Flashcards in UNIT 1 Deck (43)
What is a food matrix
complex nonhomogenous mixtures of many chemical substances, natural & synthetic
True/false: only processed foods are complex food matrices
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:
process induced contaminants
food contact material residues
The component of interest to be analyzed is called the _____
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 ____
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
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:
(hydrophobic and lipophobic)
What does 'polarity' refer to?
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
When a chemical is hydrophobic, Kow will be (low/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?
A chemical with log Kow = 5.66 is (hydrophobic/hydrophilic)
caffeine should have a (high/low) log Kow
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)
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)
Direct Analysis in Real Time (DART) MS
Advantages of rapid analysis techniques:
no sample prep
can be done in-process
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
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?
Partitioning, also known as _____, describes what process?
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:
1. 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)
(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
examples of equilibrium driven separation techniques:
examples of kinetic driven separation techniques: