On heat and rain, harvest rush, and the nature
of fermentation  2 April 2007

Martin Moore reflects on vintage 2007 and particularly on the use of 'natural yeasts'

On being slipped a Mickey Finn
Our viticulturist, Johan Pienaar, claims to have participated in 39 vintages – I never thought him that ancient – but, more importantly, he says he has never experienced two that were the same. The number of notches on my belt is somewhat fewer, but my experience has been no different. And not one I have taken part in was predictable to the end. Without exception Nature at some stage slips you a Mickey Finn. This vintage was no different. It started off in ideal fashion, with a long spell of cool weather that promoted slow ripening of the early cultivars so that the Sauvignon blanc when it came in was of a beautiful quality. And so were the grapes of that other early ripener, Pinotage, as well as of the Shiraz and Merlot that were also picked earlier.

But then the weather started playing games. We had a heat wave in January and a cold front with lots of rain in February followed by another hot spell. The heavy dew typical of autumn started earlier than usual and various types of rot such as “slip skin” made their appearance in the vineyards. It is mainly Cabernet Sauvignon that is still out there but I am not all that concerned about it as this cultivar has always been known for its high resistance to disease.

I have often referred to - and will always be grateful for – our being so close to the sea, with False Bay to our left, Table Bay to our right, both clearly visible from our perch up in the hills. For this mass of water just helps to smooth out the peaks and valleys in the temperature. On one of the days during the hot spell, at five ‘o clock in the afternoon, we were bathed in a comfortable 24°C when a friend phoned from Stellenbosch to say they were sweating away in 35°C. Are we cool or what?

Same mad rush to Easter
Despite these ups and downs in the weather I am very happy with what we have in the tanks for bottling. We still have some way to go bringing in the harvest, for another peculiarity of this vintage is that although the early ripeners were ready for picking earlier than usual, the late ripeners will be as late as usual which means (a) that nothing came of my prediction that we were going to experience intense peaks with everything ripening at the same time, and (b) that we will have the usual mad rush to get the last grapes in before the Easter weekend.

In the meanwhile we are as busy as bees in the cellar where the young wine from each vineyard block is either settling down or still fermenting away happily in their tanks. Getting them in there isn’t always all that easy and we sometimes get ourselves horribly tied up doing so. Imagine four presses running almost full-time producing streams of must that have to be guided to different tanks. That means coupling and uncoupling pipelines continuously, giant spaghetti strings that, if you are not careful, somehow snake up and under and over one another and end up in the most horrendous knots. Unfortunately Alexander the Great’s ingenious way with knots doesn’t work for us, so we have to laboriously unravel them. Thank goodness for nimble young helpers (but then they were probably the ones creating the mess in the first place!).

 

Cultured or natural yeast?
I am always fascinated by the way what starts off as marketing hype, through some strange alchemy gets converted into fact in the minds of consumers. A case in point is that wild yeast (also referred to as natural or ambient yeast) is somehow better than cultured yeast. The simple truth is – and my apologies for bursting the bubble – that cultured yeasts are nothing else but selected wild/natural/ambient yeasts.

There is also a second fallacy, namely that the spontaneous fermentation is started by wild yeasts present on the skins. Not so. Laboratory tests show the desirable yeasts for fermentation are present on roughly only one of a thousand berries - and can easily be washed off by rain.

Yeasts, wild or otherwise, constitute a complex world of their own. Let’s start at the beginning. Wine is the fermented byproduct of grape juice. Leave an open container with grape juice in a warm spot and within two to three days it will start fermenting on its own. Why? Because yeasts present in the air have dropped in, in search of food, started multiplying and now turn the sugar into alcohol. In a case of “too much of a good thing” the yeast will after a while die of alcohol poisoning, leaving behind a fermented product.

Several natural yeasts, moulds and bacteria are also present in the grape juice, but only the ones resistant to higher alcohol, sulphur dioxide and low pH will have an impact on fermentation. Very few of the natural yeasts can survive standard sulphur dioxide levels and, if they can’t, their presence results in off-flavours, sluggish fermentation or, even worse, stuck fermentations.

What I have described here is spontaneous fermentation. In winemaking today we control the process by inoculating the juice when we want to and with yeast strains of our choice. The cultured yeasts we use possess the very characteristics that we need for a particular style of wine or that in our view work best for a specific cultivar. I do not like fermenting my Merlot with my favourite yeast for Sauvignon blanc selected for its ability to do well during cold fermentations, and vice versa.

Space does not allow me to write more about what is for me a fascinating topic and I will return to it in the next issue.