Location: Citrus and Other Subtropical Products Research
2023 Annual Report
Objectives
1. Enable the commercial use of steam explosion fibers from citrus fruit peel for food applications.
2. Resolve unknown microbial modifications of steam exploded citrus peel flavonoids for conversion into high-value byproducts.
3. Conduct a novel immunologically-based assessment of citrus pectin for use in raw and processed foods, and industrial products.
Approach
One of the greatest opportunities for reducing waste in the processing of agricultural commodities is the conversion of these materials to high value co-products. At an average proportion of 45% of fresh citrus fruit weight the amount of the fruit biomass (peel) that is directed towards low value side streams is currently (2018-2019) 9.55 · 106 metric tons worldwide and 1.51 · 106 metric tons domestically. The domestic side stream from juice production would contain 1.33 · 105 metric tons of gluten-free fiber, 3.5 · 105 metric tons of pectic hydrocolloids and 6.8 · 104 metric tons of phenolics and flavonoids. We will enable a technology for isolating a gluten free fiber from citrus juice processing side streams that can be used to impart beneficial properties to food when used as an ingredient including improved nutritional value and water retention without negatively impacting color and flavor. Also, we will enable a technology for microbial modifications of the flavonoids in the water washes of steam exploded citrus juice processing side streams (i.e. peel) so that new higher value compounds will be recovered. This will enhance the value of the flavonoids that are already commercialized. But the steam explosion methods will allow easier and more complete recoveries of these flavonoids than currently available. Newly produced compounds will serve as starting points for further products, as well as for further product development. Anticipated products relate to creating a process to convert food waste (fruit peels, pulp, and pomace) into value-added healthful bioactive ingredients. Finally, we will enable a rapid immunological based method to define, measure, and preserve/enhance/reduce factors that impact quality and marketability of the structural/functional properties of pectin. Anticipated products relate to creating a novel methodology to enhance or predict the quality and utilization of agricultural products providing information to assess product quality and to detect factors that diminish quality.
Progress Report
Properties of steam exploded citrus fiber and commercial citrus fibers were determined to include rheology, particle size, color, water and oil holding capacity, water swelling, compositional sugars, and total dietary fiber.
Alternative gluten-free food fibers with little to no color are desirable for food applications. Citrus fiber is gluten-free but the associated color limits its use. Therefore, researchers at Fort Pierce, Florida, are investigating methods for decoloring citrus fibers (Objective 1). Size reduction methods of whole soybeans was investigated and the resulting soy flour which contains the lipoxygenases has been used to remove color from a commercial citrus fiber based on established methods in the literature. Once the experimental conditions for decoloring the commercial fiber are optimized, tests on steam exploded citrus fiber will be completed.
Extraction of citrus seed oil and proteins, two by-products of orange juice production, were modified to improve yield. Both byproducts can be used as alternative biofuel and in foods.
The most important functionality of pectin is its gelling property, which is primarily determined by the degree and distribution pattern of methyl ester along the pectin backbone. Under Objective 3, a new immunological method was developed to assess pectin gelling properties, in which the degree and distribution pattern of methyl ester can be discerned based on antibody responses of several pectin-recognizing antibodies.
Furthermore, we explored a new method for modification of pectin in plant tissue with high-pressure processing treatment of fresh orange peel before pectin extraction to generate pectin with desirable structural features. The data indicate that the new method may be an efficient and economical way to generate high-quality pectins with increased gelling capacity and a broadened scope of applications, in addition to an increased pectin extraction yield.
A method was perfected to encapsulate thymol, and antimicrobial volatile compound from thyme oil, for slow release experiments in fruit packaging performed by ARS collaborators.
Accomplishments
1. Florida oranges can be used for domestic pectin production. The global pectin market is currently valued at 967 million USD and is expected to grow to a value of 1.2 billion USD by 2028. Most pectin is obtained from apple pomace and citrus peel when juicing those fruits. Florida is a major citrus juice producer but there are currently no pectin production facilities in that State or even in the United States. Establishment of a pectin production facility in Florida would allow for a domestic source of pectin and increased production value of Florida citrus. ARS scientists in Fort Pierce, Florida,identified the optimum pilot scale conditions for pectin production from Florida sweet oranges. This work served to support the design, engineering, and commercialization efforts of a citrus juice co-product manufacturing facility in the state of Florida. ARS scientists continue to remain engaged with and provide support to the collaborator in their efforts to establish this manufacturing facility which would be a first of its kind in the United States and would serve to increase the value of a major fruit crop in the state of Florida.
Review Publications
Dorado, C., Cameron, R.G., Manthey, J.A., Bai, J., Ferguson, K.L. 2021. Analysis and potential value of compounds extracted from star ruby, rio red, and ruby red grapefruit, and grapefruit juice processing residues via steam explosion. Frontiers in Nutrition. 8:691663. https://doi.org/10.3389/fnut.2021.691663.
Zhao, W., Yang, K., Cameron, R.G. 2022. A novel multiplex lateral flow assay for rapid assessment of pectin structural/functional properties. Food Hydrocolloids. 133 : Article 107988. https://doi.org/10.1016/j.foodhyd.2022.107988.
Cameron, R.G., Ferguson, K., Zhao, W., Dorado, C. 2022. Commercial pectin production from dried Florida orange peel, effect of process conditions on pectin structure and function. Journal of Food Processing and Preservation. https://doi.org/10.1111/jfpp.17193.
Xu, Y., Sismour, E., Britland, J., Sellers, A., Abraha-Eyob, Z., Adnan, Y., Rao, Q., Kim, J., Zhao, W. 2022. Physicochemical, structural, and functional properties of hemp protein vs several commercially available plant and animal proteins: A comparative study. ACS Food Science and Technology. https://doi.org/10.1021/acsfoodscitech.2c00250.
Moser, B.R., Dorado, C., Bantchev, G.B., Winkler-Moser, J.K., Doll, K.M. 2023. Production and evaluation of biodiesel from sweet orange (Citrus sinensis) lipids extracted from waste seeds from the commercial orange juicing process. Fuel. 342. Article 127727. https://doi.org/10.1016/j.fuel.2023.127727.
