Lecture 15 - Minor Components Flashcards
what are minor components of food?
- nutraceuticals
- pigments
what’s nutraceutical?
product isolated or purified from foods generally sold in medicinal forms not usually associated with food. also shows physiological benefit against chronic disease.
name some nutraceuticals
- resveratrol
- curcumin
- Epigallocatechin gallate (EGCG)
- Epicatechin gallate (ECG)
- Epigallocatechin (EGC)
- phenolic compounds
what are phenolic compounds?
consist of an aromatic ring linked to one or more hydroxyl groups. includes functional derivatives (esters, methyl esters, glycosides, etc)
how many phenolics are there out there?
over 8000, and counting
into what classes can phenolic compounds be classified?
1) phenolic acids
2) flavonoids
3) tannins
4) stilbenes & lignans
name some phenolic acids in foods
hydroxycinnamic acids - p-coumaric - caffeic - ferulic - sinapic hydroxybenzoic acids - gallic - protocatechuic
what effect do phenolic compounds have?
positive: - free radical scavengers (anti aging) - reduce risk of coronary heart disease - reduce some cancer types - color - lipid retention negative - undesired changes in color (enzymatic browning) - protein and CHO binding, reducing digestibility
what kinds of methods can we use to determine phenols?
- spectrophotometric
- chromatographic
- Near Infrared
- Mass Spec
what spectrophotometric method is used for phenolic determination?
Folin-Ciocalteu assay
describe the Folin-Ciocalteu assay
based on the chemical reduction of the FC reagent by phenolic compounds, making a blue complex.
measure at 765 nm
what are the steps used in the Folin-Ciocalteu assay?
- gallic acid calibration standard
- FC reagent (phosphomolybdic/phosphotungstic acid)
- sodium carbonate
what kinds of chromatographic methods are there for phenolic determination?
- HPLC
- HSCCC (high counter current chromatography)
- SFC (supercritical fluid chromatography)
- PC
- TLC
true or false: you have to extract phenolic compounds before using chromatographic techniques
true
what is HSCCC?
high counter current chromatography
separation between 2 liquid phases by use of centrifugal or counter current during mixing of 2 liquid phases
what methods of extracting phenolics are there?
- liquid liquid extraction
- solid-liquid extraction (leaching)
- supercritical fluid extraction
describe liquid liquid extraction
- mass transfer operation
- liquid solution initially containing one or more solutes is thoroughly mixed w/immiscible liquid
- solvent exhibits preferential affinity toward one or more the components
- solvent containing the compound of interest is separated w/separating funnel
describe solid-liquid extraction
- mass transport
- compound contained in a solid matrix migrate into solvent
what can enhance the mass transport phenomena during solid-liquid extraction?
- changes in concentration gradients
- diffusion coefficients
- boundary layer
what can solid-liquid extraction be used for?
recover food components
- sucrose in cane or beets
- lipids from oil seeds
- proteins in oilseed meals
- polyphenolic compounds from plants, fruits and veggies
describe supercritical fluid extraction
close to its critical point, a solvent changes its properties rapidly with only slight variation in pressure
what is the most utilized fluid for SFE?
supercritical carbon dioxide
why do we analyze for pigments in food?
- color impacts first impressions of food
- quality indicator
- safety indicator
what are some reasons colors are added to food? (4)
- replace lost color
- enhance color already present
- minimize batch-to-batch variations
- color otherwise uncolored foods
food colors are divided into what 4 categories
1) natural colors
2) nature-identical colors
3) synthetic colors
4) inorganic colors
give examples of natural pigments
- anthocyanins
- carotenoids
- chlorophyll
how can you analyze for anthocyanins?
anthocyanins are polar, so you can extract the using polar solvents (alcohols, acetone, dimethyl sulfoxide, and water)
choice of extraction method should maximize _____ _____ with a minimal amount of ______. method should also minimize _____ or alteration of natural state
maximize pigment recovery
minimal amount of adjuncts
degradation
describe the analysis of anthocyanins
acetone extraction and chloroform partition of anthocyanins
- acetone extracts anthocyanins
- chloroform partitioning further isolates and partially purifies
- adding chloroform results in phase separation
- aq = anthocyanin, phenolics, sugars, organic acids, others
- bulk phase = immiscible organic solvents, lipids, carotenoids, chlorophyll pigments, and others)
give the steps of extracting anthocyanins
1) mix powdered plant material w/acetone
2) filter to separate anthocyanin extract and insoluble plant material
3) re extract plant material with acetone until clear/faintly colored solution is obtained
4) add chloroform in separatory funnel
5) store for a while until clear partition is obtained
6) purify using column chromatography
what kind of columns can are used to purify anthocyanin samples?
- water and HCl (separates sugars/acids)
- ethyl acetate (separates phenolics)
- methanol (elutes the anthocyanins)
what method can be used to analyze for anthocyanins?
3-measure step: 1-UV-Vis Spectroscopy
based on structural transformation of anthocyanin chromophore as a function of pH, measured w/optical spec
what is the 1-UV-Vis spectroscopy method also known as?
ph-differential method
is the pH-differential method fast?
yep
anthocyanins undergo (reversible/irreversible) structural transformation with change in pH
reversible
colored oxonium form predominates at pH ___
1.0
colorless hemiketal form predominates at pH ____
4.5
