what are examples of naturally occurring substances?
water
CHO
peptides
pigments
what are examples of synthetic substances?
functional additives
food colorings
flavorings
what are examples of undesirable chemical substances?
environmental contaminants
process induced contaminants
agrochemical residues
food contact material residues
define analyte
component of a system to be analysed
define matrix
components of the sample other than the analyte
define matrix effect
combined effect of all components of the sample other than the analyte on the measurement of the quantity
define interference
when a specific component is identified to be causing a matrix effect
describe a small molecule
- low molecular wt (below 900Da)
- simple sugars,
AAs, FAs
describe a large molecule
- up to several hundreds of thousands of Da
- proteins, complex CHOs
describe polar compounds
give examples
- soluble in water and protic organic solvents
ex:
- simple sugars
- oligosaccharides
- AAs
- small proteins
describe non-polar compounds
give examples
soluble in non-polar organic solvents (hydrophobic)
ex:
- fats
- phospholipids
- sterol
- liposoluble vitamins
- carotenoids
when the chemical is hydrophobic, Kow will be… (high/low)
high
when the chemical is hydrophillic, Kow will be… (high/low)
low
what is Kow? what is the equation?
octanol-water partition coefficient
Kow = conc (octanol) / conc (H2O)
measure of the difference in solubility between two compounds, which tells you how hydrophobic or hydrophillic the compound is
define solubility of a solute
- analytical composition of a saturated solution
- expressed in terms of the proportion of a designated solute in a designated solvent
what can solubility be expressed as?
concentration molality mole fraction mole ratio etc...
define a non-volatile compound
give examples
- low vapor pressure or high boiling point
- ex: sucrose, NaCl
define a volatile compound
give examples
- high vapor pressure or low boiling point
- ex: essential oils, low molecular wt FAs, flavor compounds
what are some challenges of food analysis?
- complex matrices
- matrix composition may vary among samples (origin and different processes)
- analyses usually need to be performed within a few hours to a few days to maintain sample integrity and respond quickly to the requester
why do analyses usually need to be performed within a few hours/days?
- to maintain sample integrity (microbiological, physical, chemical degradation)
- respond quickly to requester (client’s request, inspection, regulatory compliance)
what are some technologies that allow for direct analysis of food components without sample prep/separation?
- X-ray fluorescence
- infrared spectroscopy and near infrared
- guided microwave spectrometry
- magnetic resonance imaging
is it possible to analyze food without manipulation? how?
yes. Some technologies allow direct analysis of specific food components without sample prep
what is the Bruker handheld XRF food scanner?
- type of portable analyzer that doesn’t require sample prep
some tasks includes:
- salt analysis for iodine
- milk analysis
- nutrient verification
- etc…
what are advantages of direct analysis?
- no sample prep = overall shorter analysis time
- avoidance of cross-contamination
- large potential for automation
- less hazardous chemicals
- less chemical wastes
- no specific chemical facilities
overall: direct analysis = less manpower, consumables or facilities
