- Fruits: grapes
- Education and Training: demonstration, on-farm/ranch research
- Farm Business Management: feasibility study, value added
- Sustainable Communities: sustainability measures
For the 2013 grape harvest, we were again able to obtain the pomace from approximately 48 tons of whole grapes. Each weekend from the first week of August until the first week of October, we obtained and processed the pomace from approximately 5 tons of whole grapes.
During last year’s harvest we used hand-screens, such as an individual winery might use to hold down costs, to separate the seeds from the skins. For this year’s harvest we decided to try to automate the screening process, such as a regional cooperative might use to handle a larger volume of pomace from multiple wineries in their surrounding area.
To automate this process, we obtained a used Seed Cleaner (see project photos and power point presentation) that we repurposed as a trommel. These Seed Cleaners are widely available throughout the Midwest and are used to clean corn or soybeans before they are delivered to the elevator. Most of these Seed Cleaners have an inner screen and an outer screen. When used for cleaning corn or soybeans the seed passes through the first screen and any debris larger than the seed is separated and passed out the machine. The seed stays within the second screen and any debris smaller than the seed falls out the bottom.
For our purpose of separating grape seeds from skins, we use both the inner screen and the outer screen to separate the seeds from skins. We needed to replace both the inner and outer screens with a smaller mesh (hardware cloth) to suit our purposes. After several trials, the sizes we found to work best were #4 mesh for the inner screen and #5 mesh for the outer screen. We also had to reduce the pulley size on the electric motor that turns the trommel to reduce its rotation rate because centrifugal force was not allowing all of the seed to pass through the second screen given its much closer tolerance. These modifications consisting of new inner and outer screens and smaller pulley cost around $400 and were relatively simple to make. On our Seed Cleaner model the screens are held in place with 4 long metal bands along the length of both the inner and outer screen. We simply removed the bands, pulled out the existing screens and replaced them with our new screen and then replaced the metal bands. We purchased our new screen from the internet (http://www.twpinc.com) and it comes in long rolls that we then had to cut to length after measuring the circumference of each screen tube.
After making all of the modifications we were very pleased with the result. The inner screen separates about 80% of the skins and the outer screen separates another 10% to 15%. Our new trommel reduced the labor from 1 hour (2 persons) for hand screening down to just 20 minutes and only requiring 1 person. Once the seeds were separated we employed the same solar drying method used in year 1 and described in our Initial Report.
- Grape Seed/Skin Separator
- Red and White seeds solar drying
- Seed Dryer
- Hand Screen
- Seed Cleaner repurposed as grape seed/skin separator
In 2013 we were finally able to start using our Grape Seed Oil (GSO) Press. We purchased the M-70 Seed Oil Press from the AgOilPress Company which is an American company located in Wisconsin. After many hours of research on various different presses we selected the M-70 because of its cost, throughput, and its technical support. They were one of the few company’s that we were able to speak to on the phone and were willing to answer any of our questions. This tech support proved to be crucial to the success of this project as I will describe below.
When we first attempted to use the press, we would initially start to produce Grape Seed Oil but usually within 30 minutes to an hour the press would jam and we would need to tear the press apart to clean it out and start over. It turns out that grape seed is extremely difficult to press because it is a very hard seed and contains a low amount of oil as compared to other seeds such as soybeans. Over the next several months we basically entered into an informal product development process to improve the M-70s ability to process grape seed oil. During this time, AgOilPress made several modifications including a reengineered crush plate, reengineered the press screw with a ball bearing to focus axial load in the center of the shaft so the bearings would not burn out, increased the size of the press nozzle and increased the horsepower of the motor. With these modifications we have now been able to process the grapeseeds from over 100 tons of whole grapes without the press seizing up. AgOilPress now sells a grapeseed version of the M-70 model. With the press now able to function properly, we were able to process the seed from both 2012 and 2013.
Throughout the process of pressing the grapeseed to produce grapeseed oil we documented several lessons learned.
(1) If you are pressing on a cold day it is good to preheat the seed (without exceeding 125F for definition of cold pressed) prior to pressing. AgOilPress produced a heater for us that the seed would pass through prior to going into the press. We typically would warm the seed to about 90F with good results.
(2) Shiny parts equal less friction. Buffing all of the internal parts prior to commencing press operations is time well spent.
(3) Soybeans are your friend. Running soybeans through the press for the first 10 minutes warms up all of the parts and because soybeans contain a lot of oil all of the parts are well lubricated.
(4) Do not allow your seeds to dry below 10% moisture or they will be difficult to press.