Pressurized Solvent Extraction of Paulownia Bark Phenolics

Paulownia bark is mostly utilized jointly with wood, but the possibility of a separate valorization through the pressurized extraction of bark bioactives has been assessed. Subcritical water extraction and supercritical CO2 extraction are green technologies allowing shorter times than conventional solvent extraction under atmospheric shaken conditions. Subcritical water extraction was carried out at temperatures ranging from 140 to 240 °C and supercritical CO2 extraction was performed at different pressures (10, 20 and 30 MPa), temperatures (35, 45 and 55 °C) and ethanol concentrations (0, 10 and 15% (w/w)). Subcritical water extraction under a non-isothermal operation during heating up to 160 °C (19 min) provided extraction yields up to 30%, and the extracts contained up to 7% total phenolics with an ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) radical scavenging capacity equivalent to 35% the activity of Trolox, whereas at 240 °C, the yield decreased to 20%, but the phenolic content reached 21%, and the antiradical activity was equivalent to 85% of Trolox. Supercritical CO2 extraction at 30 MPa, 45 °C and 30 min reached a global yield of 2% after 180 min of extraction, but the product showed very low antiradical capacity. Gallic acid, vanillic acid, vanillin and apigenin were the major phenolic compounds found in the extracts.

The Influence of the Parameters of the Subcritical Water Extraction Process on the Efficiency of Isoflavones Elicitation from Soy Meal

Topicality. Incidental products of soy processing (okara, meal, millcake) contain a large amount of protein, and, additionally, other valuable biologically active substances. Among them, isoflavones are of particular researchers’ interest. Subcritical water extraction is a promising method for elicitation biologically active substances from plant raw material. However, such a method of extracting isoflavones, and its rational parameters for soy meal, remain insufficiently investigated. Aim and methods. The aim of this work is to study the influence of parameters (temperature: 120...160°С, duration of extraction: 5...15 min, hydromodule: 1:15...25) of the extracting process of soy meal with subcritical water on the isoflavones content in the dry material of the extract. The empirical research method is applied, using the second-order orthogonal compositional outline for a fractional factor experiment. The samples of soy meal extract are obtained using the experimental setup, based on the high-pressure reactor “RHP-2-500”. The total isoflavones content in the dry extract material is defined in terms of gallic acid with absorption spectrophotometry method. Results. Based on the obtained results, the quadratic interpolation model is constructed. This model links the total isoflavones content in the dry extract material with the extraction parameters. The analysis of the constructed model makes it possible to establish rational measures of extraction parameters. Conclusions and discussion. In this study, the intensive growth of soflavones content in the dry extract with highing the temperature process, and a relatively small influence of the process duration on this indicator, were defined. The influence of the hydromodule is ambiguous. The lowest yield of isoflavones is noted at hydromodule ≈1:21,41. Its increase or decrease lead to the growth of isoflavones content in the extract. In this paper, for the first time, the existence of rational measures of parameters in the process of extracting isoflavones with subcritical water from soy meal is studied and established. The obtained results can be used in the elaboration of the technology for producing isoflavones enriched soy protein concentrate.

Kinetics Study of Hydrothermal Degradation of PET Waste into Useful Products

Kinetics of hydrothermal degradation of colorless polyethylene terephthalate (PET) waste was studied at two temperatures (300 °C and 350 °C) and reaction times from 1 to 240 min. PET waste was decomposed in subcritical water (SubCW) by hydrolysis to terephthalic acid (TPA) and ethylene glycol (EG) as the main products. This was followed by further degradation of TPA to benzoic acid by decarboxylation and degradation of EG to acetaldehyde by a dehydration reaction. Furthermore, by-products such as isophthalic acid (IPA) and 1,4-dioxane were also detected in the reaction mixture. Taking into account these most represented products, a simplified kinetic model describing the degradation of PET has been developed, considering irreversible consecutive reactions that take place as parallel in reaction mixture. The reaction rate constants (k1-k6) for the individual reactions were calculated and it was observed that all reactions follow first-order kinetics.