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Kids’ Science Challenge - Make Your Own Yogurt 1

Make Your Own Yogurt

Saucepan

Captions

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

Kitchen Thermometer

Water

Find What You Need... • Ameasuringcup• Water• Amarker• Plasticcups• Wholemilk• Asaucepan• Akitchenthermometer

• Plainyogurtfromthegrocerystore(make sureitsays“activeculture”)• Powderedmilk• Aluminumfoil• Acooler• 4smallplasticsodabottles• 3cupshotwater

Marker Whole MilkYOGURT

POWDEREDMILK

ALUMINUM FOIL

SODA

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

Plain Yogurt Active Culture

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

Powder Milk

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODAAluminum Foil

Cooler

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

Plastic Cups

Small Plastic Soda Bottles

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

YOGURTPOWDERED

MILK

ALUMINUM FOIL

SODA

3 Cups Hot Water

We recommend that an adult

help lead this activity.

Kids’ Science Challenge - Make Your Own Yogurt 2

*Are your hands really clean after you wash

them? Design an experiment to test how many microbes live on your hands when they’re really

dirty, compared to after they’re cleaned in different ways. For example, you could test the difference between using cold and warm water, and between regular soap and anti-bacterial

soap, for example.

Brain Buster:

Kids’ Science Challenge ScienceProjectsarepresentedbytheaward-winningradioseries,PulseofthePlanet

Made possible by theNationalScienceFoundation

©2010JimMetznerProductions.Allrightsreserved.

FromChampionship Science Fair Projects,adaptedwithpermission,©2004SudiptaBardhan-Quallen,www.sudipta.compublishedbySterlingPublishingCo.,Inc.

1. Usingthemeasuringcup,pour1cupofwaterintoaplasticcupandmarktheleveloftheliquidwiththemarker.Repeatsothatyouhavethreeplasticcupsmarkedatthe1-cupmark.

2. Heat3cupsofmilkinasaucepanonthestovetopuntilthemilkreachesatemperatureof175ºF.Checkthetemperatureusingthekitchenthermometer.Letthemilkcooluntilitis120ºFsothatitiseasiertoworkwith.

3. Pourthemilkintoeachofthethreeplasticcups,stoppingatthemarkerlines.

4. Microwaveafewtablespoonsofyogurtfor10secondstoheatitup.

5. Labelonecup“MilkOnly”andsetitaside.

6. Labelanothercup“MilkandYogurt.”Add1tablespoonofyogurttothiscupandmixwell.Setitaside.

7. Labelthelastcup“Milk,PowderedMilk,andYogurt.”Add1tablespoonofpowderedmilkand1tablespoonofyogurttothiscupandmixwell.Setitaside.

8. Coverallthreecupswithaluminumfoilandplacetheminsidethecooler.

9. Fillthefourplasticsodabottleswithveryhotwaterandsealthemtight.Placetheseinsidethecooleraswell.

10.Usethethermometertomonitorthetemperatureofthecooler,whichneedstostayatabout110ºFfortheentiretimeyouculturetheyogurt.Ifitstartstocooldown,refillthewaterbottleswithhotwater.

11.Aftersixhours,checkonthecups.Recordanychangesinappearance,texture,andodor.

12.After12hours(orovernight),checkonthecups.Recordanychangesinappearance,texture,orodor.

Things to Notice:• Thecuplabeled“MilkOnly”willlookandsmell

moreandmorelikerottenmilkastimepasses.

• Thecupslabeled“MilkandYogurt”and“Milk,PowderedMilk,andYogurt”won’tlookorsmellrotten;instead,theywillappearyogurt-y.

• Thecuplabeled“Milk,PowderedMilk,andYogurt”willhaveathickerconsistency,morelikeyogurt,thanthecuplabeled“MilkandYogurt.”

Things to Try:• Tryusingstarterculturesfromflavoredyogurts

ordifferentbrandsofyogurt.Doesthismakeadifference?

• Tryusingmilksubstitutes(heavycream,infantformula)insteadofmilk.Howdoesthisaffecttheyogurt-makingprocess?

• Whathappensifyouuselactose-freemilkinthisexperiment?