Analysis and Potential Value of Compounds Extracted From Star Ruby, Rio Red, and Ruby Red Grapefruit, and Grapefruit Juice Processing Residues via Steam Explosion

Abstract

Culled whole grapefruit (WG) and grapefruit juice processing residues (GP) are currently incorporated into low-cost animal feed. If individual chemical components found within these side streams could be recovered as high-value coproducts, this would improve the overall value of the grapefruit crop. In this study, pectic hydrocolloids, sugars, volatiles, phenolics, and flavonoids were extracted from Star Ruby, Rio Red, and Ruby Red GP and WG using a continuous pilot scale steam explosion system. Up to 97% of grapefruit juice oils and peel oils could be volatilized and contained 87–94% d-limonene. The recovery of pectin, as determined by galacturonic acid content, was between 2.06 and 2.72 g 100 g−1. Of the phenolics and flavonoids analyzed in this study, narirutin and naringin were extracted in the amounts of up to 10,000 and 67,000 μg g−1, respectively.

Steam Explosion (STEX) of Citrus × Poncirus Hybrids with Exceptional Tolerance to Candidatus Liberibacter Asiaticus (CLas) as Useful Sources of Volatiles and Other Commercial Products

“…A continuous pilot-scale STEX system, described previously [ 21 ], was used to process the citrus hybrid residues. Briefly, residues were manually fed from the buckets into a hopper.…”

“…The water vapor and volatiles were allowed to cool overnight in the tank to allow the formation of an upper organic layer containing the volatiles and a lower aqueous layer of the condensed water vapors. A schematic of the continuous pilot-scale STEX system was published previously [ 21 ]. The volatiles were collected separately from the aqueous layer in a glass bottle, sealed, and placed in cold storage (4 °C).…”

“…Peel oil content was determined as described previously [ 21 ] using the Scott bromate titration method [ 28 ]. Averages of triplicate analysis and the corresponding standard deviations are reported.…”

“…Therefore, STEX was explored as a pretreatment method to extract and isolate high-value compounds within citrus residues. It was demonstrated that pectic hydrocolloids, sugars, phenolics, flavonoids, and volatiles from sweet orange and grapefruit residues could be obtained in high yields using STEX [ 18 , 20 , 21 , 22 , 23 , 24 , 25 ]. The total potential value that could be obtained from these citrus residues using STEX in a single season ranged between USD 70 and 760 million depending on the variety processed in Florida [ 20 , 21 , 22 ].…”

“…It was demonstrated that pectic hydrocolloids, sugars, phenolics, flavonoids, and volatiles from sweet orange and grapefruit residues could be obtained in high yields using STEX [ 18 , 20 , 21 , 22 , 23 , 24 , 25 ]. The total potential value that could be obtained from these citrus residues using STEX in a single season ranged between USD 70 and 760 million depending on the variety processed in Florida [ 20 , 21 , 22 ]. With the current HLB-blighted environment stymying citrus juice production, farmers can use the highly tolerant hybrids to produce a valuable chemical feedstock that serves a variety of industries.…”