Food Analysis Flashcards
Which type of HPLC analysis involves the use of a polar stationary phase and a non-polar mobile phase?
Normal phase HPLC
What types of carrier gases are used to carry samples in a gas chromatograph?
Helium and Nitrogen
What test is used to detect adulteration of milk with water?
Freezing point analysis
What symbol is used to express the O/R potential of a system?
The symbol Eh
What statistic is equal to the square root of the sample variance?
Standard deviation
What property is the Westphal balance used to measure?
Specific gravity
What property does a piezometer measure?
Pressure
What phenomenon occurs when a compound absorbs light and then immediately re-emits energy as light of a longer wavelength?
Fluourescence
What law describes the relationship between absorbance and concentration?
Beer’s law
What is the unit of expression of transmittance in spectrophotometry?
%T
What is the standard method for determining total nitrogen in food?
Kjeldahl Nitrogen Determination
What is the specific gravity of sulfuric acid used in the Babcock Test for milk?
1.82-1.83
What is the scale to measure percent sugar?
Brix
What is the principle of Atomic Absorption Spectroscopy?
Determination of elements based on absorption of radiation by the free atoms
What is the official method for determining sulfites in foods?
Modified Monier-Williams Procedure
What is the most commonly used test for the detection of improperly pasteurized milk?
Alkaline Phosphatase test
What is the most accurate and sensitive method for quantitative determination of metals and metalloids?
Atomic Absorption Spectroscopy
What is the Michaelis Menten equation?
Vo = Vmax[S] / Km + [S]
What is the Henderson Hasselbach equation?
pH=pKa + log [base]/[acid]
What is the denominator of a t-test?
Standard error of the mean
What is the common term used to describe -log(H+)?
pH
What is provitamin A?
β-carotene
What is an Operating Characteristic or OC curve?
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).
What is a type II error?
Falsely accepting a null hypotheses
What is a Mojonnier test used for?
Percentage milk fat
What instrument is used to determine Brix?
Hydrometer or refractometer
What instrument is used for measuring optical activity of compounds?
Polarimeter - Dextrorotatory (+), Levorotatory (-)
What does the Schaal Oven test measure?
Susceptibility of fat to undergo lipid oxidation
What does the phenol sulfuric acid assay measure?
Reducing sugars
What does the ninhydrin assay measure?
primary amines; amino acids
What does the Karl Fisher test measure?
Water concentration
What does the Fiske-Subbarow assay measure?
Phosphate
What does AOAC stand for?
Association of Official Analytical Chemists
What does ANOVA stand for?
Analysis of Variance
What color is produced by the addition of iodine to amylose?
Blue
What color is produced by the addition of iodine to amylopectin?
Red-violet
What color is phenolphathalein under acidic conditions?
Colorless
What can the Peroxide Value tell you about your product?
Extent of lipid oxidation
What AOAC method is used to measure Vitamin C in juices?
Dichloroindophenol titration method
The thiobarbituric acid (TBA) test measure what secondary product of lipid oxidation?
Malonaldehyde
The term used to describe the relative masses of equal volumes of a material being measured and water at a stated temperature is what?
Specific gravity - the ratio of the density of a food (or other substance) to that of water
The number of grams of Iodine absorbed by a 100 gram sample of fat is called what? What does this measure?
Iodine Value; unsaturation
The extensigraph, mixograph, and farinograph are empirical rheological devices most commonly used for assessment of what product?
Dough
The difference between adsorption and desorption curves on an isotherm is called what?
Sorption hysteresis
The Carr-Price method determines the content of which vitamin in foods?
Vitamin A
The Bostwick viscometer was invented for use with what types of products?
Ketchup/tomato sauce
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?
Thiochrome
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?
Small-angle neutron scattering (SANS) OR spin echo small-angle neutron scattering (SESANS)
Name a reagent used to determine the amount of reducing sugar present in food:
Benedict’s reagent (reacts with aldolases, but not ketones)
In which type of absorption chromatography are interactions between solute and stationary phase primarily electrostatic in nature?
Ion-exchange chromatography
In the phosphatase test for proper pasteurization of milk, raw milk would appear would appear what color?
Blue
In signal detection theory, what term is defined as the number assigned to the threshold level?
Criterion
In gas chromatography, what are the two phases?
Liquid & gas
How many times more acidic is something with a pH of 2 than a substance with a pH of 5?
1000 times more acidic
How many radians are in 360 degrees?
2 pi (about 6.28)
How is the variance of a data set related to the standard deviation of the data set?
Variance is the square of the standard deviation. s2 = variance, s =standard deviation
How is O-R potential measured?
With a platinum redox electrode attached to a pH meter
For whom is the GAB Model for sorption isotherms named?
Guggenheim, Andersen, and de Boer
For whom is the BET Model for adsorption isotherms named?
Brunauer, Emmett, and Teller
For what part of a proximate analysis is the Soxhlet apparatus used for?
Crude fat determination
Determination of the water or moisture, fat, protein, minerals and carbohydrates in a food sample is known as what?
Proximate analysis
BET and GAB are equations to determine what?
Isotherms
Attributes data is a function of what type of distribution?
Binomial distribution
At what pH does phenolphthalein change color?
8.3 (colorless-red)
An ion-exchange material that binds or removes positive ions is called what?
Cation
A plot of 1/initial velocity vs. 1/[substrate] is called what?
Lineweaver Burk Plot (double reciprocal plot)
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
c. energy available from foods
What is the difference between pH and titratable acidity?
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.
What is a PERT chart and how do food companies use them?
PERT-Program Evaluation Review Technique. Used as an organization tool for food product development.
What does MALDI-TOF stand for? What is it a form of?
Matrix-assisted Laser Desorptions/Ionization Time of Flight; Mass Spectrometry
What are the three main steps of the original Kjeldahl Method for measuring protein content?
Digestion, neutralization/distillation, titration
Name two tests used to track lipid oxidation.
Peroxide value, thiobarbituric acid test, activated oxygen method, GLC, total volatiles, total carbonyls
Name three assays used to measure antioxidant capacity of a food
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)
Name 2 wet methods to determine fat content in milk.
Babcock, Gerber, Mojonnier
Give the equation for Beer’s Law and explain what each variable
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.
Determine the number of carbon, hydrogen and oxygen atoms in a trisaccharide of glucose molecules.
C18 H32 O16 (3 x C6 H12 O6 = C18 H36 O18; C18 H36 O18 - H4 O2 = C18 H32 O16)
Define accuracy and precision
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.
Calculate the milliliters of 20% acid required to neutralize 12 ml of 5% base.
C1V1 = C2V2; 20(X) = 5(12); X = 3 ml
