Transcript Making Yogurt! - Welcome | NAAE Communities of Practice

Hey, there’s SCIENCE in my
YOGURT!
Or… how to make life science
more interesting!
A little bit about me…
• Ag Science teacher at Zane Trace High
School near Chillicothe,Ohio
• In a two-teacher program, so I specialize
in the “science” side of agriculture
education by teaching Food Science, Ag
Biology and Animal Science courses
How’d I get this idea?
• Science Fun With Dairy Foods 4-H Project
– Ohio Cooperative Extension Service Pub 490
– One of the assignments was to make yogurt
– Never had Ag class in HS so, when I started I
used a lot of my 4-H books for resources
– Lesson went really well, kids liked it, I’ve
repeated it every year since then
Yogurt making today
• Today yogurt is one of the most popular
dairy foods we eat!
• Go-gurt, smoothies and new flavors make it
more convenient to eat
• Marketed to MANY different groups (kids,
teens, athletes, probiotics for immunity, etc)
• Many ethnic groups eat yogurt with food
– Indian, greek, middle eastern
When to teach this…
• It fits in lots of different subjects, but I
usually do this lab at the beginning of the
year with my Freshmen to get them
excited, then later in the year with other
classes.
• This lab can be extended to fit just about
any agriculture class – more about that
later…
Getting ready…
• Most of the items you need can be
purchased easily or found around the shop
• You’ll need a way to heat the milk and
store the yogurt after incubation period
– I’ve used the consumer sciences lab before
– Portable burner and fridge in teacher’s lounge
is good too.
Gathering supplies
The rest of the stuff you need can be picked up
at your local grocery store (I like Kroger)
*1 gallon of Milk (you’ll have enough for 4 batches with a gallon)
*1 carton PLAIN yogurt (again, this is enough for 4 batches)
*Plastic containers (Glad ware is awesome!)
*Saucepan (hit a yard sale and get one cheap)
*Wisk
*Candy Thermometer
How to introduce to students…
• Depends on your subject…
– Ag Bio = what do living things need to grow?
also, intro to scientific method & biotech
- Food Science = product development, sensory
evaluation, nutrition label calculation, dairy foods
- Business = marketing, product development,
advertising campaign
- Animal Science = Dairy cattle and products
What does it cost to make it?
• Milk (whole is best!)
– Bought at Kroger for $1.98
• PLAIN Yogurt with live bacteria
– Bought at Kroger for $2.99 – Dannon brand
• Candy Thermometer = $3.99
• Plastic Tubs = 6 for $1.99 (could be free if you saved them)
• Saucepan - $1.00 at yard sale
• Whisk – 25 cents at yard sale
• 5th burner hot plate = $2.00 at yard sale
• Incubator (someplace to keep it warm) – free bag from
National Convention!
• GRAND TOTAL for 4 classes = $14.20 Whatta deal!
History of YOGURT
• Thousands of years ago shepherds used
dried out sheep stomachs to store milk.
• A certain bacteria that lived on grass was
still living in the sheep stomach when milk
was put in it.
• That bacteria changed it’s behavior, fed on
the sugar in the milk, turning it into
YOGURT!
Questions to Ask…
• Is this Biotechnology?
• How is yogurt made today?
• What kind of bacteria are needed to
make yogurt?
• What conditions do the bacteria need in
order to grow?
• What changes occur in the milk as it
becomes yogurt?
• How do companies like Yoplait and
Dannon make new varieties of yogurt?
Steps for yogurt
1. Measure out 4 cups of milk and heat to
161 degrees F
– Kills harmful bacteria (Pasteurization)
– If we didn’t do it, harmful bac could grow
– Don’t HAVE to do this if milk is already
pasteurized, but I do just to show the process
2. Place the pan of hot milk on a bucket of
ice to cool it to 115 degrees F quickly
– Keeps bacteria in air from contaminating milk
– 115 degrees is good temp for yogurt making
bacteria to grow in.
Steps for yogurt
3. Add in 1 cup of PLAIN yogurt with ACTIVE
CULTURES
– This introduces yogurt making bacteria to the milk.
Lactobacillus bulgaricus, Streptococcus
thermophilus
– They will “eat” the LACTOSE (sugar) in the milk and
produce LACTIC ACID as a result.
– This process is called FERMENTATION
– The ACID will cause the protein in the milk to
DENATURE or thicken.
– The ACID makes the milk SOUR and the denatured
protein makes it THICK
Steps for yogurt
4. Allow the yogurt to sit in a warm place
(over 100 degrees) for 5-8 hours
– This gives the bacteria time to grow and eat
– Longer time = more sour, thick yogurt
– As soon as you put it in the fridge, the
bacteria stop growing.
Steps for yogurt
5. Take out yogurt the next day and let
students go crazy with it!
-You can provide items to flavor yogurt
with or make them bring their own.
-Make sure they measure items if they
plan to calculate nutrient info later…
-Conduct sensory evaluation when
finished – have them “grade” their flavor
Extending the lesson…
-Allow “Do-overs” with yogurt varieties
-Experiment with variables such as:
-Incubation time
-Whole vs 2% Milk
-Using culture vs yogurt to produce
-Using different incubation methods
-Create marketing plan, packaging, nutrition
label, etc. for variety created.
-Ask “what if” questions afterwards…
And Now, a word from my students!
Three video clips from my Freshmen Ag Bio
classes on the day that they made and
tasted their yogurt varieties.
See if you can guess which class is the one
that meets right after lunch period!
More Info? Sure!
For those of you who use AgEdNet.com…
-FS 111 – Fermentation in Food Production
-FS 113 – Dairy Foods
-FS 001 & 002 – Nutrition Labels lessons
-LA 189 & 190 – Milk & Milk components lessons
New England Cheesemaking Company
-www.cheesemaking.com
-if you want more info on ordering culture,etc
Yogurt Making Website w/videos!!
-www.makeyourownyogurt.com
Thanks so much for listening!!
Good luck making your own yogurt!
If you have any questions, just drop me an
email at:
[email protected]
This presentation will be on the Zane Trace
school website: www.zanetrace.org