Food Chemistry Chapter 17 in Green / Damjii

F.1: Food Groups

Homework

• Read F1 – Food Groups - pp. 475-476• Do Qs 1-6 • on p 490

F.1: Food Groups

• F.1.1: Distinguish between a food and a nutrient

Food

• Any substance we deliberately take into our mouths and swallow.

• Any natural or artificial material intended for human consumption

• Contains one or more nutrients

Nutrient

Component of food that is used by the body to • provide energy• Aide in growth and/or repair of tissue

A lack of these nutrients may cause • malnutrition

Major Nutrients

• Lipids• Carbohydrates• Proteins

Other Nutrients

• Vitamins• Minerals• Water

F.1: Food Groups

• F.1.2: Describe the chemical composition of lipids (fats and oils), carbohydrates, and proteins.

Major Nutrient - Lipids

Fats and Oils are…• Source of Energy• Vital in constructing cell membranes

Major Nutrient - Lipids• Contain C, H, O• Esters of glycerol and 3 fatty acids– Aka triglycerides

http://www.ilri.org/infoserv/webpub/fulldocs/ilca_manual4/images/fig_pg9.gif

Triglycerides“R” group can be…• SATURATED (no double or triple bonds)

– Tend to be SOLIDS at room temperature– Tend to come from animal products– “Fat”

• Unsaturated (has one double or triple bond)– Tend to be LIQUIDS at room temperature– Tend to come from plant material– “Oil”

• Polyunsaturated (has multiple double or triple bonds)

Nature of “R” group determines physical and chemical properties.

Which of these lipids is saturated?

Unsaturated? Polyunsaturated?

A

B

C

Which of these lipids is saturated?

Unsaturated? Polyunsaturated?

http://wpcontent.answers.com/wikipedia/commons/thumb/b/be/Fat_triglyceride_shorthand_formula.PNG/220px-Fat_triglyceride_shorthand_formula.PNG

http://www.biology.lsu.edu/introbio/Link2/triglyceride.gif

http://www.chm.bris.ac.uk/motm/ethylacetate/triglyceride.gif

Citations for images on previous slide

What about this one?

http://www.bio.miami.edu/~cmallery/150/chemistry/c4x5fatmolecule.jpg

Which of these lipids is saturated? Unsaturated?

Polyunsaturated?

Major Nutrient - Carbohydrates

Carbohydrates are…• Source of Energy• Vital in cell construction

Major Nutrient - Carbohydrates

• Empirical Formula = CH2O

Major Nutrient - Carbohydrates

• Simple Carbohydrates • Monosaccharides = (CH2O) n>2 = simplest

carbohydratesEx: Glucose

fructose

Major Nutrient - Carbohydrates• Disaccharide – formed from condensation of 2

monosaccharides.

Major Nutrient - Carbohydrates• Polysaccharides – formed from condensation

of many monosaccharides.Starch

Major Nutrient - ProteinsProteins …• build up, maintain, and replace tissues

(muscles, organs, imunne system) in your body • Primary component in hair and nails• make enzymes, hormones, and other body

chemicals• building block of bones, muscles, cartilage, skin,

and blood.

Major Nutrient - Proteins• Contain C, H, O, and N…

– And some contain P and S• Are polymers of amino acids• 22 important amino acids

– 13 body makes, 9 are “essential”

Major Nutrient - Proteins

Major Nutrient - Proteins

The R groups represent side chains of the amino acids involved and can be the same or different.

Food Chemistry Chapter 17 in Green / Damjii

F.2: FATS AND OILS

• Read F2 – Fats and Oils - pp. 476-477• Do Q 7-11• on p 491

Homework (Done in advance!)

F.2: Fats and Oils• F.2.1: Describe the difference in structure

between saturated and unsaturated (mono- and poly-unsaturated) fatty acids

Remember… 3 molecules of fatty acids react with 1 molecules of glycerol to form a lipid

F.2: Fats and Oils• F.2.2: Predict the degree of crystallization

(solidification) and melting point of fats and oils from their structure, and explain the relevance of this property in the home and in industry.

F.2: Fats and Oils• Melting point and hardness (degree of

crystallization) depend on– Length of hydrocarbon chain

• Longer chain = greater molar mass = more vdW forces = higher mp

– Degree of unsaturation• More double bonds = crooked chains = less contact =

fewer vdW forces = lower mp

– Cis or trans conformation• more cis = more crooked chains = less contact = fewer

vdW forces = lower mp• more trans = less crooked chains = more contact = more

vdW forces (compared to cis) = higher mp

Triglycerides• SATURATED (no double or triple bonds)– Tend to be SOLIDS at room temperature– Tend to come from animal products– “Fat”– Examples:• Coconut oil• Butter • lard

Triglycerides• Unsaturated (has one double or triple bond)

– Tend to be LIQUIDS at room temperature– Tend to come from plant material– “Oil”– Examples

• Olive oil• Canola oil• Peanut oil

• Polyunsaturated (has multiple double or triple bonds)– Example

• Sunflower oil• Corn oil• Fish oil

F.2: Fats and Oils• F.2.3: Deduce the stability of fats and oils

from their structure.• Unsaturated– More reactive, less stable– C=C double bond reacts with oxygen (auto-

oxidation)• Especially in sunlight (photo-oxidation)• Margarine gets discolored

– Hydrogenation– Degradation by microbes

F.2: Fats and Oils

• F.2.4: Describe the process of hydrogenation of unsaturated fats.

Hydrogenation• Addition of hydrogen– Hydrogen @ high pressure– Temp ~ 200 C– Nickel catalyst

F.2: Fats and OilsF.2.5: Discuss the advantage and disadvantages

of hydrogenating fats and oils. • A hydrogenated product is

– more saturated… or fully saturated…– semi-solid or solid…

• Advantages of a hydrogenated product is– Form is more convenient for some cooking

techniques– More stable (rate of oxidation is decreased)– Texture can be controlled ( hardness / plasticity)

can be controlled

F.2: Fats and OilsDisadvantages: …. health related• Mono- and poly-unsaturated are healthier for

the heart than saturated fat.• Partial hydrogenation can form trans-fats– trans-fats don’t occur naturally – difficult to

metabolize– accumulate in fatty tissues of body– Increase levels of LDL chloesterol (associated with

atherosclerosis… strokes… heart problems)

What is this?

Olestra – a fat substitute that isnot digested by the body

Copyright © 1997 by Daniel J. Berger.

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