UNIT 1 Flashcards
What is a food matrix
complex nonhomogenous mixtures of many chemical substances, natural & synthetic
True/false: only processed foods are complex food matrices
False
What are some naturally occurring chemicals in food?
water, carbs, AA, peptides, lipids, vitamins, flavors, inorganic components…
Examples of synthetic substances in food:
functional additives, food coloring, flavorings
food may be contaminated with undesirable chemical substances such as:
environmental contaminants
process induced contaminants
agrochemical residues
food contact material residues
The component of interest to be analyzed is called the _____
analyte
What is the ‘matrix effect’
combined effect of ALL components in the sample (other than analyte) on measurement of the analyte (interference)
The sample is composed of the analyte contained in the ____
matrix
How are molecules classified according to size?
small: low molecular wt (<900Da) - simple sugars, AA, FA
large: (100000s of Da)
Protein, complex carbs
True/False: hydrophobicity is the same thing as lipophilicity
False:
often used interchangeably, but not exactly the same thing
(hydrophobic - doesn’t like water; lipophilic - likes fat)
Example of compound that is hydrophobic but not lipophilic:
fluorocarbons
hydrophobic and lipophobic
What does ‘polarity’ refer to?
solubility
polar: soluble in water, protic organic solvents (hydrophilic)
nonpolar: soluble in nonpolar organic solvent (hydrophobic)
examples of polar compounds:
simple sugars, oligosaccharides, AA, small protein/peptide, B and C vitamins
examples of nonpolar compounds:
fats, PL, sterols, A, D, E, K vitamins, carotenoids
hydrophobicity of a compound can be expressed as a ______ coefficient
Octanol-Water partition coefficient
Kow
When a chemical is hydrophobic, Kow will be (low/high)
high
How do you calculate Kow?
ratio of concentration in octanol vs concentration in water
in separatory funnel
What are the units of Kow? how is it usually expressed?
no unit
log Kow
A chemical with log Kow = 5.66 is (hydrophobic/hydrophilic)
hydrophobic
caffeine should have a (high/low) log Kow
low
How is the ‘solubility of a solute’ defined?
proportion of solute in designated solvent, when saturated (max amount that can be dissolved)
expressed in concentration, molality, mole fraction, etc
Classifications of compounds according to volatility:
nonvolatile: (low vapor pressure/high boil pt) - sucrose, NaCl
Volatile: (high vapor pressure, low boil pt) - essential oil, low mol. wt FA, flavor compounds…
Challenges of food analysis: (3)
complex matrices
varied compositions among samples
need to be fast (maintain sample integrity, respond quickly to clients)
some technologies that allow rapid analysis, without manipulation: (5)
X ray fluorescence Infrared spectroscopy (FTIR, NIR) Guided Microwave Spectrometry (GMS) MRI Direct Analysis in Real Time (DART) MS
Advantages of rapid analysis techniques:
no sample prep automated convenient rapid can be done in-process nondestructive safer, no hazardous chemicals efficient - less energy/manpower/chemicals
What technology can be used for in-process analysis, and is even starting to be adapted for smartphones?
Near Infrared Technology
What technology can be used for elemental analysis, and what are its advantages?
total reflection xray fluorescence
little to no sample prep
little sample needed (few ug/uL)
What can be analyzed with the portable handheld XRF scanner?
monitor preservative Ca coatings elemental nutrient verification animal feed assessment/risk analysis analyze salt/sodium compounds in salty snacks milk/dairy/powder analysis for Fe and Ca Salt analysis for Iodine
Current limitations of direct analysis:
low sensitivity and selectivity
surface vs bulk composition
not standardized or approved
instrument cost
What is the definition of separation?
separating components of a mixture without modifying them substantially
Carl Wilhelm Scheele was the first to do what?
separate citric acid by crystallizing it from lemon juice
What is partial vs complete separation?
partial: isolate one component of interest, others remain mixed
complete: isolate all different components
Separations can be done based on what physicochemical characteristics?
size/mass
charge
polarity
volatility
Partitioning, also known as _____, describes what process?
distributing
solute is distributed amount phases (reaching equilibrium); certain % in each phase
What is adsorption?
distribution processes occurring between solute and the SURFACE of the phase
What is absorption?
distribution processes occurring between solute and the BULK of the phase
What is equilibrium?
system reaching a state where the properties (activity, concentration, etc) remain unchanged
*driving force for many separations
The 2 types of ‘driving force’ for separations:
- equilibrium (system tries to attain equilibrium)
2. nonequilibrium (kinetic): rate at which solutes migrate provides driving force
Differential centrifugation is what type of separation? (driving force)
kinetic
separation caused by particles moving at different rates due to various density/sizes
In differential centrifugation, the (more/less) dense particles will reach the bottom first
more
examples of equilibrium driven separation techniques:
partition chromatography Extraction distillation precipitation crystallization
examples of kinetic driven separation techniques:
dialysis electrophoresis exclusion chromatography centrifugation filtration sedimentation membrane methods
what are hybrid/hyphenated techniques?
combination of instrumental methods
GC-MS, LC-MS, SPE-HPLC, CE-FTIR…
