STEM Electrophoresis with Food Dyes
Bio-Rad Biotechnology Explorer™ IDEA and STEM Kits
Instructors - Bio-Rad Curriculum and Training
Specialists
Sherri Andrews, Ph.D., Eastern US
sherri_andrews@bio-rad.com
Damon Tighe, Western US
damon_tighe@bio-rad.com
Leigh Brown, M.A., Central US
leigh_brown@bio-rad.com
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Why Use Bio-Rad?
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
Guaranteed to work

Easy to prep

Cost Effective per student group
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Easy, inexpensive first exposure to electrophoresis
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Independent inquiry opportunities for what dyes are present in food
items, what is the charge of the dyes, can they be separated based on
charge/size?

Engineering inquiry with STEM kit ranging from optimizing metal
composition and diameter for electrodes, gel matrix composition, buffer
composition, etc.

Extensions including paper chromatography, spectroscopy, and
researching food dyes commonly used
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Separation technology: How do you separate
two or more compounds from each other?
Materials to be Separated
Property Used to
Separate Components
Explanation
Iron filings from other metals
Magnetism
Iron filings will be attracted to a magnet
while other metals will not
Salt from sand
Solubility
Salt will dissolve in water and can be
separated from the sand
Caffeine from coffee beans
Solubility
A solvent is used that selectively
dissolves the caffeine (such as
dichloromethane or ethyl acetate) but
not most of the remaining coffee oils
Ethanol from fermented grain
Boiling point
Ethanol will boil off at a lower
temperature than the other
components of the fermented grain
Wheat from chaff
Density
Wheat kernels are more dense and will
fall to the ground while chaff can be
blow away by the wind
Tea from tea leaves
Size
Filtration can be used to separate the
liquid extract from the large tea leaves
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Electricity can be used to separate molecules by
charge
-
Acetate ions
O
CH3 C
O-
-
+
-
+
+
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+
Tris ions
NH3+
HO CH2 C CH2 OH
Apply an electrical
charge
CH2 OH
+
-+
+
+
+
-
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- - -+
Sieves can be used to separate materials by
their size
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Electrophoresis separates molecules by
CHARGE and SIZE
Electrophoresis means “to carry with electricity”
Molecular
sieve
Electricity
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Food dyes – What have you recently eaten?…
Did you eat any cheddar
cheese? Was it orange?
Starbucks Strawberry
Frapuccino?
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Food dyes – Color tells our brains about foods.
What flavor is this Skittle?
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Food dyes – We have been dying our foods
for hundreds of years
 In the early 1800s some cheese and
cayenne pepper was colored with
LEAD tetroxide
 Pickles with COPPER sulfate
 Green tea with COPPER carbonate
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Food dyes - Regulation
There was NO control or regulations on food dyes
until the early 1900s in the US
•Food and Drug Administration (1902)
•Due to public outcry over adulterated foods
•Upton Sinclair – The Jungle (1906)
•Elixir sulfanilamide Poisoning, 100 dead (1937)
Food Drug and Cosmetics Act (1938)
•Synthetic Dyes – Seven approved for use
•Natural Dyes (derived from plants or animals)
can also be used and are not regulated
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FD&C Dyes and Natural dyes
FD&C Synthetic Dyes
FD&C Red 40 or FD&C Red 40 Lake
FD&C Yellow 6 or FD&C Yellow 6 Lake
FD&C Yellow 5 or FD&C Yellow 5 Lake
FD&C Blue 1 or FD&C Blue 1 Lake
FD&C Blue 2 or FD&C Blue 2 Lake
FD&C Red 3 or FD&C Red 3 Lake
FD&C Green 3 or FD&C Green 3 Lake
Natural Dyes
Beetroot red or betanin (from beets)
Curcumin (from tumeric)
Caramel coloring (from sugar)
Annatto (seeds of achiote trees)
Carminic acid, carmine, or cochineal (from ground up beetle abdomens)
Lycopene (from tomatoes, watermelons, papayas, and red carrots)
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Food dyes in the news
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Food dyes have an intrinsic SIZE and CHARGE
and thus can be separated using Electrophoresis
Food dye
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Molecular
weight
Charge
FD&C Blue 1
792.86
-2
FD&C Yellow 5
534.37
-3
FD&C Yellow 6
452.37
-2
FD&C Red 40
496.43
-2
Carminic Acid
492.38
0
Beetroot red
551.48
+1
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So how do we design an electrophoresis chamber
to separate food dyes?
Dye Electrophoresis
Commercial versus built box comparisons
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Combining Science, Engineering and Math to
Develop a Separation Technology
Engineering – Design
parameter based; no single
“correct answer”
Science – Hypothesis
driven; try to find specific
cause/effect
Conducts electricity,
moldable, inexpensive,
non-toxic, correct pore
size
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Analysis
Measurements
Best electrode material
Understanding the
Conducts well, has low
chemistry of metals in salt
reactivity, inexpensive
solutions, physics of
conductivity and currents
Best gel matrix
Polymer chemistry,
melting points, gelling
properties
What are some of the design factors we want to
think about?
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Dye extraction from candies
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Building and running your electrophoresis system
to separate the dyes
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Building and running your electrophoresis system
to separate the dyes
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Building and running your electrophoresis system
to separate the dyes
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Building and running your electrophoresis system
to separate the dyes
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Building and running your electrophoresis system
to separate the dyes
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Extensions
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Paper chromatography
Spectroscopy
Food diary
Electrochemistry study
Copper
electrode
– pH changes at the cathode and anode
– Effect of material choice for electrode
 Optimization of STEM box system
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–
–
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Electrode material choice and thickness
Different materials for gel thickness
Impact of TAE Concentration and Volume
Gel percentages
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Gelatin matrix