Like many good ideas, the ACE (accentuated cut edges) maceration technique was inspired by a simple question.
 
Realising, during her work on the phenolic components of Pinot Noir, that it seemed to make a difference whether the tannin came from the skin or the seed, Angela Sparrow asked her university supervisor why no-one had tried to isolate one or the other in wine. The answer, essentially, was that it was just too hard.
So I asked if anyone actually knew which was better’, Angela said. ‘And he said “no, not really”.’
 
That was just the challenge Angela (now Dr Sparrow, a Research Consultant with her own business Vinventive) needed for her PhD studies at the University of Tasmania.
 
I started taking Pinot Noir berries apart and making wine using just clear juice and skins, or juice and seeds or without the grape pulp or with one component doubled to make various combinations and came to the conclusion that it’s better to have more skin tannins with a little bit of seed tannin for the mouth feel, she said.
 
So the question was how to get more tannin out of the skin tannin. I realised that’s probably what everyone was trying to do with conventional maceration techniques, but it takes time, energy and labour and potentially exposes their wine to too much seed tannin. So what I worked on was how to get the skin tannin out more efficiently.’
 
Brainstorming with colleagues, they came up with the theory that if you cut the skins into fragments, surely more components were going to leak out of the broken edges. To try to work out how to do that without also cutting up the seeds, Angela and team went in search of the ideal blade assembly.
 
First we went overkill with a laboratory bench blender but that cut the living daylights out of everything’, she said. ‘And the resulting wine was not an improvement.’
 
There was much more success with a stick mixer, which pulses and shreds rather than homogenising the grapes. Next they tried incorporating blades into a grape crusher, but that failed because the gaps between the blades quickly became clogged and essentially useless. In 2014, Angela and her team developed a separate apparatus that incorporated a cutting assembly into the must line and ‘hey presto’.
 
Following completion of her PhD, Wine Australia funded a new project where Angela continued her work and tested the commercial potential of ACE maceration.
 
I took it to six wineries last year just to see whether the in-line technique worked and it did, and the winemakers were quite impressed with what came out the other end of the must line’, she said.
‘They compared it with wine made the normal way. For the ACE treatment, I just came in with my equipment and cut up the grapes that were on route to the fermentation tank.
 
Each one of them was looking into the tank and I said “you’re looking for a cut seed aren’t you?” and they said “yes”, because it’s curtains for a wine if there are too many seeds, so I said “let me know if you find one because I haven’t as yet”.’
 
Later, Angela ran a blind tasting in which the winemakers tested the two versions of their own wine, and five out of the six ACE wines were scored higher than the wine made by conventional methods.
The other showed little difference. ‘The distinction seems to be influenced by the grape variety and also the fruit quality.’
 
Angela and her team plan to refine the equipment to make it more robust, as the current version is small and is not likely to go all day and all night for a fortnight during vintage. They also anticipate that further modifications can be discussed with equipment manufacturers.
During vintage 2016, Angela will be working with commercial wineries to test the ACE technique for a range of red wine varieties in a nationwide trial. This may be in combination with other techniques, such as early press-off of the grape solids.
 
She presented the result of wine made using the ACE technique at the ASVO symposium 2015 and Crush 2015 conference in Adelaide in November to a very responsive audience. This year, she will present two papers on the ACE technique at the International Cool Climate Wine Symposium in the UK.
REFERENCE

Angela M. Sparrow, Helen E. Holt, Wes Pearson, Robert G. Dambergs and Dugald C. Close; Accentuated Cut Edges (ACE): Effects of Skin Fragmentation on the Composition and Sensory Attributes of Pinot noir Wines; Am. J. Enol. Vitic. ajev., January 2016, 67 (1)