Thermodynamics of Popcorn

Michael Bachmann, Tony Ghaly, Kathlyn Herrick, Sean Rodney Ireland, Brian Lewis, Mohit Moondra, Neel Patel, Evan Rosenman, Juliet Savits

Advisor: Paul Victor Quinn Sr. Assistant: Evan Kimberly

History of Popcorn

• New Mexico’s Bat Cave

• Aztecs• The Great Depression• Movie Theaters

Why Fluffier Popcorn?• The demand for corn is skyrocketing

– Biofuel consumes about 1/4 of corn crop

– Price has risen from ≈$2.40 to over $3.30– Tortilla prices in Mexico have doubled

• Efficient popcorn is paramount– 40% rise in popcorn prices from 2006 to 2007

S

D

Why Fluffier Popcorn? (cont’d)

• 30% of popcorn is consumed outside the home

– About 5 BILLION quarts at films, stadiums, etc.– Prepopped popcorn is also popular in the home

• Economies of scale are possible– A 10-15% efficiency rise could

mean big profit rise for 36 oz. popper– High market value of popcorn would

offset the cost of vacuum• Few cents of corn pop a $5 dollar bucket

Thermodynamics

• Ideal Gas

PV=nRT

• Adiabatic ProcessP1V1

γ= P2V2γ

• .

Goals

• Increase size of popped kernels (π)

• Increase volume per mass (σ)

• Decrease number of unpopped kernels (ω)

Microwave Apparatus

Microwave ApparatusProcedure

• 10 g. bag samples in microwave chamber

• Vacuum pump reduces pressure

• Pop for 2 minutes 15 seconds

• Measure volume and calculate σ, π, ω

Expansion Volume (σ) vs. Pressure

Flake Size (π) vs. Pressure

Waste Percentage (ω) vs. Pressure

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0 5 10 15 20 25 30 35

Pressure (in. Hg less than atmospheric pressure)

ω (

kern

els

un

po

pp

ed/t

ota

l ker

nel

s) y= 0.534exp(-0.276x)+0.101RMSE = .0379

Variables Affecting Microwave

• Age of popcorn kernels

• Limitations of bags

• Lifetime of microwave

• Inconsistency with timing

Movie Maker Apparatus

Movie Maker ApparatusProcedure

• 85 g. samples

• Vacuum pump lowers pressure

• Release vacuum after popping

• Measure volume and calculate σ, π, ω

Expansion Volume (σ) vs. Pressure

y = 0.3001x + 38.177

R2 = 0.9928

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25

Pressure (in. Hg less than atmospheric pressure)

σ(m

L/g

ram

)

Flake Size (π) vs. Pressure

The Popcorn Pot

Popcorn Pot Procedure

• Pre-heat 20 minutes• 20 g. samples• Vacuum pump lowers pressure• Periodically shake pot• Release vacuum and turn off heat• Measure volume and calculate σ, π, ω

Expansion Volume (σ) vs. Pressure

Flake Size (π) vs. Pressure

Waste Percentage (ω) vs. Pressure

Expansion Volume (σ) Comparison

0

5

10

15

20

25

30

35

40

45

50

Microwave Movie Maker Popcorn Pot

σ (

mL

/g)

Atmospheric Pressure

Reduced Pressure

• Decreased pressure increased volume.

Flake Size (π) Comparison

0

1

2

3

4

5

6

7

8

Microwave Movie Maker Popcorn Pot

π (

mL

/nu

mb

er o

f fl

akes

)

Atmospheric Pressure

Reduced Pressure

• Decreased pressure increased individual flake size.

Percent Waste (ω) Comparison

0

10

20

30

40

50

60

70

Microwave Movie Maker Popcorn Pot

ω (

Per

cen

tag

e)

Atmospheric Pressure

Reduced Pressure

• Decreased pressure decreased percent waste for microwave and popcorn pot.

Conclusions

• Decreased pressure resulted in increased volume

• Microwave best demonstrated theory

• Movie Maker is most practical application