HNSC 2150 Pigments

Which of the following is NOT true about pigments?

Colorants are not pigments but chemical compounds that impart color to food

What are the two main groups of pigments?

Synthetic and natural

What is the function of a pigment in a living organism?

Pigments may have properties beyond that of a colorant&such as acting as energy receptors or protecting against radiation

Which of the following is an example of a natural pigment?

Chlorophyll is a natural pigment found in plants that imparts a green color

Which of the following is NOT a group of plant pigments found in fruits and vegetables?

Anthocyanins are not one of the three main groups of plant pigments found in fruits and vegetables

What is the main color associated with chlorophyll?

Green is the main color associated with chlorophyll

Which group of plant pigments is responsible for the red&orange&and yellow colors in fruits and vegetables?

Carotenoids are responsible for the red&orange&and yellow colors in fruits and vegetables

Where are chlorophyll pigments found in a plant?

Chlorophyll pigments are found in chloroplasts in plant cells

Which group of plant pigments is water-soluble?

Flavanoids are water-soluble and are found in cell sap in plant cells

Which of the following is NOT a pigment responsible for color changes in plants?

Flavanols are not pigments responsible for color changes in plants

What is the main pigment responsible for the green color in plants?

Chlorophyll is the main pigment responsible for the green color in plants

What happens to chlorophyll during the ripening process of some fruits?

During the ripening process of some fruits&chlorophyll degrades and other pigments are unmasked

Which pigment is responsible for the red color in apples and grapes?

Anthocyanins are responsible for the red color in apples and grapes

Which pigment is responsible for the orange color in tomatoes and oranges?

Carotenoids are responsible for the orange color in tomatoes and oranges

What is the central ion in the porphyrin ring of chlorophylls?

Magnesium is the central ion in the porphyrin ring of chlorophylls

What is the primary function of chlorophylls in plants?

The primary function of chlorophylls in plants is photosynthesis

What happens to the chlorophyll content of fruits and vegetables as they ripen?

As fruits and vegetables ripen they lose chlorophyll

What is the role of ethylene in the ripening of fruits and vegetables?

Ethylene stimulates the ripening of fruits and vegetables

What protects chlorophyll from degradation?

Cytokinins protect chlorophyll from degradation

What is required for chlorophyll synthesis?

Light is required for chlorophyll synthesis

What are some factors that can cause degradation of chlorophyll?

pH&oxidation&and chlorophyllase can cause degradation of chlorophyll

What happens to chlorophyll when the Mg2+ ion is replaced with H+ ions at low pH?

Chlorophyll becomes dull olive-brown pheophytin when the Mg2+ ion is replaced with H+ ions at low pH

What is pheophytin?

Pheophytin is a type of chlorophyll molecule lacking a central Mg2+ ion

What is chlorophyllase?

Chlorophyllase is an enzyme that removes the phytol group from chlorophyll

What is blanching?

Blanching is a process that involves subjecting vegetables to heat treatment to inactivate enzymes that destroy color

What is the role of Lox enzyme in the degradation of chlorophyll?

Lox enzyme catalyzes oxidative reactions that lead to the degradation of chlorophyll to colorless compounds

What is the main reason for degradation of carotenoids in foods?

Oxidative reactions

What is the difference between carotenes and xanthophylls?

Carotenes are entirely hydrocarbon while xanthophylls contain oxygen

Which of the following can degrade carotenoids in foods?

Lox

What is the importance of the double bonds in the trans position for carotenoids?

They allow the molecules to be fully extended

How does heating affect the trans configuration of carotenoids?

It changes it to a cis configuration

What is the effect of changing to the cis form on carotenoid color?

It decreases the color intensity

Which carotenoid has more double bonds lycopene or β-carotene?

Lycopene

What can cause a blue-colored anthocyanin to convert to a red color?

A change in pH from neutral to acid

What can bleach the color of anthocyanin to produce a yellowish color?

Presence of sulfites

What are carotenoids responsible for?

Many of the yellow&orange and red colors of plant and animal products

What kind of compounds are carotenoids?

Lipid-soluble

Are carotenoids polyunsaturated compounds?

Yes

Do all carotenoids have a ring at one or both ends?

No

What are the two main groups of carotenoids?

Carotenes and Xanthophylls

Which carotenoid is responsible for the major yellow color of marigold petals?

Lutein

Which carotenoid is commonly found in carrots?

β-carotene

Which carotenoid is commonly found in tomatoes?

Lycopene

What is the basic structure of flavanoids?

Two benzene rings held together by a three-carbon chain&together with oxygen

What is the most common type of flavanoid in nature?

Anthocyanins

What colors do anthocyanins give to fruits?

Red&mauve&violet&and blue

What is the meaning of the Greek words "anthos" and "kyanos" in relation to anthocyanins?

Flower and blue

In what form do flavanoids occur in nature?

As glycosides

What are anthocyanidins?

The aglycones of flavanoids

What factor determines the color of anthocyanidins?

The group substitution in the structure

How does the presence of OCH3 affect the color of anthocyanidins?

It makes the color more red

What is the effect of increasing pH on the color of anthocyanidins?

Shifts the color to blue

Which metal ions can anthocyanidins form complexes with?

Iron&calcium&and tin

What can cause the loss of anthocyanidin color?

Sulfur dioxide

What is the purpose of blanching vegetables?

To inactivate enzymes that destroy color

What is myoglobin?

A protein found in meat

How does the quantity of myoglobin impact meat color?

The more myoglobin the darker the meat

How does myoglobin content change with age within species?

Myoglobin content decreases with age

What is the myoglobin content in pork?

2 mg/g

What is the myoglobin content in lamb?

6 mg/g

What is the myoglobin content in beef?

8 mg/g

What is the difference between "red" and "white" muscle fibers in terms of meat color?

"Red" muscle fibers have more myoglobin than "white" muscle fibers resulting in a darker meat color

What causes meat cooked well-done to turn brown?

The iron atom is in the +3 oxidation state

Which of the following is an antioxidant that can retard the conversion of reduced myoglobin and oxymyoglobin to metmyoglobin?

Vitamin E

What is the impact of wrapping film on meat color?

It can prevent oxygen from reaching the meat and causing discoloration

How does vitamin E feeding of cattle impact meat color?

It retards the conversion of reduced myoglobin to metmyoglobin

What is the normal pH range of muscles before post-mortem changes occur?

5.5-5.7

What is the effect of slow pH decline on meat color?

Darker color