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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCED UTILIZATION OF CARBOHYDRATES AND POLYSACCHARIDES FROM CITRUS PROCESSING WASTE STREAMS

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2006 Annual Report


1.What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter?
Developing new byproducts as outlets for the 5 million tons of waste residue generated annually by the Florida citrus processing industry is critical to industry health. With low profit margins from juice sales and increased competition from foreign imports, the revenue obtained by production of waste stream byproducts is becoming increasingly important for the Florida Citrus Industry to remain profitable. Currently, most citrus processing waste is dried to make citrus pulp pellets for use as cattle feed. Unfortunately, citrus pulp pellets have not had sufficient value to cover production and transportation costs for over 6 years. The cost and environmental impact of putting this waste in landfills eliminates this as an option if the citrus industry is to remain profitable and survive. The citrus waste stream contains numerous phytochemicals with demonstrated human health benefits, and large quantities of carbohydrates in the form of simple sugars, pectin and other polysaccharides. The development of new by-products from the citrus processing waste stream via integrated and economical new processes offers a tremendous opportunity to increase crop value. The investigators will characterize the structure and functional properties of the carbohydrate fraction. They will develop new and use existing procedures including chemical, physical or enzymatic processes to modify and produce polysaccharides, value added polymers, or resins with unique functional properties, either isolated or while still contained in the bulk waste stream residue. These new materials will be tested for use in industrial applications requiring metal chelating and ion-exchange materials, as additives to modify building and construction materials, as paper additives, other non-food related applications. Economically viable and environmentally friendly processes will be stressed. Processing citrus peel waste into fuel ethanol, while recovering valuable co-products such as pectin, flavonoids (antioxidants) and limonene is also under investigation.

This work is relevant to citrus growers and citrus juice processors who will benefit by realizing increased value for their products. The impact of this project for the citrus industry is increased crop value, more competitive U.S. citrus products, and a reduction in biomass pollution and disposal problems. Other customers of the research are industrial manufacturers of building and construction materials, paper additives, and industries requiring materials for waste water remediation that are environmentally friendly. It is also possible that the applications developed by this project to produce new by-products from the citrus waste stream could be applied to other fruit and vegetable processing waste streams rich in polysaccharides, such as those produced by the apple and sugar beet industry. This project is 100% devoted to addressing Component 2 (New Processes, New Uses, and Value-Added Foods and Biobased Products) of NP 306, "Quality and Utilization of Agricultural Products". We seek to enhance the value and competitiveness of the U.S. citrus industry by developing new by-products and industrial applications for existing and newly developed citrus by-products through the use of economical, environmentally benign, and efficient processing methods.


2.List by year the currently approved milestones (indicators of research progress)
Year 1 (FY 2005) 1. Investigate effects of enzyme, acid, and base treatments on modifications to pectin and release from cellulose. 2. Show feasibility of isolating non-calcium sensitive pectins in yields greater than 15% from fresh peel. 3. Separate and characterize multiple PMEs, begin determining their structural modification of pectin.

4. Identify 2 or more industrial partners interested in pectin/cellulose formulations.

5. Begin accumulation of PME modified pectins and preliminary investigations of functional properties.

6. Establish methodology and instrumentation for studying physical properties of new products from citrus peel.

Year 2 (FY 2006) 1. Show feasibility of ultrafiltration and alternative filters to isolate pectin and initiate technology transfer. 2. Characterize pectins isolated from fresh peel and initiate technology transfer. 3. Continue determining PME structural modification of pectin and technology transfer.

4. Start scale up on promising pectin modifications with chemicals to provide testing material to industry.

5. Continue to accumulate PME modified pectins and determination of their functional properties, initiate technology transfer.

6. Initiate chemical modification of citrus peel materials and begin testing of new products.

Year 3 (FY 2007) 1. Continue modifications on pectin, using enzymes, acid, base, and initiate experiments with crosslinked resins. 2. Complete studies on disaggregation using proteases and surface-active agents and continue technology transfer.

3. Continue determining PME structural modification of pectin and continue technology transfer.

4. Continue scale up of pectin modifications, provide test materials to industry partners.

5. Continue to accumulate PME modified pectins and determination of their functional properties and technology transfer.

6. Continue modification of citrus peel and testing and initiate technology transfer.

Year 4 (FY 2008) 1. Continue with resin crosslinking studies and continue technology transfer.

2. Incorporate disaggregation improvements into isolation process and continue technology transfer.

3. Finish determination of pectin structural modifications and continue technology transfer.

4. Continue scale up pectin modifications, provide test materials to industry partners.

5. Continue determination of functional properties of PME modified pectins and technology transfer.

6. Continue modification of citrus peel and testing and initiate technology transfer.

Year 5 (FY 2009) 1. Finish technology transfer with ion exchange product for industry.

2. Complete technology transfer/Objective 1.

3. Complete technology transfer/Objective 2.

4. Finish technology transfer of processes and additive by-products for building products industry.

5. Finish determination of functional properties of PME modified pectins and technology transfer.

6. Complete physical properties testing of new products and finish technology transfer.


4a.List the single most significant research accomplishment during FY 2006.
Effect of pH on pectin structure that can affect industrial applications: The effects of pH on pectin structure resulting from demethylation with the citrus salt-independent PME were determined at the ARS, Citrus & Subtropical Products Laboratory, Winter Haven, FL. It was demonstrated demethylated block size could be manipulated through control of the final average degree of methylation and reaction pH. Subsequent testing of functional properties of the modified pectins demonstrated that calcium sensitivity and rheology (yield stress) were manipulated by these structural changes. The information will be used to aid in optimizing pectins for different industrial applications such as chelation and use as suspension aids and relates to NP 306, "Quality and Utilization of Agricultural Products", Component 2, "New Processes, New Uses, and Value-Added Foods and Biobased Products".


4b.List other significant research accomplishment(s), if any.
Feasibility demonstrated for conversion of citrus peel waste to ethanol on a pilot plant scale: In the commercial scale up for converting citrus waste carbohydrates to ethanol for use as a biofuel, feasibility for a process at the 1000 gallon scale was demonstrated at the ARS, Citrus & Subtropical Products Laboratory, Winter Haven, FL. The process involves enzyme hydrolysis of the complex carbohydrates to simple sugars, which are then fermented to ethanol. The flavonoid fraction in the fermented residue was also characterized for possible recovery and utilization in products other than as a cattle feed. Conversion of citrus peel waste to ethanol would provide a more economic by-product than the current situation where peel is converted to cattle feed and relates to NP 306, "Quality and Utilization of Agricultural Products", Component 2, "New Processes, New Uses, and Value-Added Foods and Biobased Products".


4c.List significant activities that support special target populations.
None.


5.Describe the major accomplishments to date and their predicted or actual impact.
Methodology was developed and improved for quantification of individual galacturonic acid oliogmers separated from pectinaceous material. Latest developments allow separation of pectic fragments containing more than 70 galacturonic acid units. This procedure facilitates mapping of pectin structure and modifications made to pectin with treatment with enzymes and chemicals. It allows for determining functional properties related to introduced structural features.

A method was developed for preparative fractionation of polygalacturonic acid fragments into several weight classes (low, medium, and high degree of polymerization) of polygalacturonic acid.

Three of the four isozymes of PME present in citrus fruit peel have been prepared as monocomponent preparations and characterized for their physical and biochemical properties. Conditions have been described that favor activity of one isoform over the others which will allow for their use in tailoring the structural and functional properties of modified pectin or fruit peel fragments for industrial utilization.

Assay procedure for determination of pectin, the major component of citrus peel,was developed. This will assist in quantitation of this important component as new products and processes are developed for its modification and release from peel. This technique could be of value in all future products involving pectin in citrus peel.

Demonstrated non-calcium sensitive pectins could be isolated from washed orange peel in yields representing approximately 15% on a dry weight basis. This is approximately half of the total available pectin present in the peel. These pectins were extracted under relatively mild reaction conditions, that simplifies the process and aids in technology transfer.

A scalable process for the conversion of citrus waste sugars and polysaccharides into ethanol for use as a biofuel was developed and demonstrated at the 100 and 1000 gallon process levels. Limonene is also recovered during the process, which is another valuable by-product with an already established market. This helps make the process economically feasible in addition to reducing concerns about volatile organic emissions from citrus processing plants.

All the above accomplishments relate to NP 306, Component 2, "New Processes, New Uses, and Value-Added Foods and Biobased Products".


6.What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end-user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products?
CRADA with local industry partner who is interested in the commercial development of a process to convert waste citrus carbohydrates into ethanol for use as a biofuel is continuing. It is expected the technology will become available during FY 2007.

CRADA with an international supplier of food gums has been established to study the commercial applicability of a citrus pectin modifying enzyme.


7.List your most important publications in the popular press and presentations to organizations and articles written about your work. (NOTE: List your peer reviewed publications below).
Luzio, G.A. Evaporative light scattering detector as a mass detector with MALLS for determination of pectin molecular weight. International Light Scattering Symposium, Santa Barbara, CA, October 24-25, 2005.

Flores, A. Ethanol feedstock from citrus peel waste. Agricultural Research Magazine, April, 2006, pg. 19.

A radio interview on converting citrus waste to fuel ethanol was done with WFLS Radio in Fredricksburg, VA, April, 2006.

Kennedy, K. Juiced up. Lakeland Ledger, April 13, 2006, B1.

Widmer, W.W. Status on converting citrus waste to ethanol. Florida Citrus Growers, Lake Wales, FL, April, 2006.

Keller, A. Starter fuel. Florida Trend Magazine, May, 2006, 98-101.

An interview with FOX 13 news on converting citrus waste to ethanol and other products took place on May 19th 2006, and was shown on the evening news.

Anonymous. Fuel up with peels. Citrus & Vegetable Magazine, May, 2006, pg. 29.

Levesque, W.R. Squeezing fuel from oranges. St. Petersburg Times, May 31, 2006.

Levesque, W.R. Discarded orange peels may make viable ethanol. Lakeland Ledger, June 1, 2006.

Widmer, W.W. Producing ethanol from citrus waste. Indian River Citrus League, Vero Beach, FL, July 2006.


Review Publications
Luzio, G.A. 2006. Use of an evaporative light scattering detector coupled to malls for determination of polysaccharide molecular weight. Journal of Liquid Chromatography and Related Technologies. 29:185-201.

Wilkins, M.R., Widmer, W.W., Cameron, R.G., Grohmann, K. 2006. Effect of seasonal variation on enzymatic hydrolysis of Valencia orange peel. Proceedings of Florida State Horticultural Society. 118:419-422.

Cameron, R.G., Savary, B.J. 2005. Progress in determining pectin methylesterase mode of action and structural mapping of modified pectin. Subtropical Technology Conference Proceedings. 56:14.

Widmer, W.W., Wilkins, M.R., Grohmann, K. 2005. Citrus waste to ethanol and other byproducts: an update. Subtropical Technology Conference Proceedings. 56:15.

Luzio, G.A. 2006. Determination of molecular weight citrus pectin using ion chromatography. Florida State Horticultural Society Meeting. Paper No. 56.

Luzio, G.A. 2005. Rheological and functional properties of block deesterified pectins. Subtropical Technology Conference Proceedings. 56:9.

Cameron, R.G., Luzio, G.A., Baldwin, E.A., Narciso, J.A., Plotto, A. 2006. Production of narrow-range size-classes of polygalacturonic acid oligomers. Proceedings of Florida State Horticultural Society. 118:406-409.

Cameron, R.G., Goodner, K.L., Luzio, G.A. 2006. Structural characterization of pectin following demethylation with a salt-independent pectin methylesterase. National Meeting of Institute of Food Technologists/Food Expo. Abstract No. 014-03.

Luzio, G.A., Cameron, R.G. 2006. Functional and rheological properties of highly esterified pectin after treatment with an orange pectin methylesterase. National Meeting of Institute of Food Technologists/Food Expo. Abstract No. 014-06.

Luzio, G.A., Cameron, R.G. 2006. Rheological properties of non-calcium sensitive pectin after treatment with the citrus salt independent pectin methylesterase. Pacifichem Symposium. Paper No. 23.

Cameron, R.G., Luzio, G.A. 2006. Effect of pH on de-esterified and methyl-protected block size in pectin treated with the salt-independent pectin methylesterase from citrus fruit. Pacifichem Symposium. Paper No. 22.

Last Modified: 4/21/2014
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