Chestnut peels are a poorly characterized, underexploited by-product of the agri-food industry. This raw material is rich in bioactive compounds, primarily polyphenols and tannins, that can be extracted using different green technologies. Scaling up the process for industrial production is a fundamental step for the valorization of the extract. In this study, subcritical water extraction was investigated to maximize the extraction yield and polyphenol content. Lab-scale procedures have been scaled up to the semi-industrial level as well as the downstream processes, namely, concentration and spray drying. The extract antioxidant capacity was tested using in vitro and cellular assays as well as a preliminary evaluation of its antiadipogenic activity. The temperature, extraction time, and water/solid ratio were optimized, and the extract obtained under these conditions displayed a strong antioxidant capacity both in in vitro and cellular tests. Encouraging data on the adipocyte model showed the influence of chestnut extracts on adipocyte maturation and the consequent potential antiadipogenic activity. Chestnut peel extracts characterized by strong antioxidant power and potential antiadipogenic activity were efficiently obtained by removing organic solvents. These results prompted further studies on fraction enrichment by ultra- and nanofiltration. The semi-industrial eco-friendly extraction process and downstream benefits reported here may open the door to production and commercialization.

Since the beginning of this century, the world has experienced a growing need for enabling techniques and more environmentally friendly protocols that can facilitate more rational industrial production. Scientists are faced with the major challenges of global warming and safeguarding water and food quality. Organic solvents are still widely used and seem to be hard to replace, despite their enormous environmental and toxicological impact. The development of water-based strategies for the extraction of primary and secondary metabolites from plants on a laboratory scale is well documented, with several intensified processes being able to maximize the extraction power of water. Technologies, such as ultrasound, hydrodynamic cavitation, microwaves and pressurized reactors that achieve subcritical water conditions can dramatically increase extraction rates and yields. In addition, significant synergistic effects have been observed when using combined techniques. Due to the limited penetration depth of microwaves and ultrasonic waves, scaling up entails changes to reactor design. Nevertheless, the rich academic literature from laboratory-scale investigations may contribute to the engineering work involved in maximizing mass/energy transfer. In this article, we provide an overview of current and innovative techniques for solid-liquid extraction in water for industrial applications, where continuous and semi-continuous processes can meet the high demands for productivity, profitability and quality.

Interest in essential oils has consistently increased in recent years. Essential oils have a large variety of applications in multiple fields, including in the food, cosmetics and pharmaceutical industries. The volatile fraction (VF) in hops (Humulus lupulus L.) fits within this domain as it is primarily used in the brewery industry for the aromatization of beer, and is responsible for the floral and fruity tones. This work aims to design an optimized extraction protocol of the VF from hops, using microwaves. Microwave-assisted hydrodistillation (MAHD) has been developed to reduce energy and time consumption in lab-scale reactors up to industrial-scale systems. Hops are principally available in three forms, according to a brewery’s applications: (i) fresh (FH); (ii) dried (DH) and (iii) pelletized (PH). In this work, all three forms have therefore been studied and the recovered volatiles characterized by means of GC-MS. The optimized lab-scale MAHD protocol gave the best extraction yield of 20.5 mL_VF/kg_{dry matrix} for FH. This value underwent a slight contraction when working at the highest matrix amount (3 kg), with 17.3 mL_VF/kg_{dry matrix} being achieved. Further tests were then performed in a pilot reactor that is able to process 30 kg of material. In this case, high yield increases were observed for PH and DH; quadruple and double the lab-scale yields, respectively. In addition, this industrial-scale system also provided marked energy savings, practically halving the absorbed kJ/mL_VF.

Pomegranate (Punica granatum L.) is well known for its high content of bioactives, including polyphenols, flavonoids, and tannins, which have been shown to exhibit a wide range of biological activities, such as antioxidant, antimicrobial, and anticancer effects. It is worth noting that the majority of these molecules are found in the peels, which are usually disposed of after processing, causing a significant amount of waste, amounting to more than 3.6 million t/y. This work investigates microwave-assisted extraction (MAE) in water for the recovery of antioxidants from pomegranate peels (PP), including the optimisation of temperature and extraction times. The total phenolic, anthocyanin, flavonoid, and tannin contents of the recovered extracts were determined, as well as their antioxidant activities, which were found to be 356.35 mgGAE/gExtr, 303.97 µgCy3G/gExtr, 37.28 mgQE/gExtr, 56.48 mgGAE/gExtr, and 5.72 mmolTE/gExtr, respectively (according to the adopted reference). All results were compared with those obtained using a conventional protocol. In addition, the potential for water recycling by means of downstream nanofiltration in optimised MAE was investigated, leading to overall water reuse of approx. 75%. Power consumption (20.92 W/mgGAE) and common green metrics, Reaction Mass Efficiency (RME), E-Factor, and the Process Mass Intensiti/efficiency (PMI, PME), were considered in evaluating the proposed PP valorisation strategy. Finally, the biological activities of the main products were assessed. The antimicrobial properties of the PP extracts against three Gram-positive and three Gram-negative bacteria and their antiproliferative activity towards human cancer cells were tested. S. aureus bacteria was the most susceptible to the PP extracts. All tested products displayed antiproliferative activity against HeLa cells when higher concentrations were tested, with D-PP/NF (obtained from dried PP and sequential nanofiltration) being the most effective. This result was also confirmed via clonogenic analysis, which generally indicated the possible anti-cancer activity of pomegranate peel extracts obtained using this green approach.

This work presents the extrusion-based preparation of new biocomposites from two plant fibres (namely Cannabis sativa L. and Opuntia ficus-indica Mill.) that are added to two different polymers (an ethylene–octene elastomer and polylactic acid), which act as matrices. Structural and morphological characterization (using X-ray diffraction and field emission scanning electron microscopy) have been used to correlate the interactions between the biomass and the polymers employed with the efficiency of the proposed approach. It was found that Opuntia-based composites can be easily formed in a range of biomass/polymer ratios. However, the interaction between hemp and the matrix means that only specific ratios can form tightly bound composites. The present communication thus paves the way for more complex and comprehensive studies on the formulation of biocomposites containing these matrices.

Pomegranate (Punica granatum L.) is well known for its high content in bioactives including polyphenols, flavonoids and tannins, which have been shown to exhibit a wide range of biological activity such as antioxidant, antimicrobial and anticancer effects. It is worth noting that the majority of these molecules are found in the peels (PP), which are usually disposed of after processing, causing a significant amount of waste, amounting to more than 3.6 million t/y. This work investigates MW-assisted extraction (MAE) in water for the recovery of antioxidants from PP, including the optimization of temperature and extraction times. The total phenolics, anthocyanin, flavonoid and tannin contents of the recovered extracts have been determined, as have their antioxidant activities, which were found to be 356.35 mgGAE/gextr., 303.97 µgCy3G/gextr., 37.28 mgQE/gextr., 56.48 mgGAE/gextr. and 1.43 µmolTE/gextr., respectively (according to the adopted reference). All results have been compared with those obtained using a conventional protocol. In addition, the potential for water recycling by means of nanofiltration downstream in optimized MAE has been investigated, leading to overall water reuse of approx. 75%. Energy consumption (20.92W/mgGAE) and the common green metrics, RME, E-Factor and PMI (PME), have been considered in evaluating the proposed PP valorization strategy. Finally, the biological activity of the main products has been assessed. The antimicrobial properties of the PP extracts against three Gram-positive and three Gram-negative bacteria, and their antiproliferative activity towards human cancer cells have been tested. The S. aureus bacteria was the most susceptible to the PP extracts. All tested products displayed antiproliferative activity in HeLa cells when higher concentrations were tested, with D-PP/NF being the most effective. This result was also confirmed in a clonogenic analysis, which generally indicated the possible anti-cancer activity of pomegranate peel extracts obtained using this green approach.