Textbook Notes (368,060)
Canada (161,608)
Food Science (205)
FOOD 2010 (197)
Chapter 6

Chapter 6 summary.docx

6 Pages
Unlock Document

Food Science
FOOD 2010
Massimo Marcone

Chapter 6: Food Chemistry III, Color, Flavor and Texture 6.1 Food Color Chemistry What is color?  color is a perception of a physical attribute of food arising from a collection of sensations  Food object is either absorbed, reflected or transmitted  Reflected light determines the color of a food  Surface color of food objects can be characterized by 3 qualities: 1. Hue: actual color name (red, blue, green) 2. Saturation or chroma: clarity and purity of the color 3. Intensity: the range from lightness to darkness of color o Surface appearance characteristics: (1) shinny, (2) glossy, (3) cloudy and (4) translucent Pigment molecules  Red color of ground beef= presence of special molecules in beef called pigment molecules  Chromophoretic (pigment): compounds in foods constitute a structurally diverse group and posses extremely complex chemical and physical properties The color chemistry of red meat  Myoglobin: single polypeptide, a globular protein containing the globin protein part and a prosthetic group called heme - globin= polypeptide: composed of amino acids (attached to heme) - has the ability to bind oxygen because of its globin polypeptide tertiary structure and heme (iron porphyrin ring complex; composed of 4 pyrrole units that are connected by methane bridges and has 4 nitrogen atoms in corners) - oxidation of iron causes the color  Oxymyoglobin: myoglobin derivative responsible for a bright red color th - oxygenation: Fe 2+ myoglobin binds oxygen at 6 binding site and oxygen becomes part of pigment complex  Metmyoglobin: myoglobin derivative associated with aged meat exposed to air, producing a grayish of brown meat color - iron in metmyoglobin changes from the reduced Fe2+ to Fe 3+ which alters the color  Nitric oxide myoglobin: bright pink-red myoglobin reacted with nitric oxide  Other types: choleglobin and sulfmyoglobin: result form bacterial action on contaminated meat to yield green colors (oxidation of porphyrin ring) The color chemistry of fruits and vegetables  Appealing color of fruits + vegetables is due to occurring plant pigments that absorb and reflect light at certain wavelengths  Conjugated double bonds: all plant pigments are composed of these. These are alternating single and double carbon to carbon bonds: C = C – C = C  color is result of resonance within the ring structures in porphyrin rings and conjugated carbon chains (resonance electron spread across atoms contain single and double bonds; movement across carbon-carbon bonds = color 3 GROUPS OF PLANT PIGMENT MOLECULES: 1. Phenolic based pigments Anthocyanins: are water-soluble flavonoid compounds that range in color from deep purple to orange-red - flavonoid: chemically related phytochemicals, contains 2 phenol rings and intermediate ring of variable structure - pigment color is pH sensitive - chemical structure  combination of aglycone molecule attaché to sugar molecule by glycosidic bond - anthocyanidin: anthocyanin broken apart into sugar and free aglycone (e.g. pelargonidin, cyanidin, delphinidin) Anthoxanthins: colorless or white pigments that can become yellow. Contribute slightly to food color. (found in animal) Betalains: group of 2 types of water-soluble plant pigments (betacyanins: 50 violet-red pigments. Betaxanthins: series of 20 yellow pigments) (e.g. betanin, betanidin, vulgaxanthin) 2. Carotenoids: class of fat-soluble plant pigments that consists of carotenes (hydrocarbon, polymers of isoprene) and xanthophylls (oxygenated carotenoids) (example of carotenes: beta-carotene and lycopene) (example of xanthophylls: lutein) red, orange, yellow, easily oxidized 3. Chlorophylls: green-lipid soluble plant pigments that contain a porphyrin ring complexed to magnesium, fat soluble - chlorophylls a and b with acid, heat, Mg2+  produce pheophytin: gray- green and olive-green degradation product - pheophytin + heat + CO2CH3= pyropheophytin - chlorophyll + chlorophyllase (enzyme) = chlorophyllide - chlorophyllide + acid + heat Mg2+ = Pheophorbide - chlorophyllide heat + CO2CH3 = pyropheophorbide The color chemistry of food colorants  Colorant: pigments used to impart color to a food or beverage (1) natural colorants (naturally derived) (2) synthetic colorants FD&C colorants - all color ingredients are additives - certified as safe by FDA for use in food, drugs and cosmetics. - all contain phenolic ring having double bonds and various functional groups - dyes: water soluble chemicals that are used to color entire food products - lake: insoluble powder formed by precipitation of a water-soluble food colorant. They are derived from dyes and used to color the surface of foods or fat-based products, including chocolates. Exempt colorants  Cochineal extract: derived form dried bodies of cochineal insects. Is a anthraquinone, major pigment is carminic acid  Caramel color: coloring agent used at low concentrations in foods and beverages. Formation of caramel is through nonenzymatic thermal: caramelization 6.2 Food flavor chemistry Flavor: property of food material and the receptor mechanisms of human body (taste + aroma) Chemical structure and taste - substance to produce taste has to be water soluble  pungency - sensation of spicy heat, due to specific chemicals from cruciferous veggies and chili peppers - causes warming sensation in the mouth and lips - endorphins are released, causing pleasure amongst pain - Capsaicinoids: pungent alkaloid compounds that occur in chiles (capsaicin, dihydricaosaicin) - Scoville heat unit: unit of measure of hotness in chiles  cooling sensation - due to methanol and its isomers causing a minty flavor and aroma - coolness sensation in the mouth - can also be due to sugar alcohols - Polyols: are polyhydric alcohol counterparts of the sugars maltose, sucrose and xylose; maltitol, mannitol, sorbitol (has humectant properties; prevent products rom drying out) and xylitol Process and reaction flavors - Nonenzymatic browning: duration and temperature of thermal processing affect flavor of cooked foods (e.g. caramelization of sugar) - e.g. in baking of bread the Maillard reaction generates dicarbonyl compounds such as glyoxal. These can react with amino acids through a series of steps called Strecker degradation to produce pyrazine. These contribute to flavor and aroma of bread  Producing food flavors - Food flavorists isolate and develop flavoring ingredients; flavor compounds or additives (see table 6.9 on p.165) - process flavor substances are obtained by heating a variety of substances (including at least one nitrogen and a reducing sugar) - reaction technology can produce reaction flavors - reaction flavors are produced by chemical reactions under c
More Less

Related notes for FOOD 2010

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.