In my last blog I said science lesson was over. Well, it's back on! Today a bit about what makes wine kits stay fresh, and what the march of science brings us.

Louis-Lou-aye, me gotta go now . . .

Louis Pasteur is one of my favorite hero-scientists. He had a gigantic brain on him, and used it. He pioneered germ theory, chirality, vaccination (having had rabies shots, I have mixed feelings on that one), numerous discoveries in the fields of chemistry and molecular biology and most especially, the process that came to be called Pastuerisation. I work with it every day, and many of the prepared and packaged liquid or liquid-packed foodstuffs you come in contact with have been Pasteurised.

It's pretty simple, and anyone whose momma (or, increasingly in these days of receding home handiness, grand-momma) did canning will be familiar with it: you take an appropriate food in a liquid media suitably low in pH and you heat it until the organisms that could spoil it or produce pathogens (illness-causers) die. You keep it completely sealed and it lasts for an extended period.

Pasteurisation is not without its flaws: extended periods at high heat cook foods: jam never tastes like fresh berries and pickles never resemble a fresh cucumber. Back in the bad old days (about 25 years ago) when juices and concentrates for winemaking were Pasteurised old-school, inside sealed cans for six hours at boiling  and then cooling for 24 hours on a shop floor, they came out tasting of brown sugar, browned colour, and a lot of just plain 'brown'. 

Aseptic filling head in action!

Now we use a program called HTST, High Temperature Short Time. Essentially you use pressurised steam (which is much hotter than regular steam) to subject your product (in this case our grape juice) to much higher temperatures than mere boiling water can afford. Depending on the pH of the juice, the biological load, the solid levels,  and a bunch of other factors you heat it very quickly from 4 degrees Celsius (the maximum density of water before it forms ice crystals) to between 65 and 80 degrees Celsius for less than two minutes (often a lot less) and then just as quickly cool it back down to packaging temperature with a set of heat exchangers. This kills spoilage organisms and prevents the juice from moulding or fermenting in the bag. 

It all works pretty well, and the staggering number of medals kit wines win in competition seem to bear out the idea that Pasteurisation is pretty benign to quality. But there are other options. The most obvious is freezing, but that adds a lot of cost: not just the energy necessary to freeze a big lump of grape juice solid, but also the shipping and storage of the product in retailer's stores make this prohibitive. There are, however, sciencey ways to tackle it.

Stand back everyone, I'm going to use SCIENCE!

There's ultra-filtration, the process whereby you filter out everything larger and 0.2 microns (three hundred times smaller than the diameter of a human hair) and this takes out all the bacteria and spoilage organisms. Unfortunately it takes out other stuff that turns out to be important too--no dice.

A spanking new technology (for wine) is UV sterilisation. There are lots of applications for using ultra-violet light to kill bacteria (heck my barber has a UV steriliser on his counter for clippers and such, and anyone who has ever hung laundry out on a washline has used UV sterilising) and pool filters have used them for a while. Unfortunately there has always been a trade-off in foodstuffs with the UV harming the flavour or aroma characteristics of more delicate items. It turns out now that the crafty South Africans have refined the technology considerably while I wasn't looking. According the bumpf at SurePure, they've tuned the UV to specifically disrupt bacterial DNA without hurting flavour and aroma compounds.

This is your DNA.                                                  This is you DNA on UV.

It sounds pretty fine, but there needs to be a whole lot more adoption and data generated before it filters (NPI) down to juice processing in our industry. Nobody had done the long term studies on unfermented juices intended for winemaking yet, but I'd love to get my mitts on one of these units for messing about . . .

An old technology, but one filled with curiostiy (and in one case, fear and loathing) is chemical beverage sterilising, using a chemical to treat the juice so that it will not spoil if kept tightly sealed. A version of this is in practise around the world, with ultra sulphiting and subsequent sulphite distillation. You take fresh juice, and add a stupendous overdose of sulphite to it, a hundred times more than you'd add to anything you wanted to drink again. It renders the juice inert, nothing can grow and it even bleaches red grape juice completely white. You can store it at room temperature indefinitely and it will neither spoil nor oxidise. When you want to use it, you simply run it through a cone distillation unit and poof! The sulphite is extracted without leaving any residue, and the juice is as fresh and ready-to-use as the day it was pressed.

I'm not aware of any wine kit company using ultra-sulphiting in their own facility, but some of the major juice suppliers use the process to store juice year-round--not just for kits, but for wineries around the world. The big hold-up is the cost of the cone: they're very expensive and require substantial infrastructure. Unless you're keeping the cone busy reducing alcohol or volatile acidity for wineries, it's too expensive to amortise its use just for juice production.

Wanna take 'er for a spin?

Still, the technology is useful, if mostly on the head-end of juice supply.

The fear and loathing part comes from a problematic beverage sterilant called Dimethyl Dicarbonate. It was invented by a subsidiary of Bayer chemicals, DMDC is a legally allowed 'beverage sterilant'. Added (very, very carefully) to wine it instantly kills every single living organism dead as a doornail, because it's hideously poisonous. Pound for pound you might as well snort nerve gas as huff the stuff out of the bottle.

So why use it when it's so lethal? Because as soon as it hits a low pH environment (ie, grape juice or wine) it hydrolises down into unimportant levels of relatively innocuous compounds. Poof, it's gone, but meanwhile your juice is sterile and pure as the driven snow. There are companies specialising in mobile dosing lines that go around to wineries to add DMDC to the  tanks (this prevents the winery from having to handle the raw DMDC and reduces worker's comp liability) and many of the wines you may have purchased that say 'unfiltered' have been dosed with it to increase bottle stability.

I experimented with the Velcorin brand of DMDC over 15 years ago at another company. I took a 23 litre pail of freshly pressed French Colombard juice, innoculated it with a very strong culture of Lalvin EC1118 yeast (a potent, virtually unstoppable fermenter) waited until staining indicated >10 million live yeast cells per millilitre of volume, donned a space suit inside our flow-booth and dosed the bucket with the specified amount, stirred and sealed it, placing it next to another bucket, similarly dosed with yeast but not hit with Velcorin.

In 72 hours the control bucket had fermented dry. The dosed bucket showed zero live cells. Three months later I bottled the control bucket, and the dosed bucket still had not fermented. I opened it, dosed it with EC1118 and it started fermenting immediately. At three months/six months/1 year the wines were identical. 

Velcorin dosing machine--looks like soft-serve to me

So why don't we use it? It's hard to market a kit that has to declare on the label, 'Now with deadly poison!' As non-standard food repackagers we have to declare everything add do to our products right on the label, whether they stay in the bag or not.  Because labelling laws are very different for wine, wineries are not obligated to disclose DMDC use--it's not in the finished product, it's not on the label. 

So what's in the future? Probably not regulatory changes that will allow us to use Velcorin any time soon, but the future always brings new ideas and new challenges. I hope I'll always be around to see the next great step, in a long line coming down from Uncle Louis.