phenolic compounds 1
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how do phenolics influence the properties of food products?
• colour and appearance • food flavour (taste + adour) • enhance stability and shelf-life (antioxidant + antimicrobial effect)
what produces phenolic compounds
plants
name some foods that are high in phenolics
black tea, dark chocolate, filter coffee, dried oregano, red wine, blue berries
definition of phenolic compounds
a molecule that contains at least one aromatic ring with one or more hydroxyl-groups
important parameters of PC are? (Give 3)
• polarity • reactivity (oxidation + antioxidant activity) • size of conjugated system (sequence of alternating double and single bonds)
What is the rule of thumb for having a colour in your conjugated system?
a conjugated system less than 8 conjugated double bonds is colorless
what is glycosylation? And what is the effect of glycosylation of a phenol on molecular properties?
substitution of the aromatic ring with a saccharide. It will increase polarity of the phenol, and decrease reactivity
what is carboxylation? And what is the effect of glycosylation of a phenol on molecular properties?
substitution with a carboxylic acid group (-COOH). It will increase polarity, and it will lower the pKa with will enable the modification (change of the molecule)
True or false: a phenoxy-radical that is stabilized by renosance is less reactive
True
what is metal chelation? And what is the result of metal chelation?
The binding of metals by phenolics. Bound metal ions are less likely to participate in redox reactions
what enzyme contributes to oxidation (enzymatic oxidation is usually faster than autooxidation)
Polyphenoloxidases (PPOs)
why does in plant tissue enzymatic oxidation by PPOs not take place?
because phenolic compounds and PPOs are not in contact with each other, they are present in different compartments
what are the factors influencing the formation of o-quinones?
• overall PPO activity varies between sources • characteristics and properties of the specific PPO • structure of the phenolic compound conditions in the food process, ingredient or product
what is the catecholase activity?
the conversion of o-dipehnols to o-quinones
what is the cresolase activity?
the conversion from monophenols to o-dipehnols