Custardy battle

Everybody likes custard, but who likes lumpy – or even chunky – custard? Today I’m presenting 4 simple techniques to keep the chunks out of your custard.

Before we start, I should clarify that by custard I mean the real deal: made with milk or cream, sweetened with sugar and thickened by either whole eggs or just the yolks.

This is not to disrespect the stuff you make using custard powder, which can be quite yummy and fascinating in its own right, being a non-Newtonian fluid that gets more viscous when you apply more pressure. But let’s be honest: real custard, or crème anglaise if you will, is a much better companion for plum pudding, and you can’t make ice cream out of custard powder.

Like I said, it’s thickened with eggs, but it’s very easy to go too far and end up with lots of lumpy, grainy curds. For this reason many people are intimidated and won’t go near it, despite the culinary temptations. But you can remove some of the mystery using science; and my main reference is as usual Harold McGee’s book On Food and Cooking, an invaluable resource for any kitchen.

Alright, we’ll get the primary but least interesting technique out of the way early: method 1 you will see in just about every recipe: strain out the lumps.

That may sound obvious, and if so, good on you. What you’ll find with most of the other methods is that you’ll reduce the lumps, but there’ll often still be a few. So it’s safest just to strain them.

Okay, method 2 is a bit more scientific: use a thermometer. Here’s where we need to understand how eggs work.

Eggs of course are wonderful devices, designed to protect and nourish baby chickens. If you take a 55g egg, most of it, about 41g, is water. There’s 6g of fat, only 0.6g of carbohydrate, 213mg of cholesterol, and what we’re interested in, 6.6g of protein.

There are many different kinds of protein in both the yolk and the white, all designed to do different jobs: obviously, they provide food for the chick, but they also protect against infection, prevent them from being nutritious for predators – laboratory animals fed on raw egg actually lose weight – and physically protect the embryo.

The proteins – and remember proteins are long chains of amino acids all joined together – are folded up tightly into little knots floating in the liquid. This is why the white starts off transparent.

Coagulation of egg proteins: on the left an uncooked egg, with tightly bound knots of proteins; on the right, the cooked egg with unravelled proteins forming new networks (picture adapted from Harold McGee's book, and is obviously not to scale - nor are eggs oblong)

But when you heat the egg, the proteins jostle around and break the bonds that fold them so tightly together – we say they denature, or lose their natural form.

They unfold into long chains which then bump into and bond to each other, forming a network or messy web of protein throughout the material. This is when the egg sets or coagulates, becoming solid and opaque.These proteins are actually joined together using disulfide bonds, that is, involving bonds between sulphur atoms. So you can add certain chemicals like sodium borohydride (NaBH₄) which break those bonds and can “uncook” the egg.

Anyway, the different proteins coagulate at different temperatures, but overall a whole egg, that’s yolk and white combined, sets at about 73°C. But in custard it’s diluted – a basic recipe is one whole egg to 1 cup of milk and 1 tbsp sugar – so it thickens at a higher temperature, about 78-80°C.

You get the lumps when you overheat it: then the proteins bind too tightly together, forcing out the water from their little networks and becoming hard little lumps. That happens at only another 5 or so degrees, so you need to watch the temperature very closely. Try to keep it below 85°C.

Method 3 is actually the most reliable: add flour or cornflour, or even cocoa. The starch granules absorb water and also dissolve a bit, all getting in the way of the proteins bonding.

You can even bring the temperature up to the boil, in fact, as McGee says, if you want a thick, stiff custard like crème pâtissière you must boil it, because the egg yolks contain an enzyme called amylase that digests starch and will make it all runny again unless you kill the amylase first by boiling it.

So there you go. Making custard is just like doing a chemistry experiment: understand the basic science, use the right ingredients, and watch the conditions.

Wait, what about method 4? That’s easy: practice, practice and practice, and get really good at it. Sounds facetious, but after enough times heating it slowly – like by using a double boiler – and using a kitchen thermometer to keep it just a bit over  80°C, you’ll get used to how it thickens, becomes glossy, and coats the back of a wooden spoon, as the professionals say.

Really, the art of cooking is just science with practice.

Graphene: a Nobel Prize experiment in your own home

Carbon has been known to humankind since before recorded history, so it’s not surprising that discovering a new form of it – especially a form as remarkable as graphene, the wonder material of the 21st century – nets one a Nobel Prize. What is surprising is that it was discovered using everyday office supplies.

(Before you get alarmed about this unashamed and unfashionable pro-carbon stance, let’s be clear: too much carbon dioxide in the atmosphere leading to climate change = bad, carbon the versatile element that’s the basis for all life on Earth = good.)

Apart from the fact that there are more known compounds containing carbon than all the other elements combined (except for hydrogen of course, but we won’t mention that) pure carbon itself comes in many forms.

Diagram showing eight different forms or allotropes of pure carbon: a. diamond, b. graphite (with its layers of graphene), c. lonsdaleite, d. buckminsterfullerene or buckyball, e. C540 fullerene, f. C70 fullerene, g. amorphous carbon and h. a single-walled carbon nanotube (image by Michael Ströck, via Wikimedia Commons)

There’s non-crystalline amorphous carbon, found in coal and charcoal and soot and such. And of course if you subject it to high temperatures and pressures, like in Superman’s fist, it forms the crystals we call diamonds.

Then there are the more complicated structures. The year 1985 saw the arrival of buckyballs, or to give them their proper name, buckminsterfullerene (named after Richard Buckminster Fuller, inventor of the geodesic dome), which are spherical molecules of 60 carbon atoms arranged in the shape of a soccer ball.

But the most recent and perhaps the most amazing form of carbon comes from one of the most common.

Graphite is best known for being the raw material of pencil leads, but it has many other uses including being a dry lubricant. This is because it’s made out of millions of tiny flakes of 2-dimensional crystals with carbon atoms arranged in a hexagonal pattern (see allotrope b in the diagram above). These flat crystals can slip and slide against each other, or flake off to make marks on paper.

Individually, these 2-dimensional crystals are called graphene. And of course, they’re not really new – we’ve known they exist for a long time - but it wasn’t until 2004 that anyone figured out how to extract graphene from graphite and do experiments on it.

The secret is amazingly simple. Starting with graphite extracted from, say, a HB pencil, it’s possible to peel off individual layers using common sticky tape. And because the tape is transparent, you can put it under a microscope and find the pieces of graphene crystal.

Sticky tape can be used to peel off powdered graphite, leaving a single layer of graphene

It sounds nothing special, but because no one had thought of it before it won Andre Geim and Konstantin Novoselov the 2010 Nobel Prize in Physics.

But why the big deal? Well, graphene has a lot of interesting properties:

• Clearly, it’s very thin: just one atom thin. Which means it’s nearly transparent, letting through 97.7% of visible light.
• And yet it’s practically impermeable. The carbon atoms in graphene are only 0.142 nanometres apart, so not even the smallest gas atoms (i.e., helium) can get through.
• It’s also incredibly strong, more than 100 times stronger than steel of the same thickness.
• It’s a great heat conductor, about 10 times better than copper.
• It’s easily turned into a better electrical conductor than copper. In fact, electrons move through graphene as if they had zero mass, a fact that was the subject of that episode of The Big Bang Theory where Sheldon Cooper had to get a job at the Cheesecake Factory so that he could figure out why.
• Being both transparent and such a good conductor, graphene has great potential for use in the next generation of touch screens – that would be strong, flexible touch screens – as well as in lighting panels and solar cells.

Newer, more sophisticated techniques are needed to make sheets large enough for industrial purposes – now up to 70 cm wide – but it’s amazing that it all started with two physicists mucking around with sticky tape.

Burger myth is a load of rot

If you hang out on the internet much, you’ve probably come across video/photos/email similar to the following, in which a McDonald’s Happy Meal doesn’t appear to rot:

What does this mean? Are McDonald’s burgers made out of undigestible material, meaning you can eat as many as you want and not get fat? Or are they a miraculous, non-spoiling food source that could feed hungry millions in places without access to fresh produce or refrigeration?

Well, J. Kenji López-Alt of the Burger Lab has found a more mundane yet scientific answer, by comparing spoilage of a McDonald’s Quarter Pounder with a homemade control burger using good, honest, all-natural ingredients. Both burgers ended up with pretty much the same lack of mould or visible rot.

The main reason seems to be that the burgers in question are small enough to quickly dehydrate when left out on the kitchen bench. Together with the fact that the burger patties are essentially sterilised in the cooking process, they lack both starting mould spores and the environment in which to grow them.

This was further verified by sealing a McDonald’s burger in a plastic bag, which caused it to grow mould just like that loaf of supermarket bread you’ve left for too long.

The moral of the story? Don’t believe everything you see on the internet, at least not without thinking about what it actully means. And one demonstration on YouTube is not the same as a controlled experiment…

For the proper study, with control burgers and everything, head on over to the Burger Lab at Serious Eats.

Recently on the radio

We’ve been a bit quiet recently on the Lost in Science blog. But that doesn’t mean the team hasn’t been busy, oh no!

Here are some links to go with our recent radio broadcasts. Or, you can download the podcasts, for our shows from 3 November 2011 (25:54 min / 12 MB) and 10 November 2011 (28:09 min / 26 MB).

• Analysis of corporate ownership networks shows that out of 43,060 transnational companies, only 147 of them – mostly banks – control 40% of the wealth. Read more in New Scientist, or see the entire paper in the arXiv database.
• Protesting about this risks exposure to pepper spray, or Oleoresin Capsicum, which uses the chemical capsaicin ((CH₃)₂CHCH=CH(CH₂)₄CONHCH₂C₆H₃-4-(OH)-3-(OCH₃)), extracted from chilli peppers, to cause eye and skin irritation. Read about its health effects in Investigative Opthalmology and Visual Science and the North Carolina Medical Journal, or see treatment recommendations from Melbourne’s Royal Children’s Hospital.
• The Berkeley Earth Surface Temperature study, partly composed of and funded by climate change sceptics, has performed a massive re-analysis of global land temperature records and verified that yes, the world really is warming.
• Aside from being real, climate change seems to have caused Australian seaweed species to move between 50 and 200 km south, risking the habitat of many other species that depend on them. Read more at ABC Science, or see the paper in Current Biology.
• In more extinction news, Tasmanian devils are currently threatened by a contagious cancer, which seems to spread due to their genetic similarity. Hope is held for a small, genetically different and mostly disease-free population in the northwest of the state, research into which has won a team of scientists the 2011 Eureka Prize for Environmental Research (also see their paper in Conservation Biology). Although the recent discovery of devils with facial tumour disease in even that remote area has increased concern for this unique species.
• (A good friend of ours, John Cook of Skeptical Science, was also awarded the 2011 Eureka Prize for Advancement of Climate Change Knowledge. Congratulations John!)
• Speaking of genetic diversity, research on the Sandy Island mouse has shown that polygamous females produce more viable embryos. See the paper in Ecology Letters, or read more at the University of Western Australia.
• Finally, to space. Three recent discoveries have shed new light on how solar systems like ours form: there’s a planet called LkCa 15b, 473 light years away, which has been discovered in the process of forming; water seen in the planet-forming disk around the young star TW Hydrae (175 light years away) supports the theory that it collects around grains of dust to make comets, which then deposit the water on planets like Earth; and photos of the asteroid Lutetia, taken by the European Space Agency’s Rosetta probe, suggest that, at around 3.6 billion years old it’s a relic of the early Solar System, and have given clues to its formation.

Have you missed any other shows? Catch up on our old episodes!

Nitrogen cycle to the moon

The discovery of bacteria that can turn urine into rocket fuel has, unsurprisingly, gotten a lot of media attention in recent weeks. But despite the slight exaggeration – NASA has given up the idea of flying to Mars on wee power any time soon – it’s actually a key component in a mechanism essential to supporting life in the ocean.

Nitrogen is an essential part of biology, making up substances like amino acids and DNA. However, despite the fact that it makes up 78% of the Earth’s atmosphere, its gaseous form, N₂, is mostly inert and hard for plants and animals to use.

As a result, we rely on a complex series of chemical reactions, known as the nitrogen cycle, in which N₂ is “fixed” by bacteria or chemical processes into a form we can use; and then, when we’ve finished with it, either through waste or decomposition, it’s turned back into nitrogen gas.

It’s this second part where the rocket fuel comes in: the nitrogen-containing waste product that comes from decomposition, or particularly, urine, is ammonium, NH₄. In the deep oceans, where naturally there is no air, ammonium is turned back into N₂ by a reaction called anaerobic ammonium oxidation, or anammox for short.

Marine nitrogen cycle, showing the role of anammox in turning ammonium into N2 in the deeper anoxic region (without oxygen). PON stands for "particulate organic nitrogen", which includes phytoplankton; DON is "dissolved organic nitrogen"; and DNRA is, wait for it, "dissimilatory nitrate reductase to ammonium" (Image from Nature)

In a letter recently published in the journal Nature, scientists from Radboud University Nijmegen in the Netherlands have described the chemical mechanism used by bacteria that perform this anammox reaction. And an important part of it involves the chemical hydrazine, N₂H₄. And hydrazine happens to be a very unstable compound used in rocket fuel.

As I mentioned earlier, NASA has dismissed this as a way to travel to other planets using astronaut wee. But this is still a useful discovery, apart from the fact that it explains the production of 50% of the N₂ released from the oceans.

Being anaerobic (that is, not needing oxygen), this reaction is useful for treating human waste. And potentially it means we could create other useful biofuels from sewage treatment.

Which might not quite be rocket fuel, but it’s nothing to piss on.

Kartal B, Maalcke WJ, de Almeida NM, Cirpus I, Gloerich J, Geerts W, Op den Camp HJ, Harhangi HR, Janssen-Megens EM, Francoijs K-J, Stunnenberg HG, Keltjens JT, Jetten MSM & Strous M 2011, “Molecular mechanism of anaerobic ammonium oxidation”, Nature, published online 02 October 2011, doi:10.1038/nature10453

If it quacks like homeopathy…

There is a lot that can be said about homeopathy, particularly on a science blog like this one. And most of it is not very nice – but I’m going to say it anyway.

To cover the basics, homeopathy was invented by Samuel Hahnemann in 1796, based on the “Law of Similars”, or the idea that “like cures like”. This essentially involves treating disease using substances that cause the same sort of symptoms – except that you dilute it as much as possible, because supposedly if high concentrations cause an illness, then low concentrations must cure it.

(This is something I’ve never understood. Homeopaths like to claim that, unlike regular doctors, they treat the whole person and not just the disease. Yet their remedies are based on merely addressing the symptoms, which is supposed to be more “holistic” than, say, fixing what caused the problem.)

But the concentrations used mean there should be absolutely nothing left of the original substance. For instance, one popular homeopathic remedy for the flu is Oscillococcinum, made from duck organs (yes, really). It’s prepared at what they call 200C, which translates to a concentration of 1 part in 10⁴⁰⁰. To put that in perspective, most estimates put a limit on the number of particles in the entire universe as somewhat less than 10⁸⁷. (The good news is that means it’s probably safe for vegans.)

A duck, whose heart and liver are used to make Oscillococcinum, a homeopathic remedy for cold and flu. Its feathers can also be used. (Photo by H. Zell, via Wikimedia Commons)

Don’t get me started on claims that water has a memory, or that there’s some sort of magical quantum effect. Quantum mechanics may do very strange things that don’t make sense in our familiar macroscopic world, but physicists actually understand it very well. It’s not some magic word you can just use to bluff your way through anything.

But the main point is that it simply doesn’t work: see the reviews from our old friends at the Cochrane Library (and yes, I’m aware of claims that science somehow doesn’t work on homeopathy; but this is a science blog, so I’m going to stick with it).

With all this damning lack of evidence, Australia’s National Health and Medical Research Council (NHMRC) is quite sensibly preparing a statement on homeopathy. According to leaked drafts, they’re likely to conclude that “it is unethical for health practitioners to treat patients using homeopathy, for the reason that homeopathy – as a medicine or procedure – has been shown not to be efficacious.”

And it’s not just the rather amusing scientific reasons listed above that make it unethical, but also the serious fact that people have died after only taking homeopathic remedies for otherwise treatable illnesses: a baby in NSW that died from severe eczema and a WA woman who died of colorectal cancer.

It also follows a similar finding from the UK House of Commons Science and Technology Committee (PDF 1.6 MB).

Unsurpisingly, homeopathy’s supporters are trying to fight this conclusion. The Aurum Project – “commitment to the health and wellbeing of children” – is recommending their followers write to the NHMRC to complain.

Well, why not take their lead but do the opposite? Write to the NHMRC and tell them you support their goals.

After all, the way that science works is that the truth eventually wins out – but it doesn’t hurt to help it along.

Wash your hands with plain soap, not antibacterial

So many products these days are sold as “germ free”: soaps, sponges, toys, even hands-free hand cleaners. But do these antibacterial products do any good, or do they make things worse?

On of the most commonly used antibacterial chemicals in consumer products is triclosan, or if you prefer, 5-chloro-2-(2,4-dichlorophenoxy)phenol. It’s quite effective against bacteria, inhibiting the action of enzymes used in fatty acid synthesis. Enzymes which, crucially, are not used by humans, so it shouldn’t affect us the same way.

Tube of Dettol Antiseptic Cream, with active ingredients chloroxylenol and triclosan, both at 3mg/g, or 0.3% concentration, the recommended safe amount.

But there are other problems. Thanks to the wonders of natural selection, over-use of antibacterial chemicals can lead to the bacteria evolving resistance, which can then limit our ability to control them in future.

Triclosan also seems to spread throughout the environment, which is potentially bad news for “good bacteria” and even photosynthetic algae. It also means that if there is any danger to humans, it’s hard to avoid.

So far there isn’t any proof that it’s hazardous to humans, but some studies have shown harmful effects on animals, like liver damage in mice and disruption of growth hormones in frogs. Again this raises environmental concerns – particularly for freshwater species – but also the question of whether there is a yet-to-be-discovered risk for humans.

For this reason, the United States Food and Drug Administration (FDA) is currently reviewing the safety of triclosan. Australia doesn’t have a directly equivalent body, but the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) has recommended labelling and adopting a maximum safe concentration of 0.3% in cosmetics, which is consistent with the European Union (see the NICNAS report – PDF 140 KB).

But still, triclosan does kill bacteria, so should you use it to keep yourself clean despite these unverified risks?

Interestingly, some studies have shown that washing your hands with antibacterial soap – containing triclosan – is no more effective at removing bacteria than ordinary soap (see for example Aiello AE, Larson EL & Levy SB 2007, “Consumer Antibacterial Soaps: Effective or Just Risky?”, Clinical Infectious Diseases, 45 (Supplement 2): S137-S147, doi: 10.1086/519255).

So drop the hands-free hand wash, and keep yourself clean the old-fashioned way.

Geoengineering as climate change plan B

Clearly, the best way to address climate change caused by greenhouse gas emissions is to stop emitting greenhouse gases. Which is great, except we don’t seem to be very good at that – particularly in terms of getting international cooperation.

So what do we do if it turns out we can’t cut emissions quickly enough to avoid catastrophe? Or to put it another way, science and technology kind of got us into this mess, so can it get us out of it?

Satellite image of fires and deforestation on the Amazon frontier, Rondonia, Brazil, on 12 August 2007. Intact forest is deep green, while cleared areas are tan or light green. Clearing forest like this releases a great amount of carbon dioxide and removes a valuable carbon sink, so why not try and reverse the process? (By Jesse Allen and Robert Simmon of NASA Earth Observatory, via Wikimedia Commons)

What we’re talking about is geoengineering. It may sound far-fetched, or perhaps like a super villain plot, but it’s being given considerable thought by seriously serious bodies like Intergovernmental Panel on Climate Change (IPCC) Expert Meetings and, more locally, a Pilot Workshop on Asian perspectives.

But what exactly is geoengineering? Well, the options analysed in an influential 2009 paper by the UK Royal Society can be split into two categories: carbon dioxide removal and solar radiation management.

In the list below, we rate these options by their predicted effectiveness and craziness – the inverse of the Royal Society’s assessment of affordability, timeliness and safety.

All aboard the science truck

Last week on the show, I interviewed Dr Katherine Kirk from the Scientific Branch of the Queensland Fire and Rescue Service. Dr Kirk’s main responsibility is to identify hazardous substances using the mobile laboratory in her science truck.

Dr Katherine Kirk with Chris in the Lost in Science studio at 3CR. No hazardous materials were encountered.

If this sounds cool, it’s because it is. Listen to the podcast of the show (MP3 – 11 MB) to find out more.

And for podcasts of other episodes, remember to check out our Listen to the Show page.

Complex mistakes in protein chemistry

Evolution by natural selection works by favouring different traits in a population. But where do these differences come from?

Well obviously there are genetic mutations, or random changes in the DNA, some of which can be beneficial and win out in natural selection. But new research has shown how errors in proteins can also lead to complexity.

Diagram of the primary, secondary, tertiary and quaternary structure of proteins (Image courtesy National Human Genome Research Institute, via Wikimedia Commons)

Proteins are quite complex molecules. They’re constructed from chains of amino acids, the combination of which is encoded in the DNA. But the way they join and fold up determines the way they interact with other chemicals in the body.

Although now it seems that small changes in the way they fold can make it possible for the proteins to combine in more complex ways, without necessarily causing much difference in adaptation. If the population is small and the changes don’t seriously affect the way the proteins function, they can quickly spread throughout the group. And this then gives more complexity for natural selection to play its games.

As one of the researchers, Ariel Fernández, said:

“Natural designs are often one notch more sophisticated than the best engineering. This is another example: Nature doesn’t change the molecular machinery, but somehow it tinkers with it in subtle ways through the wrapping.” (Science Daily)

Fernández A & Lynch M 2011, “Non-adaptive origins of interactome complexity”, Nature, doi:10.1038/nature09992