Author: Maddie Van Beek

As you all know, last Thursday was Thanksgiving! Today, we are going to research the history of Thanksgiving, test out Squanto’s gardening methods, and learn how to track our daily diets! 

We all picture the first Thanksgiving as a day spent with the pilgrims and the Native Americans chowing down on a Thanksgiving feast. Did you know that there were actually several “first Thanksgivings?” 

Learn more about the American history of Thanksgiving!

What were the other “first Thanksgivings?” 

Did you know November is National American Indian and Alaska Native Heritage Month? What a great time to learn more about Native American history and culture, especially as we celebrate Thanksgiving! 

More information on Native American histories and tribes: 

While Thanksgiving is a great time to spend with family and celebrate an abundance of food, it is also important to remember the roots of Thanksgiving. We don’t often remember the Wampanoag’s point of view during the first Thanksgiving. Take some time to consider how the Wampanoag’s might have felt when the first white settlers arrived. 

Quickwrite: Write in the perspective of a member of the Wampanoag tribe when the white settlers arrived at Plymouth. How do you feel? 

The Wampanoags were the Native American tribe that befriended the settlers and accompanied them in the “first Thanksgiving” meal. Squanto was one of the Wampanoags that is well known for aiding the settlers in their time of need. One way Squanto helped out was to assist them in growing corn by using fish. Check out Squanto’s gardening methods!

Hypothesize: How might fish emulsion help or harm the growth of a corn plant? Will it really make that much of a difference? 

YOU WILL NEED:

• Water
• Corn seeds
• Fish emulsion
• Milk cartons 
• Scissors
• Soil

YOU WILL DO:

1. Use the scissors to cut the top off of two half-pint milk cartons (ask an adult for help).
2. Fill both cartons with soil. 
3. Read and follow the directions on your corn seed packet to plant one seed in each carton. 
4. Push the corn seed 1-2 inches into the surface of the soil. 
5. Label one milk carton “Control” and one milk carton “Variable.” 
6. Your control plant will be watered only with plain water. 
7. Your variable plant will be watered with a mixture of water and fish emulsion. 
8. Follow the package instructions on the fish emulsion to dilute it with water. 
9. Water your Control plant with water and your variable plant with the diluted fish emulsion. 
10. Place both plants in the sun. 
11. Water both plants each day and record your observations in a daily log. 
12. Measure both plants’ growth each day and record. 
13. What differences do you see in the two plants? 
14. Create a graph at the end of your experiment to show the differences in growth. 
15. Reflect: How did the fish emulsion make a difference in the growth of the variable plant? Why do you think this is? 

Now that we’ve talked about GROWING food, let’s think about EATING food! 

Did you know that the average American eats over 4,000 calories on Thanksgiving day?! Wow! To put that in perspective, the average diet is only about 2,000 calories/day. 

Calories in a Thanksgiving meal: 

Here’s an idea of how many calories you should have in a day:

Keep in mind that physical activity increases your caloric need! Think of your body like a car--let’s say your car holds 15 gallons of gas. You fill it up with 15 gallons. If your car just sits in the garage, it doesn’t lose any gas, but if you go for a drive, it burns gas. Is your tank still full after a 200-mile drive? No! If you want your gas tank to be full, you would have to refuel. It’s the same way with your body! For example, if my daily caloric need is 2,000 calories, and I burn 500 calories on a run, then I should actually consume 2,500 calories so my body still gets the calories it needs to stay fueled.

Here’s more information about what you can do to have a healthy, balanced diet: 

How many calories are in your daily schedule? 

Are you eating a balanced diet? 

Create a food diary to see what your diet is really like! The point is not for you to count every calorie you eat--the point is that when we pay attention to what we put into our bodies, we are more conscious of what we are consuming. Being cognizant of the way you eat will help you make healthy choices for YOUR body! 

Predict: 

How many calories do you think you eat in a normal day? 

Do you think you have a balanced diet? 

What do you think you eat too much of? 

What do you think you don’t get enough of? 

Each day for one week, write down everything you eat for breakfast, lunch, dinner, and snacks. Each time you write down a food, determine whether it is a fruit, vegetable, grain, dairy, protein or fat. 

At the end of the week, look back at your food chart and reflect on your diet. About what percentage of your diet is protein? Fat? Does your daily diet look like the My Plate recommendation? Are you getting enough fruits and vegetables? Being conscious of your diet is the first step to taking care of a happy, healthy body! 




Other References:

http://www.educationworld.com/a_lesson/02/lp286-03.shtml

http://www.loc.gov/teachers/classroommaterials/presentationsandactivities/presentations/thanksgiving/celebration.html#

http://www.tolatsga.org/Compacts.html#Wampanoag

We’ve discussed refrigeration and canning as ways of preserving our food from spoiling.  We now know that refrigeration works by keeping food cold, thus slowing down the growth of bacteria and other microbes.  We also know that when we can food we heat it first, thus killing microbes and preventing new ones from entering the food.  However, we know there are foods that are not refrigerated, and not canned either, yet they still seem to remain safe to eat for long periods without spoiling.  Some examples are dried foods like fruits and jerky, cereals, and seasonings.  Although these foods may not taste as good after an extended time, they are still usually safe to eat.  Why don’t these foods spoil?

To understand why these foods never seem to develop bacterial or mold growth, we must ask what it is that these microorganisms need to grow.  If microorganisms (also called microbes) are present on our food, they will need four basic things to cause food spoilage:

1.       Food—the sugars and proteins in our food provide food for the microbes to multiply

2.       Warmth—refrigerator temperatures (20°F) are cold enough to slow bacteria down considerably

3.       Time—microbes require some time to grow, however under ideal conditions some can produce a new generation (that is, they can be multiplied by two) every 20 minutes!

4.       Water—most food has some water in it, which allows bacteria to digest the food

If any one of these things is not available, microbes will not grow, or at least will grow very slowly.  Anything that prevents the microbes from getting these basic needs will prevent them from growing, and will thus preserve our food. 

Water is extremely important to microorganisms, as it is to all life!  Water makes up an average of 70% of all living things, and it has many necessary roles.  Water makes up most of the interior fluid of the microorganisms, their food is dissolved in water, and all the processes that take place inside them to keep them alive must have water to happen.  Without water, all these processes would grind to a halt, and the organism would die. 

While canning works by removing the microbes themselves from the food and refrigeration works by removing warmth, other preservation methods work by removing water.  Some foods by themselves are dry enough to last in our pantry without needing to be canned or put in the refrigerator; dried pastas are a good example, as are some ingredients like flour and cornmeal (provided they stay dry).  However other foods need help—this is where dehydration comes in!

When it comes to dehydrating foods, there are essentially two methods:

1.       Air drying

2.       Freeze drying

Let’s start with air drying.  If you have a food dehydrator at home, you already have a device that will air dry food!  These machines are very readily available in department and kitchen stores, and they work by using a heat source and fan to blow warm air over whatever food is inside.  This air flow removes moisture, leaving a dry piece of food that will resist microbial growth.  This process may also be done in an oven, or by simply putting food out in the sun. 

Next, freeze drying.  If you have ever tried “astronaut food”, you’ve had freeze dried food!  Freeze drying works by taking food that is frozen at a very low temperature (around -40°F!) and placing it in a vacuum while maintaining its frozen state (for more information about vacuums, see our blog on the subject).  This causes the water molecules to go directly from their frozen state to the gas state, a process called sublimation.  What is left is a dry, airy food product that also resists microbial growth.  This works well on foods that have lots of liquid in them, like ice cream or fruit (astronaut ice cream is delicious, and can be purchased on astronauticecreamshop.com).

While removing water from food does prevent microbial growth, many dehydrated foods have a preservative added to them also to ensure that no bacteria can grow in any water that may remain, and sometimes to protect the food’s flavor.  Preservatives commonly added to dried foods include antioxidants (such as ascorbic acid and tocopherols) (Source: Bhat), various salts, and sugar, as well as some synthetic compounds. 

Antioxidants work by preventing loss of electrons to oxidizing agents, which can cause fruits to discolor and fats in meat to turn rancid (for more information, please see our lesson on antioxidants).  As an example, let’s look at what happens when the flesh of an apple starts to oxidize, and then what happens when we add an antioxidant—ascorbic acid from lemon juice:

Both salt and sugar work by pulling water out of the microbes.  This happens through a process called osmosis.  During osmosis, water flows from areas with fewer solutes (salts or sugar) to areas with more solute through the outer membrane surrounding the microbe, causing them to shrivel and die.  Traditional sugar plums are soaked in sugar water before drying for this reason, and it made the fruit sweeter! 

TRY PRESERVING SOME FRUIT THROUGH DRYING!

Here’s what you’ll need:

1.       Two cups of a fruit of your choice.  Small fruits like cherries should be cut in half and the pit removed.  Fruit larger than ½ inch in diameter should be sliced evenly into about ¼ inch slices. 

2.       One large baking sheet

3.       One large cooling rack

4.       An oven set to the lowest possible temperature, 130°F to 200°F

5.       One extra piece of fruit, the same kind as you dehydrate

6.       Two small, sealable containers

Here’s what to do:

1.       Place the cooling rack on top of the baking sheet.

2.       Spread the fruit on the cooling rack in a single layer.  Don’t let any of the pieces touch each other.

3.       Place the baking sheet with rack in the preheated oven

4.       Allow the fruit to dry for at least 6 hours, or until the fruit feels like soft leather

Store this fruit at room temperature for five days in an open container to allow any excess moisture to evaporate, stirring it every day.  Then cover the container and store for up to 10 months!

To demonstrate the ability of this dried fruit to withstand spoilage:

1.       Take one piece of fruit you dried, and place it in one of your sealable containers. 

2.       Take one ¼ inch slice of the same kind of fruit that has not been dried, and seal it in the other container

3.       Allow these containers to sit at room temperature for one to two weeks, observing them daily for changes and microbial growth.  Make sure they are kept in the same place to ensure they both experience the same conditions.

What did you observe?  How long did it take for you to see changes in the fresh fruit?  Were there any changes in the dried fruit?  Be sure to write down all your observations!

References for further reading:

Bhat, Rajeev; Alias, Abd Karim; Paliyath, Gopinadham (2011). Progress in Food Preservation. Retrieved from http://www.eblib.com

Image licenses:

GNU Free Documentation License

Last week we discussed how refrigerators work to keep your food cold (click here for a review).  Keeping food cold or frozen is very important to prevent it from spoiling—if you keep milk on the counter at room temperature it will spoil in only a day or two, but if you keep it in the refrigerator it will stay fresh for at least one week.  Keeping food frozen will prevent it from spoiling even longer—it should be safe to eat for years, although it may develop a rubbery texture!  But what about food in a can?  Canned foods can last for years, and never need refrigeration (as long as the can is sealed).  How can this be?

Before we discuss why canned foods can last so long without refrigeration, we need to understand why food spoils.  We’ll use milk as an example:  think about the last time you opened a carton of milk that had spoiled (gone sour).  It had a sour, rotten smell, and it may have looked chunky or curdled.  This spoilage is caused by bacteria that grow in the milk. 

Bacteria are very tiny, single-celled living things  (organisms); most are just a few micrometers long (one micrometer is 1/1,000,000 of one meter)—that’s less than half the width of a human hair!  These bacteria live in the milk, eating the sugars and other nutrients, and releasing the by-products of acid and other smelly compounds.  If left to themselves, these bacteria will continue to grow and multiply until the milk has so much acid in it that it curdles (acid makes the proteins in milk curdle—for more information see our lesson on adding acid to milk).  At this stage there are so many bacteria that the milk smells bad, too!  If left at a warm temperature these bacteria will grow quickly, causing the milk to spoil in less than one day.

The reason milk keeps fresh much longer in the refrigerator is because the bacteria grow much more slowly at cold temperatures.  Slowing down the growth of the bacteria prevents them from eating the sugar in the milk and reproducing, preventing spoilage.  Foods that are frozen will not spoil for a very long time because freezing foods usually stops the growth of bacteria completely!  This is true for other microorganisms that can cause food spoilage, such as yeasts and molds (if you’ve ever seen a piece of green, fuzzy bread...that’s mold!).

We know we can prevent food spoilage by slowing down or stopping the growth of microorganisms (like bacteria) in or on the food.  In general, there are two ways to do this:

1.       Slow down or stop the growth of microorganisms that are already there

2.       Kill all the microorganisms in the food, then prevent any new ones from getting in

Canning works using this second method. 

When foods are canned, they are sealed in metal cans or in jars and heated to 100°C (212°F) or higher for enough time to kill the bacteria and other microorganisms living in the food.  All microorganisms in the food are now dead, and so cannot feast on the sugars or other nutrients, multiply, and cause spoilage.  Because the can is sealed, no new living microorganisms can get in.  This is how canned foods can sit at room temperature for over a year and not spoil (Source: Shepard)!

TRY THIS!

Here’s what you’ll need:

1.       Two 1-pint canning jars, with lids

2.       Two packets of yeast

3.       Four tablespoons of sugar

4.       Two pints clean water

5.       One large pitcher

6.       One small saucepan

7.       A stove, cook top, or hot plate

8.       One large pot or canner

Here’s what to do:

1.       Clean the canning jars very thoroughly in very hot soapy water, or simply run them through a dishwasher on the sterilize cycle.  Wash the lids in very hot soapy water, rinse them well, and keep them soaking in hot water.

2.       In the pitcher, combine the two pints of water, two packets of yeast, and four tablespoons of sugar.  Mix well until all the sugar dissolves.

3.       Pour some of this mixture into one of the jars, and some into the small saucepan.  Only fill the jar to 1 inch from the top of the rim!  Be sure to wipe the rim of the jar clean with a paper towel before placing the lid on the jar. 

4.       Place the saucepan on the stove over high heat, and bring it to a boil.  Once the mixture boils, take it off the heat and pour it into the other jar.  Carefully place the lid on the jar, being sure to wipe the rim of the jar clean with a paper towel.  Make sure the lid is on the jar tightly!

5.       Place the jar with the boiled yeast mixture in the canner or pot, and fill with water until the water comes up just to the lid of the jar.

6.       Bring to a boil, and keep at a boil for 10 minutes.

7.       When the 10 minutes of boiling are up, carefully remove the jar from the hot water and place it at room temperature beside the jar with the un-boiled yeast mixture.  As the jar cools the lid should not bounce back when pressed—this means the jar has sealed.

8.       Observe the jars carefully for up to 4 hours.  Watch for signs of yeast growth, including bubbles and froth forming at the surface of the water. 

9.       After 4 hours, remove the lids of the jars and observe the liquid carefully.  Take note of the way the liquid looks, as well as how it smells.

What did you observe in the two jars?  How is the boiled liquid now different from the un-boiled liquid?  Did you hear or smell anything different when you opened each jar?  Be sure to write down all your observations!

For an additional challenge, you could prepare these two jars again, but this time prepare a third jar without boiling, and place it in the refrigerator.  How do you think these three jars would be different from each other after 4 hours?

References for further reading:

Shepard, Sue. "Pickled, Potted, and Canned: How the Art of Food Preserving Changed the World." "Canning." Simon and Schuster. New York, 2000.

Licenses for image use

GNU Free Documentation License

Creative Commons Attribution-Share Alike 3.0 Unported license

Easter is a wonderful holiday; it means many things to many people.  While there are numerous traditions associated with Easter time, one of my personal favorites is Peep Jousting!  For those unfamiliar with this game, two Peeps (those marshmallow candies shaped like chicks and rabbits and such) are placed in the microwave, each armed with a toothpick stuck in its chest.  The microwave is set to run for one minute, and as the microwave is running the peeps swell up!  Whichever peep’s toothpick touches the other first wins!

As much fun as this game is, there is some very interesting science behind why it works.  It starts with the microwave.   A microwave oven (usually just called a microwave) works by bombarding the food inside with electromagnetic radiation, which is a form of energy that moves through space as waves.  To understand this a little better, think of what happens when you drop a pebble into a lake or a pond.  It forms ripples, like this:

These ripples are just small waves that are made when the pebble gives some of its energy to the water as it falls.  These are a bit like the waves the microwave uses to give some energy to the Peeps, although you can't see the microwaves!

The energy that the microwave gives to the Peeps causes the water inside them to heat up.  As the water heats up, it heats up the sugar in the Peep, which makes it softer, and it also heats up the air inside the Peep.  As the air in the Peep gets warmer, the air molecules start moving faster and faster, and this causes the air to expand.  This expanding air is what causes the Peep to get bigger and bigger!

TRY THIS!!

NOTE:   You need to plan ahead for this one, at least one week—or two weeks if you can.  Buy the Peeps now, since they are hard to get after the Easter season (if you don't have them already)!

Here’s what you’ll need:

1.       One package of Peeps (or plain marshmallows, if you cannot find Peeps)

2.       A resealable zip-top bag

3.       Paper plates

4.       A marker or crayon

5.       Microwave oven

Here’s what to do:

1.       Open your package of Peeps (or regular marshmallows), and remove all of them.

2.       Place one half of the package in the resealable zip top bag, and seal it very carefully.

3.       Leave the other half of the Peeps on the counter or on the same shelf as the ones in the zip-top bag exposed to the air for one or two weeks (the longer the better!).

4.       After one or two weeks have gone by, remove your Peeps from the shelf and place two of them on a paper plate: one that was stored in the zip-top bag, and one that was exposed to the air.  Be sure to remember which Peep is which!  You may want to make a mark with a marker or crayon on the paper plate next to the peep from the zip-top bag to help with this.

5.       Place the paper plate with these Peeps in the microwave, and set the microwave to run for 1 minute on its highest setting.

6.       Watch both Peeps carefully to see what happens!  Be careful that neither of the Peeps start to burn (if you smell something burning or see smoke, STOP THE MICROWAVE IMMEDIATELY!!).

What happened to the Peeps while the microwave was running?  What happened to the one that was kept in a zip-top bag?  Did the one kept exposed to air behave any differently?   What could be the explanation for any differences?   (Remember that the reason the Peeps get bigger is because of the water inside them.)  Be sure to write down everything you observed!

Marshmallow Peeps® are a trademark of Just Born, Inc., Bethlehem, PA, USA.

Let me say from the beginning, I love to cook.  I’ve been cooking since I was a
small child (with my mother’s help during the early years of course), and have
always found the transformation of inedible (and sometimes unappetizing)
raw ingredients into fine cuisine particularly fascinating. While cooking is
often considered an art, it is also very much a science, and often it is the
first real exposure to science we have as children.  Needless to say, learning
some cooking skills early in life is very important—it is both a necessary life
skill, and a valuable science lesson! 

While we prepare and consume cooked food every day, seldom do we hear much about what is really going on when food is cooked.  What is really happening?  That is, what is really the difference between cooked food and raw food?  Usually, this can be boiled down (no pun intended) to just one word: heating.  
When we heat our food, several things take place:

1.    Proteins denature; that is, the shape of the proteins change, as the weak bonds and interactions within
their structures break and they unravel.  This is what causes the whites of an egg to go from clear to white as they cook.

2.    Changes in water content; in many types of food and cooking, such as roasting fresh vegetables,
heat causes some of the water to evaporate which changes the flavor and texture of food.  In other types of food, such as beans or dried pasta, the food absorbs water which makes it softer and more palatable.

3.    Cells walls are weakened or broken; vegetables (carrots, broccoli, etc.) have tough cell walls
made up of cellulose.  When they are heated the cellulose weakens and often the cells burst, resulting in a softer texture.

These are common effects for most cooking, and yet foods prepared in different ways look and taste very different.  This is because the method we use to cook our food can result in some different reactions, depending on the amount of heat used.  As an example, let’s look at potatoes.  
 
If we boil potatoes, they become soft and tender, but they remain pale in color and their flavor is rather bland—perfect for mashing with butter and milk.  However, if we fry our potatoes they turn a golden brown color and take on a pleasant flavor, which is good to enjoy without additional ingredients. These are the same potatoes, and yet the flavor and appearance is so different.  This is because when we fry potatoes (or roast them at a high enough temperature), two things happen to create this appearance and flavor: caramelization, and the Maillard reaction.  

Caramelization occurs when the sugars in the potatoes decompose (break apart) into volatile compounds (compounds that evaporate) and residual organic material.  The process is very complex, and involves many reactions, but the result is brown color and complex flavor.  Caramelization requires temperatures above 230°F (110°C), the exact temperature depending on what type of sugars the food contains.

The Maillard (pronounced May-ard) reaction happens when sugars react with amino acids (the building blocks of proteins) above 300°F (148°C), creating brown color and a complex variety of new flavor compounds.  This is another reason our potatoes turn golden brown when we fry them.  The Maillard reaction is also responsible for the aroma of roasted coffee, and gives baked breads and pretzels their brown crust.  The Maillard reaction and caramelization may make food look (and taste) similar, but the Maillard reaction involves sugars reacting with amino acids, while caramelization only involves sugar.  

TRY IT!


REMEMBER, THIS INVOLVES HIGH HEAT SO BE SURE TO HAVE A PARENT HELP YOU!!


Here’s what you’ll need:

1.    Potatoes, as many as you’d like, chopped into one-inch chunks

2.    A large enough pot to hold your potatoes and enough water to cover them

3.    A frying pan large enough to hold all your potatoes

4.    Two tablespoons of vegetable oil

5.    A spatula

6.    A spoon

7.    A stove 
 

Here’s what to do:

1.    Bring your pot of water to a boil over high heat.


2.    When the water starts to boil, begin heating your vegetable oil in your frying pan over medium-high
heat.

3.    When the oil in the frying pan is hot, and the water is boiling, add half of your potato chunks to
the boiling water, and half to the hot oil.  Be sure the potatoes in the oil are spread out.

4.    Carefully watch the potatoes in the oil, turning them every 3-5 minutes to make sure they don’t
burn.  Stir the potatoes in the boiling water every 5 minutes as well.

5.    After about 20 minutes, turn off the stove and remove your potatoes from the boiling water and the
oil.

6.    Allow them to cool for about 5 minutes before touching them.
  

Look at the potatoes.  What do the ones from the boiling water look like?  What about the ones from the oil?  How are they different?  Why do you think this is?  

 
Taste one of the potatoes from the boiling water. Describe the flavor and the texture. Now taste one of
the potatoes from the oil.  How are the flavor and texture different?  Why do you think that is?  Be sure to write down all your observations.

 
Make up a new experiment! 
What other foods could you try this with?  What other cooking techniques could you try (Hint: try the microwave!  Based on what you see, how do you think the microwave cooks food?)  Always be sure to have a parent or teacher help you and write down all your observations!