Food 2010 DE
Chapter 6: Summary
6.1 Food Color Chemistry
• Food technologists can address quality assurance issues regarding color stability,
important in both unprocessed foods and processed foods during storage.
• Color describes a perception of a physical attribute of food arising from a
collection of sensations. These sensations come from the rods and cones in the
retina of the eye.
• Rods are sensitive to lightness and darkness while the cones are sensitive to RGB
color. Reflected light is the light that determines the color of the food.
• If a food object reflects all of the colors then it is assumed to be white, while one
that absorbs all of them is black.
• The three classes of cones tend to overlap in their sensitivity to color, which
means that many shades of the color such as green are possible since green light
stimulate not only green cones but also red and blue ones as well.
• Pigment (Chromophoretic) compound sin foods constitute a structurally diverse
group and possess extremely complex chemical and physical properties. Color
can also be classified based on its chemical structure.
• Five major groups of natural food pigment molecules can be found in the plant
kingdom while the fifth one can be discovered in the animal kingdom. Lipid
soluble chlorophylls, carotenoids, watersoluble anthocyanins and betalins are
found in the plant kingdom while heme protein myoglobins are found in the
• Myoglobin is the reason why fresh meat consists of a red color. Myoglobin is a
single polypeptide and a globular protein, which contains heme and is composed
of amino acids.
• Myoglobin has the ability to bind oxygen because of its globin tertiary structure
and cause of heme (iron porphyrin ring). Iron is present in the center of the
porphyrin ring, which is surrounded by methane bridges and nitrogen atoms. The
oxidation and reduction phases of myoglobin are the reason why meat changes
color from red to brown.
• When meat is cut the myglobins iron portion binds loosely to oxygen to create
oxymyoglobin, which produces a bright red color (Oxygenation). If the meat is
continued to be exposed to oxygen then oxidation occurs which turns the myoglobin to met myoglobin, which is responsible for the transformation of meat
• Meat color at the point of purchase is based on packaging material, the number of
bacteria, the species of animal, the animals age, the amount of myoglobin in the
animal’s tissue, and the particular muscle source
• All plant pigment molecules contain conjugated double bonds
• Chlorophyll contains metal coordinated porphyrin ring. Color is based on the
resonance within the ring structures in porphyrin rings.
• Plant pigment molecules are classified into 3 groups: 1. Phenolic based pigments
2. The carotenoids 3. Chrophylls
• Anthocyanins: Are watersoluble flavonoid compounds that range in color from
deep purple to orangered. PH sensitive being red in strong acids and colorless at
pH 4 and blue at neutral level
• Anthoxanthins: Colorless or white pigments than can become yellow
• Betalains: Represent a group of two types of watersoluble plant pigments. 1.
Betacyanins, which encompass about 50 violet red pigments. 2. Betaxanthins a
series of about 20 yellow pigments
• Carotenoids: Fat soluble plant pigme