Food Chem 2- Pigments

The flashcards below were created by user Morgan.liberatore on FreezingBlue Flashcards.

  1. What are pigments?
    Substances that add color to compounds/products
  2. What are some food sources of pigments?
    • Chlorophyll (fruits, vegetables)
    • Heme (muscle food)
    • Carotenoids (eggs, fish, crustaceans, dairy products, fruits and vegetables)
    • Anthocyanins (fruits, vegetables, microorganisms)
    • Flavanoids (fruits, vegetables, microorganisms)
    • Melanins (shellfish, dried fruits and vegetables, microorganisms
  3. What is chlorophyll?
    • Green color
    • Found in plants, green algae, bacteria
    • Methylene bridges to form a tetrapyrol ring structure
    • 1 pyrol ring esterified to long chain hydrocarbon alcohol known as phyto
    • Another of the rings is esterified to methanol
    • Several different chlorophylls, predominant ones are 'a' and 'b'
  4. What is the different between chlorophyll-a and chlorophyll-b?
    In chlorophyll-b, the CH3- group at position C-3 of chlorophyll-a is replaced by a formyl group
  5. What causes color loss in chlorophyll and how?
    Irradiation of foods form free radicals can cause peroxidation of the unsaturated bonds in chlorophyll and cause color loss
  6. Where is chlorophyll obtained commercially?
    Chlorophyll is obtained commercially from afalfa and spirallina for use as colorant for food beverages, cosmetics, drugs, ertc, however it is unstable and the green color is lost readily
  7. How is chlorophyll made more stable as a colorant?
    When produced complexed with Ca, chlorophyll becomes more stable for use as a colorant
  8. What are the two forms Ca exits in the blood?
    • Complexed with a protein to form ceridoplasmin
    • Free Ca++ that binds to albumin- excess free Ca generates free radicals that prouce reactive oxygen species (ROS) such as superoxidase.  These species can cause damage to tissues and biomolecules in the body
  9. How does cooking effect chlorophylls?
    Makes pheophytins
  10. How does dehydration effect chlorophylls?
    Bleaching by photodegredation (lipoxidase)
  11. How dos exposure to O2 effect chlorophylls?
  12. How does blanching effect chlorophylls?
    Produces pheophytins and pheophobides
  13. Where are heme pigments found?
    Found exclusively in animals- red meats and other muscle foods
  14. What is myoglobin?
    Single polypeptide with central atom (Fe)
  15. What is the hemoglobin structure?
    4 myoglobins assembled together
  16. What is the function of hemoglobin and myoglobin?
    Function as O2 carriers
  17. What is the central atom of heme pigments?
  18. What happens to heme pigments during the storag and cooling of meats?
    • Fe2+ gradually oxidizes to Fe3+ and some protein may be denatured
    • Oxidation of iron in meats is accompanied by a color change from purplish/bright red to a brownish color
  19. What does iron uptake depend on?
    • Iron uptake depends on the oxidation number
    • Fe2+ is absorbed more readily than Fe3+
  20. What is the difference in nutrition of well cooked meaasts vs not well cooked meats?
    Well cooked meats have more digestible proteins and little or no microbial load; however the Fe3+ is less readily absorbed
  21. What is curing of meats?
    • Involves using nitrates or nitrites to preserve meats
    • Adds color to meats
    • Flavor
    • To control growth and proliferation of clostridium
    • Nitroso myoglobin (Mb-NO) - red in color
  22. What is the brown colored product formed from cooking meat?
  23. What is oxymyoglobin?
    • Bright red color of fresh meats
    • Fe pesent as ferrous (Fe2+) form
    • Mb + O2 --> MbO2
    • Mb (purple color, Fe2+)
    • MbO2 (bright red; Fe2+)
  24. What is metmyoglobin (Met-Mb)
    • Brownish color (Fe3+)
    • MbO2 <--> Mb --> Met-Mb
    • MbO2 (bright red)
    • Mb (purple)
    • Met-Mb (brown)
  25. What is similar between heme pigments and tetrapyrolle?
    Both Mb and Hb are tetrapyrolle compounds like chloropyll
  26. Where are carotenoids found?
    • Plants
    • Microorganisms
    • Animals
  27. What color are carotenoids?
    Responsibe for bright red, orange and yellow
  28. What is the commercial source for carotenoid pigments?
    Phaffia rhodozyme 
  29. How are carotenoids derived?
    All carotenoids derived from 5 carbon compound known as isoprene
  30. Why do carotenoids act as antioxidants?
    They have a high degree of unsaturation which enables them to act nas antioxidants by absorbing free radicals or deactivating reactive oxygen species
  31. What are the 2 different types of carotenoids?
    • Hydrocarbon
    • Oxygenated hydrocarbon
  32. What happens when beta-carotene is hydrolyzed?
    Forms 2 molecules of vitamin A
  33. What happens to carotenoids when cooked?
    • When it is uncooked, the pigments exist predominantly in the trans-from; when it is cooked, the molecules assume the cis-form predominantly
    • Cooking also renders the pigment more absorbable
  34. How does vitamin A help us see?
    Vitmain A (aka retinol) can bind to opsin (a protin in the eye) to form zhodopsin which enables us to distinguish light and dark
  35. What happens to carotenoids in high temperature processing?
    High temperature processing can cause destruction of the pigment 
  36. What happens to carotenoid pigments in dehydration?
    Dehydration conditions (such as freezing) enhance the activity of the naturally present enzymes lipoxidases that can cause bleaching of the pigment
  37. What is lycopene?
    • A major pigment in tomatoes and apricots
    • Lycopene is symmetrical, but unlike alpha- or beta-carotene, the ring structures in lycopene are open
  38. Why does shellfish change color when cooked?
    • Carotenoids in crustaceans are complexed with proteins to form carotenoprotein complexes
    • The proteins offer protection to the pigments
    • During cooking, the protein is either denatured, or disloged from the pigment which results in color change
  39. What is lutein?
    • Found in green leaves and egg yolks
    • Molecule is similar to alpha-carotene- asymmetrical, but rings are hydroxylated; so has no vitamin A activity
  40. What is canthaxanthin
    • Present in microorganisms, plants and animals (mushroom, red pepper, brine shrimp, and flamingos)
    • Commercially produced by chemical synthesis
    • Used as feed supplement for cultured salmonids and imitation seafood products
    • Has no vitamin A activity
  41. What is astaxanthin
    • Major carotenoid pigment in salmonids and crustaceans; also redfish, ocean perch/red snapper
    • Produced on a commercial scale by chemical synthesis
    • More stable than canthaxanthin for use as colorant for fish flesh
    • Has no vitamin A activity
  42. What is cryptoxanthin?
    • Major carotenoid pigment in peaches, yellow corn and egg yolk
    • Structure similar to alpha-crotene, except for presence of -OH group on one ring
    • No vitamin A activity
  43. What is Zeaxanthin?
    • Widely distributed in nature
    • Major carotenoid in yellow corn and egg yolk
    • Cimilar structure to beta-carotene, but has 2-OH goups in addition 
    • No vitamin A activity
  44. How does handling and processing effect carotenoids?
    • O2 and light- major cause of destruction
    • Not lost to cookin water
    • Destroyed by dehydration
  45. What color are anthocyanins?
    Red, blue and violet colors
  46. Are anthocyanins water soluble?
  47. What is the basic structure of anthocyanins?
  48. What is a flavilium ion?
    • Basic structure of anthocyanins
    • Comprises of a a pyrilium ion linked with 2 benzne rings
  49. What makes an anthocyanin more bluish or reddish?
    High -OH content tends to make a molcule more bluish while high methoxy content makes it reddish
  50. How do sugars effect anthocyanins?
    • Anthocyanins are sugar esters of anthocyanidins
    • Water solubility increases with sugar content
  51. What is a monoside?
    Anthocyanidin with 1 sugar
  52. What are biosides?
    Anthodcyanidins esterified with 2 sugars (either 1 dissaccharide, or 2 monosaccharides)
  53. What are triosides?
    Anthocyanidin esterified with 3 sugars (either 1 disaccharide + 1 monosaccharide, or 2 monosaccharides)
  54. Why are anthocyanins lost in cooking?
    High solubility in water
  55. How does high sugar content effect anthocyanins?
    High sugar content can cause color changes via glycosylation of the -OH groups on the flavylium ion
  56. How does pH affect anthocyanins?
    • pH changes can cause changes in color of the piGment by the influence of pH on -OH and -CH3 groups
    • Acidic conditions change pifments to red color
    • Alkaline conditions change pigments to shades of blue or colorless
  57. Which additives cause color change in anthocyanins?
    Additives such as sulfites, ascorbic acid, H2O2 can cause color loss in anthocyanins
  58. How do anthocyanins effect enzymatic browning?
    Because of their phenolyc structure, they can serve as substrates for enzymatic bowning in the presence of O2
  59. Where is cyanidin found?
    • Orance-red color
    • Found in apples, cherries, oranges, plums, raspberries and cabbage
  60. Where is delphinidin found?
    • Blue-red color
    • Found in grapes and oranges
  61. Where is malvindin found?
    • Blue-red color
    • Blue grapes
  62. Where is pelargonidin found?
    • Orange color
    • Found in strawberries
  63. Where is peonidin found?
    • Orange-red color
    • Found in cherries and plums
  64. Where is petunidin found?
    • Blue-red color
    • Found in blueberries
  65. How do metals effect anthocyanins?
    Form purple grey colors
  66. How are anthocyanins effected by temperature?
    High temperatures cause destruction of anthocyanin pigments (spray drying)
  67. How does sugar effect anthocyanins?
    Hgih sugar content and the presence of O2 enhance destruction of anthocyanins
  68. What causes 'pinking' of canned pears?
    Colorless forms of anthocyanins may undergo oxidatiom in the presence of O2 to form colored products
  69. How do glucosidases effect anthocyanins?
    • Glucosidases or anthocyanases nremove the sugars from anthocyanins, thus destabilizing the molecule and causing loss of color
    • Deleteriouis effects of these enzymes curtailed by microwave blanching
  70. What are flavonoids?
    • H2O- soluble pigments found in plants and microorganisms
    • Most abundant polyphenols in the diet
    • aka anthoxanthins (glycosides with a benxopyrone nucleus)
    • Most common sugar- rutinose
    • Many are antioxidants
  71. What is the general structure of flavonoids?
    Glycosides with a benzopyrone ring
  72. What are the 5 classifications of flavonoids?
    • Flavones (double bond at 2:3 position)
    • Isoflavones (Benzene ring at 3 position)
    • Flavonols (Flavonols (-OH group at 3 position; no dbl bond at 2:3)
    • Flavonones (no dbl bond at 2:3 position)
    • Flavonols (-OH group at 3 position)
  73. What are flavones?
    Double bond at 2:3 position
  74. What are Isoflavones?
    Benzene ring at 3 position
  75. What are flavonolos?
    • -OH group at 3 position
    • No double bond at 2:3 position
  76. What are flavonones?
    No double bond at 2:3 position
  77. What are flavonols?
    -OH group at 3 position
  78. What is quercitin?
    • Flavonol
    • Induces astringency in the mouth and contributes to flavor
    • Causes preipitation of proteins in saliva and induces the dry sensation
  79. What is neringenin?
    • Flavonone
    • Bitter taste found a lot in bitter fruits such as citrus - grapefruit in the pith and in the rind
  80. How do flavonoids interact with vitamin C?
    Enhance vitamin C by increasing the uptake
  81. Why are flavonoids substrates for enzymatic browning?
    Because of their polyphenolic structure
  82. What are betalaines?
    • H2O-soluble plant pigments
    • Glycosides
    • Betacyanins (red)
    • Betaxanthins (yellow)
    • Found mostly in beets
    • Degraded by thermal processing
    • Some color lost to cooking in water due to high solubility
  83. How are betalaines effected by sulfites?
    Additives like sulfites can cause bleaching
  84. What are tannins?
    • Complex plant pigments with varying degrees of solubility in H2O, based on different sizes
    • Wide range of colors- from colorless to yellow or brown
    • Contribute to astringency in foods
    • Participate in enzymatic browning reactions
  85. Where are tannis predominantly found?
    Tree bark
  86. What are quinones?
    • H2O-soluble pigments
    • Present in plants and microorganisms
    • Range in color from yellw to black
    • Extensively used as a natrual dyestuffs and purgatives
  87. What are some common quinones?
    Emodin, spinulosin
  88. What are Xanthones?
    • Plant pigments with structureal resemblance to flavonoids and quinones (glycosides)
    • H2O-soluble and yellow in color
  89. What is a common xanthone?
  90. What are melanins or malanoids?
    • Brown colored pifments found in fruits, vegetables, fundi (mushrooms) and crustacea
    • Formed from plymerization of phenolic compounds by PPO and Cu++
    • Formation of melanins desirable in certain foods, but undesirable in others
  91. How are melanins formed?
    Formed from polymerization of phenolic compounds by PPO and Cu++
  92. What are the 2 types of non-enzymatic browning reactions?
    • Caramelization
    • Maillard reactions
  93. What is caramelization?
    • From carbohydrates by heating
    • Has a nutty taste/smell
  94. What is maillard browning?
    • From interactions of sugars with amino groups from amino acids, proteins, eptides, amines
    • Maillard browning is enhanced by heating
Card Set:
Food Chem 2- Pigments
2012-10-24 01:43:53
Food chem

Show Answers: