Search

Long a thermodynamic curiosity, supercritical fluids (SCFs) have gradually gained ground in today's life, generating an increasing number of new, efficient processes in diverse industrial sectors and fueling active R&D programs. Indeed, the versatility of SCFs allows them to serve a wide variety of applications. The list includes not only food processing, biofuel production, extraction of biomolecules marketable as medicines, cosmetics and nutraceuticals, but also emerging technologies for the production of electrical power, based on supercritical or transcritical thermodynamic cycles. This jointly authored article will provide a review of important applications covered by our laboratories in the agri-food, chemical and energy sectors. We will then try to detect recent trends and outline future prospects. [ABSTRACT FROM AUTHOR]

Rambutan seeds are by-products generated from fruit-processing factories; the leftover seeds are buried in landfills, generating methane emissions. This work aimed to extract polysaccharides (POLS) from rambutan seeds by using subcritical water extraction (SWE). The effects of defatting pretreatment and operating parameters in SWE were investigated using a Box–Behnken design. The results show that defatting pretreatment significantly enriched the POLS yield, while it had no significant effect on the total sugar content. Using the desirability approach, the suitable feedstock for SWE was defatted rambutan seeds. The maximum desirability of 0.86 was found at a temperature range of 145–150 °C, an extraction time of 15 min, and a liquid–solid ratio of 10:1. The POLS yield and total sugar content were in the range of 52.33–55.63 g/100 g feedstock and 83.37–87.45 g/100 g POLS, respectively. The extracted POLS had an equivalent molecular weight of 413.70 kDa that could be used as an extender in plant-based products. In conclusion, the defatting pretreatment of rambutan seeds not only improved the POLS yield obtained via SWE but also generated additional lipids that could be utilized as an unconventional source of specialty fat. [ABSTRACT FROM AUTHOR]

Rambutan seeds (RS) are industrial waste often generated in the canned fruit industry. The aim of this study was to extract polysaccharides from defatted rambutan seeds or crude polysaccharides (POLS-DRSs) with subcritical water. Defatted seed powder (DRS) was extracted by hot-water extraction (HWE) at 100 °C as a reference condition. Subcritical water extraction (SWE) was performed at 120–140 °C and an initial pressure of 2 MPa. A sample-to-water ratio of 1:10 (w/w) and an extraction time of 15–60 min were used for both methods. The results show that gravimetric extraction yields of 53.01 g/100 g DRS and 7.71–41.70 g/100 g DRS were obtained from HWE and SWE, respectively. Additionally, HWE provided a total sugar content of 30.75 g/100 g POLS-DRSs, while SWE generated a total sugar content in the range of 27.00–49.76 g/100 POLS-DRSs. The antioxidant activities of POLS-DRSs were measured with a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. An amount of 40 mg of POLS-DRSs obtained at 120 °C after 60 min provided the highest DPPH activity of 82.93% inhibition. The POLS-DRSs were suitable for growing microorganisms because they had a high sugar content and a low total phenolic content. A prebiotic activity assay will be carried out in future studies. [ABSTRACT FROM AUTHOR]

Spent coffee grounds (SCGs) are currently considered abandoned landfill waste despite retaining valuable organic compounds, especially with a high protein content of 16.64 ± 0.13 g/g dried SCGs and a high oil content of 15.48 ± 0.17 g/g dried SCGs. As a result, SCGs could serve as a potential source of valuable ingredients. However, utilizing a single technical strategy of alternative green extractions was insufficient for extracting the target compounds and hydrolyzing proteins. This work aimed to optimize the operating parameters of enzyme-assisted extraction (EAE), microwave-assisted extraction (MAE), and subcritical water extraction (SWE) using a response surface methodology. The results showed that EAE, at a papain-to-substrate ratio (E/S) of 0.5 and a duration of 15 min, generated a %DH of 93.39% and provided a water soluble protein concentration (WSPC) in the range of 400 to 800 µg/mL. Moreover, MAE provided a maximum %DH of 9.72% at 600 watts and 10 min, while SWE produced a maximum %DH of 13.41% at 160 °C in 17.5 min. However, the WSPCs of MAE and SWE extracts were comparable at ~250 µg/mL. The combination MAE−SWE enhanced the %DH of hydrolysates by more than the combined SWE−MAE, SWE, and MAE. However, the effects of differential hydrolysis on bioactivity are not directly correlated with %DH. In this study, the highest antioxidant activity was found at an E/S of 0.5 and in 15 min for EAE, at 350 W and in 10 min for MAE, and at 160 °C and in 30 min for SWE. This work demonstrated that the valorization of SCGs not only reduces the amount of waste but also yields functional cosmeceutical and nutraceutical ingredients. [ABSTRACT FROM AUTHOR]

For the on-site treatment of laboratory waste, we have been developing a compact-sized reaction system for the treatment of laboratory wastewater using supercritical water oxidation (SCWO) technology. Pharmaceutical laboratory wastewater is one of the most difficult wastewaters to treat because of its high concentration of halogenated organic compounds. We proposed a new cascade process in which two reactors are consecutively combined, carrying out hydrolysis in the first reactor followed by SCWO in the second reactor, for the complete removal of halogenated organic compounds. Dichloromethane was chosen as a representative model of chlorinated compounds. There have been many previous studies on the hydrolysis of dichloromethane, which results in the coproduction of formaldehyde and HCl. However, there has been less investigation on the kinetics of formaldehyde oxidation in supercritical water. In this study, we focus on the oxidation of formaldehyde in supercritical water with and without a catalyst. As a result, formaldehyde can be completely decomposed at 400 degrees C and 25 MPa within a very short contact time in a heterogeneous system with a MnO(2) catalyst.