11. COMPOUNDS INFLUENCING FOOD COLOUR
perception visual
colour
pigments (colouring matters, colourings)
formation
 primary compounds
natural food components
natural components of other materials (microorganisms, algae, higher plants), used as additives
 secondary compounds
enzymatic reactions (non-enzymatic browning reaction)
chemical reactions
 synthetic compounds
used as additives
colour defects
natural colours
important groups





tetrapyrrole colours
hem colours
chlorophyll colours
betalain colours
betacyans
betaxanthins
flavonoid colours
anthocyanins
anthoxanthins
phenolic and quinoid colours
phenols
quinones
carotenoid colours
carotenes
xanthophylls
plants, animals
plants
plants
plants, animals
plants, animals
TETRAPYRROLE PIGMENTS (TETRAPYRROLES)
 porphyrin pigments (porphyrins)
cyclic
hem pigments (hems)
chlorophyll pigments (chlorophylls)
 biline pigments (bilines)
linear
phycobilins
3
2
4
5
6
A
N
2
9
20
10
NH
C
N
19
18
8
B
NH
1
7
D
17
16
15
14
11
12
1
3
A
N
7
4
6
5
8
B
N
H
12
9
11
10
13
C
N
13
porphyrins
bilines
17
14
16
15
18
D
N
19
hem pigments
meat, meat products
nomenclature (book 3, tab. 9.1)
content (book 3, tab. 9.2, 9.3, 9.4, 9.5)
P
CH2=CH
CH3
N
H3C
N
Fe (II)
N
NH
N
CH2=CH
CH=CH2
H3C
CH2
His 93
CH3
CH=CH2
N
Fe (II)
N
N
N
N
CH3
H3C
HOOCCH2CH2
CH2CH2COOH
HOOCCH2CH2
CH3
H3C
CH2CH2COOH
H2O
hem (reduced haematin, Fe2+), hemoglobin
hematin (Fe3+), myoglobin (P = globin residue,16,8 kDa)
protein
protein
N
myoglobin
O2
N
Fe (II)
N
N
N
Fe (II)
N
N
oxymyoglobin
N
O O
H2O
protein
N
metmyoglobin
N
Fe (III)
N
N
OH
myoglobin (Mb)
oxymyoglobin (MbO2)
metmyoglobin (MMb)
dark red
scarlet
red to brown
reaction of MMb during temperature processing of meat
metmyoglobin

globin denaturation (70-80oC)

globin hydrolysis

hematin or hem
 (loss of Fe3+ or Fe2+)
linear tetrapyrroles
stabilisation of meat and meat products colour
microorganisms in meat:
spontaneous reaction:
NO3-  NO22 Mb + NO2-  2 MMb + NO + H2O
2
Mb + NO  MbNO + H2O
MbNO  Mb(NO)2 + globin
heating:
MbNO = nitroxymyoglobin
Mb(NO)2 = nitroxyhemochrom (nitrosylhemochrom, nitroxymyochromogen)
use of ascorbic acid: MMb + H2A  Mb + A
fuscous up to green colours (sulphomyoglobin, verdochrom, cholemyoglobin)
chlorophyll pigments
green parts of fruits and vegetables
content (book 3, tab.9.7)
colour (book 3, tab.9.8)
R
CH2=CH
H3C
N
N
N
Mg (II)
N
CH2CH3
N
N
N
Mg (II)
N
H3C
CH3
CH2
CH2
O
C
O
C O
O
O CH3
CH3
methyl
CH3
CH3
fytyl
CH3
CH3
porphyrins
Mg (II) complex
without Mg (II)
without phytol
without Mg (II) and phytol
chlorophylls
chlorophylls R = CH3
R = CH=O
pheophytin
chlorophyllide
pheophorbide
chlorophyll a yellow-green
chlorophyll b blue-green
reactions of chlorophylls during processing (acids, enzymes)
slabá kyselina
feofytiny
chlorofyly
silná kyselina
silná kyselina
chlorofylasa
chlorofylidy
silná kyselina
feoforbidy
colour changes during processing (book 3, tab. 9.9, 9.10 )
colour stabilisation
3
+
N
2H
2+
- Mg
N
Mg (II)
chlorofyl
N
-2H
N
Mg
2+
Cu , - Mg
NH
N
feofytin
+
HN
N
2+
+
2+
2+
Cu , - 2H
N
N
N
Cu (II)
N
měďnatý komplex
o

chlorophylin Cu (chlorophylid Cu)
betalain pigments
beetroot, prickly pear, amaranth, flowers
betacyanins
betaxanthins
red, orange
yellow, orange
basic structure
R
+
R
1
N
H
N
H
HOOC
COOH
CH2OR
O
OH
R
O
HO
OH
O
H
+
HO
H
betanin (R = H)
COO
-
H
H
HOOC
+
N
COOH
N
N
H
95 %
HOOC
COOH
N
H
COOH
vulgaxanthin I (R = NH2) 50 %
flavonoid pigments
fruits, vegetables, flowers


anthocyanins
anthoxanthins
red, violet, blue
yellow, orange
basic structure
4
O
O
A
2H-chromene



B
C
flavan
oxidation of 3C chain (ring B)
OH groups in rings A, B, C
aglycones, glycosides
O
O
O
OH
OH
OH
OH
OH
katechiny
O
O
leukoanthokyanidiny
flavanonoly
O
O
O
O
flavanony
flavony
O
flavonoly
O
+
anthokyanidiny
colourless
colourless-light pale yellow
light yellow-yellow
red-blue
O
O
isoflavony
light yellow
OH
OH
O
O
chalcones
yellow-orange
O
dihydrochalcones
yellow-orange
O
aurones
gold-yellow
anthocyanins
basic structure
5
R1
OH
HO
O
R2
+
7
3
5
OH
OH
R1 = H
R1 = H
R1 = OH
R1 = H
R1 = OH
R1 = OCH3
R2 = H
R2 = OH
R2 = OH
R2 = OCH3
R2 = OCH3
R2 = OCH3
pelargonidin
cyanidin
delfinidin
peonidin
petunidin
malvidin
Pg
Cy
Dp
Pn
Pt
Mv
violet-red
violet
blue-violet
violet
dark red
blue-violet
saccharides:
acids:
Glu, Gal, Xyl, Ara, Rha, always at C-3, often at C-3 and C-5, seldom at C-7
p-cumaric, caffeic, ferulic
OH
OH
HO
O
+
O
HO HO CH2
O
HO
OH
OH
examples
cyanidin-3-O--D-glucoside (general occurrence)
OCH3
OH
petunidin
HO
CH3
O
OH
+
3
5
CH2OH O
O
OH
-glukosa
D
O
OH
O
OH HO
O
OH
H2C
O
OH
rutinosa
HO
OH
O
C
O
p-kumarová kyselina
OH
petanine (red coloured potato)
(E)-petunidin-3-O-6-O-(4-O-p-cumaroyl--L-rhamnopyranosyl)--D-glucopyranoside-5-O--Dglucopyranoside
anthocyanins fruits and vegetables (book 3,. tab. 9.12)
colour changes due to different factors
 pH
 co-pigmentation, eventual transformation into other pigments
 SO2
 H2O2
6
pH
1
R
R
1
OH
OH
HO
O
R
+
+
H2O, - H
2
R
-
1
O
HO
O
R
O
pH 4,0-4,5
karbinolová pseudobáze (bezb.)
-H
1
H2O
OH
2
O
O
R
glykosyl
2
1
R
OH
glykosyl
O
glykosyl
O glykosyl
O
pH 4,5-7,5
neutrální chinoidní báze (tmavě červená)
OH
HO
O
R
O
- H+
- H+
R
R
1
O
1
O
O
-
O
O
R
O
O
2
glykosyl
O
+
R
R
glykosyl
O
glykosyl
pH < 1
flavyliový kation (červený)
- H+
OH
O
glykosyl
O
O
HO
O
2
O
R
O
glykosyl
O
glykosyl
glykosyl
glykosyl
-
2
glykosyl
pH > 8
chalkon (žlutá)
2
glykosyl
pH 7,5-8
anion chinoidní báze (modrá)


copigmentation
interaction with procyanidinins (catechins = copigments)  coloured complexes
transformation into other pigments, coloured complexes  dimers (oligomers), non-soluble
condensation products, polymeric compounds
R
OH
anthokyanidin
O
HO
R
R
+
4
OR
OR
HO
OH
O
R
8
katechin
OH
OH
SO2 colourless sulfonic acids
R1
R1
OH
HO2SO
O
HO
R
O
O
OH
O
2
glykosyl
glykosyl
R2
O
glykosyl O
glykosyl
OSO2H
H2O2 colourless products
R1
OH
O
R2
C
O
HO
O
O
O
glykosyl
glykosyl
7
anthoxanthins
flavanones
 pigments of low importance
 bitter compounds of grapefruits
naringin = naringenin + neohesperidose
neohesperidin = hesperetin + neohesperidose
flavanonols
 pigments of low importance
flavones
 important anthoxanthins
flavonols
 important anthoxanthins
 antioxidant activity, rutin = kvercetin + rutinose, bioflavonoids
isoflavones
 pigments of low importance (e.g. in soybeans)
 estrogenic activity
chalcones and aurones
 important pigments of flowers
dihydrochalcones
 pigments of low importance
 neohesperidindihydrochalcone (synthetic sweet compound)
quinoid pigments
lichens, mushrooms, higher plants
 phenols
 quinones
phenols
curcuminoides (diarylheptanoides)
O
O
CH3O
OCH3
HO
OH
curcumin (curcuma, curry)
quinones
 benzoquinones
 naphtoquinones
 anthraquinones
O
O
O
O
O
O
benzo-1,4-quinone
naphto-1,4-quinone anthra-9,10-quinone
8
benzoquinones
OH
HO CH2
O
O
OH
HO
OH
arbutin (cranberry leaves, antiseptic activity)
(related terphenylquinones and pulvic acids in mushrooms)
naftoquinones
O
OH
O
juglone (leaves of walnut, 4--D-glucosid 1,4,5-trihydroxynaphtalene)
(relative gossypol in cotton seeds, related coenzymes Q, vitamins K)
anthraquinones
related emodins, bianthrons
O
HO
OH
OH
O
HO
CH2OH
OH
O
COOH
OH
OH
O
HO
HO
CH3
HO
CH3
CH3
OH
O
HO
carminic acid (cochineal, dried bodies of female beatles Coccus cacti)
OH
hypericine (St. John's wort)
carotenoid pigments
yellow, orange, red up to violet pigments of plants and microorganisms (in mammals)
composition and content in fruits and vegetables (book 3, tab.9.14)
 carotenoids (tetraterpenes, 40 C atoms, trans-isomers)
hydrocarbons
carotenes
O-derivatives
xanthophylls
neocarotenoids (cis-isomers)
degradated carotenoids (30, 20, 15, 13, 10 C atoms)
carotenes
acyclic and alicyclic hydrocarbons
CH3
CH3
CH3
CH3
CH3
H3C
CH3
lykopen
H3C
CH 3
CH 3
CH 3
CH3
H3C
CH 3
CH 3
CH 3
H3C
CH3
CH3
OH
CH 3
-karoten
lycopene: tomato, rose-hip, -carotene: carrot, apricot, mango
9
xanthophylls
alcohols, ketones, epoxides
free, bound (glycosides, fatty acids esters, carotenoproteins)
H3C
CH 3
CH 3
HO
H3C
CH 3
CH 3
CH 3
OH
H3C
CH 3
CH 3
zeaxanthin
H3C
CH 3
CH 3
HO
H3C
CH 3
CH 3
CH 3
CH 3
OH
H3C
CH 3
lutein ( -xanthofyl, kukurbitaxanthin)
H3C
CH 3
CH 3
OH
H3C
CH 3
CH 3
O
HO
CH 3
CH 3
CH 3
CH 3
kapsanthin
O
H3C
CH 3
CH 3
HO
H3C
CH 3
CH 3
CH 3
CH 3
OH
H3C
CH 3
O
astaxanthin
zeaxanthin, lutein:
kapsanthin:
astaxanthin:
generally wide-spread
red bell pepper
fish, shellfish (-crustacyanin)
retinoids
degradated carotenoids
crocin (18 C)
saffron (Crocus sativus), spice
CH3
CH3
COOH
HOOC
CH3
krocetin
CH3
OH
O
HOCH2
OH
genciobiosa
CH2 OH
O O CH2
CH3
O
C O
O O C
OH
HO
CH3
OH
HO OH
O
OH
CH3
CH3
HO
O
OH CH2
O
OH
OH
krocin
annato (20 C)
bixin (Bixa orellana)
extract 0,2-0,5 % = mixture cis/trans-isomers, cheese and margarine colouring
10
CH3
CH3
CH3
HOOC
9
,
CH3
COOH
CH3
CH3
COOH
HOOC
CH3
CH3
aromatic and gustatory compounds formed from carotenoids
H3 C
CH3
CH O
CH2OH
O O
OH
HO
CH3
OH
pikrokrocin
oxidace a štěpení
-karoten
H3C
CH3
O
H3C
CH3
CH3
+
CH3
CH3
-jonon
H3C
CH3
CH O
O
CH3
-jonon
H3C
CH3
O
O
CH3
CH3
-cyklocitral
H3C
dihydroaktindiolid
CH3 O
CH3
H3C
H3C
CH3
CH3
-damaskon
O
CH3
CH3
-iron
reactions
 hydrolysis of esters, glycosides
 dehydration of alcohols to hydrocarbons
 cis/trans isomeration (neocarotenoids, low colour intensity)
 autooxidation (low colour intensity, even decolourisation)
 antioxidants
consequences
 flour bleaching
 colour changes of orange juices
 food flavour
 beneficial food components
11
Enzymatic browning reactions
substrates (book 3, tab. 9.15)
HO
R
HO
R
HO
phenols, diphenols (polyphenols), esters (depsides), glycosides
COOH
COOH
OH
O
OH
OH
OH
OH
3
OH
3
O
OH
OH
OH
O
O
daktyliferová kyselina
chlorogenová kyselina
OH
O
HO
HO
NH2
R
R
OH
HO
O
HO
3,4-dihydroxyfenylethylamin
terfenylchinony
enzymes
polyphenoloxidases
 catecholoxidase
OH
kresolasa
OH
katecholasa
OH
1/2 O 2
O
O
1/2 O 2
- H2 O
R
fenol

R
R
o-difenol
o-chinon
laccase
OH
lakkasa
OH
O
O
1/2 O 2
- H2 O
R
R
o-difenol
OH
lakkasa
O
1/2 O 2
- H2 O O
HO
R
R
p-difenol
catechin oxidation
chlorogenic acid oxidation
DOPA oxidation
o-chinon
p-chinon
yellow quinone
yellow-orange quinone
orange quinone
12
mechanisms
reakce s R-SH, R-NH2
OH
O
OH
O
OH
1/2 O2
R
+
R
R
R
O
oxidace
O
OH
oxidace
R
hnědé
pigmenty
R polymerace
- H2O
HO
HO
komplexy s kovy
OH
OH
inhibition of browning (book 3, tab. 9.16)
 inhibition of enzymes (oxygen elimination , decrease of pH)
 chelatation of metals (Cu2+)
 use of reducing compounds (ascorbic acid, SO2)
desirable reactions
 tee fermentation
 cocoa fermentation
 olive fermentation
black tea
precursors in green tea
 epigallocatechingallates
 epicatechins
 epicatechingallates
 epigallocatechins
main types of black tea pigments
 theaflavins (oxidised flavonoid dimers), orange-red (seven-carbon tropolone cycles)
OH
H
OR
OH
O
HO
H
O
O
HO
H
OH
1
OH

H
OR
OH
thearubigines (polymers, 700-400 000 Da), red-yellow up to orange-brown
13