Comparison of the static, dynamic and static-dynamic pressurised liquid extraction modes for the removal of nitrated polycyclic aromatic hydrocarbons from soil with on-line filtration-preconcentration

High-Pressure Technologies for the Recovery of Bioactive Molecules from Agro-Industrial Waste

Large amounts of food waste are produced each year. These residues require appropriate management to reduce their environmental impact and, at the same time, economic loss. However, this waste is still rich in compounds (e.g., colorants, antioxidants, polyphenols, fatty acids, vitamins, and proteins) that can find potential applications in food, pharmaceutical, and cosmetic industries. Conventional extraction techniques suffer some drawbacks when applied to the exploitation of food residues, including large amounts of polluting solvents, increased time of extraction, possible degradation of the active molecules during extraction, low yields, and reduced extraction selectivity. For these reasons, advanced extraction techniques have emerged in order to obtain efficient residue exploitation using more sustainable processes. In particular, performing extraction under high-pressure conditions, such as supercritical fluids and pressurized liquid extraction, offers several advantages for the extraction of bioactive molecules. These include the reduced use of toxic solvents, reduced extraction time, high selectivity, and the possibility of being applied in combination in a cascade of progressive extractions. In this review, an overview of high-pressure extraction techniques related to the recovery of high added value compounds from waste generated in food industries is presented and a critical discussion of the advantages and disadvantages of each process is reported. Furthermore, the possibility of combined multi-stage extractions, as well as economic and environmental aspects, are discussed in order to provide a complete overview of the topic.

Applicability of Superheated Water Extraction for the Quantification of Pesticide Residues in Leafy Vegetables

Superheated water extraction (SWE) of pesticide residues in a cabbage sample was demonstrated. The recovery yields of several relatively polar pesticides (log P_ow < 3) by the spike-and-recovery method at 100°C were acceptable. Increasing the extraction temperature up to 150°C led to enhanced extraction efficiency except for pesticides that induced degradation. The recovery yields of some target pesticides having log P_ow values of 3.5 - 4 were effectively enhanced by increasing the number of extraction cycles. The observed concentration of fenitrothion in a cabbage sample was comparable with those by the official Japanese analytical method. These results suggested SWE is potentially suitable for the extraction of different relatively high-to-medium polarity pesticides.

Characteristics of Subcritical Water Extraction and Kinetics of Pentacyclic Triterpenoids from Dry Loquat (Eriobotrya japonica) Leaves

In this study, pentacyclic triterpenoids (PTTs) were extracted from loquat leaves by subcritical water extraction (SWE) technique in a dynamic mode. The results revealed that PTTs yield increased up to 5.38±0.12 mg/g with the increasing temperature at 180 °C for corosolic acid (CA) and up to 7.20±0.11 mg/g at 200 °C for ursolic acid (UA) within experimental times. The optimum flow rates to obtain concentrated CA and UA extracts were found to be 33.33 and 41.67 mL/min, respectively. Furthermore, extraction temperatures strongly influenced the extraction rate as demonstrated by the rate constant of each temperature tested. Moreover, the kinetic rate constant decreased as the function of temperature indicating the yield of both CA and UA were significantly influenced by subcritical temperatures and extraction times.