1999-00 -- 05-06 Academic Years
Food Chemistry and Biochemistry
26 October 1999: Shirley Hatcher (Williams School)
put us to work making our own butter. (handout) We each got our own jar (baby food jar or bottle) with a couple of marbles in it, and we half filled the jar with Dean's Heavy Whipping Cream™. With the jar tightly capped, we vigorously shook it, following Shirley's lead. Before long it got thick - it became "whipped cream" - and Shirley pointed out that the sound of the marbles "clicking" against the jar became much harder to hear. Pat Riley asked, "What is going on?" Is there a chemical change?.. physical change? Discussion led to the idea that the change was physical, breaking up the fat in the cream into smaller particles, eventually creating a colloidal suspension - butter! We could see the butter "lump" formed at the bottom of the jar, and liquid above the lump. (Curds & whey?!) Other colloids are: Jello™, ice cream, homogenized milk, cheese. Very interesting!
23 November 1999: Sophia Watson [ Manley High School]
She had volunteers dye eggs with water, food coloring, and varying amounts of vinegar, to determine if different amounts of vinegar in the mixtures would affect how well it dyed. The eggs were observed and we found that the eggs, along with two teaspoons of vinegar, dyed the best. An interesting discussion of variables and other labs ensued.
11 April 2000: Brian Cagle (Cook School)
put us to work in small groups. Each group received about 15 donuts, and then had to devise a way to put the donuts into groups based upon characteristics; eg - with or without holes. Then each of these groups were broken down into other categories. (handout) Examples of categories: chocolate, icing, double chocolate, swirl, jelly, custard, oblong, round, powdered sugar, etc. From this, a key could be made with these properties:
13 March 2001: Zoris Soderberg (Webster School) Introduction to Nutrition
She drew a picture of a pig, and marked these three regions
|Hips and thighs||Ham|
|Top: backbone||Pork chops|
Zoris then took a bag of FritosTM corn chops and read these ingredients on the list:
13 March 2001: Sarah Brennan (Robeson HS) Handout: Stoichiometry
presented us with a fudge recipe consisting of powdered sugar, cocoa, butter, milk, vanilla. For one batch, here is a recipe that gives the amounts of ingredients required and the amount of fudge produced.
|Recipe||3 2/3 cup||1/2 cup||1/2 cup||1/4 cup||1 teaspoon||48 pieces|
|#1||1 5/6 cup||1/4 cup||1/4 cup||1/8 cup||1/2 teaspoon||24 pieces|
|#2||3 cup||0.4 cup||0.4 cup||0.20 cup||0.8 teaspoon||39 pieces|
|#3||5 cup||0.7 cup||0.7 cup||1/3 cup||1 1/3 teaspoon||65 pieces|
The principles of stoichiometry are identical to those of the culinary arts. Once you find the right proportions, you simply scale the amounts of ingredients to make the right size batch. For example, consider the reaction
|#1||2 molecules||1 molecule||2 molecules|
|#2||2 moles||1 mole||2 moles|
|#3||4 grams||32 grams||36 grams|
11 December 2001:
Karlene Joseph (Lane Tech HS): Eggs and Diffusion
Karlene put some raw eggs in a container and covered them with vinegar (H+) for about 4 days. The shells (Ca CO3) dissolved, and we were left with "rubbery eggs"; ie, the raw egg surfaces were covered by remaining membranes. At first Karlene had observed bubbles, as a result of the chemical reactions
Ca CO3 + 2H+ ® Ca++ + H2CO3
H2 CO3 ® H2O + CO2
She weighed a "de-shelled" egg and found that its mass to be 85 grams. Then she placed it in a sugar solution (Karo® Syrup). After about 40 minutes we poured off the syrup, rinsed off the excess syrup, and weighed the egg again, obtaining a mass of 77 grams. Although the membranes on the egg were still intact, water had diffused out through the surface membrane, leaving the egg and mixing into the syrup, which had become more fluid. [The syrup had lower osmotic pressure (for the solute, water) than the egg, providing an osmotic pressure gradient, so that water would undergo diffusion, crossing through the semi-permeable membrane out of the egg and into the syrup.] An excellent exercise illustrating the effect of osmosis, Karlene!
24 September 2002: Fred Farnell (Lane Tech, Physics) More Instructions
After you figure out what the instructions below are for, rewrite the instructions using language that would be appropriate for the task described. Any errors in the text below are intentional. The rewrite should contain 0.000 errors.Fred suggested this might be a recipe for making Bruschetta. Here is a somewhat more practical Bruschetta recipe.
The Description of the Task
Take 4 pieces of French bread sliced to 0.200 m. Coat each piece of bread with about 1.0 g of O LEE O. Place too toe may toes with a d of 0.0400 m on top of each piece of bread. Sprinkle about 0.25 g of garlic powder on the bread. Place the bread in a pan. Allow a 12 A heating device to reach 477 K. Place the bread inside the heating device so that is is 0.1500 m from the heating element. Place some thick materials with a low thermal conductivity on your hands. Remove the bread from the heating device after 180 s. Allow heat to flow away from the bread before serving.
25 Febuary 2003: Chris Etapa [Gunsaulus Academy] Diffusion and Osmosis [7th Grade Level]
We continued the discussion concerning the differences of water present in eggs, syrup, and pure water. We concluded that nature works [sometimes magically and mysteriously!] to drive processes toward equilibrium. For the egg, the concentration of water inside and outside should become the same through the process of diffusion. Seeds must absorb water [imbibition --- drinking --- vraiment un mot Francaise] before they can sprout. In potatoes, vegetative sprouting of the "eyes" [meristematic tissue --- undifferentiated plant tissue in the process of formation -- Greek meristos / meristos: divided] results in a new potato plant. See the website The Potato: http://42explore.com/potato.htm
Osmosis practically makes the world go round. Very nice, Chris!
24 April 2004:
[Eisenhower HS, Blue
Chemist's Recipe for Chocolate Chip Cookies
Brad brought in the recipe, which is given on the website The Chemist's Recipe for Chocolate Chip Cookies: http://f2.org/humour/cooking/chem-cookie.html.
Delicious as well as educational! Thanks, Brad!
11 November 2004:
Carol Giles [Collins
Objective: To introduce students to the fungi kingdom by creating a mold zoo (a version of this lab can also be found in the SMILE archives).
Carol gave each of us slices of ordinary white bread. We used each slice as a swab to wipe at various places in the classroom and environs (to see what mold spores we would pick up). After swabbing, each slice was sprinkled lightly with water and placed inside a sealable sandwich bag and taken home to incubate. As a control Carol had us each take a piece of bread, not swab anything with it, and spray it with a bleach solution; each control slice was sealed inside its own sealable bag.
The swabbed slices will pick up various mold spores which are so tiny that we cannot see them with our naked eyes. But after ~1-3 weeks (the time will vary from experiment to experiment) each spore will multiply, using the bread as a food source, into a “colony” with huge numbers of identical cells. The colonies will be easy to see and will grow in size as time goes by. The number of different types of spores picked up on a single swabbed slice of bread will be reflected in the different types of colonies on the bread (they will differ by color, texture, etc.); this “survey” can be extended to all the colonies on all the bread slices swabbed by the entire class.
The control slices should confirm that what grew on the swabbed slices was, in fact, due to spores picked up during the swabbing, and not to spores originally on the bread.
Because we had only one presenter today, we had a long discussion of various topics in biology and chemistry. Ken Schug pointed out that the bleach used in the control experiment (above) kills cells by oxidizing various essential biological molecules, so that they no longer function properly.
Chris Etapa asked about the elodea experiment in which this alga is placed in a test tube containing water in the dark and the light. In the light bubbles of oxygen are given off during photosynthesis and in the dark respiration releases carbon dioxide, which can cause a precipitate if the elodea is placed in “lime water” (the Ca++ ion in lime water forms a calcium carbonate precipitate in this experiment). Chris said that she was having a hard time getting a precipitate with the lime water in the dark; Ed Scanlon suggested using a pH indicator instead, which might be more sensitive (the carbon dioxide given off during respiration in the dark will acidify the medium).
Barb Lorde asked about why her house plant is dripping water. It is in a humid room, and the “transpiration” of water from the roots, through the xylem vessels all the way to the leaves, continuously brings water from the roots and it must go somewhere after it gets to the leaves. Normally the water is given off as vapor, but presumably in Barb’s humid kitchen, it is given off as a liquid.
We had a long and interesting discussion about stem cells, in humans, other animals, and plants. In the course of this discussion we used our wireless internet connection to find out that human children can regenerate fingertips up to the age of about six years!! We also discussed a bit about how the sequence of DNA is determined (for example, in the human genome project).
23 November 2004:
Carol Giles [Collins
HS] Bread Mold,
We examined the (hoped for) moldy bread from Carol Giles' presentation two weeks ago. They had been sitting in Ben's office for the last two weeks. All of the "experimental" slices did in fact grow mold, and every single control slice was without mold—a spectacular result!. As a class we found about a dozen different species of mold that we had picked up swabbing various areas in the classroom.
It was a beautiful phenomenological lesson, Carol!
26 April 2005:
Sister Mary Lucy Adetunji [Gale Elementary
Vinegar & Eggs
SR Mary had tried two experiments, but they didn't work out, so she is going to repeat it for us to see if we can figure out why they didn't work When SR Mary put a hard boiled egg into vinegar, she expected the shell to dissolve (the CaCO3 of the shell would be converted to NaCO3) and the egg to shrink (instead the egg swelled). The egg must have had a higher overall salt concentration (lower osmotic pressure) than the vinegar, and that is why it happened in this way. Soeur M also put a chicken bone into vinegar and expected the hard part (CaPO4) of the bone to dissolve (much as what happens with the egg shell) and the bone to get rubbery. But the bone stayed rigid. Probably there was not enough vinegar compared to the mass of the bone; changing to fresh vinegar or using a much larger volume of vinegar to begin with would provide enough acid equivalents to completely dissolve the CaPO4. For more details see the presentation of Chris Etapa in the SMILE writeup.
Ken Schug continued with the "egg in a bottle" trick using SR Mary's hard-boiled egg. He lit a paper and then dropped it into a large Erlenmeyer flask. Ken immediately placed the egg in the mouth of the flask. As we watched, the egg appeared to squeeze itself slowly into the flask! How come? A partial vacuum had been produced inside the flask. That is, room air has a greater pressure than the gas inside the flask. The gas inside is heated by combustion, so that it expands -- some of it being expelled from the flask past the egg. When the egg is placed on the mouth, combustion soon stops, and the air inside the flask becomes cooler. A pressure differential is thereby created, producing a net force on the egg, pushing it into the flask through the mouth. The egg can be removed from the flask by forcing air into the flask while inverting it. Again, the egg gets caught in the mouth of the flask, and the pressure inside is now greater than that outside, and the egg is forced back out.
Following instructions on handout sheets, SR Mary had us do the following activities designed for primary grade students:
04 October 2005: Ben Stark (Professor of Biology,
Mrs Levine's Pickle Recipe
Ben planted seedlings of pickling cucumbers grown last spring in the lesson given by Chris Etapa, and he harvested pickles from them this summer. He used these to make homemade pickles. Pickling is a natural fermentation process that is used to make fermented cabbage and other fermented vegetables as well as silage. It demonstrates lessons in both microbiology and biochemistry. The pickling cucumbers have a natural bacterial flora that is fairly complicated. The cucumbers are sliced and placed into brine and then sealed. The brine (high salt) inhibits growth of "spoilage" microorganisms but allows growth of Lactobacilli, which ferment sugars in the fruit (also in cabbage, beets, silage, etc.) into lactic acid by a particular fermentation pathway. Eventually, the pH drops so far due to the acid production that the Lactobacilli die. But by this time (7- 14 days, depending on the temperature at which the jars are stored), the pickles are done. One brine recipe is given here:
"Silage or Ensilage: succulent, moist feed made by storing a green crop in a silo. The crop most used for silage is corn; others are sorghum, sunflowers, legumes, and grass. In a sealed silo, typically in the past a tall cylindrical structure but often today in a surface pile covered tightly with heavy-gauge plastic, the crop ferments for about one month. This fermentation process, called ensiling, produces acids and consumes the oxygen in the silo, preserving the plant material. In pit ensiling, compacted silage ferments in an unsealed underground enclosure. Silage replaces or supplements hay for cattle, horses, and sheep. It is rich in carotene, an important source of vitamin A. A machine called an ensilage harvester cuts and chops the crop in one operation, preparing it for storage in the silo."Also, it was pointed out that the pickle man played a starring role in the 1988 film Crossing Delancey: [http://www.washingtonpost.com/wp-srv/style/longterm/movies/videos/crossingdelanceypghowe_a0b1bf.htm]. Thanks for the insights, Ben!
13 December 2005:
Carl Martikean [Proviso Math and Science
Biochemistry of Cheese
Carl then passed out samples of Mozzarella cheese that he had made from regular pasteurized whole milk (see http://answers.google.com/answers/threadview?id=550085). There is also a recipe for Ricotta -- in Italian it is called ricotta because it is made from recooked whey, a byproduct of preparing basic cheese. Junket Rennet tablets are located in the ice cream section of the supermarket. Four liters (a gallon) of milk makes about one kilogram (two pounds) of cheese, taking about 5 hours -- most of the time be spent between steps, waiting. Natural lactic acid production by lactobacillus serves to lower the pH in commercially made cheese. Citric acid can be used to speed up the process and to serve the same purpose -- it can also be found in the supermarkets, either as food grade coffee pot cleaner or in the Kosher food section as sour/sauer salt: http://www.spicebarn.com/citric_acid_sour_salt.htm.
Carl also pointed out that (1) European cheeses are often made from non-Pasteurized milk, which is not legal in the USA, (2) Cheese was traditionally developed to preserve milk products --- cheese lasts but milk curdles, (3) low-fat cheeses are made from skim milk, and high-fat cheeses from high-fat milk -- there is no mystery!, and (4) the most common widely milked domestic animal on earth is sheep -- and not cows or goats. Porter Johnson remarked that cheese in many European countries is marked by fat content: 10 means 10% fat content; 40+ means more than 40% fat content, etc.
Your samples were not bad, Carl! Thanks.