A small&medium farm-oriented supercritical fluid extraction (SFE) system was developed and demonstrated for garlic oil extraction as an example of high value crop plant process. The extraction conditions and operation procedure were suggested as a guideline. The potential application of this technology on farm was preliminarily investigated by visiting an organic farm in South Carolina and discussing with the farmer, extension professional and researcher. The evaluation of the scale-up system was conducted based on the current small system and future work was suggested for this technology to be extended to farm use.
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The growing nutraceutical and functional food market (global market estimated to be $63B in 2004 with an annual growth of 14%, which is expected to grow to $167 B by 2010, as published by just-food.com) is anticipated to supply an opportunity for farmers to increase their income and employment. The problem is how farmers may benefit from this growing market as much and as early as possible. Garlic oil is currently 20-100 times the value of raw garlic.
There are potential avenues for the farmers to increase their profits via by-passing the collector or processor. These alternative avenues allow for increased profit space for the farmer. For the farmers to actually increase profits in the nutraceutical market, they would not only harvest the field, but also take part in processing of the raw material. Operation of economic, smaller-scale, sustainable, separation equipment for extraction of garlic oil would increase value of the product and decrease transportation cost.
Garlic (Allium sativum) is a perennial plant of the Alliaceae related to onions, chives, shallots, and leeks. It is mainly used as a food flavoring agent and condiment in various foods and spices such as mayonnaise, salad dressing, spaghetti, pickles, etc. Garlic has been revered for its medicinal properties for centuries. This reverence has been propelled in recent years by the emergence of data revealing that in addition to antimicrobial properties it may also reduce the risk of heart disease and cancer. Commercially available garlic preparations in the form of garlic oil, rich in allicin and allyl sulfur compounds known as contribute to medicinal properties, are widely used for certain therapeutic purposes, including lowering blood pressure and improving lipid profile (Robert, 2001).
About 250 million pounds of garlic are produced in the United States. About 80% to 90% of this amount is produced in California. Garlic grows best during cool weather and is usually planted in the early winter in South Carolina for early summer harvest. Commercial garlic is only produced in Southern part of state. South Carolina has great potential for local farms to produce garlic due to its promising climate for this crop and develop value-added nutraceuticals. Supplying the processed or semi-processed garlic oil for nutraceutical manufacturers, instead of selling raw garlic, is a potential avenue for the farmers to increase their profits.
An environmentally safe processing method known as supercritical fluid extraction (SFE) would bring opportunities to local farm owners to run their “plants” and provide a feasible method to produce semi-processed & processed products for nutraceutical manufacturers. Demonstration of SFE technology for industrial applications was reported by Zosel at the Max Planck (Zosel, 1969). Because SFE has several distinct advantages, such as non-toxic, non-explosive, and low solvent temperatures, it has been regarded as a promising alternative technique to conventional solvent extraction methods. Today, SFE has become an acceptable extraction technique used in many areas, far beyond decaffeination coffee and extracting hops for beer flavoring. SFE of active natural products from herbal or more generally, from plant and microbial materials has become one of the most important application areas (McHugh and Castro, 1994). Additionally, SFE technology using carbon dioxide as solvent is GRAS or “green” status accepted in both Europe and the U.S.
Miles and Quimby (1990) extracted garlic product using supercritical CO2 and analyzed its compounds by GC with atomic emission detection. Elizabeth (1994) extracted garlic allicin by SFE. The yield of allicin from a water homogenate of fresh garlic was 98.2% and 124.6% relative to yields obtained with methylene chloride extraction, respectively using a solvent trap and a solid-phase trap. Though the study of the SFE of garlic oil is less reported in the literature, garlic oil produced from SFE is commercially available and the market is growing in recent years. The garlic oil production using SFE is only an example of a large nutraceutical industry. Crop-based nutraceuticals sold in store are at least dozens. The SFE application will be extended with the growing nutraceutical industry. At present, there is not local farm-adopted SFE technology and equipment. We have initiated this development and intend to transfer this technology to farmer’s hand by the demonstration of SFE technology to produce garlic oil.
The objectives are:
(1)To investigate the pathway and key points to SFE technology extension on small & medium-size local farms.
(2)To further optimize SFE kinetics parameters of garlic oil on the basis of on site operation.
(3)To investigate the criteria for developing the small & medium-size farm-adopted SFE equipment.
We developed a SFE system in our lab. The component and flow diagram of the SFE system are shown in Appendix A. The extraction was conducted under the optimal condition of 35 oC, 3600 psi for carbon dioxide fluid (Calvey et al., 1997). The effect of extraction time and flow rate was determined using spectrometer (Bio-tek) at 254nm.
The tested garlic was bought from local supermarket, including white garlic produced in China and Mexican Red produced in Mexico.
Garlic extracts from SFE were analyzed by a Shimadzu HPLC LC-10Avp automated liquid chromatographic system, which consisted of a photodiode array (PDA) detector and a reverse-phase Restek Pinnacle C18 column. Mobile phases are methanol-water (60/40, v/v) for the allicin determination at a flow rate of 0.8 mL/min. The analytes were detected at 205 nm for allicin identified by comparison with the available authentic standards (from Chromadex). The stand curve, Garlic extracts by SFE and commercial garlic product chromatograph identified by HPLC were showed in Appendix C-F.
The investigation of the potential use of SFE system on farm was performed by visiting farm, Good Earth Organics in South Carolina, discussion with farmer, extension professional and researcher.
1.The self-built SFE system in our lab can be used to extract essential oil from crop plant as demonstrated by garlic oil extraction. 50 g garlic (61% moisture content) in 75 ml extraction cell by 80 minutes hour run at 100ml/min carbon dioxide flow rate can extract 1.8 mg/g fresh garlic allicin in water solution, comparable to water extraction. We have not compared with the reported number of crushed raw garlic contained 3.7 mg/g dry garlic allicin (Lawson et al., 1992), due to different garlic source and storage time. The operation procedure and optimal conditions for garlic extraction was suggested in Appendix B.
2.The flow rate of carbon dioxide affects the extract recovery rate and extraction time. The determination of suitable flow rate is affected by extraction cell volume, loaded sample volume and extraction conditions. For the tested SFE system, one run requires 120 minutes if the flow rate was set at 50 ml/min and 80 minutes (plus 20 minutes loading, unloading and equilibration time) if flow rate was 100 ml/min as showed in Appendix G-H. According to this extraction efficiency, the system with double 7.5 L extraction cell of 100 times scale-up can process 144 kg garlic for one day (24 h). Then 0.1 acre of garlic (for small garlic grower and according to yield of 3,000 kg/acre) require 2 days to complete process.
3.The preliminary investigation of visiting Good Earth organics farm and conversion with grower, extension professional and researcher showed that this technology interested them and had the potential to be extended to application on high value product extraction from garlic. The grower suggested that labor costs could be compensated with garlic extraction compared to sales of fresh garlic at lower value.
Considering the safety of high pressure of carbon dioxide and its release to atmosphere, we have not demonstrated the technology on site application. Secured recycle and re-compression system of carbon dioxide should be added to the current system for the site operation.
Educational & Outreach Activities
The developed SFE system and method similar to garlic extraction are integrated into dissertation “Fungal bioconversion and supercritical fluid processing for higher quality canola oil”
We developed an easy operated and small&medium farm-oriented SFE equipment and initiated the investigation of its potential application. This small step would be a great contribution to the final extension of this technology on the farm after more work being done in the future.
According to the garlic product of Garlicforce, Hexane-Free Capsules, 30 capsules per container, containing 2% stable sulphur-nutrients from allicin equal to 4 mg fresh garlic per capsule, $18.99 per container, 0.1 acre of garlic has potentially $47,475 product (according to yield of 3,000 kg/acre), compared to $ 9,900 for direct sale (according to $3.30/kg). Comparing to the product made by traditional extraction methods the SFE-processed product has 5-15 times the value. The cost of the SFE system is big part of production. This expense maybe compensated by higher product quality and price and the use of mobile extraction units that move from farms in close area.
Areas needing additional study
1.Greater investment to modify the SFE system for mobile use and scale-up for higher process capacity.
2.Encourage and supplement farmers to attend the extension of this technology.
3.Enhance the communication and demonstration of technology among administration, researcher, extension specialist and farmer.