Location: Citrus and Other Subtropical Products Research
2024 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
Researchers in Fort Pierce, Florida were able to successfully decolor steam explosion citrus peel fibers using soybean flour in small scale experiments. This will help enable the use of steam explosion citrus peel fibers for food applications that require limited impact on color of the final product.
Researchers in Fort Pierce, Florida were able to develop a novel lateral flow assay (LFA) system that utilizes pectin-recognizing antibodies to quickly assess pectin structural properties that are related to its functionality. The developed method was validated by testing series of known experimental pectins and commercial pectin products.
Accomplishments
1. Faster, safer, cheaper field diagnostic kit. Researchers in Fort Pierce, Florida and research partners have found a faster, safer, and less expensive way for growers to detect the invasive Lebbeck mealybug that feeds on and damages citrus and ornamental plants. It is currently found in Florida and may spread to other states. To control Lebbeck mealybug populations and prevent their spread, growers can use field diagnostic kits for early detection to properly identify the pest. The established method uses 10% potassium hydroxide to identify the Lebbeck mealybug. However, researchers in Fort Pierce were able to prove that 5% sodium hydroxide is just as effective, less hazardous, less expensive, and readily available. This work was published and featured is several external news outlets.
2. A new process for producing high-quality, low-cost pectin with increased gelling capacity and a broadened scope of application. Researchers in Fort Pierce, Florida and ARS collaborators have developed a process to utilize endogenous pectin demethylation enzyme to modify pectin in source plant material to a desirable structure and thus improved the gelling capacity of extracted pectin. Commercial citrus pectin extraction initially results in high-methoxyl (HM) pectin which requires high sugar and low pH for gelling. HM pectin is treated either chemically or enzymatically to produce desirable low-methoxyl pectin, which can be costly and leave undesirable residues. The developed process involves a pretreatment of fresh orange peel with high-pressure processing (HPP), which activated the endogenous pectin demethylation enzyme in the orange peel to modify pectin structure prior to pectin extraction. The new process increased pectin yield by 41% and improved the gelling capacity of the extracted pectin. This work will have a profound impact on commercial pectin extraction and modification because it allows pectin to be modified in source plant material, decreases cost, and increases both yield and quality.
Review Publications
Zhao, W., Xu, Y., Dorado, C., Chau, H.K., Hotchkiss, A.T., Cameron, R.G. 2023. Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part I. The effects on pectin extraction and structural properties. Food Hydrocolloids. 149. Article 109516. https://doi.org/10.1016/j.foodhyd.2023.109516.
Zhao, W., Xu, Y., Dorado, C., Bai, J., Chau, H.K., Hotchkiss, A.T., Yadav, M.P., Cameron, R.G. 2023. Modification of pectin with high-pressure processing treatment of fresh orange peel before pectin extraction: Part II. The effects on gelling capacity and emulsifying properties of pectin. Food Hydrocolloids. 149. Article 109536. https://doi.org/10.1016/j.foodhyd.2023.109536.
Fan, Z., Jeffries, K.A., Sun, X.N., Olmedo, G., Zhao, W., Mattia, M.R., Stover, E., Manthey, J., Baldwin, E., Lee, S., Gmitter, F., Plotto, A., Bai, J. 2024. Chemical and genetic basis of orange flavor. Science Advances. 10(9):2051. https://doi.org/10.1126/sciadv.adk2051.
Xu, Y., Sismour, E., Tucker, F., Rasberry, J., Zhao, W., Rao, Q., Zhao, Y., Haff, R.P., Yousuf, A., Gao, M., Chen, A. 2024. Structural and functional properties of Kabuli chickpea protein as affected by high hydrostatic pressures. ACS Food Science and Technology. 4(2):528-536. https://doi.org/10.1021/acsfoodscitech.3c00640.