phenolic compounds 4

Question 1

flavour is the combination of taste & aroma? True or false

Answer 1

taste (non volatile)
aroma (volatile)

Question 2

effects of phenolics on food flavour

Answer 2

1. bitterness
2. astingency
3. inherent aroma
4. participation in aroma formation reactions

Question 3

which of these names are bitter? naringerin, naringin, narirutin, neohesperidin, hesperidin, hesperitin

Answer 3

naringin & neohesperidin

Question 4

What linkages taste bitter? (1-2) or (1-6) linkages

Answer 4

1 –> 2 linkages

Question 5

how do aroma compounds form via o-quinone reactivity?

Answer 5

1. (free!) nucleophilic groups in amino acid side chains of proteins, can react with o-quinones
2. followed up by a stecker degradation
3. leads to the formation of an aldehyde from the amino acid

Question 6

is the fermentation of black tea enzymatic?

Answer 6

yes

Question 7

how can phenolics improve the stability and shelf -life of food

Answer 7

by radical scavenging and metal chelation

Question 8

The aglycons (naringenin and hesperitin) and rutinosides (narirutin and hesperidin) are not perceived as bitter.. True or false

Answer 8

true

Question 9

whereas flavanone glycosides with neohesperidose (naringin and neohesperidin), are perceived as intensely bitter

Answer 9

True

Question 10

When is the astringency of condensed tannins highest? In which range of degree of polymeratisation?

Answer 10

between 5 and 7

Question 11

What are the odours phenolic aroma compounds are assiciated with?

Answer 11

smoky, woody, spice and or sweet

Question 12

only starts after disruption of plant tissue to enable phenolics, PPO, O2 to get into contact with each other

Answer 12

browning

Question 13

happens when di- and oligomeric phenolics interact with salivary proteins and precipitate in the mouth

Answer 13

Astringent taste

Question 14

can be caused by specific structures, e.g. the flavanone glycosides naringin and hesperidin

Answer 14

bitter taste

Question 15

one of the underlying mechanism is via the formation of resonance-stabilised phenolic radicals

Answer 15

antioxidant activity

Question 16

can be either covalent and irreversible, or non-covalent and reversible

Answer 16

protein phenolic interactions

Question 17

can be influenced by food processing, e.g. by treatment of fruit juice with enzymes that hydrolyse flavonoids’ glycosidic linkages

Answer 17

bitter taste

Question 18

occurs when o-quinones react with non-oxidised phenols

Answer 18

browning

Question 19

can be prevented by removal of phenolics via complexation and precipitation with gelatin or PVPP

Answer 19

protein phenolic interactions

Question 20

one of the underlying mechanisms is via binding of metal ions, also referred to as metal chelation

Answer 20

antioxidant

Question 21

Strecker degradation to form amino acid-derived aromas can take place when an o-quinone reacts with a free amino acid, because the carboxylic acid and amino group have to be available to participate in the reaction.

Answer 21

true