an autodidact meets a dilettante…

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An interminable conversation 6: trying to understand inductive cooking.

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the guts of an induction cooker, I believe

Canto: So, with all the fuss and excitement about renewables, we should continue the near impossible task of trying to get our heads around electricity, never mind renewable sources of electricity. It’s still electrickery to me. For example, Saul Griffith in The Big Switch recommends inductive electric stoves as a replacement for gas, which many swear by because they appear to heat your pot immediately, or at least very quickly compared to those old ring electric heaters…

Jacinta: Yes, but as Griffith says in that book, you can tell the gas isn’t too efficient because you feel yourself getting hot when you’re near the stove. That’s heat that isn’t going into the pot. Apparently that doesn’t happen with inductive electricity, which heats the pot just as rapidly if not more so, but almost nothing’s ‘wasted’ into the surrounding air.

Canto: Unless you like to feel toasty warm in the kitchen. Anyway we’re talking about induction cooktops,to give them their proper name, apparently. The old electric cooktops had those coils, and they’re what we grew up with. Here’s a summary from the Forbes website:

Also known as radiant cooktops, electric cooktops offer centralized heat. Electric cooktops have an electrical current that flows through a metal coil underneath the glass or ceramic surface. The coil becomes hot and starts glowing due to the electrical resistance. It will transfer its heat through the glass using infrared energy. This means the burner holding your pot or pan is the one that gets hot. Your food is then cooked by the transfer of heat between the cooktop and the pot. There is residual heat for an undetermined amount of time with electric cooktops, which is why these ranges tend to have an indicator light letting you know that the burner is still warm.

Jacinta: Metal coils under glass or ceramics…? As I recall, they were just coils, not under anything. They were grey. But maybe they were ceramic, with metal embedded within, or on the underside. I wish I was the type who pulled things apart to see how they worked, like geeky kids. And wtf is ‘infrared energy’? As far as I remember, the coils turned visible red when hot, not invisible infrared.

Canto: You see the red light but you feel the infrared heat. The heat you feel from the sun is in the non-visible part of the spectrum – the infrared and beyond. On the other side of the visible spectrum is the ultraviolet and beyond. I think.

Jacinta: So which side has the long wavelengths and which side has the short? – not that this would mean much to me.

Canto: Infrared radiation is about longer wavelength, lower frequency waves than visible light, and ultraviolet radiation is higher frequency and shorter wavelengths. So they bookend invisible light, if you will. But the longest wavelength, lowest frequency waves are radio waves, followed by microwaves, while the highest frequency, shortest wavelength radiation is gamma rays. Whether there are forms of radiation beyond these ends of the spectrum, I don’t know.

Jacinta: I’ve heard of gravitational waves, which were only detected recently. What about them?

Canto: They can have almost infinitely long wavelengths apparently. So to speak. Obviously if they were ‘infinitely’ long, if that’s even meaningful, they’d be undetectable. But let’s get back down to earth, and the most useful energy. Here’s how the Red Energy website describes induction cooktops:

Basically, a standard electric or gas cooktop transfers heat (or conducts heat) from the cooktop to the pot or pan. Whereas, an induction cooktop ‘switches on’ an electromagnetic field when it comes into contact with your pot or pan (as long as the cookware contains a ferrous material like iron or steel). The heat comes on fast and instantly starts cooking the contents.

Jacinta: Okay that explains nothing much, as I don’t know, really, how an electromagnetic field works (still stupid after all these years). As to ferrous cookware, I didn’t realise you could use anything else.

Canto: Well the same website says that, given the speed of heating, you might need to upgrade to cookware that can take the stress, so to speak. As to the electromagnetic field thing, Red Energy doesn’t really explain it, but the key is that an electromagnetic field doesn’t require the heating of an element – those coily things.

Jacinta: They’ve eliminated the middle man, metaphorically speaking? I’m all in for eliminating men, even metaphorically.

Canto: Thanks. So I’m trying to get my head around this. I need to delve further into the meaning of this magical, presumably infrared, heat. The essential term to explore is electromagnetic induction, and then to join that understanding to the practical aspects, yer everyday cooking. So this goes back to the working-class hero Michael Faraday, and the Scottish hero J C Maxwell, which will be fun, though of course I’m not at all nationalistic, but…

Jacinta: Canto isn’t a particularly Scottish name is it?

Canto: My real name is Camran Ciogach Ceannaideach, but I prefer a simpler life. Anyway electromagnetic induction has a great variety of applications, but this is the ultimate, i.e Wikipedia, definition:

Electromagnetic or magnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic field.

Jacinta: None the wiser. What’s an electromotive force?

Canto: Called emf, it’s ‘the electrical action produced by a non-electrical source, measured in volts’. That’s also Wikipedia. So a non-electrical source might be a battery (which is all about chemistry) or a generator (all about steam in industrial revolution days -creating mechanical energy).

Jacinta: So the infernal combustion engine somehow converts petrol into mechanical energy? How does that happen?

Canto: Off topic. This is really difficult stuff. Here’s another Wikipedia quote which might take us somewhere:

In electromagnetic induction, emf can be defined around a closed loop of conductor as the electromagnetic work that would be done on an electric charge (an electron in this instance) if it travels once around the loop.

Jacinta: Right, now everything’s clear. But seriously, all I want to know is how to get rid of that middle man. We were talking abut cooking, remember?

Canto: So emf is also called voltage, or measured in volts, which I seem to recall learning before. Anyway, nowadays electromagnetic induction is everywhere – for example that’s how money gets removed from your bank account when you connect those cards in your wallet to those machines in the shop.

Jacinta: So they’re zapping your card, sort of?

Canto: I’ve looked at a few sites dealing with electromagnetic induction, and they all give me the same feel, that it’s like weird magic. I suppose because they explain how it works but not why.

Jacinta: Shut up and calculate?

Canto: Anyway, induction cooking has been around for more than a century, but it’s really catching on now. They always say it’s more direct, because it doesn’t involve heating an element.

Jacinta: Don’t you know it’s magic?

Canto: No, it’s magnetic. Which explains nothing. But let me try another website, this time Frigidaire:

Induction cooktops heat pots and pans directly, instead of using an electric or gas-heated element. It boils water up to 50 percent faster than gas or electric, and maintains a consistent and precise temperature. The surface stays relatively cool so spills, splatters and occasional boil-overs don’t burn onto the cooktop, making clean-up quick and easy…. Induction cooking uses electric currents to directly heat pots and pans through magnetic induction. Instead of using thermal conduction (a gas or electric element transferring heat from a burner to a pot or pan), induction heats the cooking vessel itself almost instantly….. An electric current is passed through a coiled copper wire underneath the cooking surface, which creates a magnetic current throughout the cooking pan to produce heat. Because induction doesn’t use a traditional outside heat source, only the element in use will become warm due to the heat transferred from the pan. Induction cooking is more efficient than traditional electric and gas cooking because little heat energy is lost. Like other traditional cooktops, the evenly heated pots and pans then heat the contents inside through conduction and convection…. Important: For induction to work, your cookware must be made of a magnetic metal, such as cast iron or some stainless steels.

Jacinta: So I’m not sure if that gets closer to an explanation, but what’s surely missing is how magnetism, or a magnetic current, creates heat. It doesn’t use an ‘element’, but it must use something. I know that heat is energy, essentially, and presumably an electric current is energy, or force, like emf, which is also energy…

Canto: Yes it’s very confusing. The Wikipedia article gets into the maths fairly quickly, and when it describes applications it doesn’t mention cooking… Hang on, it takes me to a link on induction cooking. So here’s a definition, similar to the Frigidaire one, but a little more concise. Something to really zero in on:

In an induction stove (also “induction hob” or “induction cooktop”), a cooking vessel with a ferromagnetic base is placed on a heat-proof glass-ceramic surface above a coil of copper wire with an alternating electric current passing through it. The resulting oscillating magnetic field wirelessly induces an electrical current in the vessel. This large eddy current flowing through the resistance of a thin layer of metal in the base of the vessel results in resistive heating.

I’ve kept in the links, which I usually remove. For our further education. So it’s the resistance of the metal base of the pan that produces heat. Something like incandescent light, which is produced through the resistance of the tungsten filament, which makes it glow white (this was a light bulb moment for me). So you really have to use the right cookware.

Jacinta: Thanks for the links – yes, the key is that ‘resistive heating’, also called Joule heating. James Joule, as well as Heirnrich Lenz, independently, found that heat could be generated by an electric current, and, by experimental testing and measurement, that the heat produced was proportional to the square of the current (which is basically the emf, I think), multiplied by the electrical resistance of the wire. So you can see that the wire (or in cooking, the pot) will heat more readily if it has a high electrical resistance. This can be stated in a formula: , where P is the heating power generated by an electrical conductor (measured usually in watts), I is the current, and R is the resistance.

Canto: So we’ve made progress, but it’s the relation of magnetism to electricity – that’s what I don’t get, and that’s the key to it all. I think I understand that an electric current creates a magnetic field – though not really – and I get that an alternating current would induce an oscillating magnetic field, I think, but is this just observation without understanding? That electricity and magnetism are connected, so just shut up and calculate as you say?

Jacinta: So how, and why a high frequency alternating current creates a dynamic field, that’s what we’re trying to understand. And what’s an eddy current?

Canto: I think we’ve had enough for now, but we’re getting there….

Written by stewart henderson

August 27, 2022 at 5:20 pm

What is yeast?

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Canto: So we’re going to explore yeast now, for practical purposes. Using a bread machine, I’ve been trying to make, not so much a perfect loaf as an edible one. With beginner’s luck, my first loaf turned out as perfect as this little machine made it, but that has been followed by three failures.

Jacinta: To be fair, none of those failures was inedible, they just didn’t rise satisfactorily.

Canto: Yes, to varying degrees, and the principal and perhaps only culprit, I suspect, was the yeast.

Jacinta: So we need more detail, and then we’ll investigate yeast.

Canto: So I followed the instructions – first some 200-250 mls of lukewarm water, then some butter, salt, sugar, then some prepared flour for a linseed loaf, then some ‘bread improver’, then yeast, all in correct proportions according to a recipe, into the pan of the bread machine, switch to the desired setting, and after 4.5 hours approximately, out came a pretty-well perfect loaf. So, it can be done.

Jacinta: Proof of bread machine concept perhaps, but the experiment needs to be replicated. I believe that in science this doesn’t happen enough, because there’s little kudos in replicating someone else’s experiment – or, in this case, even your own. 

Canto: Well, although I cannot live on bread alone, my desire to replicate the experiment was definitely based on my stomach. So my next effort was perhaps a week later, and I repeated all the steps, or so I believed, but what came out was a shrivelled, concentrated lump. More or less edible as you say, but far from optimal. In fact, a failure. So I went back over my steps and realised I’d forgotten to warm the water. I was thinking the yeast, which I’d taken from the fridge, might’ve needed some warming to get started. 

Jacinta: Well, that’s a hypothesis. So what about the next attempt?

Canto: Well, to be honest, I didn’t try again for some months. But what with the state being in lockdown recently, out of sheer boredom, more or less, I tried again. This time I did all the required steps correctly… well, not quite – I forgot the bread improver.

Jacinta: And I told you it wasn’t a really necessary ingredient, though now I’m not so sure. 

Canto: Yes, because this effort was the most disastrous. The bread didn’t really rise at all – it was flat as a very dense pancake. Or not quite – it was about an inch and a half thick – about as compressed as all those ingredients could be. And that was when I really started thinking about yeast. I’d used the same yeast, from a package I’d opened before the first bread-making attempt. I couldn’t see any use-by date, and I knew that yeast was some kind of living organism. Maybe it was now dead yeast? 

Jacinta: Right. Are we ready to explore yeast in a general way now? 

Canto: Well not quite. So I tried again, this time using a new yeast package – vacuum sealed, but kept in the fridge. So, cold. I did it all correctly this time, but again without the bread improver. Need to know what ‘bread improver’ actually is. Anyway, it kind of half-worked, it definitely rose, but only by half of the tin. So, either the cold state of the yeast, or its only half-aliveness, perhaps, or the lack of bread improver, was responsible. More experiments required. 

Jacinta: Right. And again, the last experiment did result in edible, indeed tasty bread, but a little too compressed. Which brings us to yeast, which is a single-celled egg-shaped fungus, Saccharomyces Cerevisiae (‘sugar-eating fungus’). There are some 20 billion cells in a gram of yeast. These cells derive their energy from the consumption of sugars – remembering that you’ve added brown sugar to the mix (but maybe not enough?), and there is sugar in the pre-mixed linseed flour that you used. Flour contains maltose, a kind of starch, which binds two glucose molecules together. It’s important in brewing. So when the yeast consumes the sugars in your mix, it releases useful end products, such as carbon dioxide and ethyl alcohol. The released carbon dioxide gas becomes trapped in the dough and causes bubbles, which expand as the CO continues to be released, causing the dough to rise. And according to my source:

The ethyl alcohol (and other compounds) produced during fermentation produce the typical flavor and aroma of yeast-leavened breads.

Canto: I haven’t particularly noticed this aroma, but the mention of fermentation is interesting.

Jacinta: Yes, Louis Pasteur did a lot of work on fermentation, in the narrow sense of the byproducts, or end-products, of yeast activity, for example noting that carbon dioxide and ethyl alcohol weren’t the only by-products, and it was later also found that other glucose-consuming organisms and tissues, for example muscle tissue, also engage in a form of fermentation, which we call glycolysis. 

Canto: Right, so there are many types of yeast – for example ‘baker’s yeast’ and ‘brewer’s yeast’. 

Jacinta: Oh yes, there are many forms of Saccharomyces Cerevisiae, the general term for both brewers and bakers. It’s a good source of B vitamins (but not B12), and it’s a favourite ‘superfood’ for those who believe in such things…

Canto: Okay, what is ‘bread improver’?

Jacinta: Well, it’s more yeast. And according to one site: 

It usually also contains emulsifiers, which help to make the loaf soft and fluffy. It may also contain an enzyme which can improve the texture of the bread as well as help it to last longer, or asorbic acid (vitamin C), which can help the dough to rise.  

So it’s likely that using the bread improver would help. Make sure you use it next time. Although  observing use-by dates is probably important for these things. There’s of course a lot more to say about the biochemistry of yeast and the processes of glycolysis and fermentation, and their importance for the energy pathways of all sorts of organisms including humans, but that’s the thing. You start with one simple question and it eventually leads you to how the whole world works. Or at least the living world. But that leads you eventually to the non-living, matter and all that matters. So that’s enough for now.

References

What is Yeast?

https://www.sciencedirect.com/topics/medicine-and-dentistry/maltose

https://www.britannica.com/science/fermentation

https://www.healthline.com/health/brewers-yeast#side-effects

https://www.bestrecipes.com.au/baking/articles/bread-improver/xpkotf0j

Written by stewart henderson

July 30, 2021 at 11:51 am

Posted in bread, glycolysis, yeast

Tagged with , , ,