College aantekeningen
FREE Notes Food Chemistry - Knowledge clips Phenolics
- Instelling
- Wageningen University (WUR)
Free document that contains notes about the knowledge clips about Phenolics.
[Meer zien]Voorbeeld 2 van de 9 pagina's
Voorbeeld 2 van de 9 pagina's
In winkelwagengesponsord bericht van onze partner
Voorbeeld van de inhoud
Knowledge clips - Phenolic compoundsIntroduction
Functions
o Provide colour
o Can cause browning reactions (brown banana)
o Complex with saliva proteins (astringency)
o Give special taste when heated
o Anti-oxidative properties
Basic skeleton
o Benzene ring (C6) and hydroxyl group (OH)
o Can be multiple OH groups.
o Can by aliphatic C-chains attached
o Can be more than 1 benzene group
Other names: polyphenols or phenolics
Examples
o Caffeic acid: benzene ring with two OH groups and aliphatic chain
o Anthocyanidin: two benzene rings that are linked
o Lignin: a lot of benzene rings
Abundance
o Minor quantities are present in food: 1-2% of dry basis
o Exceptions: coffee, cocoa, tea
Classification
o Monomeric phenolic compounds: only one benzene group =
hydroxybenzoic acids (phenolic acid), hydroxycinnamic acid
o Dimeric phenolic compounds: two benzene rings = stilbenes,
flavonoids, lignans
o Oligo/polymeric: more than 2 benzene rings = lignins, condensed
tannins, hydrolysable tannins.
Can be present free or bound. Cranberry contains a lot of phenolics. A lot of
them are free, so not bound. Corn, wheat, oat and rice have more bound
phenolics.
Most of phenolics intake is by fruit, non-alcoholic beverages and vegetables
Mainly flavonoids, hydroxy cinnamic acids, proanthocyanidins (tannins) are
consumed.
Apple, egg, nut, wheat, meat: phenolic compounds are present in plant food,
not in meat and egg!
No free OH group = no phenolic compound. Tyrosine amino acid is actually
also a phenolic compound based on its structure.
Mono- and dimeric phenolic compounds
Monomeric: hydroxycinnamic acids
o Benzene ring and unsaturated aliphatic chain and one or two OH
(caffeic or coumaric acid)
o Can also be esterified with methyl
o Benzene ring contains double bonds! Normal C6 ring not.
o Present as free molecules (apples), as ester in mono-oligosaccharides.
Bound to sugar unit or wheat arabinoxylans.
, o Binds to metal ions. Complex if formed, stable complex. Cook potatoes
after harvesting: no change in colour. After harvesting, iron in potato is
bound to citric acid (anionic form of citrate) = colourless complex.
Upon storage: there is no citrate left because it is all metabolised. Iron
complexes with the chlorogenate to form a black complex cooking
darkening. Iron-chlorogenate complexes.
o Substrate for enzymatic oxidation. Polyphenol oxidase. Oxidises the OH
groups present in the phenolic compound into a quinone moiety.
Because of the oxidation, the molecule polymerizes into brown
pigments.
Dimeric: flavonoids
o C6 (benzene ring), C3 (aliphatic chain), C6 structure (benzene ring)
o C3 can form a C-ring (pyran-C-ring) which is oxidized in between the
benzene rings. Now you have a structure of 3 rings: two benzene rings
interlinked with a C-ring.
o A and B ring are benzene rings and C ring is from the aliphatic chains.
o Subclasses
Flavonols
Flavones
Anthocyanidins
Flavanols
Flavanones
All subclasses differ in substitution and oxidation level of C ring.
Double bond or OH or ketone group present…
o Occur free or bound to sugars.
o Occur in many plants (protect against UV, give colour so insects are
attracted)
o Act as an antioxidant, give colour to food, substrate to enzymatic
oxidation.
o Free form: aglycon, not very water soluble. Mainly flavonols (catechins)
o Bound form: glycosylated, you add polar groups (sugar) so increased
solubility. For instance flavonols, flavones, anthocyanidins and flavanols
o Nomenclature.
No sugar present: anthocyanidin!
When saccharide is added: anthocyanin! Bigger molecule =
shorter name
Glycoside: two sugar units attached
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper bsc_msc_food_technology. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €0,00. Je zit daarna nergens aan vast.
Is Stuvia te vertrouwen?
4,6 sterren op Google & Trustpilot (+1000 reviews)
Afgelopen 30 dagen zijn er 48298 samenvattingen verkocht
Opgericht in 2010, al 15 jaar dé plek om samenvattingen te kopen