FDSCI 501 - Pigments

What are the main forms of myoglobin in muscle foods?

Deoxymyoglobin, oxymyoglobin, metmyoglobin, and nitrosomyoglobin (cured meats)

Describe deoxymyoglobin

Native protein; ligand = none (or H2O); iron = Fe2+ (ferrous); color = purple-red (vacuum packaged meat)

Describe oxymyoglobin

Native protein; ligand = O2; iron = Fe2+ (ferrous); color = bright cherry red (fresh meat exposed to air)

Describe metmyoglobin

Native protein; ligand = H2O; iron = Fe3+ (ferric); color = brown (oxidized meat)

Describe nitrosomyoglobin (cured meat pigment)

Denatured (after cooking); ligand = NO; iron = Fe2+; color = pink/red (cured meats like ham)

What is a nitrosamine?

A class of compounds formed from reaction of nitrite (NO2−) with secondary amines; many are carcinogenic

How are nitrosamines formed in cured meats?

Nitrite reacts with amines (especially during high heat cooking) to form nitrosamines

Key structural differences between chlorophyll and myoglobin

Chlorophyll contains Mg2+ (not Fe), has a phytol tail, lacks a tightly bound protein structure, and has a modified porphyrin ring (extra पाँच-membered ring)

What metal is in chlorophyll vs myoglobin?

Chlorophyll: Mg2+; Myoglobin: Fe2+/Fe3+

What is phytol and how does it differ between chlorophyll and myoglobin?

Chlorophyll has a long hydrophobic phytol tail; myoglobin does not

List chlorophyll derivatives and their properties

Chlorophyll (Mg, phytol, fat soluble); pheophytin (-Mg, phytol, fat soluble); chlorophyllide (Mg, -phytol, water soluble); pheophorbide (-Mg, -phytol, water soluble); chlorins (-Mg, -phytol, oxidized, water soluble)

Which chlorophyll derivatives are lost during canning (heat processing)?

Water-soluble forms: chlorophyllide, pheophorbide, and chlorins

What are key properties of carotenoids?

Fat-soluble, highly conjugated (color), isoprene-based polymers, sensitive to oxidation, provide yellow/orange/red colors

What are xanthophylls?

Oxygenated carotenoids (contain O groups such as hydroxyl or ketone); more polar than carotenes (e.g., lutein, violaxanthin)

Examples of carotenoids used in fish feed

Astaxanthin and canthaxanthin (used to give pink/red color to fish like salmon)

Where are betalains found?

Mainly in beets (red beets) and some plants; water-soluble red pigments

List common anthocyanins and their sources

Cyanidin (apples, berries, cabbage); delphinidin (grapes, blueberries); pelargonidin (radish); peonidin (plum); petunidin (grapes, blueberries); malvidin (grapes)

Why are anthocyanins not used in foods with pH > 4?

They are unstable at higher pH, losing red color and degrading into colorless or undesirable forms

What are the benefits of using synthetic food colors over natural colors?

More stable to heat, light, and pH; more consistent color; higher intensity (need less); lower cost; wider range of colors; longer shelf life

What does FD&C stand for?

Food, Drug, and Cosmetic; colors approved for use in foods, drugs, and cosmetics

What does D&C stand for?

Drug and Cosmetic; colors approved for drugs and cosmetics but not necessarily foods

What are lakes in food coloring?

Insoluble forms of dyes made by precipitating them onto aluminum salts; used in fat-based or low-moisture foods (e.g., coatings, candies)

Why are lakes used instead of dyes?

They are more stable in certain applications and disperse better in fats/oils where water-soluble dyes cannot

What are some common natural food colors?

Carotenoids (beta-carotene, annatto), anthocyanins (fruit pigments), chlorophyll, turmeric, paprika, saffron, beet powder

What is carmine?

A red natural color derived from carminic acid, which is extracted from dried female cochineal insects; used in products like beverages, dairy, and candies

What is a key concern with carmine?

Can cause allergic reactions in some individuals and must be labeled on food products