Kitchen Science: Perfect Pancakes

Ah, pancake day. You have to love a day that encourages you to eat pancakes for every available meal of the day. Personally I’m aiming for at least breakfast and dinner. I don’t have access to pancake making facilities at work so I might have to forgo lunch pancakes. Unless I find some way to transport pancakes in my handbag, which probably isn’t a great plan.

Anyway, my personal pancake orgy plans aside, pancakes are quite amazing. So few ingredients for such a spectacularly yummy outcome. And there are hundreds upon thousands of recipes out there for the perfect pancake, many of which I’ve tried. This is mainly because, for some reason, batter-based baking remains something that I cannot get the hang of. I think it’s partly the speed of the reaction, but I never feel quite in control of what I’m doing. So, this year I decided to try and understand the science behind pancakes, so that I can get a grip on what’s actually happening and hopefully avoid the yearly ritual of ending up with pancake mix splashed around the kitchen with me wailing a series of four letter words, scraping batter splodges off the frying pan and covering them with enough Nutella than people don’t notice how wrong it all went (although to be fair, I’ve never actually had any complaints about this strategy).

As is so often the case with baking, one of the key structures involved in perfect pancakes is gluten. Gluten is formed from two proteins, glutenin and gliadin, which most of the time co-exist fairly sensibly. However, when they get wet, in this case due to the addition of egg and milk, and are mixed together to help loosen them up, they become suddenly very attracted to one another. Moisture and a bit of movement are a serious aphrodisiac to these proteins. They begin to glue themselves together wherever possible, forming the sticky web we know as gluten.

Gluten hardens when it’s heated, and the thing that hardened gluten is best at, really, is trapping air bubbles. However, for this to work, you of course need to MAKE air bubbles. You can do this by beating the living daylights out of your mixture, which will only incorporate a relatively small number of weeny air bubbles. This basic pancake mixture, eggs, flour and milk, will make traditional pancakes, fairly flat but pleasantly fluffy. It’s quite important not to beat the mixture TOO hard, however, otherwise you create a gluten web so tight that no air can actually get in. You want to loosen up the proteins enough that they start throwing themselves at each other, but not so much that they stick together with no room for any air to join the party.

This pancake batter benefits from 30 minutes to an hour standing around. In this time, gluten is relaxing slightly, which it needs to do after all that over-excited bonding together. It’s calming down now, loosening some of its bonds, the frenzy is over, and this period of relaxation gives your pancakes a lighter and less chewy texture. The other thing that happens during this time is that starch in the mixture absorbs liquid from the surrounding batter, causing it to become slightly thicker and creamier, for that perfect pancake texture.

Delicious pillowy blueberry pancakes, as made for me by my husband, who can cope with batter without panicking.

Delicious pillowy blueberry pancakes, as made for me by my husband, who can cope with batter without panicking.

So that’s the perfect English pancake. Then, of course, there are American style pancakes, which are thicker and bouncier. This is because they have a lot more air in them. The way this air is added is by using a super cool and speedy chemical reaction: very simply, you mix an acid and an alkali to make salt, water and carbon dioxide, which come out as glorious fizzy bubbles. You can create this chemical reaction in two ways, you can either add bicarbonate of soda (alkaline) and buttermilk (acidic) to get the bubbly party started, or you can cheat and add baking powder, which is bicarbonate of soda, plus powdered acid. The two don’t react until they get wet, so it’s a foam party by any other name, really.

Now, with American pancakes, because you’ve created so many pockets of air, you don’t want to let them escape. This means it’s better to fry American pancake batter pretty much as soon as you’ve made it, trapping all the air and keeping your pancakes like little fluffy, delicious pillows. Sometimes with added blueberries. Blueberry pillows. If you sat your batter to rest, the air bubbles would start to escape and the pancakes would end up sad and flat, not springy and fluffy.

And that’s that, the science of perfect pancakes. Now, if anyone needs me, I’ll be making an enormous and delicious mess with batter. Happy Pancake Day, folks!

What’s your blood type?

Do you know your own blood type? Well, maybe, but do you know what it actually means? I bet most of you probably don’t. I’ll put my hand up and admit that while I’ve known vaguely that I was O negative, I’ve never really considered what that actually means. What’s the difference between my blood and other blood?

The reason I started thinking about this is that it turns out having a negative blood type is relevant to me now that I am pregnant. To understand why, you need to understand what the positive/negative business is actually all about. The NHS helpfully sent me lots of really great information on this, but being incurably interested meant that I felt compelled to go away and research it even more.

So, there are two parts to your blood type, the letter, which is either A, B, AB or O and the positive/negative side.

Easy as A, B… O?

The surface of red blood cells are covered in proteins. Most of these aren’t relevant here, but one specific type is. Agglutinogens hang out on the surface of red blood cells, flaunting themselves at passing immune cells and generally having fun. There are two types of agglutinogens, A type or B type, and they’re made by two slightly different enzymes. Both enzymes are coded for by the same gene in your DNA, so you can either have a gene that produces an enzyme that makes A-type agglutinogens or a gene that produces an enzyme that makes B-type agglutinogens. These enzymes are very specific craftsmen, they’re old and set in their ways, they either make A-type or B-type proteins, they can’t make both. However, seeing as you get one gene from your biological father and one from your biological mother, you can end up with one gene for each type, which in this case would give you both enzymes because the A gene and the B gene are co-dominant, neither one overrides the other. Therefore in this example you would have blood cells with both agglutinogens types dancing around the surface, this is type AB blood. There is also a fourth and final option, you can have a gene that produces a broken enzyme. In this case, you have no agglutinogens at all, and this is classified as O-type blood. Continue reading

…and we’re back!

Hello,

It’s been a long time, hasn’t it? I’m sorry it’s been so long, team. It wasn’t you, it was me. Have a cookie and know that I still think you’re awesome. I shan’t bore you with the myriad of reasons why it’s been such a long time, except to mention one particularly relevant one: I’m currently pregnant. The reason this is relevant is that it turns out pregnancy is really really fascinating. So, for the next few months you can expect a few posts on the incredible science of growing a baby, in between some of the usual posts on the body in general, kitchen science, and all sorts of everyday molecular madness. Lots to look forward to.

This will be starting this week with a post on blood types and their particular relevance in pregnancy. Sounds interesting? You bring the cake then, and we’ll have a party.

The Friday Question: What causes brain freeze?

 

 

This question actually came from my husband, but I have wondered this before myself, and been asked by others. What causes brain freeze, or ice-cream headaches?

There’s just nothing worse than brain freeze, is there? Well, okay, there are many things worse, but it’s particularly upsetting as it usually comes when you’re enjoying ice-cream, or an ice lolly, or a long cold refreshing drink on a hot day.  Plus, I just find it fascinating how our bodies respond to the world around us, and how simple things can cause seemingly unrelated responses… because I’ve always found it bizarre that eating or drinking something cold can actually make your head hurt. It’s a strange sensation, as well, it doesn’t feel like anything else I’ve experienced, so I’ve always wondered what is going on.

It turns out, what’s happening is a really good demonstration of how your body responds to the outside world, and how your brain interprets messages. It’s pretty cool, actually. Pun 100% intended.

Yes, this is an entriely gratuitous picture of ice-cream.
Image source.

It’s clever, your body. It has awesome ways of regulating itself, including regulating its temperature. When something very cold hits the roof of your mouth, all the blood vessels just below the surface shrink and contract, probably shouting “yikes!” or other four letter words, in response to the sudden cold. I imagine messages being shouted all over the place… “it’s flipping freezing here, sort it out!”. Moments later, your body tries to sort it out by dilating all the blood vessels that have shrunk in the cold, forcing them to relax and widen out again. This increases blood flow to the area, which warms everything back up. So far, so good. Your blood vessels grumblingly get over the shock of having ice-cream applied to them without warning, and carry on carrying blood around.

However, that isn’t all that’s happening. The sudden dilation of the blood vessels triggers pain receptors. This is designed to let your brain know that something has suddenly changed, and all might not be well. Your pain receptors don’t understand that sometimes sudden cold can simply mean that you’re enjoying a refreshing ice-cold drink, because actually extreme cold can be dangerous, just like extreme heat, and so your pain receptors are programmed to interpret the sensation as potentially damaging, particularly when it’s very sudden or overwhelming, perhaps because you gulped down an iced drink, or tried to fit an entire Magnum in your mouth at once. This is the same reason that sometimes touching something incredibly cold can feel painful.

So, the pain receptors in your mouth aren’t aware that ice-cream is not a potentially harmful thing, they just notice that something might be wrong and they react in the standard way: they release chemicals, prostaglandins, whose job is to cause inflammation. This triggers a message to be sent to the brain along the trigeminal nerve that alerts the brain to the chilly danger. Your brain interprets the message as pain. The problem is that the trigeminal nerve doesn’t just carry messages from the mouth, though, it also receives and sends messages from the forehead and the sinuses. When the brain receives the “Hey! Cold stuff! Ouch!” messages, it doesn’t know precisely where they came from, and so it interprets the pain as coming from the wrong bit, which is why you feel the pain in your forehead, even though the cause is in your mouth. This is what is known as referred pain.

It usually takes about 10 seconds for your blood vessels to constrict, dilate, alarm your pain receptors enough that they alarm your brain, and for you to feel the referred pain. Luckily, however it doesn’t last long. And it is possible to try and avoid it, by not taking such large mouthfuls of ice-cream (I’m talking to myself here), and by generally putting very cold things in your mouth more slowly, and holding them there for longer, so your blood vessels can get accustomed and won’t panic quite so much.

And that’s it, the science behind brain freeze. I’m not sure this will necessarily be much comfort next time you have a face full of ice-cream and a headache, but I still think it’s pretty awesome to understand the way your body interprets the outside world and responds to it.

Your Body: Lactose intolerance and milk allergies

Quite a few people, including most recently my own lovely Mummylase and the ever-wonderful Aisling, have asked me to write about lactose intolerance and milk allergies, the differences between them, and how they both work. It’s actually a really interesting area, personally I absolutely did not know until recently that there were two different reasons that people might need to eat dairy-free, so once again I got the excitement of learning new things, which always makes me quite stupidly happy.

The crucial difference between the two problems is that one is an allergy, an inappropriate immune response to a usually harmless stimuli, and the other is an inability to properly digest something.

Lacking lactase

Lactose is a complex sugar that is found in milk, whether it be from cows, goats or people. It’s actually the lovely little molecule that gives milk it’s slightly sweet taste. Because lactose is produced in human breast milk, humans possess a gene containing the instructions to build an enzyme called lactase. Lactase exists purely to chop lactose into little bits that can be absorbed by the body; stripping lactose for parts is its vocation in life.

Normally, in human babies lactase is produced so the baby can digest milk from its mother and absorb the sugars without any digestive issues. As the child gets older, and is weaned off a milk diet, the enzyme then stops being produced. The really interesting thing about lactose intolerance is that this seems to be the original way that things worked… we were supposed to stop producing lactase after we were weaned, because way way back in our evolutionary history, we didn’t really eat or drink any milk once we’d stopped breastfeeding. We’re programmed, or at least we were once programmed, to be lactose intolerant as adults, because frankly the body doesn’t bother producing enzymes that aren’t going to be useful. No-one wants cells full of bored unemployed lactase, hanging around with nothing to do.

If you eat lactose and your body has no lactase to break it down, your body can’t absorb it. The lactose  heads for your colon, undigested, and there is metabolised by your friendly gut bacteria. In this case, you might not consider them to be quite so friendly, though, since what they do as a result of metabolising lactose is produce excess gas, causing you considerable discomfort. The sugar and gas can also lead to increased water heading to the colon… which means diarrhea as well.

Clearly, though, a lot of us aren’t lactose intolerant. We can eat milk and ice-cream and yoghurt and lots of things that are packed with lovely sweet lactose, without the ill effects. This is because we’ve evolved to continue to make the lactase enzyme, even after we’ve stopped breastfeeding, mainly in order to be able to digest cow’s milk. This is actually a really good example of where a genetic mutation can be beneficial. A single very straightforward change in the stretch of DNA that controls the production of the lactase gene can keep the gene switched on into adult life. This is basically a mutation that has allowed us to eat ice-cream. I think it’s my new favourite genetic mutation. And, obviously, natural selection has helped us to hang onto this mutation, because the ability to digest milk is a bit ace, so that it has become more and more common in certain parts of the world to be able to digest lactose.

 
Coping with casein

The other reason someone might need to be dairy free is a milk allergy. This means that your body considers one of the proteins in milk to be a dangerous invader, despite the fact that it’s actually harmless. Once the immune system thinks something is an invader, though, it’s going to respond. It’s suspicious and efficient like that.

The most common milk protein to be allergic to is alpha-S1-casein. This protein is structurally different in different species, so a body might happily accept the form in human milk, but react nastily to the one in cow or goat’s milk. The alpha-S1-casein is recognised by an IgE antibody as an invader, and an immune response is launched, complete with sirens and wildly flashing lights, and all sorts of dramatic goings on. IgE binds to receptors on mast immune cells, which in response release immune chemicals, including cytokines, histamine, and other members of the Inflammation Squad.

The Inflammation Squad can cause a range of symptoms, from digestive discomfort and issues like flatulence, vomiting and diarrhea, through skin rashes and headaches, all the way to severe anaphylaxis. They’re a bundle of fun, honestly. This is your allergic reaction.

So, that’s the key differences between the two conditions, although both mean the same thing to some extent… you need to cut out dairy products. Next week there’ll be a kitchen science post on lactose and alpha-S1-casein in food, and why people can eat certain things and not others. My Mummylase, for example, cannot drink cow’s milk but can still eat cheese, a fact for which she is endlessly grateful.

The Friday Question: How Does Suncream Work?

Hello again, Team Science! Apologies for the extended blog break, after I got back from eating All The Pasta and Gelato in Italy, I had a busy week at work, I was lucky enough to get to spend some time attending two regional Big Bang Near Me fairs, in Crawley and London, where young people exhibit STEM projects that they’ve carried out. They were brilliant fun, and I’m now completely in awe of the young scientists and engineers of the future!

So, it is now officially summer. It’s July, and in the UK the sun is Actually Shining, which has pretty much stunned the whole nation. I’m going to have to go shopping, because I haven’t yet bothered to buy summer work clothes, I didn’t think it was going to be necessary. Anyway, the point is, the sun is out, and that means so is the suncream. You can probably imagine that with my obsession with understanding how things work on a molecular level, I’ve always been pretty intrigued by suncream. In fact I spend a good 30 minutes reading the back of my suncream whilst lying by a pool in Italy. Never let it be said that I don’t know how to have fun.

A large amount of the energy released by the sun is in the form of UV waves. UV waves are invisible to the naked eye, but that doesn’t make them any less damaging, sadly. UV rays are so potent that if you hung around in outer space stark naked, you’d be burnt in mere seconds. And, of course, you wouldn’t be able to breathe, but that’s not entirely the point. Luckily for us, the Earth’s atmosphere absorbs a lot of UV rays, so we don’t have to spend our whole lives wrapped up in space suits to avoid frying. Some UV-A and UV-B rays do make it through, though, and they are what suncream protects against.

When UV-A enters your skin, it produces reactive oxygen species, chemically active molecules that in high numbers can swarm and attack DNA, I’m envisioning them as the minions in Despicable Me, although they are actually far more efficient than that at causing DNA damage. UV-B by contrast, acts differently. It doesn’t bother creating an army of minions to do its evil bidding and harm your DNA, it ploughs right on in there and does it alone. UV-B causes photo-damage to DNA by forming pyrimidine dimers; these are formed when bits of DNA that shouldn’t really be sticking together, stick together, which messes up the whole beautiful helical thing that DNA has got going on, and prevents the DNA from being replicated or used to produce proteins, or anything else useful like that.

Nefarious UV-V rays messing with your DNA.
Image credit.

Luckily, the human body does have defence against the nefarious UV rays. In the multi-storey scaffold that are the layers of your skin, there live cells called melanocytes, whose main job is to produce melanin, the pigment responsible for your skin colour.  When reactive oxygen species are produced by UV-A waves, this leads to a state known as oxidative stress. Under oxidative stress, melanocytes release any melanin that they have in storage, to try and absorb the radiation and stop it creating minions and causing havoc. This might create a temporary tan, as the melanin reacts, but no extra melanin has been produced, so there’s no additional protection against any more incoming UV rays.

When large amounts of UV-B radiation hits the skin, however, there’s no time to stop it causing photo-damage to your DNA. Melanocytes react to this photo-damage by producing more melanin, to absorb the UV-B. This increase in melanin leads to a change in skin tone, which we see as a suntan or as sunburn. The important thing here though is that to develop a tan, you already have to have suffered damage to your DNA. The production of melanin is stimulated by DNA damage, so if your skin has changed colour, then your DNA has taken a bit of a hammering. There are of course mechanisms in your body to try and fix or correct DNA damage, but you know, it’s usually better not to have to.

So, what can you do to stop DNA damage? Well that’s where suncream comes in. There are actually two types of protection in suncream, sunscreen and sunblock. Sunscreen contains organic and inorganic chemicals, which absorb UV rays. For example,  para-aminobenzoic acid and cinnamates absorbs UV-B waves, and benzophenones and ecamsules absorb UV-A waves. They’re like the front line of sun protection chemicals, a row of cavalry that will stop most, but not all of the UV filtering through. By comparison,  sunblocks reflect the UV rays, they’re like an army wielding shields, scattering the UV waves away so that they never even make it as far as your skin. When suncream seems to make your skin look pale and white, this is the reflective particles, usually zinc or titanium oxide.  Most suncreams these days, however, use tiny reflective nanoparticles, that are invisible to the naked eye, but still pretty bad-ass when it come to deflecting UV.

Your defensive army cannot stand forever though, as many films and books have taught us, so the SPF factor in suncream refers to how long you can stay in the sun without UV-B rays effectively making it through the defensive suncream barriers. Lower SPF factors provide less protection, so with them you can stay in the sun for shorter periods of time without opening yourself up to damage. They also might be more useful for people whose skin is naturally darker, this is because it contains more melanin and is better protected naturally. The paler your skin is, the more you want to supplement your natural protection.

So, that’s suncream. Now next time I get to lie on a sun lounger, I won’t need to wonder why I’ve just spent 20 minutes covering myself in the stuff. Instead I can enthusiastically tell everyone around me about it. I’m pretty sure they’re all looking forward to that.

Your Body: Iron, Haemoglobin and Anaemia, Oh My!

Hello Team Science! Before today’s post, just a tiny little note to say that on 30th June I will be running the Race for Life with a team of amazing women, led by the brilliant Aisling of Any Other Woman. Our sponsorship page is here, so if you do have any spare pennies lying around, and would like to use it to help fight cancer, chuck them our way. We will be hugely and endlessly grateful. I’ve lost people I loved to cancer, and I’ve seen how vicious it can be, how heartbreakingly cruel and unfair. Anything we can do to fund research into fighting it is one step closer.
Also, I will be on holiday next week, living it up in Italy, by which I mean I will be lying around reading and eating gelato, so no posts next week Im afraid. But I’ll be back in July, full of science and gelato, a winning combination…
 
Today’s post is about anaemia, and what it actually means. I’ve been diagnosed as anaemic in the past, and although I always knew it meant I was iron-deficient, and needed to start eating spinach like Popeye in an emergency, I never really connected that to why it made me so tired all the time. As always, I think it’s kind of awesome to understand how your body works, and how things can shift and go wrong, and the effects that can have. Your body is so interconnected, everything works together in such a smoothly organised way, that when something is off balance, it can have some major effects.
To understand anaemia, we really need to get to grips with the role of iron in the body. Clearly it’s important, or the lack of it wouldn’t make me so droopy and inclined to curl up in a ball under our duvet and try to refuse to come out for anything less than nuclear war, or the promise of ice-cream (garnished with spinach, naturally). Iron is involved in the transport of oxygen in the blood. It’s the sidekick of a protein that lives in red blood cells, called haemoglobin.
Haemoglobin is actually one of  my favourite proteins (and that’s a tough top ten to call, trust me). Basically, it transports oxygen around the body. It’s the circulatory system’s taxi service for all O2 molecules with someplace important to go. Haemoglobin is made up of four subunits, which stick together to form a perfect oxygen carriage. Each of the four units is made up of two parts, a heme group and a globular protein chain. The protein chain forms the structure of the carriage, and the heme group is the oxygen’s comfy little seat.

This is haemoglobin, with it’s four carriages. The heme ‘seats’ are in green.
Image source.

The seat for oxygen is not just any seat, it’s pretty special, what with oxygen being a VIP in the body, it deserves first class transport around the place, and anyway, it’s far too much of a diva to get around on its own. The heme group consists of a chemical ring known as a porphyrin, with a charged iron molecule held in the centre. Oxygen climbs into its ‘seat’ by binding to the iron molecule.
This is the bit that makes me love haemoglobin, because each carriage has four seats, four spaces for oxygen molecules to bind. However, each seat doesn’t gain an oxygen haphazardly, the process of binding is cooperative. So, when the first oxygen straps into its seat, the iron ion shifts back slightly. Because the entire protein carriage is built and fitted together so neatly, this shift, and it really is only a very very tiny movement, causes the other three units to also shuffle around slightly. This very minor shuffle results in a slightly changed position for the three remaining seats; making it easier for oxygen to hop on board. When I first learnt about this, I had one of those mind-blowing “the body is INCREDIBLE” moments… it’s developed a system where the binding of one oxygen makes it easier for successive oxygen molecules to bind. This makes the whole thing take less energy, which is ace because everyone knows saving energy is important. How amazing is your body?!
 
Anyway, it’s pretty clear from the way that oxygen binds to iron in order to be transported speedily around that body that iron is an Important Thing. Without sufficient iron, the body cannot produce enough haemoglobin, and without enough haemoglobin, there’s a limit to how much and how quickly oxygen can be ferried around the body. This is what happens when you get iron-deficiency anaemia. There’s just not enough oxygen getting around your body, so you feel tired and lethargic. You might also, in more serious cases, experience shortness of breath and a pale complexion. Luckily, it’s fairly simple to fix this, you just need to Get More Iron. Although this isn’t entirely straightforward, because your body needs to absorb the iron before it can do anything vaguely useful, but the way the body takes up iron is a subject for another post, I think!
 
So that’s anaemia in a nutshell, you need hulking strong iron molecules to transport diva-ish oxygen around the place and give you sufficient energy to run around and do stuff. It’s a simple thing, with a big effect. Biochemistry rocks.
 
*As always, I want to make it clear that Im a science nerd with a bizarre habit of anthromorphising molecules in my spare time, Im not a doctor or qualified in any health profession at all. If you think youre suffering from anaemia, see your doctor. Thats an Actual Order. Thanks.*

How Drugs Work: The Morning After Pill

I have written before, elsewhere, about the pill and how it works, but the other day I was wondering… does the morning after pill work in the same way? I think I may also have said before, here or elsewhere, I can’t keep track of my own ramblings, that I think contraception and emergency contraception are hugely important and valuable things to have. They’re a very empowering tool for women, they let you take control of your body to a certain extent. This doesn’t mean that I advocate the regular use of the morning after pill, emergency contraception is for emergencies, after all, but if something does go wrong, or fail, or worse, if you’re the victim of sexual assault or rape, the ability to try and prevent unwanted pregnancy is, to me, just invaluable. It’s a way to take some control of your situation. And that we can do this, we have the knowledge and ability and understanding to take that control… that’s just amazing.

So, anyway, how does it work? I’ve explained the menstrual cycle before, when I was discussing the pill, but to recap (and blatantly repeat myself), this is how it goes down…

Hormones are the messenger system of the body, they dart around the place attaching themselves to cells and relaying instructions to make them do things, or stop doing things, or do more of a specific thing. In my head, hormones have loudspeakers and clipboards and are called efficient-sounding names like Barbara and Robert. The whole of your reproductive cycle is a delicately balanced system of hormones, all shouting instructions at cells at exactly the right moment, culminating in the production of an egg, ready to be fertilised.
In addition to progesterone and oestrogen, there are a few other key hormones involved. Together, they form Team Reproduction. Some of them even have capes to match their clipboards. They are gonadotropin-releasing hormone (GnRH), follicle stimulating hormone (FSH) and luteinising hormone (LH).  The instigator in the process in GnRH, it is produced by the hypothalamus in the brain and production is regulated by progesterone. On production it races off to the anterior pituitary gland, there to shout at cells until they start producing FSH.  FSH, once produced by the pituitary gland, flies down to the ovaries and tells them that it’s time to start prepping the egg, which they do by growing follicles, one of which will become an egg when it grows up. Although it would probably rather be a ballerina, it doesn’t get that option. The ovaries, alongside their egg-prepping, start to release oestrogen, which scoots back up to the brain to tell the pituitary gland to slow down on the FSH production. At the same time, another deputation of oestrogen hormones are busy encouraging the hypothalamus to produce even more GnRH. Because by this time the hypothalamus probably needs some moral support or something.
This oestrogen cheerleading squad results in a sudden increase in GnRH production from the hypothalamus, which tells the pituitary gland to stop messing around with FSH and produce a mega-load of LH. Pretty soon an squad of LH molecules has amassed, and once this cheerleading squad is ready it marches upon the ovaries chanting “IT’S GO TIME”. And the ovaries release the egg. If there’s a sperm in the area and all the conditions are right then, in short, a baby gets made.
Where other contraceptive pills can try and stop this happening at an earlier stage, by stopping the egg being developed and produced in the first place, the role of the morning after pill is to stop pregnancy occurring at this point.
It is thought to do this by attempting to delay the egg being released, to try and stop it coming into contact with the sperm. Because levonorgestrel, the active drug in the morning after pill, is an international hormone of mystery, it’s not 100% clear how it actually does this. The theory is that levonorgestrel is a synthetic progesterone-like hormone, a very clever spy of a hormone disguised as progesterone.  Very high levels of  hormones-pretending-to-be-progesterone, when taken in pill form, effectively just go into your system and really screw everything up. This is possible because your  hormone cycle is really delicately balanced, so an influx of any one hormone can really throw things of course. A temporary surge in progesterone (or stealthy fake progesterone in this case) from a morning after pill can theoretically cause sufficient havoc to delay release of the egg and prevent it meeting up and getting frisky with a sperm.

This is how I envisage the morning after pill, with it’s sneaky progesterone hat disguise on.

There is also a further theory that levonorgestrel might make it difficult for a fertilised egg to implant into the wall of the uterus. This would mean that even if the egg and the sperm did manage to meet up, like star crossed lovers in your fallopian tubes, they still couldn’t make a baby, because they’d have nowhere to settle down and get it on.
So that’s how it works, a clever international spy hormone of mystery sneaks into your system and causes minor chaos for long enough that the egg and the sperm are kept apart. It sounds very much like a molecular James Bond movie, actually. The only risk is that if you do have unprotected sex at just the wrong moment, and the sperm and the egg meet, fall in love and settle down together happily in the wall of the uterus before you get a chance to take the morning after pill, there’s nothing that levonorgestrel can do. This is why doctors advise women to take the morning after pill as soon as possible after having unprotected sex, and certainly within 72 hours. The quicker you take it, the more likely it is that the James Bond hormone can get involved and call a halt to proceedings. Before drinking a cocktail, naturally.
*As ever, I am an enthusiastic science nerd, not a doctor, if you think you need to take the morning after pill, you need to speak to your doctor or a pharmacist now. Right now. Stop listening to me and go… thanks*

Kitchen Science: Pastry

Ah, pastry. Pastry is one of my weaknesses in life. Pasties and pork pies and strudel, and apple pies and lemon meringue pie… and custard slice and cream puffs. I could go on. Sometimes I think these kitchen science posts read like the food porn inside of my mind; like delicious science with added drooling.

Pastry IS amazing, though. It’s one of those things that sort of blows your mind when you really think about it… the same basic ingredients, in slightly different amounts and proportions, mixed together in different ways can result in such incredibly different textures. It’s kind of miraculous, because you’d think that flour, fat and water mixed together would always end up the same. I would have thought so anyway, but luckily chemistry has other, far tastier ideas than me.

Because there are lots of different types of delicious pastry, this is going to be a two-parter. I’m currently taking bets on how long I last writing these two posts without caving in and making a pie (odds are on that it’ll probably be about 3 minutes, if I’m feeling strong)

What’s in pastry, then? Flour, fat and water. And possibly some other bits and pieces, but these three are the key players, the stars of the show.

Flour is the structural backbone of pastry; it’s the thing that gives strength and shape to the whole affair. However, it’s not quite as structured as it is in cake, for example. In cake, gluten from the flour forms a stretchy web that spreads throughout the whole cake and holds the whole business together. In pastry, the flour particles are deliberately segregated in specific ways, and then coated in fat.

Fat is key to pastry, it coats the flour particles and keeps them apart, isolated into a tiny prison, with no water allowed in or out. Fat is always a bit fascist about water. When the mixture is heated, the gluten in the flour particles can’t get to water, becuse they fatty prison guards won’t let them, so instead they gelate together in terror, to form a dry and crumbly texture. When you eat this, you get the combination of crumbly gluten and melty butter. Who’d have thought terrified isolated flour particles would taste so good?

The amazing thing about pastry to me though is the differing textures you can get; and this depends on the way that the flour particles are segregated. In crumbly pastries, like shortcrust, the butter is mixed into the flour in chunks that are slowly integrated together by manually… squishing them together. I believe the technical term is rubbing, but I prefer squishing. This results small lumps of flour, clinging together, surrounded by butter. In some shortcrust pastries, egg is also added and the protein from the egg provides an extra scaffolding, to stop the pastry crumbling away completely. Although it is still possible to create pastry that crumbles completely, even with egg, as I can testify. I’ve been there.

Mmmm. Shortcrust pastry. I wish I could say I’d made this, but when I make pastry, it doesn’t last long enough to be photographed.
Image source.

By comparison in, puff pastries, or laminate pastries, the flour and gluten is distributed differently. Rather than being squished into the butter, and trapped, the process is longer and far more tortured for the gluten. If you were so empathetic that you could feel sorry for flour, you’d definitely never make puff pastry. Equally, if you were highly impatient, you probably wouldn’t either.

So, to make laminate pastries, you mix flour with a small amount of water to form a just-about dough. Then you place a block of butter, heated until it’s just pliable but not completely melted and useless, on top of the block of dough. Then, you fold the whole thing up, and roll it out. Then you turn it, fold it, and roll it some more. In between bouts of rolling and folding, you chill the whole business in the fridge so that it’s good and cool. The process of rolling the dough allows the gluten to develop, but it is a bit tortured and stressful. The chilling in the fridge stage gives the gluten some much-needed downtime in which to relax. You know, before it gets tortured again. The result of this time-consuming process is that the flour-gluten is stretched into hundreds and hundreds of teeeny tiny thin layers, isolated between layers of butter. This differs to shortcrust pastry, where the flour particles were in clumps, not super-thin sheets.  And the result of this is that when the whole thing heats up, the flour particles do still cling together, but they form sheets not crumbly chunks. And the evaporation of water into steam between the sheets causes them to puff right up, into a light, crunchy, delicious sheet.

I can forgive the torture of gluten for this.
Image source.

So, that’s the basics of two types of pastry, terrfied and tortured flour plus delicious buttery prison warders. Come back next time for more science drooling, and more pastry.

The Friday Question: Fizzy Drinks

This Friday’s Friday Question comes from Gemma, and it is… “Why does shaking a carbonated drink make it fizzier?”

The answer is all about physics, which is pretty awesome. If slightly unnerving to a molecular structural bioloy nerd, it’s not often I fully understand physics!

The fizz in fizzy drinks comes from carbon dioxide, which is forced into the liquid under high pressure. The pressure means that there is a lot of carbon dioxide gas trapped into a small space; gas molecules whizz and bounce around in the neck of the bottle, and hit the surface of the liquid below, where they dissolve. Some of them escape back out again into the neck of the bottle. For a time, everything inside the bottle is manic and chaotic, molecules are bouncing around crazily, hitting each other, hitting the water, fleeing the water, generally acting a bit out of control. Over time, though, things settle down. An equilibrium establishes itself, this means that the rate of carbon dioxide leaving and entering the liquid is exactly the same; everything is stable.

If you opened the bottle at this point, you’d hear a hissing sound as the pressure was released, but that’s it, you wouldn’t get accidentally coated in fizzy drink. And then, once the drink was exposed to the Great Wide World, and all the air in it, all the carbon dioxide would eventually flee the liquid and escape into the air. Carbon just wants to be free, and this is why fizzy drinks go flat.

So what does shaking do to change everything? The bottle is sealed, so shaking makes no difference to the pressure. However, what shaking DOES do is disturb the liquid. Liquid has a surface tension; this means that the molecules in it have a tendency to be really friendly and stick together. It takes energy to prise the super friendly liquid molecules apart, which is what you need to do to form a bubble. Because liquid is SO friendly, overfriendly to be honest, the actual process of starting a bubble is Very Hard Work. Bubbles are frankly exhausted by the time they even come into being. Unless you give them a helping hand, in the form of a good old shake.

Shaking shifts everything around, and all a bubble needs to get started is the opportunity to find a crack in the surface tension of the liquid. A teeny tiny microscopic crack will do it, such as might be formed if liquid was bashed against an microscopically uneven surface, like the side of a bottle or can. Baby bubbles form in the liquid. Once a baby bubble exists, it takes a lot less energy for it to grow into a bigger bubble. It’s always the first step that’s the hardest to take.

Shaking also shifts the equilibirum; and some of the carbon dioxide gas that was in the neck of the bottle or the top oft he can, is mixed up with the liquid and can join any baby bubbles that have bravely managed to form. This means that that liquid suddenly contains a lot more bubbles, and if you open the bottle at THIS point, the change in pressure will cause  all these bubbles to rush to the surface and escape. Very quickly. Into your face, and all over your clothes. We’ve all been there, I think.