John Szabo shares some Research from Italy

Latest Research Promises Lower Alcohol Wines and Elimination of Sulphites

John Szabo, MS

John Szabo, MS

The Sicilian Regional Institute of Oil and Wine (IRVOS) released the results of recent experiments to a group of professionals at the 9th Vino Vip conference, held from July the 13 -15, 2013 in Cortina d’Ampezzo, northern Italy. In response to increasing market demands for softer, lower alcohol wines, the Institute has identified and isolated a native strain of yeast, Candida zemplinina, that has been shown to yield wines that are lower in alcohol, with higher glycerol, than control samples. IRVOS also revealed protocols for the production of wines without added sulphites to address the growing percentage of the population that is sensitive or allergic to the natural preservative.

New Yeast Strain Produces Less Alcohol, Softer Texture in Wines

It’s widely agreed that global warming and the expansion of vineyards into warm regions, in addition to more efficient viticulture and the widespread cultural preference for ripe flavours in wine has led to an overall increase of average alcohol levels worldwide. Yet at the same time, growing consumer backlash against high alcohol wines has left many producers wondering how to manage their vineyards and winemaking techniques to satisfy world markets.

IRVOS panel

IRVOS panel

Daniele Oliva, head of the technical and scientific department of IRVOS began a research project with the 2005 and 2006 harvests in Sicily with the aim of identifying consistent and controllable ways to increase wine complexity using multiple strains of yeast for alcoholic fermentation, as happens during wild or indigenous fermentations, but without the associated risks of such uncontrolled fermentations. Research has shown that mixed yeast fermentations can produce more complex wines than those conducted by a single strain of inoculated yeast.

Oliva and his team set about studying the biodiversity of native Sicilian yeast populations, focusing in particular on non-Saccharomyces strains (the dominant yeast in most fermentations). Among the species identified, Candida zemplinina was one of the most abundant. IRVOS’s consulting enologist, Graziana Grassini, then conducted micro-vinifications of musts inoculated with zemplinina to assess the technological and quality characters of the strain. The researchers discovered that the Candida strain produces wine with half a percent lower alcohol and 50% more glycerol on average than the control samples fermented with Saccharomyces cerevisiae alone.

Glycerol contributes to the body and mouthfeel of wine, with increased levels associated with a fuller body and softer texture overall.

It was also determined that the inoculation of Candida zemplinina produced a fermentation in two stages; zemplinina alone couldn’t finish the fermentations, and that mixed Candida-Saccharomyces fermentations were necessary to produce fully dry wines.

Tasting experimental wines

Tasting experimental wines

From tastings conducted at Vino Vip comparing two pairs of the native Sicilian varieties frappato and nero d’Avola, one made using a mixed zemplinina-cerevisiae fermentation and the other from pure cerevisiae-inoculated must, I observed a significant difference between the frappato samples, and somewhat less pronounced differences in the nero d’Avola pair. In both cases, the zemplinina samples showed less pronounced fruit aroma/flavour, and more spice, earth character. The texture of the zemplinina frappato was markedly softer and rounder, with slightly less alcoholic warmth. The differences on the palate of the nero d’Avola samples were less obvious, findings that are consistent with the results of earlier triangle taste tests conducted by IRVOS, leading to the conclusion that the taste effects could be variety dependent. The measurable differences of alcohol and glycerol, outside of organoleptic differences, appear so far to be consistent.

Similar results have been obtained using genetically modified yeasts, but since GMOs are not permitted in the European Union, Oliva is excited to have identified a naturally occurring species with these characteristics. He cautions that it is still early days, however: “Here we are really at a completely experimental stage, because this yeast has never been produced. We are talking about experimental wines, a kind of prototype”.

Oliva knows of only two other institutes currently researching Candida zemplinina. He predicts that the yeast will be ready for sale to winemakers within three years. The commercial implications are huge; I would expect demand for non-GMO yeasts capable of producing less alcoholic, softer wines with good complexity to be extremely high. “Some Sicilian wineries are already interested in producing them, as long as the production costs are on par with those for wines made with Saccharomyces yeasts”, says Oliva. An un-named large-scale producer will begin experimenting with this yeast this year.

Protocols for Producing Suphur-Free Wines

Virtually all consumable products contain sulphites as a preservative, and wine is no exception. Sulphur is added to wine in varying amounts to protect it from oxidation and unwanted microbial activity. Even wines to which no sulphur has been added usually contain sulphites, which are naturally produced during alcoholic fermentation. Although the amount used in wine is generally below threshold, a growing number of people appear to be allergic to sulphites. Zero added sulphur wines are not new; many small producers around the world who adhere to the “natural” wine movement eschew the use of sulphur, while other large companies such as Boutari in Greece have conducted small experiments on single lots of wine made without any added SO2.

Graziana Grassini

Graziana Grassini, consulting enologist

But the Sicilian Regional Institute of Wine and Oil (IRVOS) decided to experiment with and design winemaking protocols for the production of added sulphur-free wines on a large commercial scale, and more importantly, to share those protocols with winemakers in Sicily with the aim of improving the quality and image of the large island’s wines. IRVOS is the first research institute to my knowledge that has undertaken such a project for the benefit of many rather than a single commercial enterprise.

The experiments were carried out during the 2012 harvest by consulting enologist Graziana Grassini under the guidance of Daniele Oliva. Organically grown grillo and nero d’Avola were fermented at IRVOS’s Winery in Marsala in duplicate batches to compare conventional methods using sulphur to those employing no sulphur.

Subsequent sensory analysis by 30 trained tasters was repeated several times comparing samples using duo-trio tests (two wines with added sulphites and one without) and preference tests. “During the first sensory analysis some slight differences were found, but not a preference for one or the other. From recent tastings we are convinced that these differences are decreasing”, explains Oliva. Grassini adds that “In any case, we can claim that with the use of our vinification procedure, without the use of sulphites, it has been possible to obtain wines that are just as enjoyable as those made with sulphites”.

The full details of the sulphur-free protocols have not yet been released, but according to Grassini, there are a few basic points:

1)      Grapes must be hand harvested

2)      The winery must be scrupulously clean; a quasi sterile environment is needed

3)      Grapes/grape must/wine must be protected at all times from oxidation from vineyard to bottling through the use of inert gases: argon, nitrogen and carbon dioxide. Argon and CO2 are heavy gases, heavier than air, nitrogen is lighter but useful in some cases.

It’s acknowledged that red wines are easier to make without added sulphur than white wines thanks to their generally higher level of tannins, which are natural anti-oxidants.

At Vino Vip, a pair of whites made from grillo and reds from nero d’Avola were compared, one of each made without any added sulphites. In both cases I preferred the zero sulphur sample, although the white grillo evolved much more quickly in the glass and lost aromatic quality over time. The differences between red samples were less obvious, and the unsulphured red held up well in the glass.

An analogy came to mind, perhaps a little extreme, but the aromatic differences observed were like the difference in the scent of essential oils versus synthesized aromas. While synthesized aromas can be quite pretty (most perfumes and eau-de-toilet are made from manufactured aromatic compounds), there’s a purity to essential oils that can’t easily be reproduced. The unsulphured wines had a higher degree of purity, like the fruit itself rather than something that reminds you of the fruit.

The results were by no means unanimous, however. Most tasters at the conference, which included winemakers as well as importers, distributors and journalists, preferred the conventionally-made grillo, while there was more of an even split of preference for the red samples. It was acknowledged during the discussion after the tasting that both consumer and trade education is needed when approaching sulphite-free wines. It will take some learning and exposure, especially for the trade used to squeaky-clean wines, to introduce sulphur-free wines into their lexicon. Tolerance for low degrees of oxidation would have to increase.

A potential side benefit of introducing such protocols is that it might lead to better winemaking overall, given the extra attention to detail needed to succeed in making sulphur-free wines, starting in the vineyard and finishing with bottling.

But there are several other issues to consider. For one, consumers can expect to pay a premium for sulphur-free wines, as there are additional production costs involved: the use of relatively expensive materials like dry ice and inert gases like argon, the gas of choice, which costs 30% more than more commonly used nitrogen, for example, not to mention the higher labour costs that come with more attentive vineyard management, hand harvesting, and cellar micro-management to name but a few factors.

The question remains: will the value added by producing sulphite-free wines offset these extra costs? In other words, will consumers be willing to pay more? There is also the challenge of communicating the differences between un-sulphured and conventional wines without casting a negative shadow on the latter, which still represents the overwhelming majority of wines produced today.

And while I support the move towards low/no-sulphur wines, I also question the adaptability of the protocols for large-scale production: the larger the volume, the bigger the risks. Will large producers be willing to take such risks? I think it’s unlikely, unless consumer demand really grows exponentially. Also, many existing wineries, particularly old, traditional cellars constructed from materials difficult to keep scrupulously hygienic like wood, and cellars carved from natural rock may not be able create a suitably safe environment for the production of sulphur-free wines. And are corks a suitable closure for such wines? Or would the relatively greater security afforded by screwcaps or glass stoppers be preferable? And would wineries willing to make the switch?

Most agree that sulphur-free wines age more rapidly and thus have a shorter shelf life than sulphured wines, another point that needs to be delicately communicated to consumers. And importantly, there are potential issues with transportation, considering that sulphur-free wines are less stable and more susceptible to spoilage from temperature variation.

Considering these and other issues, one has to wonder if sulphur-free wines won’t remain the domain of small artisanal producers selling most of their production from the cellar door. I, for one, hope they do gain wider acceptance and distribution, as I do love the pure scent of essential oils.

John Szabo, MS

John Szabo, MS

About Vino Vip

Vino Vip is a biennial conference that takes place in Cortina d’Ampezzo, northern Italy, and is organized by the Italian wine Publication Civiltà del Bere under the direction of Alessandro Torcoli. The event gathers a selection of Italy’s top producers, industry stakeholders and journalist to discuss important issues in the world of wine and examine future trends, in addition to comprehensive tastings of top Italian wines. 


Recent Posts: