Proof of Concept and Prototype Development of a Novel Grape Washer Apparatus for the Small Family Farm Vineyard and Winery
Our 2012 vineyard management regimen utilized synthetic fungicides (Captan 50WP, Manzate 75DF, Tebucon 45DF, Scala SC, NuFilm P, MicroThiol) for the first time following six unsuccessful years of trying every conceivable organic farming practice. The spray program was adapted from that published by Kinkead Ridge Vineyard under the supervision of Owner and Master Viticulturist, Ron Barrett.
Three hundred vines were subjected to the noxious synthetic fungicides by means of an airblast backpack sprayer, whereby the operator wore protective clothing and breathed through a Hazmat mask filter. In spite of the immense disease pressure that had built up over the previous six years, the spray program was a complete success. Both anthracnose and black rot were absent from the vines and fruit, and very little phomopsis was observed.
Weeds were controlled as always by hand mowing to 2-4 inches height. Insects have never been a problem for this vineyard, although the fruit was unmercifully attacked by ground bees before and during harvest for the first time; never before a consideration, we wondered whether the fungicides were penetrating grape cuticles by this means and whether our project results might be compromised.
While vineyard operations were ongoing, several prototype grape washers were devised and tested with plastic grape clusters substituting for the crop not yet ready for harvest. The wash hopper and recirculating filtration system worked flawlessly. The homemade conveyor proved problematical in the extreme. No matter what belt material was used (including 6 mil plastic, nylon ropes, rubber mat runners), and regardless the sophistication of alignment techniques used, the belt failed to consistently track without binding. The conveyor’s purpose is to move the washed grapes to the elevated crusher/stemmer machine while allowing wash water to drain back to the hopper, and at the same time the grapes are subjected to forced hot air for drying. After discussing the tracking problem with several conveyor manufacturers, it was revealed that belt-tracking is achieved by crowning the rollers that drive the belt. With this modification, “fairly reliable” tracking was finally realized.
• Grapes may be automatically washed without any discernible uptake of wash water through the cuticle skin
• Brix, pH, and TA parameters do not significantly differ from unwashed grapes
• Filtering wash water removes particulate matter including leaves, dirt, insect parts, and presumably -- but not tested -- synthetic fungicide chemicals
• Grape juice resulting from rough handling of fruit during harvest cannot be reclaimed from filtered wash water
• Drying time is a significant bottleneck in grape-washing
The processing of grapes during harvest is both a labor intensive and time consuming period. It may be appreciated that considerable additional effort was expended measuring Brix, pH, and total acidity on batches of grapes having undergone various wash times, as well as on control batches (not washed) but processed in parallel. The Hanna HI84102 automated titrator instrument proved indispensable for accomplishing that task. We were fortunate to determine that the washing process had no significant effect on the measured parameters as long as the washed grapes were thoroughly dried before crushing. This happy finding was in spite of the trauma the fruit underwent in the vineyard by bees, by hand harvesting, and by rough transport to the winery. Even the rapid rolling surges of wash water that the grapes were subjected to in the hopper failed to compromise the grape cuticles. (One observer did point out that if the grapes had evidenced bunch rot or were of the more thin-skinned variety, the experiment might not have been so successful).
Although the project was not designed to measure wash water contamination, it was obvious by examining (and cleaning) the filter cartridge that harvested grapes are quite dirty. A more extensive measurement system at greater expense could determine how effective the washing process can be for removing residual synthetic fungicides. Perhaps a master’s candidate at one of our local universities might consider undertaking such an endeavor as a thesis project.
Invariably some grape juice results from the rough handling of fruit during harvest. Unfortunately the washing process does not allow this juice to be reclaimed.
Whereas wash time (even up to twenty minutes) does not affect measured parameters, drying time is a significant bottleneck greatly affecting throughput from crushpad to grape must production.