1. Orange residues: from waste to resource
Università degli studi di Ferrara
Corso di Dottorato in Scienze Chimiche (29° Ciclo)
XVI Giornata della Chimica dell’Emilia-Romagna
Orange residues: from waste to resource
Tutor:
Prof. Simonetta Benetti
Ph.D. Candidate:
Dott. Dario Cristofaro

2. Introduction Citrus x Sinensis
Orange is a subtropical nonclimacteric fruit, rich in vitamin (A, B, C and E) and mineral (mainly calcium, phosphorus and potassium).
Citrus x Sinensis
Navel Orange
Valencia Orange
Blood Orange
(Winter Orange)
(Summer Orange)
Cyanidine 3-O-glucoside

3. Orange and Orange Juice
Production, Supply, Demand (MT)
50% Juice
50% Waste

4. Orange Waste Fruit Unloading Grading Washing Extraction
Juice Finishing
Juice Centrifugation
Evaporation
Storage
Reconstituition
Packaging
Spoiled Fruits
Peels & Seeds
Liming (CaO)
Pressing
Wastewater
Rags
Drying
Cattle Feed
Soil

5. Orange Waste (Decanter Centrifuge)
Liquid Discharge
Feed Inlet
Solid Discharge
+ H2O

6. Orange Waste (Decanter Residue)
Oven-dried
Composition:
80-85 % Water
10-15 % Cellulose, Pectin
10-5 % Flavonoids, Terpenes
Maceration

7. Solvent Extraction Solution: Flavonoids Soluble Sugars Citric Acid
Terpenes
Solid Residue:
Pectin
Cellulose
Hemicellulose
Hesperidin
Possible Solvents:
Methanol
Ethanol
Acetone
Ethyl acetate
Cyclohexane
Extraction Condition:
Solvent to peel ratio: 3/1
Temperature: 35°C
Time: 2h
Manthey, J. A., (2004). Journal of Agricultural and Food Chemistry, 52(25), 7586–7592.

8. Flavonoids
From a structural point of view, flavonoids are based upon a fifteen-carbon skeleton consisting of two benzene rings (A and B) linked via a heterocyclic pyrane ring (C).
Flavonoids include diverse compound subclasses, including:
flavanones (e.g., hesperetin and hesperidin)
flavones (e.g., tangeretin and sinensetin)
Can occur as aglycones, glycosides, and methylated derivatives
Hesperetin
(flavanone)
Hesperidin
(glycoside flavanone)
Tangeretin
(polymethoxylated flavone)

9. Flavanones HPLC (Ethanol Extract) Column Type: C18
Mobile Phase: 0.01% H3PO4 : CH3OH
Detector: DAD (λ = 330 nm)
Hesperidin
Narirutin
Eriocitrin
Manthey et al., (1996). J. Agric. Food Chem., 44 (3),

10. Hesperidin [M-H-Rha-Glu]- [M-H]- [M-H-Rhamnose]- Hesperidin 463 m/z

11. Polymethoxylated flavones (PMFs)
HPLC Ethanol Extract
Column Type: C18
Mobile Phase: 0.01% H3PO4 : CH3OH
Detector: DAD (λ = 330 nm)
Sinensetin
Nobiletin
Tangeretin
Manthey et al., (1996). J. Agric. Food Chem., 44 (3),

12. Tetramethyl-O-scutellarein (?)
Polymethoxylated flavones (PMFs)
Nobiletin
Tangeretin
Sinensetin
Heptamethoxyflavone
(?)
Tetramethyl-O-scutellarein (?)

13. Hypothetical residue recovery
Non-polar solvent
Extraction
Polar Solvent(s)
Extraction
Pectin Extraction
Decanter Residue
Terpenes
Flavonoids and Hemicellulose
Hesperidin
Hemicellulose
Centrifuge
Flavonoids
Polymethoxylated Flavones
Flavanones

14. Pectin Extraction Sample Extraction Precipitation Purification Ethanol
Batch/Soxhlet Extraction Condition:
Solvent: Water
pH: 1,2-2.5 (hydrochloric acid, nitric acid, citric acid)
Temperature: °C
Time: 2-4 Hours
Solvent to peel ratio: 30:1 (w/w)
Yield (15-20% w/w on dry peel basis)

15. Pectin Extraction Sample Extraction Precipitation Purification
Batch/Soxhlet Extraction Condition:
Solvent: Water
pH: 1,2-2.5 (hydrochloric acid, nitric acid, citric acid)
Temperature: °C
Time: 2-4 Hours
Solvent to peel ratio: 30:1 (w/w)
Yield (15-20% w/w on dry peel basis)
Microwave Extraction Condition:
Dynamic Mode 1800 W
Solvent: Water
Temperature: 120°C
Time: 5-10 minutes
Solvent to peel ratio: 10:1 (w/w)
Yield (10% w/w on dry peel basis)
Pfaltzgraff, L. a, De bruyn, M., Cooper, E. C., Budarin, V. & Clark, J. H. (2013). Green Chem. 15, 307–314 (2013).

16. Hypothetical residue recovery
Cellulose Extraction
Non-polar solvent
Extraction
Polar Solvent(s)
Extraction
Pectin Extraction
Decanter Residue
Terpenes
Flavonoids and Hemicellulose
Hesperidin
Hemicellulose
Centrifuge
Flavonoids
Polymethoxylated Flavones
Flavanones

17. Cellulose Extraction Matrix composition: Extraction condition:
Hemicelluloses
Hesperidin (traces)
Extraction condition:
Solvent: NaOH 17,5%
Temperature: 25-30°C
Time: 2 hours
Water to cellulose ratio: 10:1
Hemicelluloses
Hesperetin

18. Cellulose Acetate Synthesis
Pretreatment
Acetylation
Hydrolysis
Precipitation
Pretreatment
Conditions:
Solvent: Acetic acid
Catalyst: H2SO4 (5%)
Time: 1 hour
Temperature: 25°C -> 0°C
Acetylation
Conditions:
Solvent: Acetic acid
Catalyst: H2SO4 (5%)
Reagent: Acetic Anhydride
Time: 1-2 hours
Temperature: 60-70°C
Hydrolysis
Conditions:
Solvent: Acetic acid
Catalyst: H2SO4 (5%)
Reagent: Acetic acid (70%)
Time: 6-12 hours
Temperature: 50-60°C
Precipitation
Conditions:
Solvent: H2O/MeOH
Temperature: 0°C

19. Cellulose Acetate Synthesis

20. Hypothetical residue recovery
Decanter Residue
Non-polar solvent
Extraction
Polar Solvent(s)
Pectin Extraction
Cellulose Extraction
Pectin
Hypothetical residue recovery
Terpenes
Flavonoids and Hemicellulose
Hemicellulose
α-cellulose
Hesperidin
Hemicellulose
Centrifuge
Flavonoids
Theoretically, from 1 kg of decanter residue:
850 g Water
20 g Terpenes
20 g Flavonoids (18 g flavanones; 2 g flavones)
55 g Pectin
55 g Cellulose (20 g α-cellulose; 35 g hemicellulose)
Polymethoxylated Flavones
Flavanones

21. Thank you for your attention!
Any Questions?
Thanks to the Organizing Committee (Maurizio Remelli, Barbara Cacciari, Paola Oliva, Elena Sarti, Valentina Albanese, Marco Visentin).
Special thanks go to Dr. Tatiana Bernardi (Department of Chemical and Pharmaceutical Sciences, University of Ferrara) for the analytical support.