Steam Explosion (STEX) of citrus x Poncirus hybrids with exceptional tolerance to Candidatus liberibacter asiaticus (CLas) as useful sources of volatiles and other commercial products

Authors: Dorado, Christina; Bowman, Kim; Cameron, Randall - Randy; Manthey, John; Bai, Jinhe; Ferguson, Kyle

Submitted to: Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2021
Publication Date: 12/7/2021
Citation: Dorado, C., Bowman, K.D., Cameron, R.G., Manthey, J.A., Bai, J., Ferguson, K.L. 2021. Steam Explosion (STEX) of citrus x Poncirus hybrids with exceptional tolerance to Candidatus liberibacter asiaticus (CLas) as useful sources of volatiles and other commercial products. Biology. 10:1285. https://doi.org/10.3390/biology10121285.
DOI: https://doi.org/10.3390/biology10121285

Interpretive Summary: Citrus production in Florida has dropped 75% because of a disease known as Huanglongbing (HLB) which is caused by a bacteria (CLas). Infected trees produce immature, green fruit and eventually die. Methods to treat CLas are very expensive and there is no cure. Hybrid varieties of citrus are known to be highly tolerant to CLas but have not been studied for their products. In this work we used steam treatment followed by water washing to recovery valuable citrus products from three citrus hybrids, US-802, US-897, and US-942. Many of the products found in oranges and grapefruits can be found in the hybrid varieties. For most of the products, more than 80% could be recovered from the hybrids using steam treatment followed by water washing. These citrus hybrids, therefore, have the potential to be an alternative citrus crop that thrives in an HLB environment producing economically valuable products that are recovered in high yields with steam and water.

Technical Abstract: There has been a 75% reduction in Florida citrus production due to Huanglongbing (HLB), a disease caused by the pathogenic bacterium Candidatus Liberibacter asiaticus (CLas). Methods to combat CLas are costly and only partially effective. The cross-compatible species Poncirus trifoliata and some of its hybrids are known to be highly tolerant to CLas, and thus potentially serve as an alternative feedstock for many citrus products. To further investigate the commercial potential of these hybrids, three citrus hybrids, US-802, US-897, and US-942, were studied for their potential as feedstocks for citrus co-products using steam explosion (STEX) followed by water extraction. Up to 93% of sugars were recovered by water extraction after STEX. US-897 and US-942 have similar volatile profiles to that of the commercial citrus fruit types and as much as 85% of these volatiles could be recovered by STEX. Approximately 80% of the pectic hydrocolloids present in all three hybrids could be obtained in water washes of STEX material. Of the phenolics identified, the flavanone glycosides, i.e. naringin, neohesperidin, and poncirin were the most abundant quantitatively in these hybrids. The ability to extract a large percentage of these compounds, along with their inherent values, make US-802, US-897, and US-942 potentially viable feedstock sources for citrus co-products in the current HLB-blighted environment.