Edible education

One subject I've had in my list to write about (once I spent the time to find some good sources) was why some leaves are edible while others aren't—completely aside from the question of toxicity, there are lots of plants that we simply can't digest. I hadn't yet got around to digging into the subject when I ran across the answer recently, along with loads of other interesting information about food chemistry.

A few weeks ago I discovered a free, online course offered by McGill University via edX, on the subject of food and nutrition. Despite being offered by the chemistry department there, it doesn't require more than high school chemistry and the ability to use a 4-function calculator as prerequisites, and I'm not even sure if it needs high school chemistry. You should probably know the difference between an atom and a molecule, and at least recognize the Periodic Table of the Elements.

I was too late to sign up for the credit version, where the assignment deadlines are enforced, but there is a non-credit, audit version (which I'm doing) where you still have access to all the video lectures, discussions, and mini-quizzes.

So back to edible vs. non-edible leaves.

In the lesson on carbohydrates, (week 4, lesson 1) they showed the chemical structure of starch vs. cellulose (video 8). Both are long strings of glucose connected by oxygen atoms, but the way they're strung together is different—and that's it. That's the difference between plants we can digest and plants we can't. (Plants we can digest still have cellulose in them and we pass that through our system no problem—but we don't get any nutrition out of it.)

(Screenshot from Food for Thought, week 4/lesson 1/video 8. Requires free course registration to view.)

They look very similar at first glance, but if you look closely, they have an important difference: every second glucose segment is upside down in the cellulose chain.

We have the enzymes necessary to digest starch. We don't, but cows and other ruminants do, have the enzymes necessary to digest cellulose.

Enzymes are complicated things which have a very specific shape, and can fit around molecules of a very specific shape. So, an enzyme that fits the shape of starch in order to cut it down to its component glucose molecules will simply not fit the different shape of cellulose, even though the components are all the same.

So that was short and sweet. Also, check out the course, it's fascinating. (Keep in mind you can adjust the playback speed of the videos. I found my attention wandering because the instructors speak kind of slowly; running them at 1.5x speed makes it easier for me to keep from wandering. You can also back up and repeat sections if you don't catch it the first time through, or pause to look at the diagrams, because it's a video.)

Unnatural or Natural

Something I've been thinking about for a while, even since before I did the greenwashing article series, is: what makes a thing "natural" or "unnatural"?

Many people would say that "natural" things are things which come from nature with minimal processing. It sounds like a reasonable definition at first glance, but when I try to get specific, I start running into trouble with the definitions of the words used to define "natural". They seem to be a bit fuzzy themselves, which makes the term "natural" hard to pin down.

So my first question is, what is meant, exactly, by "from nature"?

Oily algae

Algae, as well as other biologically sourced feed stocks, has been the subject of a lot of research in oil production, for what should be obvious reasons. There are several things about using some bio-sources that concern me, however. Using food cropland to grow corn or soy intended for conversion to fuel, for one, resulting in less food production (and contributing to higher food prices).

The bio-sources that don't bother me in this way are things like manure or other waste to bio-fuel. Even wood waste and scrap paper can be turned into either oil or syngas (which can be turned into oil, among other things).

But, an interesting comment in a recent press release about oil from algae caught my eye: "byproduct stream of material containing phosphorus that can be recycled to grow more algae."

Chlorinated hair

When I signed up for triathlon training, I had to buy a pair of swim goggles so I didn't crash into things like the lane markers, the other people swimming around me, and the wall at the end of the pool. (Ouch.) While buying that little necessity, the sales staff talked me into buying some special chlorine-removing shampoo. Naturally I was curious about whether it was actually significantly different from my normal shampoo or if it was just marketing, which is the majority of the difference between most normal shampoos, so I bought the little sample size bottle to test it out.

Using it in place of my normal shampoo after the swim didn't seem to make a difference that I could notice, but then I did make sure to pre-soak myself in the pool showers before jumping in. Hair absorbs a remarkable amount of water, so getting it to absorb low-chlorine tap water before it hits the high-chlorine pool water will provide some partial protection right there.

I remember my grandfather's white hair turning green when I was a kid and we'd go to the public pool (which I found out as an adult is due to copper from the pipes, not the chlorination). I also remember how the pool smell would cling even after that post-swim rinse.

Chilly chemical properties

Because it's the middle of winter here in Canada, I think today is a good day to talk about refrigeration.

Just kidding. Actually it's because the ISS had to replace a piece of its refrigeration system last week, and I thought that was a good excuse to talk about refrigeration.

Most modern refrigeration involves the chemical property \(\Delta H_{vap}\), or enthalpy (heat) of vaporization. Every substance has a heat of vaporization, and the amount of heat energy required to vaporize a substance is independent of what temperature the substance boils at. To choose a rather extreme contrast, water boils at 100C while lead boils at 1750C, but water requires 539cal/g to convert from liquid to gas while lead only needs 208cal/g, less than half that required by water. This amount of heat does not account for how much is required to get to the boiling point, and if you remember your high school chemistry, the temperature does not change with the additional heat input while it changes from liquid to gas.

The basic principle in use here is that when a substance evaporates, it draws heat energy from its surroundings (or the more familiar form: when you add heat to a substance, it will evaporate), and when a substance condenses, it releases heat energy back to its surroundings. Put an insulated barrier between these two sides of the process, and you have refrigerators, freezers, and air conditioners which get colder "inside" and warmer "outside".

Studying long

Looks like November wasn't a great month for posting, for me. Well, I'm back, and this time with another medical term. As with the others, if a medical doctor reads this and I'm wrong about something, I would love to hear about it so I can fix it. I am writing from a non-medical person's perspective for other non-medically trained people, but I hope I'm not making any doctors cringe.

So this time it's "longitudinal study". The basic idea behind a longitudinal study is that the study follows specific people for a long time—years, or decades. These can be used to tease out things like what affects aging or why some kids develop asthma but others don't, and many more.

Chemical telephones

The folks at UCLA have come up with a way to use cell phones to test for allergens in food. And we're not talking looking it up in a database somewhere, we're talking an actual lab test, which tests the actual piece of food in front of you.

Potentially useful if you have a life-threatening allergy, such as to peanuts, the example used in their paper.

While this does use the camera built into the phone, as a lab test, it is more than just taking a picture. Specifically, it uses a colorimetric process to measure how much allergen is in the sample.

I've used colorimeters before, and they are generally quick and handy (and portable, if you buy the portable version of the reader). However, that "generally" is important. While I've used some colorimetric kits that only take 5 minutes, I've used some that take over half an hour, and that's not counting sample preparation time.

And all of those kits require sample preparation of some sort, adding chemicals, and waiting for the reaction to finish before measuring. Most of the stuff I tested required dilution of a water sample to bring it into the testing range. The peanut test described requires the sample to be finely ground and dissolved first, and is described as taking 20 minutes, not including grinding time.

The good kits come with either pre-measured chemicals or easy quantities of liquid chemicals to measure, such as with a standard pipette or a supplied dropper, to minimize test error. The reaction of the compound of interest with the added reagents causes a colour change, which the sensor (or camera) measures. Generally, at least for the kits I've used, the darker the colour, the more of the compound of interest is present. From the paper, it looks like the peanut test turns red.

Realistically, now that the photo processing and colour measurement has been sorted out, any pre-existing colorimetric kit could be adapted for cel phone use. But then, most people who might get these things for personal use would be more interested in allergens than the stuff I have tested for at work. Most people don't care all that much how much calcium is in their water, because it isn't a health issue.

(Ok, technically this one is almost year old, but I don't restrict myself to only talking about new discoveries.)

Food chemicals

I was tossing around the idea of doing some posts on the various food additives one sees (and which some people are frightened by, due to their long chemical names) when I ran across Science Fare's list of The Ingredients of Scientific Cooking. Some of these every cook has used (sodium bicarbonate aka baking soda; sodium chloride aka table salt; ethanol aka drinking alcohol, to name the three most instantly recognizable ones), and some are a bit more specialty (such as pectin to gel a jam - mmmmm, I remember my mom's jam) and some I didn't realize people used in home kitchens. Although in hindsight, the fact that I have seen a bag of MSG in the supermarket means that yeah, people do actually use them.

This list looks like an excellent resource, though I may branch out from it and look into some of the things used only in commercially produced food, because I am curious about some of these. Especially items such as preservatives, since without them, food (and even non-food items such as sunscreen) doesn't last very long and provides a potential base for bacteria and mould, some of it potentially harmful, to grow.

Chopping up pollution

Normally I just post whatever interesting bit of chemistry catches my interest on a given week, but today I'm posting about something of special interest to me. It's not about my work specifically, but it is about pollution remediation—and that, in a broad sense, is what I do.

This fascinating bit of cleanup chemistry targets some of the most difficult to remove pollutants. The unsightly colour of lignin stained water coming out of a pulp mill, pharmaceuticals passing through sewage plants (page 2), pesticide and herbicide runoff from farms, parks, golf courses, and lawns, and many others. Chemical warfare agents are even on the list of targets.

Unfamiliar noises

I had just picked up a rental car to use during a work trip, of a make and model I'd never driven before. Just as I pulled out of the parkade onto the road leaving the airport and the speedometer moved above the 10, the car shook and a made a sound that had me frantically looking in the rearview mirrors to see what piece of itself the car had just dropped on the road behind me.

Nothing. The road was clear, the car wasn't shaking or making any funny noises anymore, and was accelerating smoothly. Weird.

Just as I pulled off the airport road onto the freeway, and accelerated further, it happened a second time. This was really weird. Still nothing on the road behind me.

It was probably 5 minutes later, as I was driving around a 270 degree freeway ramp to get going the way I wanted, that I figured out what the noise and vibration was. Something not visible inside the rental car parkade, and not in my line of sight when driving the car due to keeping my line of sight on the road.

Impeccable timing on that thunder, Mother Nature.

I'm glad the funny noise wasn't a sign of anything damaged or about to fail, but I've encountered those conditions more than a few times. One reason I pay attention to them!