By: Dr Richard Smart, Dr Misha Kwasniewski, Alex Fredrickson and Dr Angela Sparrow
Think about it, if you will, what is the essence of winemaking? A very important question.
How about if wine is were made just from the juice and pulp. What an uninteresting beverage it would be. Alcohol only, with no aroma and no flavour. Spirits are not so uninteresting.
All of the chemical compounds which make wine such an interesting beverage are to be found in the skins, maybe a few in the seeds. These compounds include colour phenolics and the complex of flavour and aroma compounds which help to make varietal wines so distinctive.
So the answer to my rhetorical question is: the essence of good winemaking is in skin extraction.
This leads then to the important question of how winery practices might be conducted to facilitate extraction from the skins. I remember well my friend Dr Chris Somers, distinguished wine phenolic scientist from the Australian Wine Research Institute making the statement: ”everything that winemakers want in their wines is to be found in the pomace”. In other words the standard winemaking factors is inefficient at extraction from the skins.
How can Extraction from the Skins be Improved?
I have long thought about this remark made by Chris Somers and wondered how might extraction from grape skins be improved. I had the opportunity to investigate some solutions to this problem in 2011. As part of my consultancy with Tamar Ridge Wines near Launceston in Tasmania we had established an experimental winery. This allowed us to make pilot scale fermentations to evaluate vineyard trials aimed to improve wine quality.
This facility (in fact a converted apple-packing cum sheep-shearing shed) also offered the possibility for Angela Sparrow and I to investigate how the extraction from grape skins might be improved. Angela initially worked as a technician in the experimental winery before enrolling as a PhD candidate at the University of Tasmania in 2011.
Our first effort was a modification to fermenter design which showed little promise. The second was the light bulb moment. We figured that a simple way to improve skin extraction would be to make skin particles smaller (skin fragmentation), so that they had a larger edge to surface area ratio. There would be a smaller diffusion path of skin constituents to the skin edge from smaller rather than larger skin particles. So extraction would be enhanced.
We find in fact that most grape berries coming out of commercial crushers are simply squashed or flattened, each with a rather small broken skin edge. We call this phenomenon “flattened spheres”, each “envelope” often contains skin and seeds. We analysed a sample of Pinot Gris berries from a Bucher Vaslin crusher, and found that there were 181 flattened spheres, and only 12 skin fragments.
We evaluated fragmenting grape skins simply using a laboratory blender. We were of course mindful that such an operation should not damage the seeds, and careful checking revealed that this was the case. Therefore we proceeded to make experiments using our micro-vinification techniques, and found that the color and phenolic extraction of Pinot Noir was greatly improved, and sensory evaluation showed that so was the wine quality. We were of course thrilled!
Figure 1 shows Pinot Noir must samples one hour after treatment. The sample on the left shows typical flattened spheres after crushing, with limited color diffusion. The sample on the right was crushed then fragmented, and see the difference in color extraction!
Confirming the Results
The intensive study by Angela of grape skin fragmentation for her PhD created a considerable number of scientific publications, including both wine chemistry and sensory evaluation verification of the concept. Angela developed the term “ACE” to describe the process, the acronym standing for Accentuated Cut Edges. The first paper in the series was published in the American Journal of Enology and Viticulture in 2016. It was entitled “Reducing skin particle size affects the phenolic attributes of Pinot Noir wine. Proof of concept.” Other papers followed including wine chemistry and sensory evaluation. Always ACE shone through, producing better Pinot Noir wines.
For the next six years Angela’s studies progressed from small ferments to those in commercial wineries, helped in part by an industry research grant. A prototype machine to achieve ACE was designed and developed, and allowed ACE evaluation at commercial scale.
Enter Della Toffola and DTMA
The machine, the scientific results and wine samples were shown to Giacomo Della Toffola in Tasmania. The large Italian winery equipment company Della Toffola then proposed a joint venture with Richard Smart and Angela Sparrow to further the development commercially. The result is the DTMA machine, DTMA being the acronym for Della Toffola Maceration Accelerator.
This machine was evaluated as a prototype by Angela in Australia, New Zealand and Italy in 2016 and 2017. The DTMA machine is now commercially available in a range of capacities through the international dealerships of Della Toffola (see www.dellatoffola.it).
The machine is shown in Figure 2. It is relatively small and portable, and is connected by hoses between the crusher and the fermenter.
Coriole winery of McLaren Vale, South Australia was the first to purchase DTMA in Australia following trials conducted there by Dr Angela Sparrow. More recently the unit has been used in experiments by several researchers from the University of Adelaide. Trials have been conducted as well in California during the 2019 vintage which will be reported in the future.
Using ACE to Improve Chambourcin Tannins in Missouri
Interspecific hybrid wines are generally much lower than vinifera in final tannin content. This is in spite of some hybrid grapes having appreciable tannins in their skin and seeds. Several studies have pointed to hybrids as having trouble with tannin extraction and retention during winemaking.
This has led researchers at the University of Missouri in the U.S. to investigate the efficacy of ACE treatment on cv. Chambourcin. Alex Fredrickson, PhD. student in Misha Kwasniewski’s lab, presented preliminary results of the study at the 2019 Eastern Section of the American Society of Enology and Viticulture. Alex found that ACE treatment at crush and immediately before pressing substantially increased final tannin concentration in the wines versus control, in measurements made 6-months after pressing, as measured by Adams-Harbertson assay.
ACE at crush yielded 146 mg/L catechin equivalents (CE), ACE 24 hours to pressing was 118 mg/L CE, whereas control was only 47 mg/L CE. ACE at crushing represents a massive 310% increase in tannin! This work was part of a larger investigation that included looking into exogenous tannin addition retention as well as tannin protein interactions. The ACE treated wines were similar in concentration to a massive exogenous tannin addition of 1400mg/l at either 20° Brix (1-day after inoculation) or later at 5° Brix.
These results suggest that ACE treatment either released a large enough amount of tannin to overcome whatever factor is causing poor retention of exogenous additions, or alternatively that the ACE treatment somehow is mediating the problem. No differences were found between total protein content in ACE treated wines or control immediately after pressing; this suggests that the protein-tannin interactions may not explain the increase. Further characterization of the proteins is ongoing.
Given the promising results the work was repeated in 2019. As this work moves forward the group will be looking into impacts on wine volatiles, the consistency of treatment impacts on Chambourcin and potentially other interspecific hybrids. As well, studies continue into the underlying mechanism for the dramatic increase found in the 2018 results.
Giacomo Della Toffola believes that the ACE process achieved with DTMA will be a “revolution in winemaking”, his impression when he first viewed the results of ACE research.
Interestingly Della Toffola has been awarded an esteemed Innovation Award in Winemaking at the 2019 SIMEI Winemaking exhibition in Milano Italy.
Continuing research has shown that ACE/DTMA can considerably save winemaking costs, some of which are accentuated by vintage compression and climate change. Earlier research by Angela Sparrow has shown that following ACE treatment, red wine ferments can be taken off skins after only three days, thus allowing more use of specialized red wine fermenters and with savings in cellar labor. Early results with DTMA have shown encouraging results with aromatic white wines.
1. Dr Richard Smart: Smart Viticulture, Greenvale, Vic., Australia; firstname.lastname@example.org
2. Dr Misha Kwasniewski: Grape and Wine Institute, University of Missouri, Columbia, MO, 65211, USA. email@example.com
3. Alex Fredickson & Dr Angela Sparrow: Vintessential, Laguna, Tas., Australia