Analytical Characterization of Water-Soluble Constituents in Olive-Derived By-Products

Abstract

Olive trees constitute one of the largest agroindustries in the Mediterranean area, and their cultivation generates a diverse pool of biomass by-products such as olive tree pruning (OTP), olive leaves (OL), olive stone (OS), and extracted olive pomace (EOP). These lignocellulosic materials have varying compositions and potential utilization strategies within a biorefinery context. The aim of this work was to carry out an integral analysis of the aqueous extractives fraction of these biomasses. Several analytical methods were applied in order to fully characterize this fraction to varying extents: a mass closure of >80% was reached for EOP, >76% for OTP, >65% for OS, and >52% for OL. Among the compounds detected, xylooligosaccharides, mannitol, 3,4-dihydroxyphenylglycol, and hydroxytyrosol were noted as potential enhancers of the valorization of said by-products. The extraction of these compounds is expected to be more favorable for OTP, OL, and EOP, given their high extractives content, and is compatible with other utilization strategies such as the bioconversion of the lignocellulosic fraction into biofuels and bioproducts.

Optimization of Microwave-Assisted Water Extraction to Obtain High Value-Added Compounds from Exhausted Olive Pomace in a Biorefinery Context

“…Regarding mannitol, the amount extracted from EOP by MAWE under optimized conditions, 46.7 mg/g EOP ( Table 3 ), was higher than that obtained with water as a solvent using a Soxhlet extractor overnight (40 mg/g EOP) [ 11 ] and in a bath at 85 °C for 90 min (45 mg/g EOP) [ 7 ] or at 100 °C for 30 min (39 mg/g EOP) [ 25 ]. In addition, it is worth noting that these amounts of mannitol extracted from EOP are in the range of the values obtained from olive leaves, which are considered a rich source of mannitol [ 19 ].…”

“…Previous studies have shown that it is easier to extract the proteinaceous material from EOP than from olive leaves or olive tree pruning using hot water [ 11 ]. This can explain the partial solubilization of the EOP protein observed in this work.…”

“…Furthermore, the SEM-EDX spectra showed that carbon, potassium, and calcium are major components ( Figure 3 (a1,b1), second panel), and these elements were distributed throughout the biomass before and after MAWE ( Figure 3 (a2–a4,b2–b4), second panel). Potassium is one of the major mineral components in the olive-derived biomasses [ 11 ]. Some studies suggest that the presence of potassium can limit the application of pomace as a biofuel for heating because it causes foiling in the boilers [ 33 ].…”

“…Furthermore, recent studies suggest that EOP is not only a cheap source of hydroxytyrosol but also presents mannitol and triterpenic acids [ 8 , 9 , 10 ]. Particularly, mannitol is an authorized sweetener (E421) widely used because of its low calorie content and it is the active ingredient of some drugs and cosmetics [ 11 ]. Besides being used as an osmotic diuretic, mannitol also has the clinical potential for treating diseases such as Parkinson’s disease, cystic fibrosis, migraines, etc.…”

Valorization of Olive By-Products: Innovative Strategies for Their Production, Treatment and Characterization

“…For example, one of the papers of this SI [21] reports on the analytical characterization of four diverse pools of biomass by-products such as OTP, OL, OS and extracted olive pomace (EOP) to highlight their potential recovery of the water-extractable fraction within a biorefinery context. The final aim was to assess the occurrence of high-value-added compounds as carbohydrates, proteins, alditols and to ascertain a comparison between the four different olive biomasses of their structural composition and quantity in the water extractives.…”