Chapter 16 Food: Those Incredible Edible

Chemicals

Chapter 16 2

Food • Three main classes:

– Carbohydrates– Fats– Proteins

• Also need:– Water– Fiber– Vitamins– Minerals

Chapter 16 3

Carbohydrates

• Sugars– Used as sweetener– Absorbed directly into bloodstream

• Come in several forms: glucose, fructose, sucrose

• Lactose, milk sugar, digested by nearly all human babies, but few adults lack enzyme to start breakdown

Chapter 16 4

Complex Carbohydrates

• Starch: digestible polymer of glucose– Releases glucose when broken down– Supply 4 kcal/gram– Store small amounts in liver and muscle: glycogen

• Cellulose: indigestible polymer of glucose– Also known as fiber– Most abundant carbohydrate– No caloric value

Chapter 16 5

Fats

• High-energy food– 9 kcal/gram

• Build and maintain cell membranes

• Mainly triglycerides– Ester of glycerol and fatty acids

• Stored in adipose tissue– Insulate vital organs from shock– Insulate body against temperature changes

Chapter 16 6

Chapter 16 7

Saturated Fats

• Implicated in arteriosclerosis– Hardening of arteries

• Strong correlation between them– Typically need cholesterol as well

• Deposits form on inner walls of arteries• Blood clots get lodged

– Stroke, if it occurs in brain– Heart attack, if in heart

Chapter 16 8

Lipoprotein

• Group of proteins combined with a lipid– typically triglycerides and cholesterol

• Classified according to density

Chapter 16 9

Fats and Cholesterol in Blood

• Not all fats are bad– Prefer mono-unsaturated fats found in olive and

canola oil– Polyunsaturated fats may also be good

• Natural unsaturated fats are cis isomers

• Adding hydrogen may produce trans isomers– May raise cholesterol levels

Chapter 16 10

Chapter 16 11

Proteins

• Broken down into amino acids– Used mainly to produce useful proteins– Produce: muscle, hair, enzymes, …– Only excesses used for energy production

• Body can synthesize all but eight amino acids– Essential amino acids– Combined plant sources to get all of them

Chapter 16 12

Minerals

• Also known as dietary minerals– about 4% weight of human body

• Some used for bulk and structural uses

• Ultra-trace elements: need only at very low levels– Some have no known function

• Too much of any mineral may be toxic

Chapter 16 13

Chapter 16 14

Vitamins

• Specific organic compounds required in the diet to prevent specific diseases

• Two broad classes

• Fat soluble– Store excess– May lead to overdose

• Water soluble– Excrete excess– May be lost during cooking

Chapter 16 15

Dietary Fiber

• Takes up space in stomach

• Insoluble fiber: made of cellulose– May prevent some digestive problems

• Soluble fiber: made of sticky materials– Help remove bile acids that digest fat– May slow sugar absorption

Chapter 16 16

Water

• Makes up most of the food we eat

• Require 1–1.5 L of water per day– May need more after exercise or on hot

days

• Carbonated beverages long ago replaced water as beverage consumed most in U.S.

Chapter 16 17

Starvation

• Human body deprived of food• Weakening during starvation, makes

you more susceptible to disease• Body consumes itself in order to get

energy– Glycogen– Fat tissue– Muscle

Chapter 16 18

Processed Food

• Processing removes some of the nutrients

• Nutrients may also be removed by cooking process

• Manufacturers may add important vitamins and minerals back to food – Not all nutrients are necessarily added

back

Chapter 16 19

Food Additives

• Substances other than basic foodstuffs that are present in food as a result of some aspect of production, processing, packaging, or storage

• Sugar, salt, and corn syrup used in greatest amounts

• Used since ancient historic times

• In U.S., regulated by FDA

Chapter 16 20

Additives

• Enrichment: adding nutrients back to foods

• Many spices and flavoring agents added to improve taste – Some flavoring agents have been purified

and used directly– When used in moderation, present little in

health hazards

Chapter 16 21

Artificial Sweeteners• Developed to help combat obesity

• Tend to be polyhydroxy compounds

• Varying amounts of sweetening ability

Chapter 16 22

Flavor Enhancers

• Do not have much flavor

• Enhance other flavors

• Most common one is table salt– Enhances sweetness and may mask

bitterness and sourness

• Also use monosodium glutamate (MSG)

Chapter 16 23

Spoilage Inhibitors

• Inhibit growth of bacteria and molds– Common ones include NaNO2 and SO2

• Prevent oxidation of foods– Occurs when fats go rancid– Usually occurs by production of free

radicals– Use antioxidants to prevent this from

happening

Chapter 16 24

Food Coloring

• Expectation that foods will have certain colors– Would you drink bright blue milk?

• Many dyes exist to color food

• Label must clearly indicate if artificial colors are present

Chapter 16 25

Poisons in Food

• Some are natural– Botulism toxin– Oxalic acid– Aflatoxins

• Some cause cancer– Aflatoxins

• Some are toxic– Botulism toxin

Chapter 16 26

Incidental Additives

• Get in accidentally during production, packaging, or storage

• May include: pesticide residues, insect parts, and antibiotics given to animals– Antibiotics used to promote weight gain– Government-accepted levels of insect

parts in grain – impossible to remove all

Chapter 16 27

Life Without Additives?

• Food would be blander– No spices or flavor enhancers

• More rapid spoilage of food– Would reduce amount of food available

• Possible vitamin or mineral deficiencies

Chapter 16 28

Growing Food

Chapter 16 29

Fertilizers

• Three primary plant nutrients:– Nitrogen, potassium, and phosphorus

• Add them to increase crop production

• Replace lost nutrients in soil

• Allows support of more people on a given area of farmland

Chapter 16 30

Nitrogen• Some plants fix nitrogen out of air

– Legumes: e.g., clover and peas

• Rotate with nitrogen-consuming crops – corn

• Use chemical fertilizers to avoid having to alternate crops in a given field– Typically use ammonia-based fertilizers

Chapter 16 31

Phosphorus

• Often limiting growth factor in plants

• Used as fertilizer since ancient times

• Historically, produced from bones, guano, or fish meal

• Produced today from phosphate-containing rock– ~90% used for agriculture

Chapter 16 32

Potassium Fertilizer

• Usually abundant

• Produced from various mines around world

• Essential to fluid balance of the cell

Chapter 16 33

Other Essential Elements

Chapter 16 34

War Against Pests

• Insecticides: substances that kill insects

• Pesticides: substances that kill organisms that we consider pests

• Early pesticides contained arsenic

• May have some toxicity to other creatures

Chapter 16 35

DDT: Dream Insecticide

• Easy to produce

• Highly effective

• Did not show toxicity to humans

• Used extensively during World War II– Slowed down spread of malaria, kept lice

population in check – Saves millions of lives

Chapter 16 36

Decline and Fall of DDT

• Overuse led to insects developing resistance to DDT

• Pesticide persistence: substance did not readily break down in environment

• Toxic to fish as well as insects

• Also get biological magnification

Chapter 16 37

Biological Magnification

Chapter 16 38

Biological Insect Controls

• Use natural enemies to get rid of pests• May not be as effective as chemical pesticides• Possible to insert genes that confer pest

resistance• Many ways to do this

– Sterilization– Pheromones– Juvenile hormones

Chapter 16 39

Herbicides and Defoliants

• Herbicides: kill weeds– Allow for more abundant harvests

• Defoliants: cause leaves to fall off plants– Used to help harvest of crops– Example: makes harvesting of cotton

easier

• May see buildup of resistance

Chapter 16 40

Energy Flow of Modern Agriculture

Chapter 16 41

Sustainable Agriculture

• Organic farming uses less energy but requires more labor and produces fewer crops

• Sudden switch to organic farming could be disastrous

Chapter 16 42

Malthusian Mathematics

• Basically said: Population grows faster than food supply; humans must control birthrate

• Arises from difference in arithmetic growth vs. geometric growth

Chapter 16 43

Can We Feed the World?

• Increased food production since Malthus’ time

• Still hungry in this day and age

• Caused by: war, poverty, and lack of arable land

• Modern agriculture dependent on cheap energy