Co-product Utilization: Environmental Friendly Methods for Recovery of High-Value Products from Orange Pee

Orange processing generates waste streams including peels and pulps. Orange peels can be utilized for the recovery of high-value products such as limonene, soluble sugars, and dietary fiber. However, organic or hazardous solvents are typically used for the extraction of such components. Further, no work has reported simultaneous extraction of different bioactive components aiming at complete utilization of a co-product. The aim of this study was to evaluate different environmentally friendly methods for simultaneous extraction of oil, soluble sugars, and dietary fiber from orange peels. Enzyme-assisted aqueous extraction (cellulase) and ethanol extraction (95% v/v) methods were evaluated. After extraction, oil was recovered and analyzed for limonene, liquid fraction was analyzed for sugars, and solid fraction was analyzed for soluble and insoluble dietary fiber. Further, in enzyme-assisted oil extraction, different cellulase concentrations (0, 0.4, 0.85, or 2% of dried solids) and incubation times (1, 3, 5, or 14.5 h) were tested. There was no significant difference between oil yields from cellulase treatments by 0.85% cellulase concentration in acetate buffer for 1, 3, 5, and 14.5 h from two replications, and by 2% cellulase concentration in DI water for 1,3, and 5 h from a single replication. With 2% enzyme concentration, higher limonene contents were recovered for 1h treatment compared to longer treatment times. There was no significant different between aqueous and acetate buffer solution on the oil yield from orange peels with 0.85% enzyme treatment for 1h. Highest oil yield, 12.23 +/- 3.79 % for fresh samples and 9.28 +/- 10.51% for dried powders, was achieved by 2% cellulase concentration with 1 h incubation, however, highest limonene content, 306.40 +/- 24.19 microg/ml for fresh samples and 195.97 +/- 19.22 microg/ml for dried powders, was recovered by 0.4% cellulase concentration with 1h incubation. For ethanol oil extraction, higher limonene content, 714.54 +/- 94.36 microg/ml, can be obtained from fresh samples compared to dried powders, 96.08 +/- 4.73 microg/ml. Higher limonene contain from fresh samples can be obtained by ethanol extraction, 714.54 +/- 94.36 microg/ml, compared to 0.4% enzyme extraction, 306.40 +/- 24.19 microg/ml. Lower IDF% can be observed after enzyme-assisted extraction compared to water extraction (control). Solid fractions after ethanol extraction contained higher IDF%, 56.09 +/- 8.62 % for fresh samples and 57.29 +/- 1.37 % for dried powders, compared to enzyme-assisted extraction or water extraction (control). Higher SDFP% were obtained most after 0.4% enzyme-assisted extraction in dried powders, 24.94 +/- 0.92 %, and after 95% ethanol extraction in fresh samples, 24.30 +/- 2.57 %. These results indicate that both enzyme-assisted aqueous method and ethanol extraction could be used for recovery of functional components from orange peel, simultaneous recovery of various products and oil recovery will be better observed with suitable enzyme concentration. The fermented sugars can be obtained more in the liquid fraction of dried powders than fresh peels. For enzyme assisted extraction, the higher sucrose and glucose contents, 4.07 +/- 0.79 mg/mL and 9.82 +/- 1.88 mg/mL, was observed after 2% cellulase treatment, and the highest fructose content was observed with water treatment (control), 9.22 +/- 1.60 mg/mL from powdered orange peels. The highest glucose content, 10.86 +/- 4.38 mg/mL, was achieved after 95% ethanol extraction from powdered orange peels. To conclude, 95% ethanol extraction can extract higher limonene, IDF, and SDFP, but lower fermented sugars compared to 0.4% enzyme-assisted extraction in fresh orange peels.