I failed the first statistics test I ever wrote. It was open book (insert sad trombone sound).

This is the only test I’ve ever failed. I had no excuse other than that I firmly believed the material refused to get inside my head. (IT was stubborn… not me. Of course this is not an excuse that any self-respecting professor will accept, so I do not recommend it.) In the end, I just barely passed the course, but I don’t remember the exact details of how I managed that as I’ve buried the experience pretty deep. Or at least I had. This program, and in particular this thesis, have caused many of my previous apprehensions about statistics to resurface.

Things that keep me up at night: am I actually seeing patterns in the data? Is the dataset big enough?

Fortunately, I can now say that the thesis is written, and I am exceedingly happy about this. It was tough… the hardest paper I’ve ever had to write thanks to the statistical content. That said, I thoroughly enjoyed doing the research – reading what scientists in the US, Italy, Australia and New Zealand have discovered in their mechanical harvest experiments. I found, though, that these researchers did not always replicate conventional processes used in wineries – often pressing the grapes too hard and too fast, and not separating out the free run (higher quality) from the hard press juices, all of which could have implications for the practical applications of the results. Do they know something that I don’t? (Probably, but let’s carry on anyway. That is the scientific method, non?)

The machine harvest starts in the vineyard with this yellow behemoth named Grégoire. Grapes are destemmed as they are picked and are collected into large blue bins (we were a little rough on the berries the first time out!). At the crush pad, the bins are emptied into a hopper, which pushes the grapes into the press via peristaltic pump.

The harvest in Niagara was challenging for the experiment. Believe it or not, we were thwarted by the Asian ladybugs. October was so lovely – practically summer again, but it kept the ladybugs around. Many types of ladybug are pleasant to have around as they act as a natural predator to other bugs, but one strain in particular, Harmonia axyridis, the harlequin ladybug or Multicoloured Asian Lady Beetle, releases a rancid peanut butter odour as a stress mechanism. As younger siblings everywhere can attest, it turns out getting even a little bit squished can be pretty stressful, and as few as 5 ladybugs in one bin of grapes cause unpleasant odours in wine, we had to pause the experiment with machine harvesting after the Riesling.

I used to think ladybugs were cute, but these suckers (with “M” shaped markings on their foreheads) bite, and stink up the juice! The wet weather also brought disease pressure to some parcels in the form of rot.

The ladybugs weren’t the only thing that plagued us. October’s warm and wet weather meant the rot started to develop, so the race was on to bring them in before the rot could get to them. While machine harvesting would certainly have addressed the fast part of that need, the mechanical process did not have a sorting stage, which would allow removal of rotten bunches or berries.

The hand harvest starts with yellow bins laid out in the vineyard. Workers go through filling the bins, which are then collected by tractor and brought to the crush pad. They are then dumped onto the sorting table, where they are conveyed under watchful eyes into the press.

A scatterplot of the pH and Total Acidity values from each juice sample: the machine harvested values for free run and hard press juice (two shades of blue) are more bunched together, while the hand harvested values (yellow and brown) are more separate. Be honest, which constellation do you see here? (It’s Orion, isn’t it?)

Despite the experiment being cut short, there were enough samples taken from the week of mechanically harvesting the Riesling to yield some interesting results.The pH and acidity behaved differently in the machine harvested juices compared to the hand harvested juices overall. Remember how I said before that the free run is the higher quality stuff? Right! Because it is pressed very very gently, the free run juices preserve more acidity, and a lower pH (brown dots in the graph) which is necessary for the taste of the wine as well as its stability and longevity.

Once the press starts squeezing the grapes harder, the acidity starts dropping and the pH increases – this is what we call hard press juice (yellow dots). The machine harvested grapes got beat up a bit by the machine, so their free run juice acidity levels were lower (dark blue) than their hand harvested counterparts. Interestingly enough, the machine hard press juice (light blue) did not lose as much acidity as their hand harvested counterparts, even though they were submitted to the same level of squeezing. From an acidity and pH perspective, this is essentially telling us that the machine harvest ‘mutes’ the effect of the press and preserves acidity in hard press juices. This is really interesting and leads me to wonder if there’s an opportunity to do more research on whether grapes respond to stress differently post mechanical harvest, and if so how we could optimize press programs to potentially limit the differences due to harvest method.

I figured all this out after the fact; the harvest itself was pretty hectic and did not leave much time for trying to make sense of coloured dots on charts and graphs. Canadian Thanksgiving was in there too, and I was lucky enough to get some time off to attend family Thanksgiving (for the first time in two years!). The fall colours in Ontario were spectacular this year, and I often got to see them during the ‘golden hours’ which typically coincided with my drive to work and outdoor duties in the afternoon and early evening.

The golden hours: I passed this brightly tree-lined road soon after sunrise on my way to work every morning. Below, this late afternoon view of the Tawse vines, looking golden just before sunset. To the right, I’m the colourful one in this particular pic some friends captured while hiking one day. My view of them was a little better! If you look closely, behind Adrie and Ali you can see the birds hovering over the Niagara River, trying to catch the salmon coming upstream to spawn. (Thanks to Adrie and Enrico for the two photos on top.)

My internship was officially over at the end of October, so I immediately hied myself a few hours north of the city for a week of peace and quiet while I wrote the bulk of the thesis. It was a wonderful change of pace after the craziness of harvest, although the joke was on me as winter arrived rather emphatically while I was up there!

The weather went from calm, sunny autumn to blustery winter overnight. Brrrr!!

With the month just about over, it’s time for me to head back to France to defend my thesis, and more importantly, to stock up on French wine before I return home for good! That’s it from me for the moment – wish me luck on my thesis defense, and I shall raise a glass of good cheer* (sourced from France, bien sûr) to you and yours for the holidays.

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