Release and recovery of pectic hydrocolloids and phenolics from culled citrus fruits

Authors: Cameron, Randall - Randy; Chau, Hoa - Rose; Hotchkiss, Arland; Manthey, John

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/22/2017
Publication Date: 5/31/2017
Citation: Cameron, R.G., Chau, H.K., Hotchkiss, A.T., Manthey, J.A. 2017. Release and recovery of pectic hydrocolloids and phenolics from culled citrus fruits. Food Hydrocolloids. 72:52-61. doi:org/10.1016/j.foodhyd.2017.05025.

Interpretive Summary: The Florida citrus industry is in dire straits. Harvests have been reduced nearly 75% since 2003. Growers and juice processors are both suffering. The cause is a bacteria spread by a sucking insect. To date there is no cure, only stop gap, temporary and poorly performing fixes. Not only does the disease impact tree health it also results in smaller fruit with unwanted off-flavors. Culling this fruit would prevent the introduction of these unwanted flavor profiles into the juice stream but would also diminish yield which could economically impact both growers and processors. Recovering value added coproducts from these culled fruits could provide an alternative revenue stream. In this report we have demonstrated that these culled fruits can be used as a feedstock in our newly developed continuous, steam-explosion process enabling the recovery of highly valued pectic hydrocolloids and phenolic compounds using a simple water wash. Implementation of this technology and the proper marketing of the resulting products would prevent the off-flavored juice from degrading juice quality and provide much needed income for the industry.

Technical Abstract: Citrus worldwide is threatened by a bacterial disease Huanglongbing (HLB) spread by a sap sucking hemipteran. Before tree death, there is a period of increased preharvest fruit drop and reduced fruit size with off-flavored juice. The increasing frequency of HLB symptomatic fruit moving into the juice processing chain may become a challenge for maintaining flavor quality. An alternative use for these flavor degrading fruits providing added value to fruit growers and juice processors would be beneficial. We have used a steam explosion process for the release and recovery of highly functional pectic hydrocolloids and phenolic compounds from these fruit. Symptomatic fruit from two varieties were culled and either entire fruit or juice-extracted fruit were submitted to steam explosion. Released pectic hydrocolloids and phenolic compounds were recovered using a simple water wash. Recovery of pectic hydrocolloids ranged from 58% - 78%. Weight average molecular weight of this material ranged from 5.78×e5 - 1.02×e6 kDa and the degree of methylesterification ranged from 61% - 79%. Functionalization using alkaline, calcium sequestering compounds resulted in viscosities up to 250 mPa · s-1. Additionally, recovery ranges of 5%-100% of the polymethoxylated flavones, 2%-71% of the flavanone glycosides, >50% of the limonoids were obtained.