NATURE OF MATTER
CH 4 BASIC FOOD CHEMISTRY
SUBATOMIC PARTICLES
Proton= positive charge
Neutron = neutral
Electrons= negative charge
Orbital- space occupied by
a pair of electrons in an
atom
ELEMENTS
C, H ,O ,Na ,N ,P ,Ca ,Fe ,S
• Why are these important in food science?
• What are common in foods?
• (16 of them).. How many can you name? Pg 93
COMMON ELEMENTS IN FOODS:
Aluminum
Calcium
Carbon
Chlorine
Fluorine
Hydrogen
Iron (Ferrum)
Magnesium
Nitrogen
Oxygen
Phosphorus
Sodium
Sulfur
Zinc
IRON IN CEREAL ACTIVITY
H
O,
Na,
N,
P,
Ca,
Fe,
S
ELEMENTS
METALS AND NONMETALS
Color code your elements on your periodic chart using colored pencils:
• Alkali metals
• Halogens
• Other metals
• Transition elements
• Alkaline earth metals
• Noble gases
• Metalloids
• Lanthanides
• Other nonmetals
• Actinides
COMPLETE: TRAILBLAZING THE ELEMENTS PUZZLE
COMPOUNDS AND FORMULAS
• Compounds are two or more atoms combine that are different elements
• Chemical formulas are a combination of symbols and elements that make a compound
You Do!!!
Create a model of a benzene using marshmallows and toothpicks:
Note double bond and single bond
BENZENE RING = C6H6
BONDING:
• Force that holds atoms together
IONIC VS COVALENT BONDING PG 96-99
• Complete a Venn diagram for the two types of bonds
MATTER CLASSIFICATION:
All basic units
are the same
Non uniform
particles
Salt (NaCl)
Baking soda
(NaC2)
have carbon
Uniform distribution of particles
potassium
SOLUTION
• Homogeneous mixture of one material dissolved in another
•
Solute is material dissolved
•
Solvent is what dissolves the solute
•
Water is a common solvent
PHYSICAL AND CHEMICAL CHANGES
• Physical changes involve change in shape, physical state, or temperature
• Phase changes--- solid, liquid or gas
•
Release CO2 from soda
NON NEWTONIAN FLUID
• Characteristics of liquids and solid
• Example; ¼ c corn starch + 2 T water
CHEMICAL CHANGES
• New substances with different chemical and physical properties
•
•
Produce changes in
•
Color
•
Odor
•
Flavor
•
Release of gas
Baking soda and acid in muffins create co2 as leavener
PHYSICAL OR CHEMICAL CHANGE?
• Brewing tea
• Sweetening lemonade
• Browning pork chops
• Basting a turkey as it roasts
• Slicing tomatoes
PERMANENT VS REVERSIBLE CHANGES
• Reversible freezing juice and thawing
• Food digestion is reversible- energy stored as fat can be released and turned back to glucose
CHEMICAL EQUATIONS
• Law of conservation of
matter= matter is changed,
but not created or destroyed
CHAPTER 22
• Pg 680-690
…CHEMICAL PROPERTIES OF FOOD CONSTITUENTS AND
HOW THOSE CONSTITUENTS AFFECT THE PHYSICAL
PROPERTIES OF FOODS”
• Tissues vs Dispersions
• Major and Minor food
components
MIXTURES
• Small Particle systems
•
= less than 600 microns
• Particles of one substance are distributed (disperse phase) in another substance (continuous phase)
•
WITHOUT Dissolving
FOOD/ COLLOIDAL DISPERSIONS
• Small Particle systems
•
= less than 600 microns
• Particles of one substance are distributed (disperse phase) in another substance (continuous phase)
•
WITHOUT Dissolving
CHARACTERS OF COLLOIDAL DISPERSIONS
• A.
PG 680-690
continuous plus dispersed phase
• B. continuous phase are small molecules
• C. dispersed phase are colloids ( particles / macromolecules/ clumps of molecules)
• Examples: jelly, mayonnaise , butter, gelatin
TYPES OF COLLOIDAL DISPERSIONS
•Foams
•Emulsions
•Gels
EXAMPLE: FOAMS
• Dispersion of gas in a liquid
• Cake frosting
• Air beaten into the white is the dispersed phase
• Egg white protein is the continuous phase
COLLOID VS SOLUTE
colloid
• Up to 1000x larger particles
• Larger size causes dispersing not dissolving
• No notable impact on freezing and boiling point
• Bend/ reflect a laser passing through it
•
So laser light is visible within it
solute
• Laser light isn’t visible within it, only on each
side of the container.
• Concentration of particle affects freeze/ boil
point
Tyndall effect
FACTORS THAT KEEP COLLOIDS DISPERSED
1.Motion of the molecules 2.Electrical charge
• The lower the mass of the smaller particles of
the continuous phase, they move faster.
• Same substances have same charge
• Molecular motion keeps them dispersed
• The polarity of water cushions the colloid and
keeps it from sticking to itself and settling out
• Like charges repel, pushing colloids away from
each other
EFFECTS OF PARTICLE DENSITY
• The density of particles can make them separate if mixture is not constantly stirred.
•
ie) starch sinking to bottom of pan
•
Milk protein scorching on bottom of pan
TYPICAL FOOD DISPERSIONS
Dispersed
phase
Continuous
Phase
Name of dispersion
examples
Solid
Liquid
Sol
Starches, proteins, some plant
polysaccharides in water
Liquid
Solid
gel
Starch paste, pectin, proteins
(jams, jellies, tofu, gelatin).
Gas
Liquid
Foam
Whipped egg whites and cake frosting
Gas
Solid
Solid foam
Meringue, ice cream, bread
Liquid (0il)
Liquid (water)
Emulsion
Milk, mayonnaise, salad dressings, ice
cream, cake batters, whipping cream
Liquid (water)
Solid (fat)
Solid emulsion
Butter, margarine, Lard
MILK IS A COLLOIDAL DISPERSION AND A SOLUTION
colloidal dispersion
• Proteins in milk - stable
solution
• Lactose
• Mineral salts
• Both dissolved in the water
Fat particles – unstable until homogenization occurs
EMULSIONSTWO IMMISCIBLE LIQUIDS WHERE ONE IS DISPERSED IN
DROPLET FORM INTO THE OTHER
how emulsions work
• Two types
• Oil in water
water in oil
E.G. EMULSIONSTWO IMMISCIBLE LIQUIDS WHERE ON IS DISPERSED IN DROPLET FORM IN THE OTHER
External phase=water
External =
Continuous
phase
Internal =
Dispersed
phase
External phase= oil/fat
Oil/water emulsion
(liquid emulsion)
Oil IN water
(water/ oil emulsion
(solid emulsion)
Water IN oil
Eg. Milk, mayo,
salad dressings
Eg. Margarine, butter
Solidify during processing
EMULSIFIERS
• One polar and one nonpolar end
• Most emulsifiers require beating, agitation, or stirring
MAYONNAISE
• % of fat in mayonnaise = about 65%
• Oil phase in highest proportion’
• Remains Oil/ water (not water/ oil)
•
Unatural emulsion
• Difficult to prepare
• Unstable
• Adding oil----RATE AND ORDER is IMPORTANT
• Emulsifier
MAYONNAISE
• Oil is dispersed in vinegar ( water) with egg yolk as the emulsifier
• Egg yolk surrounds the oil droplets scattered throughout
• Vinegar or lemon juice also provide an acidic environment to ensure the presence of charged groups on
the protein
• http://www.youtube.com/watch?v=qnudmk_63r4
FOAMS:
COLLOIDAL DISPERSIONS OF GAS OR AIR BUBBLES DISPERSED IN A LIQUID
• Example) foams atop of soda/beer are unstable foams
•
whip topping, meringue, whipped cream are stable foams
• For stability 4 conditions needed:
• 1. viscous liquid ( thickness of liquid + elastic nature of protein)
• 2. dispersion needs a stabilizer to form around air bubbles
• 3. surface tension of the bubbles formed need to be less than water in the food.
• 4. the liquid needs a low vapor pressure
•
FACTORS THAT AFFECT FOAM STABILITY
• 1. temperature of ingredients, utensils, room
• 2. addition of solutes
• what( sugar bonds to hydrogen of water/ increases the viscosity)
• When
• How
• 3. Acidity
• Cream of tartar
• Age of eggs
• 4. no fat allowed
• From egg yolk
• From equipment
•
’
SUSPENSIONS
MIXTURE OF UNDISSOLVED PARTICLES IN A LIQUID
• MILK is a complex mixture: suspension and colloidal dispersion
•
Fat
and protein particles
• The larger the particles, the thicker, more viscous suspension must be
• Batters vs doughs
•
1 part liquid : 1 part dry
vs
1 part liquid : 3-4 parts dry