Smell of walnuts

Walnuts are an odd fruit…nut… I plucked one from a tree on a recent dogwalk and when I cut off the fleshy out coating this evening to get to the kernel the overwhelming odour it exuded took me right back to the first flat I shared with Mrs Sciencebase where we had a walnut tree. Of course, unprocessed you have to remove that outer flesh and then crack the soft(ish) shell and then remove the bitter pith to eat the deliciously sweet kernel. The pith is very bitter and to be honest, I don’t enjoy ripe walnuts of the kind you used to get on a Walnut Whip and that are ubiquitous in a Christmas bag of mixed nuts.

Anyway, I was curious as to what the odour of slightly unripe walnuts is musing with a chemist’s brain that there might be a single compound responsible. There isn’t, there’s a whole collection of compounds that give walnuts their distinctive scent: pinocarvone, aa-aldehyde canfolenic, chrysanthenone, trans-pinocarveol, trans-ßß-farnesene, trans-ßß-verbenol, aa a-terpinene and aa a-terpinolene (the a and aa in prefixes should be alphas, and if the betas aren’t translating, they’re betas).

Intriguingly, a quick Google on walnuts revealed some work on using these various compounds and pest insect lure compounds as alternatives to conventional pesticides, more on that here. It’s too late in the evening for me to ChemDraw those compounds (i.e. it is well past beer o’clock and I have a curry bubbling in the pan) but I may update this post if there is demand from botanical/natural product chemist friends who don’t believe I could produce the chemical structures of all those alphas and betas…

Read without your reading glasses

Here’s a neat trick for long-sighted readers that exploits the underlying concept of a pinhole camera to let you read in close-up even if you forgot your reading glasses. The video also explains what it is about a pinhole versus a fixed lens that allows it to project a sharp image of something at any distance and why depth-of-field is bigger with a smaller aperture (bigger f-stop) in your standard camera

Here’s the link for those of you whose smart phones cannot render the embedded Youtube clip ;-)

Emission control

Car manufacturers have been fiddling the books when it comes to pollutants for years, the latest scandal involving VW’s alleged “defeat device” is just the latest in a long line, the US EPA gave other manufacturers a hard slap on the wrist back in 1998, for instance.


Thing is…this “defeat device” isn’t really a device at all, it’s just engine management that detects when emissions are being tested (basically watches to see when the steering wheel isn’t moving and a couple of other things) and switches the car to low-pollution mode. So, why don’t all cars simply run on the roads in low-pollution mode if that’s something that they can do through engine management software?

Well, basically low-pollution, means low-performance, and we, as drivers, are on the whole not interested in driving cars that are unresponsive and do not accelerate quickly to the speeds at which we like to drive. Fundamentally, the emissions regulations are set too low for the kind of society we have where drivers like nippy cars. Nippy cars sell. One slight aside, manufacturing a car uses about the same amount of energy as driving it for 100,000 miles, if we take into account the cradle-to-grave lifecycling of mining and refining the metals, making the rubber tyres, all the bits of metal and plastic and the countless assembly and delivery processes (that includes non-petrol and hybrid cars too).

Anyway, bottom line: All cars pollute. Some less than others. Cleaner cars are boring to drive.

If we want to clean up the atmosphere we have to admit that and switch to low-performance, low-pollutant cars…or better still get back on our feet and on our bicycles.

Adding up Hinkley Point nuclear power station

The British government is going to sub the Chinese and EDF to build a new reactor for Hinkley Point nuclear power station. Estimates suggest Hinkley will cost £25 billion to build. But, as is the way with such things there will be delays and hidden costs. Look at London 2012 Olympics, the original estimate when we were applying to host it said something like £3billion if I remember rightly, total cost ended up being three times that, although they claimed a half a billioon saving overall!

So, let’s be generous, Hinkley will power 6 million homes eventually and probably the total bill (not counting ongoing costs) might be £50 billion. Now, solar power isn’t perfect, basically cloudy days and energy storage are an issue, but we could save a few Watts of nuclear if we panelled up those 6 million homes instead of lumbering ourselves with outdated nuclear technology. Solar cost is currently about 6000-9000 per home, so giving away the panels would cost about £42 billion, which might leave £8 billion or so to install biogas-powered fuel cells, or a couple of wind farms to help make up the difference, and all without having to dispose of nuclear waste from old-school nuclear tech…

The apple story…

…no, not that one…not that one either…just the fruit.

Now, our dog is a fruitarian. Well, actually that’s not strictly true, she’s a carnivore, a coprophyte, a toastaholic, a pescatarian, a big fan of blackberries, which she nibbles from the brambles, she’s a sloe learner too, similarly nibbling off the tiny, plum-like produce of the blackthorn bushes. In fact, I should just confess, she’s a labrador. She will eat anything, and anything foul-smelling she doesn’t eat, she will roll in. Labrador guardians will know exactly what I’m talking about. As a puppy she dug up and attempted to devour all the heathers we’d planted in the garden, she tried to tear the painted, wooden skirting boards from the kitchen walls and had a good go at the plastic handle of of my half-decent (but freebie) carving knife.

And, she likes apples. Whether we’re walking through a woodland with windfall crab apples or the little red numbers that fall from our tree in the garden, she will munch them down, seeds and all. If any of the family, their friends, just anyone in her vicinity is eating and apple (or toast), she will sit expectantly until those in the know throw her their core. Only stuff she doesn’t eat are grapes, garlic, onions and chocolate (but that’s not her choice, that’s us avoiding her being poisoned)

Okay, so that’s the backstory. This year, our apple tree is overburdened with fruit, the lower branches are bent under the weight, almost touching the lawn. They are, needless to say, very much at nose height for a canine malophile, who was caught, not one hour ago, selecting a shiny red specimen and tugging it from its arboreal offshoot. Caught red-pawed, my wife verbally chastised the dog and then proceeded to harvest the remnants of the low-hanging fruit.


For the next hour or so, I could hear the food processor with its “juicer” grinding away those apples to relieve them of their acidic liquor and into the pan it went. Not surprisingly it having taken on the brown hue of apple exposed to the air and having undergone enzymatic browning. Now, the curious thing is, my wife added some sugar and ascorbic acid (vitamin C) to this simmmering brew. The addition of the vitamin C visually reversed the browning and the pan is now gently bubbling with fifty shades of green…not even a hint of beige to be seen.

So, what’s going on? As a lowly chemist, I’d always assumed that the oxidative and enzymatic degradation of apples to that brown colour was an irreversible biochemical process. Indeed, an apple expert tells me this indeed the case, the PPO is kept separate from phenolics in a health uncut and unbruised apple; discussed in detail on the Okanagan Specialty Fruits. Obviously, you can use lemon or lime juice to stave it off (ascorbic, anti-scurvy, acid, you see?) but once it has gone over to the brown side, I’d assumed (again, as a lowly chemist) that that was it.

A quick Google, with their simplified, serif-free new logo, brought up a paper from a journal I’d not heard of, but with the obvious title of HortScience. This is promising. In a paper entitled, “Enzymatic Browning, Polyphenol Oxidase Activity, and Polyphenols in Four Apple Cultivars: Dynamics during Fruit Development” (even more promising), a team at the University of Santa Catarina in Brazil have this to say:

Enzymatic browning is one of the most important reactions that occur in fruits and vegetables, usually resulting in negative effects on color, taste, flavor, and nutritional value. The reaction is a consequence of phenolic compounds' oxidation by polyphenol oxidase (PPO), which triggers the generation of dark pigments. This is particularly relevant for apples, which are rich in polyphenols and highly susceptible to enzymatic browning.

As plant secondary metabolites, phenolic compounds produce colours, astringency, flavour, and have nutritional qualities in fruits and vegetables. Now, I should have known, and maybe I did in my past life as a lowly chemist, these compounds are perhaps acting as indicators of oxidation state and thus, as with many other indicator compounds will exist in equilibrium and thus oscillate between colours (or colourless states) depending on the concentrations of other chemicals (acids, alkalis) resident in the mix. Further Googling revealed that various people who put sliced apple in their kids’ school lunchboxes discovered that a sprinkling of vitamin C protected the slices from browning, but at least one “mom” discovered that it reversed the browning, even after a day abandoned in a lunchbox…making it fine for eating as an enforced, after-school snack for “Junior”…

There are countless web pages with tips for malophiles with the knowledge to keep their beloved fruit of life from turning brown. But, of course, you might soon be able to buy genetically modified apples approved early in 2015 by the US Department of Agriculture that have the gene for that PPO enzyme disabled, which means you should never need to just add vitamin C to keep them whiter than white, or is that greener than green?

The original condensed version of this article appeared as one of my twice-monthly Comments in the journal Materials Today.

Barefoot running – watch your step

Usually, as small children we spend a lot of time running around barefoot, as we grow shoes and trainers become de rigueur for most of us, especially if we’re involved in sport. And, Zola Budd and other top athletes aside, there were few who went running barefoot, at least until about ten years ago when barefoot, or “minimalist”, running started to become trendy. It is purportedly better for you in terms of the body’s biomechanics, the stresses and strains and the possibility of injury. Of course, unless you’re somewhere pristine, like a gym treadmill, there are the risks of thorns, stones, broken glass, dog mess and more if you’re a minimalist runner out in the field, as it were.

But, are those claims for BF running valid? A friend of mine who had a motorbike injury many years ago that left him unable to run reckons he’s rediscovered his ability to run by going minimalist. And, good luck to him! But, I did a very quick scan of the scientific literature on BF running, there are quite a few papers around and notably one published in the August issue of Human Movement Science (2015 Aug; 42:27-37. DOI: 10.1016/j.humov.2015.04.008) that suggests that just 30 seconds on a treadmill barefoot, even if you usually wear trainers to run, is enough for the body to adapt to the new format. However, there are significant changes in the kinematics and electrical activity of muscles in the lower leg, not all of which are positive, according to the paper. First, BF running seems to be performed with higher cadence and shorter strides, there is an increase in ankle ROM (range of motion) but this decreases in the knee and hip. Activity in the gastrocnemius goes up, but falls in the tibialis anterior. This preliminary study was small, just ten volunteer runners.

The team point out that although the runners adapt to barefoor running on a treadmill quickly, “these rapid adjustments in muscle recruitment and kinematics did not appear to reduce stress on the lower limb, since tibial shock was significantly higher during the BF running” at all three running speeds tested. They conclude that, “It therefore remains to be seen if a transition to running barefoot is truly desirable for improved performance or reduced risk of injury,” and add that, “Further research examining long-term injury rates is therefore required before a transition to barefoot running can be recommended.”