Carbonated Fruit

My Mother-in-law gave me a really fun toy awhile ago, an iSi cream whipper.  To use it you place some cream into the container and then screw on a cartridge filled with N₂O, shake it up, stick it in the refrigerator, and wait awhile.  While you wait the N₂O dissolves into the cream.  You put it in the refrigerator because the solubility of gases in liquids, unlike most solids in liquids, increases as the temperature decreases.  When you pull the trigger the pressure in the container pushes the cream out, when the cream hits ambient pressure the dissolved gas comes out very quickly (like when you open a soda bottle and some of the carbon dioxide comes out of the soda).  This makes the cream become frothy or whipped.  But that's not what this post is about. This post is about carbonated fruit.

The charger is also able to use a CO₂ cartridge.  To make the fruit I cut up some grapes (to increase the gas permeable membrane) and used Mandarin oranges.  I placed them in the charger and charged it with one CO₂ cartridge.  After about three hours I vented the container with the fruit in it and opened the container.  The fruit was delicious.  It tastes marvelous. The carbonation really tickles the tongue but the fruit is still just as sweet as it ever was.  When we did it again later we added sliced strawberries to the mix and they were great too.

Look at how the carbonation has made them swell.  You  can see the bubbles coming out of the fruit.

What is it?

Here are a few more SEM pictures.

These are from a fly I caught at our house.

A spider fang.  I like how you can see the hole through which it injects the venom.

This is the wispy part of a dandelion seed.  Notice how the shafts are hollow.

Happy Birthday to Me

I recently had my birthday.  My parents sent me some money and I used it to buy something I've wanted for a long time.  I've wanted a thermometer that can be plugged into my computer for a long time.  I have also been gaining an interest in electronics.  I have a simple analog voltmeter but it doesn't do anything else.  So I purchased a multimeter that also has a thermocouple that can plug into my computer via an infrared link.  The infrared link protects my computer from the electronics in the multimeter or the things I attach it to.  I put the thermocouple into a test tube full of water and dropped it into the deep freezer.  I had it sample the temperature every two seconds and recorded the graph below.

Some of the cool things to notice are the supercooling of the water before freezing.  The water cooled to -1.1 degrees before it started to freeze (~1000s) at which point it warmed up to 0.6 degrees as the water released energy as it starts to crystallize (the heat of crystallization for water is ~6 kJ/mol) .   It then cooled to 0 and stayed there for the next 25 minutes until all of the water had frozen and then it began to cool the ice.

Thanks for the great toy Mom and Dad!

Well Loved Books

I love it when I get a chemistry book or a cookbook out of the library and it has spots on the page or there are pieces of pages missing.  It is at that point that I know someone has used and loved the book.  Here are three recent examples.

This is one of the pages I printed from a digital book I have.  It is all about sulfur and I have more pictures at a future date of all the fun things I did with it.

This comes from a book entitled "Things A Boy Can Do With Chemistry"  This page is talking about silicate gardens.  I'm guessing that the yellow blotch is iron silicate.

This is from an old chemistry set that my dad had.  

Phenom-enal

Our university has a Phenom scanning electron microscope.  I was recently trained on how to use it and so I took some time after being trained to play around and learn more about the instrument.  Below are some of the pictures that I took.  See if you can guess at what they are before reading the labels.

It is a booger.

These are diatoms on the shell of a crab's claw.

This is earwax.

These three are a piece of woven cotton fabric.

These are of one of my fingernail clippings.

A Kim-wipe and a piece of notebook paper.

Gold wire contacting microelectronic pad.

The leg of a pillbug.

A pin head.

This is some of my blood.  I poked myself with the pin from the previous pictures and looked at it.  I think the regular cracking circles might be red blood cells.

Cotton from a Q-tip.

Some broken wood from the shaft of the Q-tip.

If there is anything that you would like to see under the SEM let me know and I'll see what I can do.

I Am Your Density

I've given away some test tubes and now for some ideas on how to use them. This is the first of those posts.

Density is a measure of the mass of something for a given volume, or in other words how much stuff is smashed into some space. It has a formula of ρ=m/v where:

ρ = density
m = mass
v = volume

Different materials have different densities. Old home chemistry books encouraged you to run to the drug store and get some mercury, carbon tetrachloride, water, oil, iron, a rubber stopper, and a cork. Pour the liquids in in order and then drop in the solids and you have a seven layer density column. This particular column is now very difficult to recreate because both mercury and carbon tetrachloride are no longer sold at the drug store. Steve Spangler has a great description of another 7 layer column that can be created from things found around the house.

Our set up for today is even easier. We are going to make a four layer column using three sugar solutions and plain water. So start by getting five test tubes and a pipette. Three test tubes will have sugar solutions one will have plain water and the last will be used for making the column. In the first tube put two mL of sugar, one drop of red food coloring, and fill it to the 10mL mark with water. In the second tube place four mL of sugar, one drop of green food coloring, and fill it to the 10mL mark with water. In the third tube add six mL of sugar, a drop of blue food coloring , and fill it to the 10mL mark with water. Lastly, in the fourth tube fill it with water. Now shake them until they are all dissolved. One mL of granulated sugar has a mass of about 0.8 g while one mL of water has a mass of 1 g. So your solutions have densities of:

plain water:(10g H₂O+ 0g sugar)/10 mL =1 g/mL
red: (10g H₂O+ 1.6g sugar)/10 mL =1.16 g/mL
green: (10g H₂O+ 3.2g sugar)/10 mL =1.32 g/mL
blue:(10g H₂O+ 6.4g sugar)/10 mL =1.64 g/mL

Now take a pipette full of the blue solution and add it to the empty fifth test tube. Now take a pipette full of the green solution and add it very carefully to the column. To do this you will need to slowly dribble it down the edge of the test tube. It should form a layer on top of the first one. Now do the same with the red layer and the water layer. It should look something like this.


Amazingly it will stay this way for quite a while. The next picture is the column after 12 hours. You can see that the plain water and the weakest concentration have begun mixing.


They will slowly go on mixing and after a week mine looks like this

You can still see separation between the top two and bottom two layers. After another few days in the window some mold started growing on the top so I washed it down the drain.

Now try playing with the solutions. Can you get them to stack in the wrong order? Can you make a solution dense enough to float a raisin in it? If you make alternating solutions of sugar and salt do they last as long as a column made from just sugar? Do they last longer?

I hope you all enjoy making and playing with your own density columns. Let me know how it goes.

Euclid

Geometry has always been my favorite math class. I always wanted to take a college level geometry class but I've never been able to fit it into my schedule. So I decided to read Euclid's Elements and cover the basics again. I really wanted to see the Greek (I don't read Greek but I wanted to see it) while I read the text in English. Marcelle had read and used the Elements as a text book in her days at St. John's in Santa Fe and I asked her if her text had the Greek. She said that it did not and that as far as she knew an inter-columnar version didn't exist or they would have used it.

I searched on Google and found that in 2007 Richard Fitzpatrick published a completely free and wonderful pdf version of the Elements in both Greek and English along with a Greek-English Lexicon. My plan is to print and bind the book along with blank pages in between the text so that I can work the proofs along with the text. Towards this goal Marcelle bought me a great compass so that I can make it look good to.

While I was searching for information on Euclid I decided that I wanted some old manuscripts of the Elements like this one. So I bought a sheet of papyrus from the local art store and while Marcelle and the kids were visiting her parents I acquired some papyri with parts of the Elements on them. These are pictures of them.

These first two are the definitions from the start of Book 1 "1. A point is that of which there is no part." You can see that this item is a composite of two pieces of papyrus "glued" together to make one larger piece.

This is the end of Proposition 11 from Book 4 inscribing a regular pentagon in a given circle. I haven't decided if I'm going to distress these last two like I did the first one.

This, of course, is the famous start of Proposition 47 from Book 1 proving the Pythagorean Theorem.

Liquid Diet

A few days before Christmas 2003 I had my mouth wired shut after having surgery on my jaw. I was on a liquid diet for a week and then I graduated to things like jello. I am here to tell you that you can only drink so much chicken broth before your body starts screaming "Give me a steak!" and I still gag when I think about drinking Ensure. Remembering this episode got me wondering if it is possible to survive solely on pure chemicals? While searching the literature I found out not only that it is possible but what the perfect recipe is. In a paper entitled "Evaluation of Chemical Diets as Nutrition for Man-in-Space¹" Winitz et al inform us that the perfect diet is:

Amino-acids
l-Lysine·HCl 3.58 g
sodium l-aspartate 6.40 g
l-Leucine 3.83 g
l-Threonine 2.42 g
l-Isoleucine 2.42 g
l-Proline 10.33 g
l-Valine 2.67 g
Glycine 1.67 g
l-Phenylalanine 1.75 g
l-Serine 5.33 g
l-Arginine·HCl 2.58 g
l-Tyrosine ethyl ester·HCl 6.83 g
l-Histidine·HCl·H₂O 1.58 g
l-Tryptophan 0.75 g
l-Methionine 1.75 g
l-Glutamine 9.07 g
l-Alanine 2.58 g
l-Cysteine ethyl ester·HCl 0.92 g

Water-soluble vitamins
Thiamine.HCl 1.00 mg
d-Biotin 0.83 mg
Riboflavin 1.50 mg
Folic acid 1.67 mg
Pyridoxine.HCl 1.67 mg
Ascorbic acid 62.50 mg
Niacinamide 10.00 mg
Cyanocobalamin 1.67 mg
Inositol 0.83 mg
p-Aminobenzoic acid 416.56 mg
d-Calcium pantothenate 8.33 mg
Choline bitartrate 231.25 mg

Salts
Potassium iodide 0.25 mg
Potassium hydroxide 0.83 g
Manganous acetate 18.30 mg
Magnesium oxide 0.38 g
Zinc benzoate 2.82 mg
Sodium chloride 4.77 g
Cupric acetate 2.50 mg
Ferrous gluconate 0.83 g
Sodium glycerophosphate 1.67 mg
Calcium Chloride·2H₂O 2.44 g
Ammonium molybdate·4H₂O 5.23 g
Sodium benzoate 1.00 g

Carbohydrates
Glucose 555.0 g
Glucono-δ-lactone 17.2 g

Fats and fat-soluble vitamins
Ethyl linoeate 2.0 g
α-Tocopherol acetate 57.29 mg
Vitamin A 3.64 mg
Menadione 4.58 mg
Vitamin D 0.057 mg

They point out that these diets are unique because " (a) their essential and nonessential nitrogen is provided in the form of highly pure L-amino-acids; (b) the are administered as single, crystal clear solutions which are nutritionally complete in themselves"

The dry ingredients were dissolved in distilled water to give a solution of 50-75% solids by weight which was completely sterile and had about 2-3cal per mL and could be stored almost indefinitely.

24 inmates from the California Medical Facility volunteered to drink/eat nothing but this liquid diet for 19 weeks. They were allowed to drink as much as they wanted and they could have all the water they wanted too. I can understand why they needed to use inmates because if they were on the outside after a week or so a cheeseburger looks really good.

They found that this diet provided well for these inmates and that there were no ill effects on their health. The authors go on to explain that these diets overcome some of the limitations inherent in alternative space-food sources:

"[These diets provide] high nutritive efficacy in ultra-compact form-1 ft³ of the diet as a 75% solution in water, will provide a 154-lb astronaut with all his required essential and nonessential nitrogen, salts, vitamins, and fats, in addition to his estimated requirement of 2,830 calories per day, for a period of a month; (b) complete water solubility- provides advantages in the administration of the diets in liquid form under conditions that will not permit the use of solids; (c) low bulk reduces low faecal residues and mitigates the critical problem of disposal of solid wastes; (d) complete nutrilite accessibility-allows alteration at will of the amino-acid ratios, carbohydrate content, and levels of all other components, thereby making it possible to tailor formulations to specific dietary needs of individual astronauts; (e) complete digestibility- provides dietary components in the most elemental form in the event of disturbances of the digestive system; (f) good storage stability either in the solid state or as aqueous solution."

This might be worth looking at for food storage...
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¹Winitz, M.; Graff, J.; Gallagher, N.; Narkin, A.; Seedman, D. A.; Nature 1965, 205, 741-743

Dutched Chocolate

My sister recently asked me "Why is cocoa processed with alkali in so many chocolate flavored products?"

First what is alkali processing or dutching? A solution of alkali (a base), usually potassium carbonate, is added to the cocoa nib before roasting. It's also possible to dutch cocoa liqueur or powder. Most of the cocoa liqueur used for making cocoa powder is dutched but the majority of liqueur used for making chocolate is not. Alkalising was developed in the 19th century in the Netherlands by Coenraad Johannes van Houten¹. He was trying to develop a chocolate powder that dissolved better in milk or water. Whether or not dutched cocoa dissolves better is still disputed but what the process definitely does do is change both the color and flavor of the cocoa.

The trick is to add just the right amount of base not too much because too much base will cause the triglycerides found in the cocoa butter to saponify thus giving it a soapy flavor. To avoid these off putting flavors small amounts of ethanoic or tartaric acid added to neutralize the high pH.

Some cocoa nibs are very acidic and the alkalising greatly helps flavor of the final chocolate product. Another thing that the base does is promote the formation of Miallard products (see another great article about how bases catalyze the Miallard reaction here.) Miallard products are those great flavors that form when proteins and sugar react.

The color change in the cocoa is due to reactions of the tannins in the cocoa. Tannins are polyhydroxyphenols, which means they are aromatic compounds (as apposed to an aroma compound) with several alcohol (-OH) groups. In the figure you can see a common one in cocoa, epicatechin. Depending on how the nib is fermented, dried, and roasted the tannins can join together, oxidize, and react with other chemicals in the cocoa to form color-giving molecules. This makes the cocoa much darker in color. By varying the pH, moisture content, and processing conditions it is possible to make cocoa of many different colors.

So when should you use alkali unprocessed cocoa? Well that depends on your leavening agent. Baking soda needs an acid to make it form CO₂ and cause your cake to fluff up nicely. Adding acidic unprocessed cocoa will cause it to rise. Further more, baking soda is a base and if added to the already basic dutched cocoa it can cause the cocoa butter to saponify and give soapy flavors to the dish. But because baking powder is a mixture of an acid and baking soda you want to use dutched cocoa so that it doesn't taste too acidic.

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¹Casparus van Houten, Coenraad's dad, figured out how to easily remove cocoa butter from the nibs enabling the creation of cocoa powder. The nib contains about 54% cocoa butter by weight and this butter makes it difficult to mix into water or milk to make a drink. By pressing the beans, either with a hydraulic press or with a screw press, about half of the butter is expelled from the bean and the cocoa mass that is left can be ground into cocoa powder. This then allowed others to combine cocoa powder and sugar together and then remixing it with some of the cocoa butter thus forming something very close to the of chocolate of today.

DB Lavash and dips.

During this challenge Marcelle asked me to take a turn kneading the dough. A little while later, she gave me some constructive criticism on how I knead dough. It turns out that while I thought that I was kneading the dough, I was really just folding the dough in half and smashing it flat time and time again. What I was not doing was pulling and stretching the gluten molecules into a nicely aligned mass.

Harold McGee informed me that wheat flour is special in the grain family because it is the only grain whose endosperm proteins will interact strongly enough to form a gluten (most simply, a combination of gliadin and glutenin) that will support a raised bread. It is true that some other grains (like rye) will form gluten, but the formed gluten is weak and can't support the raising of the bread. To form a good bread the dough must be both plastic and elastic. Able to stretch out of shape when pressure is applied (plastic) and able to pull back to its original shape after the stress is removed (elastic). If the dough were just plastic, all of the carbon dioxide produced by those hard-working, fermenting yeasts would just flow to the surface and escape, making something very like bricks or hockey pucks. On the other hand, if the dough were completely elastic, the CO₂ would be crammed into a few very pressurized pockets and the bread would come out looking like swiss cheese: a very dense mass with a few pressurized pockets of gas.

Unkneaded gluten is a coiled up protein that you can visualize like a Slinky. Unlike a slinky, the reason gluten stays coiled up is that there are chemical bonds (disulfide bonds) holding the spiral layers together. Kneading stretches the "gluten-Slinky" until those disulfide bonds break. Once stretched the disulfide bonds can reform with other broken disulfide bonds in the new stretched position to keep the gluten all aligned. After reading about kneading gluten doughs I realized that the disulfide breaking and forming is a lot like what is happening during a permanent wave, but this explanation will have to wait for another post. So even with my poor kneading technique the lavash was delicious, the dips were delightful (mostly), and best of all I learned some new chemistry.

I didn't find this project very challenging. My cracker experience is not vast, but I did make whole-wheat saltine/"wheat thin" type crackers once a week for our baby for about 8 months after he started eating solid foods and before I wanted to expose him to long-ingredient-list store-bought crackers. I have made a lot of pita bread--with a variety of outcomes and a ton (almost literally) of pizza dough, so flatbreads are not altogether foreign to me. The recent lavash challenge was fun and easy and made for a nice snack when we had some friends over to play games one evening.

I followed the instructions exactly, but I had a few problems; here they are, in no particular order. Despite using an oven thermometer and switching the lavash from top to bottom rack and front to back partway through baking, one pan was much darker brown than the other. The paler pan also made lavash that were puffed and chewy. I'm sure this has reference mostly to the cheap oven in our rental home, but other bakers I conferred with confirmed my experience. I used sea salt on one pan and poppy seeds on the other, but despite spraying water, 70% of them fell off before they were eaten.

For the toppings, we decided to try to the Tahitian almond spread recipe provided and also made a basic pico de gallo (tomatoes from our garden, onion, serrano chile, cilantro, salt). I also served some olivada (see Moosewood Restaurant Cooks at Home) I had made with green olives a few days before. The olivada is a long-time favorite and the pico disappeared quickly; when all the chunks had been dipped out of the bowl, the juices were very nearly drunk by our friend. The almond spread was a little weird. I love almond butter and eat it almost every day on toast for either breakfast or on an apple for a maternity snack, but putting it with garlic, cilantro, honey, orange juice and pine nuts did nothing to further endear me to a food I already enjoy as it is. I'm really looking forward to next month.