First Week

The first week we did hands on experiments in food science as part of the Farm to Table theme.

We started our discussions about food talking about what it is made of. I wanted to see what the students think about the contents of food so I knew what to talk about.

What the students said varied depending on their age but the one universally surprising thing was how strongly their lists seemed to be influenced by advertizing. Iron and Vitamin D were surprisingly high on the list.

I started to refine my question by asking what they thought made up most of the weight of the food that they eat. They are Summers-Knoll kids so of course they are clever and they mentioned water. True but not what I was looking for. Such are the perils of playing guess what the teacher wants. We did get lots of ideas and terms flowing.

I indicated that minerals, vitamins and micro-nutrients are important out of proportion to the amount of space and weight that they contribute and that there are three types of molecules that are critical to life that make up most of the non-water weight of food. The molecules of life, protein, fats(lipids) and carbohydrates. Enough talk, on to the hands on stuff!

The kindergarteners, and first and second graders took a first stab at three tests for food content. We tested for glucose (table sugar and a small carbohydrate) , carbohydrates in general and fats/oils. For glucose they used DiaStick test strips that turn from green to brown.  For carbohydrates the students prepared the sample and the teachers or I dripped iodine onto it.  Iodine changes from brown/red to dark purple) in the presence of carbohydrates.  For fats and oils they smeared or smashed the food samples onto pieces brown paper grocery bags. Stains that don't dry indicate fats and oils.

For the kindergarteners I prepared all of the materials so that they only had to stir and dip.  For the first and second graders I gave instructions and they had to follow,  collect their materials and samples from the front of class follow the procedure and evaluate the results.

After a similar discussion with the third and fourth graders about content they split into groups and followed multistage directions (recipes) to separate the proteins from whole milk and soy milk.

Their were three groups one using vinegar to coagulate whole milk, one using rennet to coagulate whole milk and the third using Epsom salt (magnesium sulfate) to coagulate soy milk. Vinegar made a cheese sort of like ricotta(not a really ricotta though). The rennet made something like mozzerella. If we have any cheese making experts in the community I would love to learn more. The reading I have done about cheese making chemistry has done little more than point out the depth of my ignorance. 

For many of the students reading through the instructions and understanding them before they started was a challenge. This is an important skill because it uses one of the most amazing capabilities of the human brain, the ability to model and predict the future.

The oldest students covered the molecules of life, "what is in food?" discussion and continued on to address the topic of calories in much more detail.  I had them break up into small groups and look up the definition of a calorie on the internet. (I give them one computer for 3 or 4 students. This was inspired by a great TED talk by Sugata Mitra called Child Driven Education. The experiment was in part the inspiration for the movie "Slum dog Millionaire."

They found that their is both a physical calorie and a dietary calorie or kcal.  The definition of a dietary calorie the the amount of heat that is needed to raise the temperature of one kilogram of water by one degree Celsius, at one atmosphere.  The high point was an attempt to measure the calories in a dorito chip.  We put 100gm of water into a pop can and lit the dorito on fire under the can. By measuring the increase in the temperature of the water we were able to calculate a lower estimate of the amount of kcals in the dorito.