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 peel from commercially juice-extracted oranges was used to convert peel pectin into pectic oligosaccharides (POSs). Surprisingly uniform populations, based on the polydispersity index (PDI; weight-average molecular weight (M_w)/number-average molecular weight (M_n)) of POSs, were obtained from the Hamlin and Valencia varieties of Citrus sinensis. The POSs from Hamlin and Valencia peel had PDI values of (1.23 ± 0.01, 1.24 ± 0.1), respectively. The M_w values for these samples were 14.9 ± 0.2 kDa for Hamlin, and 14.5 ± 0.1 kDa for Valencia, respectively. The degree of methyl-esterification (DM) was 69.64 ± 3.18 for Hamlin and 65.51 ± 1.61 for Valencia. The composition of the recovered POSs was dominated by galacturonic acid, ranging from 89.1% to 99.6% of the major pectic sugars. Only the Hamlin sample had a meaningful amount of rhamnose present, indicating the presence of an RG I domain. Even so, the Hamlin sample’s degree of branching (DBr) was very low (2.95).