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Food Chemistry 2 > Pigments: Anthocyanins, Flavonoids and others > Flashcards

Pigments: Anthocyanins, Flavonoids and others Flashcards

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1
Q

Anthocyanins:
- water or fat soluble?
- plant or animal pigment?
- imparts what 3 colors of various f and veg?
- basic structure/common central group = ?

A
  • water soluble!
  • plant pigment
  • red, blue and violet
  • flavylium ion
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2
Q

how many rings does anthocyanins have?

A

3 rings!
- 2 are fused together –> benzo 3-hydroxypyran = ring A
- 1 benzene attached to position 2 of the 3-hydroxypyran group = ring B

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3
Q

flavylium ion vs anthocyanidin vs aglycone vs anthocyanins vs glycosides

A
  • flavylium ion = basic structure of anthocyanins
  • anthocyanidin and aglycone –> anthocyanin that only has the basic structure (flavylium ion) –> no sugar glycosylated
  • anthocyanins = glycosides of anthocyanidin
  • glycosides: anthocyanidins that have sugars glycosylated to it
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4
Q

monosides vs biosides vs triosides

A
  • monosides: only 1 sugar glycosylated to anthocyanidins
  • biosides: 2 sugars! either 2 monosacs or 1 disac
  • triosides: 3 sugars! either 1 trisacs, 1 mono and 1 disacs, or 3 monosacs
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5
Q

examples of sugars of anthocyanins:
- monosacs (5)
- disacs (4)
- trisacs (3)

A

MONOSACS:
- D-glucose, D-galactose, L-arabinose, D-xylose, L-rhamnose
DISACS:
- gentiobiose, rutinose, sophorose, neohesperidose
TRISACS:
- gentiotriose, xylosylrutinose, glucosylrutinose

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6
Q

difference between gentiobiose and gentiotriose?

A
  • gentiobiose: glycosyl glucose constiting of 2 D-glucopyranose units connected by a b-1-6 linkage
  • gentiotriose: 3 D-glucopyranose units connected by b-1-6 linkage –> 3rd glucose is open(?)
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7
Q

4 sources of anthocyanins

A
  1. plants (fruits and veg)
  2. microorganisms
  3. extraction
  4. biosynthesis
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8
Q

5 steps for extraction of anthocyanins from natural sources

A
  1. source material is pretreated (drying, defatting, grinding/crushing)
  2. mix/blend powder with solvent for extraction (ie water, acidified water or acidified water + ethanol)
  3. after extraction, homogenate undergoes heat treatment –> coagulates proteins (coextracted with anthocyanins) + breaks down enzymes like anthocyanases
  4. extract is filtered to exclude insoluble material –> anthocyanins are collected by adsorption chromatography with amberlight as support material
  5. purified anthocyanin may be dried to reduce size/volume and have it in a stable form to facilitate transportation/distribution for us in various applications
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9
Q

biosynthesis of anthocyanins
1. which 2 components are condensed together
2.
3.

A
  1. malonyl-CoA + Coumaroyl-CoA –> chalcones
  2. chalcones unergoe series of changes to form various flavonoids (flavones –> hydroxyflavonols)
  3. flavonoids go on to produce anthocyanidin
  4. anthocyanidins are glycosylated to produce various anthocyanins
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10
Q

what are 4 different R groups for anthocyanins?

A
  1. OH
  2. methoxyl group (OCH3)
  3. sugars
  4. H
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11
Q

what color + which fruits/vegs?
- cyanidin
- delphinidin
- malvinidin
- pelargonidin
- peonidin
- petunidin

A
  • cyanidin: orange-red –> apples, cherries, oranges, plums, raspberries, cabbage
  • delphinidin: blue-red –> grapes and oranges
  • malvinidin: blue-red –> blue grapes
  • pelargonidin: orange –> strawberries
  • peonidin: orange-red –> cherries and plums
  • petunidin: blue-red –> blueberries
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12
Q

because of _________ nature, anthocyanins can serve as substrates for __________ ________ (by which enzyme?) –> this reaction requires what as coreactant?

A
  • polyphenolic nature
  • enzymatic browning by Polyphenol oxidase (PPO)
  • O2 as coreactant
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13
Q

anthocyanins:
- increasing OH content enhances which color?
- increasing OCH3 content enhances which color?

A
  • OH –>blue
  • OCH3 –> red (ie rosinidin)
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14
Q

effects of handling and processing on anthocyanins:
- pH: acidic vs alkaline results in what color?
- effects of cooking/wash water –> result?
- adding additives like sulfites, ascorbic acid, H2O2?
- processing with metals?

A
  • acidic = OCH3 = red VS alkaline = OH = blue or colorless
  • color lost to cooking/wash water bc anthocyanins soluble in water
  • anthocyanins can form complexes with sulfites and ascorbic acid = color changes/decolorization
  • anthocyanins can chelate metals (Cu, Fe, Zn) –> even colorless forms of pigmentation acquire pinkish, purpleish and grayish colors
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15
Q
  1. what does high temp do to anthocyanins?
  2. what does high sugar content do to anthocyanins?
  3. what does presence of O2 do to anthocyanins?
A
  1. anthocyanins are glycosides and glycosidic bonds can be cleaved at high temp = destruction of pigment = color loss
  2. high [sugar] cause glycosylation of OH groups in molecules and cause destruction of color
  3. colorless forms of anthocyanins may undergo oxidation in presence of O2 to form colored products (ie pinking of canned pears)
    ALSO presence of O2 enhances destruction of anthocyanins (bc of polyphenolic nature
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16
Q

why can anthocyanins scavenge radicals and chelate metal ions?
- what does that make them?

A
  • because of high unsaturation, aromatic form and polyphenolic nature
  • serve as antioxidants!
17
Q

which 2 enzymes can remove sugars from anthocyanins, thus destabilizing the molecule and causing loss of _______

A
  • glucosidases and anthocyanases (split glycosidic linkages)
  • loss of color
18
Q

how to curtail/reduce deletrious effects of glucosidases and anthocyanases?

A

by microwave bleaching! short time high temp treatment can destroy the enzymes!
- heat treatment not extensive enough to kill pigments

19
Q

major difference btw anthocyanins and flavonoids?
- 3 similarities?

A

central unit!
- anthocyanins –> benzo 3-hydroxyl pyran
- flavonoids –> benzopyrone (double bonded O on the right ring of the A ring)
1. both formed via common pathway
2. both can by glycosylated –> both are glycosides
3. both have polyphenolic nature –> both can serve as subtrates in enzymatic browning

20
Q

flavonoids:
- water or fat soluble?
- found in (2)
- most abundant ________ in the diet
- they are _______ with a ________ nucleus
- also known as _________
- most common sugar attached = ?
- they give certain fruits, veg and herbs their (3) colors

A
  • water soluble
  • plants and microorganisms
  • polyphenols
  • glycosides with a benzopyrone
  • anthoxanthins
  • rutinose
  • dark red, blue and purple
21
Q

flavonoids are __________ in plants and tend to occur _______, although some plant species may be ________ in particular flavonoids than others

A
  • widespread in plants
  • occur together
  • may be richer in particular flavonoids
22
Q

difference between: + examples
- flavones
- isoflavones
- flavonols
- flavonones
- flavononols

A
  • flavones: double bond at 2:3 position + benzene ring at 2 position –> apigenin
  • isoflavones: double bond at 2:3 position + benzene ring at 3 position –> genistein
  • flavonols: double bond at 2:3 position + OH group at 3 position –> quercetin
  • flavonones –> NO double bond at 2:3 position (saturated) + benzene at 2 position –> naringenin
  • flavononols –> NO double bond at 2:3 position + OH group at 3 position –> xeractinol
23
Q

quercetin
- what type of flavonoids?
- causes what feeling in mouth? why?
- present where?
- what color?

A
  • flavonol (double bond at 2:3 + benzene at 2 + OH at 3)
  • bitterness + astringency! –> quercetin causes precipitation of proteins in saliva –> gives dry sensation on cheeks and tongue
  • ubiquitous but predominant in unripened fruits + Granny Smith apples
  • yellow/brown color
24
Q

what causes bitter taste in grapefruits?
- color?

A

naringenin –> flavonone
- colorless

25
Q

what type of flavonoid + color + found where + taste
- apigenin
- genistein
- xeractinol

A

APIGENIN:
- flavone
- yellow
- fruits, veg, chamomille tea
- pleasant smell, bitter/astringent taste and calming effect
GENISTEIN:
- isoflavone
- colorless
- found in fruits, veg, legumes (soy, peas)
- bitter and estrogenic effects –> protects against osteoporosis and menopause
XERACTINOL:
- flavononols
- colorless
- found mostly in leaves
- has bitter and astringent taste

26
Q

common properties of flavonoids:
- polyphenolic nature –> gives 3 properties)
- may be involved in other ________ rxns in foods –> explain
- pro- vitamin ___ activity

A
  • substrate in enzymatic browning reactions + chelating agent + antioxidant/free radical scavenger
  • discoloration reactions –> ie may bind Fe in foodstuffs to form blue/green colors
  • pro vitamin C activity
27
Q

BETALAINES!
- water soluble or insoluble
- glycoside?
- 2 main colors + pigment names?
- which color is more powerful?
- mostly found where? (4 varieties)

A
  • water soluble!
  • glycosides! glucose commonly present
  • red: betacyanins (betanin)
  • yellow: betaxanthins (vulgaxanthin)
  • when betanins and betaxanthins coexist, red color masks yellow color!
  • mostly found in beet plants: red or vegetable beet, fodder beat, sugar beet and chard
28
Q

betalaines have what as part of their structure? describe

A

indoles!
- benzene ring + 5 membered ring with NH embedded

29
Q

betalaines:
- extensively used as a food _______
- degraded by _______ processing
- some color lost to _______ _______ due to high solubility in _____
- distinguishable feature?

A
  • food colorant
  • thermal processing
  • cooking water due to high solubility in H2O
  • intense color! we lose some in water, but so intense that we don’t even see the color difference
30
Q

TANNINS:
- occur a lot where?
- complex ______ pigments (4 examples of foods)
- water soluble? depends on what?
- wide range of colors: from _______ to _______ or _________

A
  • tree bark
  • plant pigments –> chocolate, wines, nuts, tea
  • small size = water soluble vs bigger size less water soluble
  • colorless to yellow to brown/dark brown
31
Q

TANNINS:
- 2 common molecules?
- contribute to ________ in foods
- participate in ________ _______ reactions –> even less intensely colored tannins can undergo what?

A
  • gallic acid, ellagic acid
  • astringency
  • enzymatic browning –> dark discolorations during storage
32
Q

QUINONES:
- water or fat soluble?
- present in (2)
- range in color from ______ to ______
- common examples (2)
- extensively used as natural _____ and ________

A
  • water soluble
  • plants and microorganisms (ie kiwis, peppers, papayas)
  • yellow to black
  • emodin, spinulosin
  • dyestuff (due to intense dark colors) and purgatives/laxatives
33
Q

XANTHONES:
- ______ pigment with structural resemblance to ________ and ________
- are __________
- water or fat soluble?
- what color?
- can undergo enzymatic browning? antioxidant properties?
- common molecule?

A
  • plant pigment –> flavonoids and quinones
  • glycosides!
  • water soluble
  • yellow (ie mangosteen and longan fruit)
  • yes and yes! bc of polyphenolic nature
  • mangiferin
34
Q

MELANINS or MELANOIDINS
- _______ colored pigments found in (4)
- formed by _________ of ________ compounds (example?) by ____ and ____
- formation of melanins is desirable in certain foods (ex) but undesirable in others (ex)

A
  • brown –> fruits, vegetables, fungi/mushrooms, crustacea
  • polymerization of phenolic compounds (ie quinones) by PPO and Cu2+
  • desirable in cocoa, tea
  • undesirable in fresh fruits and vegs + crustaceans
35
Q

non enzymatic browning reactions
1. caramelization formed from _______ by _______ (which loses _______)
- 3 polymers responsible for caramelization/brown colors and nutty aromas
2. what reaction?
- between what and what?

A
  1. carbohydrates by heating –> loses water
    - caramelans (C_24 H_36 O_18)
    - caramelens (C_36 H_50 O_25)
    - caramelins (C_125 H_188 O_80)
    - different sizes and unsaturation levels
  2. Maillard reaction!
    - from interactions of sugars with amino groups from amino acids, proteins, peptides, amines

Food Chemistry 2 (7 decks)

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