Monday, 16 July 2012

Compressing Confectionery at 5000m

Because most of the research I do is largely based on survey work with a dash of theoretical modelling, I don’t get to spend a lot of time working in the lab or designing experiments. However, this time I came to sea armed with a plan!


Mmmmm.... Sciencey!


As you may remember from previous cruises, people typically spend a lot of their downtime drawing designs on polystyrene cups, sending them to the seabed and letting the high pressure of the seawater crush them into miniatures. After making plenty of my own cups, the novelty began to wear off a bit and I started wondering what would happen to other things if you sent them into the abyss. In particular, I wondered what would happen to air-filled chocolates.

So, before I joined the ship I bought myself a bag of fun-size sweets containing Maltesers, Milky Way Stars, Milky Ways, Mars bars  and Starburst (or Opal Fruits if you’re still determined to remain old skool about it). With the exception of the starburst, all of them contain air-filled spaces to a greater or lesser extent, and although I didn’t formally measure the volume of air in each type, I would estimate that the maltesers have the most air with starburst having the least. I would have also liked to have sent down Aeros and Wispas to see what happens to them, but my local supermarket has a crap selection and this was all they had in the mini-sizes. Now, on to the science part!

Hypotheses
  • The high pressure of the abyss (approximate 480 atmospheres) will crush the Maltesers and Milky Way Stars (being relatively brittle) completely. (Null hypothesis: Maltesers and Milky Way Stars will not crushed by the pressure.)
  • The high pressure of the abyss will cause the Milky Ways and Mars Bars to shrink by reducing the volume of air in the nougat. (Null hypothesis: Size will remain the same.)

I didn’t really expect anything to happen to the starburst since there are no gas-filled spaces in them, but it seemed a shame to leave them out so I chucked them in as well. For science!

Study Design

Deploying the sock

Using fun-sized packets of sweets was a handy way of getting a reasonable number of replicates without wasting large quantities of chocolate to do it (which is virtually a cardinal sin when you’re at sea for a long time!). The packets were divided into experimental and control groups as shown in table 1. The experimental packets were wrapped in a plastic bag and placed into our handy sock* which was then cable-tied onto the frame of the megacorer.  The control groups were placed in a walk-in fridge set to 4°C (the temperature of abyssal seawater).

Figure 1: The test chocolates (below) and controls (above)


Table 1: Numbers of each type of sweet used in the experiment
Confection Type
No. Experimental Packets
No. Control Packets
Maltesers
2
1
Milky Way
3
1
Mars Bars
3
1
Milky Way Stars
3
1
Starburst
2
1

The megacorer was then deployed and sent down to approximately 4800m on the Porcupine Abyssal Plain before being recovered. The total trip took around 5 hours from leaving the deck to coming back on board. Once the sweets were back on the ship, the packets were opened, photographed and tasted by a (semi-) willing panel of curious masters students. 

Data Analysis

The students were delighted at the prospect of eating salty, wet chocolate.

The data analysis comprised two parts: qualitative observations and taste-tests of the experimental sweets compared to the control groups and comparative measurements of the lengths of each of the sweets. Because there is only one Milky Way or Mars Bar per packet, the lengths of these were recorded both before and after the experiment to compare the change in length. The Maltesers, Milky Way Stars and Starburst could not be effectively measured prior to the experiment since that would have required opening the packets, but since there are several individual sweets per packet that was not considered a problem.

The measurements of Mars bars and Milky Ways were made using calipers (without opening the packet), and all other measures were taken from the photographs using photoshop.

Results
General Observations
Although none of the packets had visible holes in them, seawater did manage to get into all the experimental sweets. Aside from making the taste tests more salty that we generally like, it also makes it hard to separate the effects of melting vs. pressure.

Mars Bar

Figure A: Mean lengths of the control vs. experimental Mars Bars. Error bars show one standard deviation, p > 0.05.

Figure B: An experimental Mars Bar (below) after the experiment showing no visible damage compared to the control bar (above).
The Mars bars showed no significant change in length as a result of their journey to the abyss (figure A; paired t-test: p > 0.05) and displayed virtually no signs of crushing damage at all (figure B) and the consensus on taste agreed that they tasted pretty much exactly the same as the control bar.

Milky Way

Figure C: The lengths of control and experimental Milky Ways before and after the experiment. Error bars show one standard deviation, p > 0.05.

Figure D: Milky Ways appeared to sustain more damage from the pressure than the Mars Bars.

Just like the Mars bars, the Milky Ways showed no obvious change in length after the experiment (figure C), but there were more obvious signs of having been crushed by the pressure (figure D). The taste panel agreed that the experimental Milky Ways were 'wet and disgusting'.

Maltesers

Figure E: Control Maltesers (left) compared to an experimental set (right).

As expected, the journey to the abyss had the most dramatic effects on the Maltesers which were so crushed from the trip that the experimental ones couldn't be measured (figure E). Strangely enough, these were popular with the tasting team who agreed that despite the fact that they were wet and rather salty, they were actually quite pleasant in a strange, chewy way. 

Milky Way Stars

Figure F: Experimental (left) compared to control (right) Milky Way Stars. Funnily enough, no-one was willing to try eating the experimental ones.

Figure G: Mean lengths of Milky Way Stars from each packet. Error bars show one standard deviation, p < 0.05. 
These were badly affected by water leakage and resembled a weird chocolatey soup (figure F). One of the experimental packets contained chocolates that were significantly smaller than the control (figure G; GLM: p < 0.05), but the other experimental groups showed no difference. Not surprisingly, we drew the line at tasting these and so we'll never know if they were still edible!

Starburst
Figure H: Mean width of control (red) and experimental starburst. Error bars show one standard deviation, p < 0.05.

Figure H: Experimental (left) compared to control (right) starbursts.
Figure I: An opened starburst showing the extent to which they had dissolved. 
Finally, we have the starburst. These were also badly affected by water leakage which turned them into a strange soup. Measurements taken on the wrapped sweets showed that the experimental groups were significantly wider than the control (figure H; GLM: p < 0.05), but this is likely due to the fact that they were pretty well liquefied by the time we got them (figures I & J). As with the Milky Way Stars, no-one was willing to try eating these so what salty, wet, melted Starbursts actually taste like will sadly remain a mystery.

Conclusions
It's pretty clear from this short study that the biggest issue with sending Mars funsize sweets into the abyss is non-waterproof packaging, which was generally considered a bad thing in terms of the appeal and taste of everything except the Mars Bars which seemed to be entirely unaltered by the whole affair. The effects of pressure weren't particularly exciting on anything except the Maltesers which seem to have been completely crushed by their descent to 4800m. 

Also, although students will eat almost anything, it seems that salty, melted chocolate soup is a step too far!

Thanks
Thanks to Claire, Alice, Tish and John for daring to taste these!


* Socks make useful impromptu containers because: a) SOMEONE always has an old sock they don’t mind sacrificing to the cause and b) it’s relatively easy to shove cable ties through wool.