The days of wine and pulses
USC engineers have been at the forefront of a technology known as pulsed power for decades. Notably, Professor Martin Gundersen of the USC Viterbi School of Engineering’s Ming Hsieh Department of Electrical Engineering has been developing devices that produce ultrashort, very intense electric pulses for use in fields ranging from engine research to cancer therapy.
A new area of research for this group is studying the benefits of applying nanosecond pulses to various foods. The intense electric field generated during these electric pulses has been shown to result in more oil extracted from olives, more sweet liquid from sugar beets and more juice from wine grapes.
It is the last crop that is of particular interest to two electric engineering researchers at USC Viterbi, Daniel Singleton PhD ’08 and Jason Sanders PhD ’08, who have Transient Plasma Systems, a startup in El Segundo, Calif., that manufactures commercial devices to supply pulsed power for many applications, including the production of Pulsed Electric Fields (PEF).
The duo’s company began by selling pulsed power systems to universities and aerospace companies for research on improving the efficiency of vehicles. The researchers discovered that the technology can be transferred to grapes, and they are gearing up to market to wineries in California and elsewhere.
The pivot to grapes began when Gundersen was participating in a physics meeting in Germany, where a colleague told him about work going on there with pulsed power, sugar beets and wine grapes.
Digging deeper, Gundersen and Singleton discovered that wine grapes were also being studied in Spain, where vintners have been delivering pulsed power bursts to raw grapes. PEF bursts do not heat the grapes, but rather they break down the cell structure so the grapes yield more juice.
Transient Plasma Systems is now building on the German and Spanish work, collaborating with viticulture experts at the University of California, Davis, on experiments using the company’s commercial pulsed power devices on Chardonnay and Sauvignon Blanc grapes.
“The juice yield depends on the grape type and pressing force,” Singleton said, “but 30 percent was the average increase in our lab. It was quite astounding.”
Mauri Anderson, a researcher in the Department of Viticulture and Enology at UC Davis who participated in the tests, said the PEF treatments also have the promise to extract more juice in a gentler way.
But a higher juice yield is only one potential benefit to vintners. Another is to lower or eliminate the sulfur dioxide used to control microbes from bacteria in the vineyards. Sulfur treatment for crushed grapes — the juice before fermenting — is expensive and detrimental to the wine’s flavor.
And since PEF treatment kills off the wild yeast that can occur in grapes, it allows vintners to control fermentation exclusively using dried yeast they select, creating a more predictable ferment and a more uniform product.
Data generated at UC Davis also indicated that PEF treatments increase the phenolic content of wines. Vintners like phenol because it intensifies color, and physicians recommend red wines high in phenolic content as being more beneficial to health.
Currently, winemakers amp up the phenolic content by increasing the time grape skins macerate in the fermentation vessel along with the juice. But PEF treatments make the grape skins give up their color and flavor gently and more easily, with up to 250 percent more color achieved two days faster, according to research in Spain.
Perhaps the most exciting potential benefit is PEF’s effect on wine aging.
Early tests suggested that red wine treated with PEF speeds up the aging process, making young red wine taste much more mature.
In one experiment conducted by Transient Plasma Systems, it received a batch of Pinot Noir grapes from a vineyard where Mac Chapman of USC Viterbi’s Alfred E. Mann Institute for Biomedical Engineering held an interest.
The grapes were divided into two batches — one that received PEF treatment and one that was not radiated. Both batches were fermented and a month later, were sampled in blind tastings by a group drawn from the Alfred Mann Institute and Transient Plasma Systems.
The verdict was nearly unanimous. Every taster but one found the untreated wine typically rough and immature tasting. The treated wine tasted significantly more mature, as if it had been aging much longer than a month.
Gundersen, an adviser to the fledgling company, said he believes pulsed power’s potential to winemakers lies in treating medium quality wines or, as he puts it, “turning Two-buck Chuck into Three-buck Chuck.”
He noted that when the UC Davis and USC researchers presented their findings at an American Society for Enology and Viticulture conference in 2009, the findings sparked interest. But that interest has not translated into serious grant support, he said.
Transient Plasma Systems is not the first in the world to notice the benefits of pulsed power on grapes, but the company believes its machines are more energy efficient and compact than those being used in Europe.
Bringing pulsed power to the winemaking process adds minimal additional energy costs, Singleton noted, and PEF machines can be added to production lines with little disruption.
After the viticulture conference, Singleton and Sanders arranged for students at the USC Marshall School of Business to do some preliminary marketing conversations with vintners and found enough interest for the company to decide to continue working on PEF machines for the wine industry.
When the company secures adequate funding, its next step will be to drastically scale up the technology to be able to treat much larger quantities of grapes for commercial production. Large-scale machines present tantalizing prospects for other applications, the researchers noted.
Energy interests are targeting algae for producing potential fuels, and pulsed power can help in extraction there. And a process that can kill bacteria without heat or chemicals has possible applications in many areas of food processing, such as pasteurizing milk.
“Improving wine quality with pulsed electric fields is a really exciting application of Transient Plasma Systems’ technology,” said Sanders, who anticipated that agricultural, energy and medical applications will fuel the company’s growth.
Allison Engel contributed to this story.