Significant advances in grape processing

I recently came back from helping take Lincoln University's HORT212 (Viticulture I) class around Marlborough for two and a half days, looking mostly at vineyards, but also including a very good tour through the Brancott Winery.

I think this was my 10^th time on the tour, but in any case, it's always interesting to go, as you learn new things every time, and it's also fascinating to see how the wine business changes from year to year to year.

We were given a very good talk about the future by Dr Michael Trought of the Marlborough Wine Research Centre, who mentioned new harvesting technology that is being developed as I type.

This was in the news a little while ago and has created a bit of a stir. It isn't actually all that new an idea, as this article from 2008 can confirm, but it is, as far as I'm aware, the first time the technology has actually been seen working in New Zealand.

On what is a fairly ordinary machine harvester, built by ERO, is added the innovation of on-board grape processing.

Not only does the machine harvest the grapes, but it also crushes and extracts the juice out of them them (using a centrifuge), so that instead of a mix of grape skins, seeds, pulp and material other than grape (e.g. leaves, petioles and other things that get collected by the harvester) being discharged into a bin being towed in an adjacent row, clear grape juice comes out. The grape skins and seeds are discharged to the ground in the vineyard.

As Dr Trought demonstrated to us, the juice coming out of this machine was very clear, having only a small amount of solids suspended in it (after juice is pressed from the grapes, it is normally put into a tank and allowed time for the bits of grape that came out with it to settle to the bottom of the tank - the clear juice off the top is then the premium stuff). This is desirable because there is less loss of good juice during the settling process, which probably makes up for the slightly lower litres of juice recovered per tonne of grapes that the machine juicer gets compared to the conventional press.

So what this technology can deliver is pretty clear juice straight from the vineyard.

What does this mean? Well, it means that about 20% of the weight of the fruit (skins and seeds) doesn't have to be carted to the winery, only to have to be carted back out again. There's a savings here in the number of trucks/drivers/amount of fuel needed to move the grapes to the winery and then the grape solids back to a composting facility.

It means that for those varieties that can be harvested in this way, a press is not needed back at the winery. This leads to lower capital expenditure to establish a winery.

It means that fewer people will be needed to process the grapes. A plus for the winery, but not so good for those wanting to work in wineries!

Potentially it could mean that lesser amounts of processing aids are needed to recover top-quality clear juice, leading to cost savings and more efficient use of tank space.

There are disadvantages, though. Grape waste, which is normally collected from the winery and distributed back into the vineyards, cattle yards or the composting facility, are now returned in raw form to the vineyard floor. Grape skins and seed waste has a high carbon to nitrogen ratio (C:N) of about 27:1 (Ferrer et al.2001), so leaving it out in the vineyard as it is can result in a loss of root-available nitrogen to the vines. That's not to mention that it's a bit of a slippery mess!

As well, it's pretty much useless for red wine, as the colour and mouth feel properties of the wine are tied up in the seeds and skins. If you juice the grapes in the vineyard, there is no chance for these things to be extracted into the wine.

And, as well, many white wines are made using a bit of skin contact time. That is, after the grapes are crushed, the skins are left to stew in the juice for a while. This allows flavour and aroma compounds to be extracted, as well as tannins and other compounds from the skin that can have an effect on the way the wine smells and tastes. This isn't feasible with the current machine.

A significant point for New Zealand when considering this technology is that the country's most famous wine, the Marlborough-style Sauvignon blanc, actually relies on some post-crushing skin contact time to lend it some of the aroma characteristics that it's so well known for.

It's highly likely that this time and effort-saving machine may not be able to be used with the grape that makes up almost 50% of the grape area planted.

Bummer!