Pressurized hot water extraction of bioactives

Abstract

HIGHLIGHTS  Review of pressurized hot water extraction of bioactive compounds, 2009-14  Chemical and physical properties of pressurized hot liquid water  Equipment, method optimization, applications, coupling and future prospects  Challenges with degradation and other chemical reactions during extraction ABSTRACT The purpose of this review is to give the reader a thorough background to the fundamentals and applications of pressurized hot water extraction (PHWE) for the analysis of bioactive compounds. We summarize the field in the period 2009-14, and include fundamentals of water as a solvent: equipment; method optimization; applications; coupling; and, future prospects. We highlight that solvent properties of water are tunable by changing the temperature, particularly self-ionization, dielectric constant, viscosity, diffusivity, density and surface tension. Furthermore, important aspects to consider are the risk of degradation of the analytes and other potential reactions, such as hydrolysis, caramelization and Maillard reactions that may lead to erroneous results. For the extraction of bioactive compounds, we report PHWE methods based on using water of 80-175°C and short extraction times. In conclusion, PHWE provides advantages over conventional extraction methods, such as being "greener", faster and more efficient. Why another review article on pressurized hot water extraction?Pressurized hot water extraction (PHWE) is an extraction technique that uses liquid water as extractant (extraction solvent) at temperatures above the atmospheric boiling point of water (100°C/273 K, 0.1 MPa), but below the critical point of water (374°C/647 K, 22.1 MPa) (Fig. 1). The use of PHWE in analytical chemistry started with the work in environmental analysis by Hawthorne and colleagues in the mid-1990s [1,2], and can also be referred to as subcritical water extraction (SWE), superheated water extraction and pressurized liquid extraction or accelerated solvent extraction with water as a solvent. There are a few relatively recent review articles on analytical PHWE, which the reader is recommended to read [3][4][5][6][7].The aim of this review article is to give a thorough background on the fundamental properties of water -an aspect that has been virtually overlooked in most review articles written so far about analytical PHWE. Hence, the first part of this review article concerns the fundamentals of chemical/physical properties of water and how these change with the increase in temperature, as well as how these affect the extraction performance both positively and negatively in different analytical applications.The second part deals with technical solutions of PHWE and how to conduct the experiment in practice. This technical part includes discussions on using commercially available and home-built equipment. The third part includes aspects on method optimization in PHWE. The fourth part summarizes some of the key applications and related publications mainly in the field of extraction of bioactive compounds from plants, food, ...

Life cycle assessment of tannin extraction from spruce bark

“…The PHWE batch system used is similar to the system described by Plaza & Turner (2015). The setup includes a pump, an extraction vessel, a heating oven and a collection vial.…”

“…The setup includes a pump, an extraction vessel, a heating oven and a collection vial. According to Plaza & Turner (2015), the commercial PHWE system uses a multi-step process to extract chemicals from the same bark batch multiple times with fresh water. After each extraction, the extracts were collected in a vial to undergo evaporation and spray drying.…”

Phenolics in Foods: Extraction, Analysis and Measurements

“…The use of water as an extraction solvent in PLE, as so-called subcritical water extraction (SWE), is always possible, particularly when elevated temperatures are used [100]. When temperatures around 200°C are used, a change in the dielectric water properties occurs, and then, the water behaves like a normal organic solvent, increasing their extraction eiciency [101]. The main advantages of PLE often reported by several researchers are cleanness of the extracts that PLE provides in comparison with classical maceration, Soxhlet, MAE and UAE, which results in reduced background noise during the subsequent analytical quantiication, is especially important when the LC-MS analysis due to ion-suppression efects [102].…”

Establishing the Equipment-Methodical Support for Determining the Properties of Extracts of Grape Pomace Extracts Produced in the Subcreative Water Environment

“…The most effective and innovative method of extracting plant raw materials in the food and pharmaceutical industries is currently the extraction by subcritical water (SCW) [5][6][7]. SCW -water in a liquid state at a pressure of up to 21,8 in the temperature range between the usual boiling point (100 °C) and the critical temperature (374 °C).…”

“…Extraction of SCW provides more complete extraction, there is a selectivity of the process in relation to different target products and the ecological purity of the extract obtained [4][5][6]9].…”