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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]

Defective green coffee beans are typically discarded due to their negative impacts on coffee qualities compared to normal beans. However, there are some types of defective beans that can cause volatile aroma compounds after roasting similar to those produced by normal beans. This study aimed to optimize conditions for coffee oil extraction by supercritical carbon dioxide using the response surface methodology (RSM). Furthermore, the investigation assessed the aroma-active compounds and sensory quality in extracted coffee oil. Thus, operational temperatures (33.2–66.8 °C), pressure (10–30 MPa) and ethanol (g) to roasted coffee (g) ratio (0.25:1–1.5:1) were optimized for coffee oil extraction. As a result, different oil yields with different key volatile aroma compounds concentrations were obtained and it was found that the optimum conditions for extraction were a temperature of 50 °C, pressure of 30 MPa, and ethanol (g) to roasted coffee (g) ratio of 1:1 to obtain 6.50% (w/w) coffee oil yield. Key volatile aroma compounds, including furfuryl alcohol, 5-methyl furfural, 2,5-dimethylpyrazine, 4-vinylguaiacol, furfuryl acetate, 3-ethyl-2,5-dimethylpyrazine, thiazole, 1-furfurylpyrrole, pyridine, 2,3-butanediol, and 3-methyl-1,2-cyclopentanedione which contributed to the most preferable burnt, sweet, bready, chocolate-like, and roasted flavors, were quantified. Overall, the results suggested that coffee oil extracted from defective beans could be potentially used as a flavoring agent. [ABSTRACT FROM AUTHOR]

A large energy input for preheating and recovering of high excess alcohols used are the main issue in the supercritical methanol (SCM) process. This work demonstrated the production of biofuel from used palm olein oil in SCM using a low methanol to oil molar ratio. The effects of the operating temperature (350-400 °C), methanol to oil molar ratio (9:1-12:1), and reaction time (2-10 min), and their reciprocal interactions were evaluated using a central composite design. The optimum process conditions were determined to be a temperature of 395 °C, methanol to oil molar ratio of 12:1, and reaction time of approximately 9 min through the use of response surface methodology. The modified quadratic regression model demonstrated that the triglyceride conversion (%XTG) and methyl ester content (%FAME) were sensitive to changes in the operating temperature and reaction time, while the effect of the methanol to oil molar ratio was minimal. Under the optimal operating conditions, the predicted values of %XTG and %FAME were 100% and 63.67%, respectively, which were in good agreement with the experimental values. The fuel properties of biofuel obtained from optimal conditions were examined and then compared to American and European standards for biodiesel. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The extraction of protein and sugar from rice bran and de-oiled rice bran using subcritical water was evaluated in a 30-ml semi-continuous reactor. The effects of the three main factors, operating temperature, time and pressure, on the total sugar and protein yields obtained were investigated using analysis of variance and response surface methodology. A central composite design was performed in order to determine the most likely optimum conditions for the extraction process for both substrates individually and together. The developed models had a very high regression coefficient (R2) value (0.94 - 0.98), and demonstrated that the three main factors investigated had a significant effect on the sugar yield, whilst only time and its interaction with temperature were significant factors controlling the extracted protein yield. Based on the response surface and contour plots, the optimum conditions were evaluated for maximal extracted sugar and protein yields, which reached 100% for protein, from the two materials. [ABSTRACT FROM AUTHOR]

Abstract: Extraction of Mae Moh lignite using toluene–tetralin mixture was performed in a batch reactor at a temperature range from 370 to 490°C and under initial hydrogen pressure up to 12MPa. Experiments were carried out to investigate the effects of temperature and initial hydrogen pressure on coal conversion, liquid yield and liquid composition. The effect of catalysts Fe2S3, Fe/Ni and Ni/Mo impregnated into activated carbon was also studied. In the absence of a catalyst, the oil yield decreased with temperature above 410°C and the content of naphtha and kerosene increased while light gas oil and gas oil decreased with increasing temperature. The presence of catalyst would benefit the formation of lighter components, kerosene and light gas oil. Extraction in the presence of Ni/Mo catalyst, the liquid yield reached 64.6wt% (daf) which included naphtha 2%, kerosene 72.8%, light gas oil 14.9%, gas oil 2.4% and long residue 7.9%. For GC–MS analysis, the fraction of kerosene was composed of tetralin, naphthalene, dodecamethyl-cycloheptasiloxane, methyl dodecanoate, tetradecamethyl-cycloheptasiloxane, ethyl dodecanoate, methyl tetradecanoate and dibutyl phthalate. [Copyright &y& Elsevier]

Desulfurization of Mae Moh coal with supercritical ethanol/potassium hydroxide in a semicontinuous reactor was studied. A two-level factorial experimental design was applied to study the main effects on sulfur reduction. The variables investigated in this work were temperature, pressure, time and potassium hydroxide concentration. The measured responses in the experimental design were coal yield, sulfur reduction and ash reduction. The analysis of the results from the design showed that two variables, temperature and KOH concentration, can be considered to have a significant effect on the pyritic sulfur and total sulfur reduction. [Copyright &y& Elsevier]

The techno-economic analysis of biodiesel production with supercritical methanol (SCM) at a low methanol: oil molar ratio (L-SCM) of 12:1, as well as with a homogeneous alkali-catalyzed process (Alkali-cat) and conventional SCM (C-SCM) with a methanol: oil molar ratio of 42:1 was investigated. The process simulation was performed using the Aspen plus ® software based on the plant biodiesel production capacity of 40,000 tonnes/y. Even though the L-SCM had a higher total capital investment than the Alkali-cat process ($7.19 million versus $4.91 million), it was economically viable. The L-SCM process provided a lower manufacturing cost of $37.28 million and the highest net present value (NPV) of $45.48 million. However, the C-SCM process was not financially profitable because of the large amount of methanol employed in the recycling loop. Sensitivity analysis of all the processes was investigated based on variations in the feedstock and products selling price and revealed that the biodiesel selling price and palm oil price were the major effects on the sensitivity of the NPV. [ABSTRACT FROM AUTHOR]

Abstract: A scale-up plug flow reactor was evaluated for the continuous production of biodiesel from refined palm kernel oil (PKO) with supercritical methanol and optimized by response surface methodology. The effects of the operating temperature (270–350°C), pressure (15.0–20.0MPa) and methanol:PKO molar ratio (20:1–42:1) were evaluated at a constant residence time of 20±2min by using a central composite design. Analysis of variance demonstrated that a modified quadratic regression model gave the best coefficient of determination (R2 =0.9615) and adjusted coefficient of determination (Adj. R2 =0.9273). The interaction terms in the regression model illustrated small synergistic effects of both temperature–pressure and temperature–methanol:PKO molar ratio. The optimal conditions were 325±5°C, 18.0±0.5MPa and a methanol:PKO molar ratio of 42±2:1, attaining a maximum production rate of 18.0±1.5g biodiesel/min with a fatty acid methyl ester content of 93.7±2.1%. The product obtained from the optimal conditions had high cetane number, and could be considered as a fuel additive for cetane number enhancement. [Copyright &y& Elsevier]