduce size and make homogenous
Enzymatic inactivation
Lipid oxidation protection
Microbial growth and contamination

Front 83

Why measure moisture

Back 83

Affects stability
Determines quality
Concentration of food for shipping and packaging
Ensures food meets Standard of Identity
Necessary for nutritional value calculations
Standardize results

Front 84

to minimize moisture gains or losses

Back 84

Exposure of sample to open atmosphere
Heating (by friction) of sample during grinding
Headspace in sample storage container
Optimize speed of sample weighing

Front 85

Forms of water

Back 85

Free (acts like water)
Adsorbed (held tightly to proteins)
Water of hydration (Na2SO4  10 H2O)

Front 86

Moisture analysis methods

Back 86

oven drying
distillation
Chemical method-Karl Fischer Titration
Physical methods

Front 87

“Pan Handling”

Back 87

Store in desiccator
Only use tongs; fingerprints have weight

Front 88

Sand pan technique (sand or diatomaceous earth)

Back 88

To control surface crust formation and disperse sample

Front 89

% total solids

Back 89

dry sample
-------------- X 100
wet sample

Front 90

Distillation procedures

Back 90

Co-distilling the moisture in a food sample with a high boiling point solvent (usually toluene) that is immiscible in water
spices

Front 91

Karl Fischer Titration

Back 91

Best method for many low moisture foods
Dried fruits and vegetables
Candies, chocolate

Front 92

Karl Fischer Titration
advantages
disadvantages

Back 92

Rapid
Sensitive
Does not use heat

Incomplete water extraction (grinding size important)
Atmospheric moisture can’t be present
Moisture adheres to glass
Interferences from certain food constituents

Front 93

Physical methods

Back 93

Electrical methods
Refractometry
Hydrometry
Infrared Analysis
Freezing Point

Front 94

Electrical methods

Back 94

Dielectric constant is a measure of capacitance (resistance to an electric current)
% moisture is obtained from a standard curve
Conductivity method
Conductivity of an electric current increases with the % moisture in a sample

Front 95

Hydrometry

Back 95

Science of measuring specific gravity or density
Pycnometer-most accurate

Front 96

Refractometer

Back 96

Measures refractive index of a liquid
Based bending of light as it passes from one medium to another medium of different density

Front 97

Infrared Analysis

Back 97

Measure of the absorption of near or mid-infrared radiation by molecules

Front 98

Freezing point

Back 98

Commonly used to determine if milk has had water added to it.

Front 99

Water activity

Back 99

Preferable to moisture content for
Predicting perishability
Determining textural properties

Front 100

Aw=

Back 100

partial pressure water above sample
---------------------------------------------------
vapor pressure of pure water at temp

equilibrium rel humidity around sample/100

Front 101

Ash

Back 101

the inorganic residue remaining after either ignition or complete oxidation of organic matter in a foodstuff.

Front 102

Why measure ash

Back 102

Total mineral content of food
Part of proximate analysis for nutritional evaluation
First step in specific elemental analysis

Front 103

Ash content of food is usually

Back 103

<5%

Front 104

Dry Ashing

Back 104

Muffle furnace at 500-600 C

Front 105

Wet Ashing
(Oxidation)

Back 105

Combinations of nitric acid, sulfuric acid/hydrogen peroxide, and perchloric acid

Front 106

microwave muffle furnaces
Advantage
disadvantage

Back 106

Decreased time for ashing (minutes instead of hours
Limited number of samples can be ashed at one time
Expense of equipment?

Front 107

Dry Ashing
Advantages
Disadvantages

Back 107

Safer than wet ashing
No attention needed once begun
Large numbers can be done at once
No added reagents or blank subtraction

Time (12-18 hr or overnight)
Expensive equipment (relative to wet ashing)
Loss of volatile elements and interaction with crucible (list of minerals lost on p. 106)

Front 108

Wet Ashing
Advantages
Disadvantages

Back 108

Minerals usually stay in solution
Little loss from volatilization because of lower temperature
Short time
Requires constant operator attention
Corrosive reagents
Only small numbers of samples done at one time
Special hood required for perchloric acid, since it’s explosive

Front 109

Name the oranization that sells standard reference or check samples for cereal products

Back 109

American Association of Cereal Chemists
(AACC)

Front 110

Which US government agency provides grading services for a variety of foods?

Back 110

US Department of Agriculture (USDA)