Final Report for FNC12-884
[Editor's Note: To see the videos mentioned in the report, open the attached video clips or the attached version of the report with embedded videos. The report with embedded videos will take a long time to download.]
- Project Duration: 2012-2013 2-years
- Date of Report: 30 April 2014
The Ohio River Vista Vineyard & Research Station is located in Clermont County, Ohio. The 5.42 acre site overlooks the Ohio River with a southwesterly view 200 feet below and six-tenths of a mile distant. The grapevines are trellised on terraced rows to help control erosion of the 30% sloped grade. The unglaciated soil is rich in clay over limestone underlayment, providing suitable drainage. This ideal terroir is capable of supporting 3,000 vines producing as many as 1600 cases of fine wine per year. Vinifera varietals grown include cabernet sauvignon and cabernet franc. French hybrid varietals include traminette and vidal blanc. A field research facility hosts faculty and students from four nearby universities conducting collaborative projects.
Grapevines require pruning each year to balance the crop load to promote making of fine wine. From 2007 onward, cuttings have been composted along with grape skins, seeds, and stems left over from the winemaking process. The fully-composted material is applied to the vineyard bed to promote the growth of the perennial ground cover of Ajuga that prevents erosion of the steeply-sloped hillside.
Unlike western states requiring irrigation of crops, our region receives sufficient rainfall providing more than enough water for the vineyard. This bountiful resource is collected from the roof in two, 300-gallon rain barrels for use as prewash water in the winery. To promote yet another sustainable practice, we plan on adding solar panels to the winery in the near future.
The project was conducted to determine if washing of grape clusters to remove dirt and other debris, bugs of all types, snails and slugs, etc. would reduce the quality of the grape juice for winemaking.
The construction of an economical conveyor-washer apparatus suitable for the small family farm was a desired outcome.
Neither farmers nor winemakers wash wine grapes because they believe that the sugar content and flavanols will be diluted, thereby resulting in inferior wine. Benchtop experiments whereby grapes were soaked for extended periods of time starting with one minute and extending to twenty minutes (and beyond) proved that the grape cuticle is impervious to water penetration. These experiments measured Brix, pH, and total acidity of both water-soaked and unwashed grapes. Field trials were then proposed to see if the rough handling of clusters during harvest, transportation, and crushpad processing would produce similar results, so that the significant advantageous of grape washing might be realized.
Beginning in 2006, we washed harvested grapes in 32-gallon rubber trash containers full of overflowing water. The clusters were dumped into the wash water and swirled around to loosen dirt and other debris, bugs of all sorts, snails and slugs. This material other than grapes, along with undesirable desiccated berries would float over the edges of the wash containers, after which the grape clusters would be spread onto screens for drying, prior to dumping into the crusher-destemmer hopper. In the years following, we added a pump-filtration system to cleanse and recirculate the wash water for economic sustainability. Fans were set up to dry the clusters and to discourage flying bees and multicolored asian lady beetles. For a view of this early process click on the following icon:
Clearly, only a small family farm operation could justify spending so much additional intensive labor. There had to be a better way. One obvious solution was to build a conveyor apparatus for moving the fruit clusters from a wash basin to the crusher-destemmer hopper. By hand cranking the conveyor belt, variable processing speeds could be used to allow for drying and sorting of clusters. We envisioned a much larger pump-filtration system that might be capable of propelling the washed grapes onto the conveyor belt to minimize handling of the fruit. Several labor intensive processing steps would then be eliminated. Click on the icon below to view the Prototype I Grape Washer Conveyor:
A second prototype soon followed. Added features included crowned mandrels (rolling pins) for more reliable tracking, and an adjustable belt tensioner. The next video shows prototype II working the second harvest:
Our proposal was accepted by the NCR-SARE committee allowing us to build several prototype versions of the grape washer. The truly overwhelming success of the project led to the design and construction of a final (maybe!) version grape washer that any farmer would be capable of building at minor cost less than $100. The design video follows:
The project would not have been so successful without the significant labor by our part-time worker, Casey Penn. Starting as a student volunteer in 2009, Casey became an accomplished viticulturist and willing handyman. He was able to take over the responsibilities of the Carrizalez Family in 2012 after they had to leave to assume full-time management responsibility of several farms when their employer suffered a massive heart attack. Participating in all aspects of the project from vineyard to winery to workshop, Casey was an invaluable contributor.
Thanks are also due to Nanette L. Neal of Ohio State University Extension who kindly reviewed our proposal and wrote a letter of support.
RESULTS AND DISCUSSION
Unequivocally it may be concluded that washing grapes does not significantly alter the Brix, pH, or total acidity (TA) of the fruit juice. This finding resulted from taking samples for analysis during processing of the harvest. Periodically several unwashed clusters were manually crushed and the juice measured for Brix, pH, and TA. Simultaneously juice from washed grapes was collected as it emerged from the crusher-destemmer machine, and analyzed for these three parameters. In all tests, the percentage difference between washed and unwashed samples was less than 0.9% for Brix, and less than 0.4% for pH and TA. For example, juice from unwashed cabernet sauvignon grapes typically measured 26.6 oB, pH=3.54, and TA=6.60 g/L, whereas comparable values of the washed fruit measured 26.4, 3.55, and 6.62 yielding percentage differences of 0.8%, 0.3%, and 0.3% respectively. The faster the conveyor was cranked, the less drying of wash water took place, so that more water was added to the grape juice, but in no case did the samples vary by as much as 1%. When a fermenter was full of 2000 lbs of crushed grapes, analysis of these parameters yielded percentage differences of 0.4%, 0.0%, and 0.1%, all of which were within the tolerance range of the various instruments.
Of course these results would be better supported by an analysis of flavanol compounds in each sample, but the costly instrumentation for testing this was not available. Likewise we had no means for testing whether or not the fungicides sprayed on the vineyard (per standard practice and government regulation) or whether any residues of breakdown compounds remained on the washed and unwashed grapes. Such a project might be suitable for a Master’s thesis at a University with a well-equipped chemical analysis laboratory. Then too, it may be questioned how different the resulting wine might taste, but as much fun as conducting that test would be, it was also beyond the scope of this project!
Outreach to local growers and winemakers was by invitation and word-of-mouth in late winter of 2013. The first prototype grape washer was not a thing of beauty! It had served as a problem discovery device, which led to considerable improvements for the second prototype used in the fall 2013 harvest. In the spring of 2014 we hosted a gathering attended by 18 regional growers and winemakers. The final version of the grape washer conveyor was demonstrated and the advantages thoroughly discussed. The overall consensus was that wine grape washing would be a positive selling point for health-conscious consumers valuing organic produce. Several winemakers agreed that if nothing else, the homemade conveyor would be a welcome addition to their operation for transferring the harvested fruit from picking bins to crusher-destemmer and a ready-made means for sorting grapes, which for the most part is only done by large winemaking operations. The analysis instruments drew a lot of interest and considerable envy. But it was the free-flowing wine tasting and endless hors d’oeuvres that stole the show! Although the audio did not turn out for the demonstration, the following shots are somewhat presentable:
Publishing the award recipients’ proposal applications could encourage other small family farmers to apply for research grants.
Grape Washer Original (Pre-award) 2007 Version
Grape Washer Prototype I
Grape Washer Prototype II
Grape Washer Conveyor - Final Version
The North Central Region is recognized as the most difficult multi-state area of the United States for growing vinifera (European/California style) grape varietals for winemaking. The combined conditions of extremes of temperature and humidity along with a short growing season account for much of this problem. The exceedingly high fungal disease pressure exacerbates this situation. It is not surprising then that there are no commercial winegrowers making organic wine from organically-grown grapes in the Ohio River Valley, which until 2008 was the largest American Viticulture Area (AVA).
Beginning in 2006 our research station has tried every combination of Organic Materials Review Institute (OMRI) approved means for organic grape growing in a quarter-acre test plot set aside for that purpose. Neither ionic copper (Kocide3000TM) or sulfur (MicroThiolTM), nor microbiological (SerendadeTM), nor immunological stimulant (RegaliaTM) commercial OMRI-approved products have been effective against the extremely high disease pressure of this area. Moreover, contrary to Internet and anecdotal claims, so-called “home remedies” such as soaps, baking powder, vinegar, milk, and natural oils have been equally ineffective. Six years of unsuccessful trials pitting organic measures against the region’s fungi population has convinced us that vineyards within range of the Ohio River’s morning fog are not suited for organic growing of either vinifera or French-American hybrid grapes.
By necessity then, commercial winegrowers of this extensive region continue to disperse synthetic fungicides to control black rot, phomopsis, anthracnose, and both powdery and downy mildews. The Environmental Protection Agency of the federal government regulates the use of synthetic pesticides according to the manufacturers’ specifications for application quantity and frequency, protective clothing (and in some cases breathing apparatus) to be used, post-application vineyard restricted entry interval (REI) and pre-harvest interval (PHI) (1). However, no monitoring or inspections of pesticide use is conducted at any level other than the record-keeping of the grower. Wineries and consumers are completely dependent on the manufacturers’ safety claims and on the conformance of the grower to the manufacturers’ prescribed dosage.
Having conceded that our farm’s site is not suited to organic grape production, we have researched the various synthetic fungicides to settle on ethylenebisdiothiocarbamate (EBDC) for future trials. Grape growers in the NCR SARE region have effectively used EBDC for fungi control as far back as the 1940’s (2). Present trade names under CAS Registry No. 8018-01-7 include Mancozeb TM, Aazimag TM, Fore TM, Dithane M-45 TM, and Manzate 200 TM (3). It is significant to recognize that whereas the manufacturers of EBDC are quick to point out that their products have negligible vapor pressure and are quickly hydrolyzed with a half-life less than two days, it is thanks to independent researchers that we are made aware of the breakdown products of EBDC’s, one of which (ethylenethiourea) is classified by the EPA as a group B2 probable human carcinogen having caused cancer in experimental animals (4).
Given this quandary whereby carcinogenic byproducts of synthetic fungicides are tolerated for effective control of fungi, washing of wine grapes to remove pesticides immediately comes to mind. Unfortunately winemakers consider grape-washing to be an unacceptable practice. It is taken as gospel that the sugar content (Brix) as well as fruit pulp flavanols would be diluted, thereby adversely affecting the sensory quality and salability of the wine.
It is well known that fruit quality is compromised by rainfall immediately prior to harvest. Winegrowers typically measure the parameters of Brix, pH, and total acidity on a daily basis within one week of harvest, so they know the undesirable effects of rainfall occurring at this time. We believe that this observation results from the systemic uptake of water rather than the trans-membrane movement of water through the relatively tough grape skin cuticle. Preliminary results testing these parameters on grapes soaked in water for various time periods suggest that this is indeed the case.
This project intends to address all concerns of the local winemakers from whom we have solicited comments and criticisms. Rightfully, regional winemakers have been quick to point out that hand-washing of whole clusters under laboratory conditions is quite different from the rough treatment grapes undergo during harvest and transport to the sorting table for additional handling. Thus we believe that design and development of a grape-washing apparatus to be tested under field conditions is warranted. Likewise, vineyard spray treatments must conform to the local regimens which utilize a full spectrum of synthetic fungicides, surfactants and oils.
Following harvest and crush, but before fermentation starts, the sugar content (Brix), hydrogen ion concentration (pH), and total acidity (TA) will be tested. These are the three most commonly measured parameters influencing a winemaker’s subsequent cellar operations. This standard practice will be adhered to throughout the project’s parallel batch processing. The control batch parameters will be compared to those measurements made on the test batches. The test group will in all instances be handled identically to the control batch. The only difference will be the elapsed wash time of each test batch. To start, 5, 10, and 20 minute wash times will used. If no significant difference in measured parameters is found, then successive wash times will be doubled (40, 80, 160 minutes) until a change due to washing is observed. If at any time there is a significant difference in measured values, then that particular test will be repeated. On verification of change, additional longer wash times will be used to test the extent and linearity of the compromised treatments.
Because it is important to conduct this experiment under field conditions, a prototype grape washing apparatus will be constructed. The test fruit clusters will first be dumped into a wash basin and for the prescribed wash time will be buffeted about by a motorized filtration system. At the end of the wash time, the grapes will be removed from the wash solution by a hand-operated conveyor and allowed to dry under forced air during which time a control batch will be dumped directly into the stemmer/crusher and processed as usual. The washed test batch will then follow through the identical stemmer/crusher processing. While the next test batch is undergoing its wash time, the Brix, pH, and TA will be measured for the previously handled control and test batches. This procedure will continue until a significant difference in measured values is obtained. Also, to get an idea of how roughly the test clusters have been treated, for example skin bruising and breaking, wash solution samples will be collected after each trial. These solutions will be tested against saved standards used at the start of processing to determine if compounds have been leached from the washed grapes.
Sustainable practices will be followed. Water will be drawn from a rainwater rooftop collection system. Washing solutions will be recirculated and filtered for repeated use.