Location: Citrus and Other Subtropical Products Research
2021 Annual Report
Objectives
Objective 1: Enable the commercial use of steam explosion fibers from citrus fruit peel for food applications.
Objective 2: Resolve unknown microbial modifications of steam exploded citrus peel flavonoids for conversion into high-value byproducts.
Objective 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
Objective 1: Steam explosion was completed by ARS researchers in Fort Pierce, Florida, on samples of citrus juice processing side stream using 3 temperatures/pressures and 4 hold times. Samples were dried in preparation for analysis. Equipment allocation and installation is underway for fiber analysis of samples. ARS researchers in Fort Pierce, Florida, are currently conducting research into methods to complete in-house gelling and water holding capacity testing. Currently optimizing anzymatic hydrolysis conditions for monosaccharide analysis via HPLC.
Objective 2: Progress was made by ARS researchers in Fort Pierce, Florida, in the start of the microbial transformation of compounds in citrus peel water extracts, using initially the abundant lavanone glycosides, into high value anthocyanins. An experimental protocol to achieve the needed transformations was established. An extensive list of primers needed for DNA transformations was compiled. Designs to construct the final plasmid were made. These were obtained from Adagene, with the appropriate paperwork. The bacterial transformations/production of mutants were completed by ARS researchers in Fort Pierce, Florida,, and cells are stored at -80 deg C for proper storage. The next stages of laboratory work are planned and will be conducted as pandemic created restrictions allow.
Objective 3: ARS researchers in Fort Pierce, Florida, have characterized a series of commercial pectin samples for use as control pectins for the immunological characterization of pectin structural and functional properties. The characterized properties include sugar composition, molecular weight, polydispersity index, intrinsic viscosity and rheology. Additionally, ARS researchers in Fort Pierce, Florida, have collected preliminary data on the degree of blockiness and charge distribution of these control pectins. Other, previously characterized, control pectins have been used to establish an immunochromatographic assay, in the format of a test strip, for rapid assessment of pectin’s structure and function. ARS researchers in Fort Pierce, Florida, results indicate the method is able to quantitate pectin, and discriminate between pectins having different amounts and distribution of charge.
Accomplishments
Review Publications
Ferguson, K.L., Cameron, R.G., Dorado, C., Bai, J., Ferrarezi, R., Da Cruz, M.A. 2020. Impact of Huanglongbing (HLB) on grapefruit pectin yield and quality during grapefruit maturation. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2020.106553.
Sun, X.N., Cameron, R.G., Manthey, J.A., Hunter, W.B., Bai, J. 2020. Microencapsulation of tangeretin in a citrus pectin mixture matrix. Foods. 9:1200. https://doi.org/10.3390/foods9091200.
Cameron, R.G., Branca, E.M., Dorado, C., Kim, Y. 2021. Pectic hydrocolloids from steam exploded lime pectin peel; effect of temperature and time on macromolecular and functional properties. Journal of Food Science and Nutrition. https://doi.org/10.1002/fsn3.2158.
Dorado, C., Cameron, R.G., Manthey, J.A., Ferguson, K.L. 2021. Bench scale batch steam explosion of Florida red and white grapefruit juice processing residues. Future Foods. 3(10):1016. https://doi.org/10.1016/j.fufo.2021.100020.
