phenolic compounds 1

Question 1

how do phenolics influence the properties of food products?

Answer 1

1. colour and appearance
2. food flavour (taste + adour)
3. enhance stability and shelf-life (antioxidant + antimicrobial effect)

Question 2

what produces phenolic compounds

Answer 2

plants

Question 3

name some foods that are high in phenolics

Answer 3

black tea, dark chocolate, filter coffee, dried oregano, red wine, blue berries

Question 4

definition of phenolic compounds

Answer 4

a molecule that contains at least one aromatic ring with one or more hydroxyl-groups

Question 5

important parameters of PC are? (Give 3)

Answer 5

1. polarity
2. reactivity (oxidation + antioxidant activity)
3. size of conjugated system (sequence of alternating double and single bonds)

Question 6

What is the rule of thumb for having a colour in your conjugated system?

Answer 6

a conjugated system less than 8 conjugated double bonds is colorless

Question 7

what is glycosylation? And what is the effect of glycosylation of a phenol on molecular properties?

Answer 7

substitution of the aromatic ring with a saccharide.
It will increase polarity of the phenol, and decrease reactivity

Question 8

what is carboxylation? And what is the effect of glycosylation of a phenol on molecular properties?

Answer 8

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)

Question 9

True or false: a phenoxy-radical that is stabilized by renosance is less reactive

Answer 9

True

Question 10

what is metal chelation?
And what is the result of metal chelation?

Answer 10

The binding of metals by phenolics.

Bound metal ions are less likely to participate in redox reactions

Question 11

what enzyme contributes to oxidation (enzymatic oxidation is usually faster than autooxidation)

Answer 11

Polyphenoloxidases (PPOs)

Question 12

why does in plant tissue enzymatic oxidation by PPOs not take place?

Answer 12

because phenolic compounds and PPOs are not in contact with each other, they are present in different compartments

Question 13

what are the factors influencing the formation of o-quinones?

Answer 13

1. overall PPO activity varies between sources
2. characteristics and properties of the specific PPO
3. structure of the phenolic compound
   conditions in the food process, ingredient or product

Question 14

what is the catecholase activity?

Answer 14

the conversion of o-dipehnols to o-quinones

Question 15

what is the cresolase activity?

Answer 15

the conversion from monophenols to o-dipehnols