Review of ultrasound combinations with hybrid and innovative techniques for extraction and processing of food and natural products.

Ultrasound has a significant effect on the rate of various processes in food, perfume, cosmetic, pharmaceutical, bio-fuel, materials, or fine chemical industries, despite some shortcomings. Combination with other conventional or innovative techniques can overcome these limitations, enhance energy, momentum and mass transfer, and has been successfully demonstrated in many recent studies. Various ultrasound combined hybrid and innovative techniques are systematically summarized in this review for the first time. Ultrasound can be combined with diverse conventional techniques including Soxhlet, Clevenger, enzyme, hydrotropes, ionic liquids, Deep Eutectic Solvents (DES) or Natural Deep Eutectic Solvents (NADES), to enhance mixing and micro-mixing, reduced thermal and concentration gradients, and selective extraction. Moreover, combinations of ultrasound with other innovative techniques such as microwave, extrusion, supercritical fluid, subcritical and pressure liquids, Instant controlled pressure drop (DIC), Pulsed Electric Field (PEF), Ultra-Violet (UV) or Infra-Red (IR) radiations, Counter-current chromatography (CCC), or centrifugal partition chromatographs (CPC) can enable reduced equipment size, faster response to process control, faster start-up, increased production, and elimination of process steps. The theories and applications of these ultrasound combined hybrid and innovative techniques as well as their advantages and limitations are compared, and further perspectives are proposed. This review provides new insights into advances in ultrasound combined techniques and their application at research, educational, and industrial level in modern food and plant-based chemistry.

Solubility study and intensification of extraction of phenolic and anthocyanin compounds from Oryza sativa L. 'Violet Nori'.

Oryza sativa L. 'Violet Nori' is an Italian cultivar of spontaneous growing aromatic purple rice which is particularly rich in polyphenolic compounds, especially anthocyanins, conferring it an excellent antioxidant capacity. The present study aimed at increasing the extraction yields of its antioxidant compounds with green strategies and it is divided into two steps. The first step concerned a solubility study of the targeted polyphenols in different ethanol:water mixtures by means of a theoretical prediction method, using the simulation program COSMO-RS, and the subsequently confirmation of the computational results by practical experiments. Once the best extraction mixture was identified, the second step of the work was performed, with the purpose of intensifying the extraction yield. Therefore, various innovative green extraction techniques, including ultrasound, using both the probe system and the ultrasonic bath, bead milling, microwave and accelerated solvent extractions were tested and compared to conventional maceration. Results, expressed in terms of total phenolic and total monomeric anthocyanin contents, showed that the best extracting solvent for 'Violet Nori' rice was the mixture ethanol:water (60:40 v/v), being COSMO-RS computational predictions in good correlation with the experimental results. Moreover, the most efficient techniques to extract the antioxidant compounds resulted to be both ultrasound-assisted extraction probe and bead milling, that in only 5 min got the same extractive efficiency obtained after 3 h of conventional maceration.

Application of ultrasound for green extraction of proteins from spirulina. Mechanism, optimization, modeling, and industrial prospects.

A green and innovative method, manothermosonication (MTS), for proteins extraction from dry Arthrospira platensis cyanobacteria assisted by ultrasound was designed in this work. Manothermosonication (probe, 20 kHz) was compared to a conventional process performed in the same conditions without ultrasounds. The extraction was carried out with a continuous flow rate at 15 mL/hour. Extraction parameters were optimized using a central composite design. Moreover, mathematic modelling and microscopic investigations were realized to allow a better understanding of ultrasound physical and structural effects on spirulina filaments and mass transfer phenomena over time. Crude extract and sections stained with toluidine blue were analyzed with optical and scanning electron microscopies. According to experimental results, MTS promoted mass transfer (high effective diffusivity, De) and enabled to get 229% more proteins (28.42 ±â€¯1.15 g/100 g DW) than conventional process without ultrasound (8.63 ±â€¯1.15 g/100 g DW). With 28.42 g of proteins per 100 g of dry spirulina biomass in the extract, a protein recovery rate of 50% was achieved in 6 effective minutes with a continuous MTS process. Microscopic observations showed that acoustic cavitation impacted spirulina filaments by different mechanisms such as fragmentation, sonoporation, detexturation. These various phenomena make extraction, release and solubilization of spirulina bioactive compounds easier.

Microscopic imaging as a tool to target spatial and temporal extraction of bioactive compounds through ultrasound intensification.

Unravelling a chain of events in ultrasound-assisted extraction (UAE) of bioactive compounds from plants has to start with a detailed description of destructuration at macroscopic and microscopic scale. The present work aims to study the impacts and interactions of UAE on the extreme complexity and diversity of plants structures. Three plant species were selected for their difference in specialized structures and their spatial distribution of secondary metabolites: bitter orange leaf (C. aurantium L.), blackcurrant leaf (R. nigrum L.), and artichoke leaf (C. scolymus L.). Different microscopic techniques (Cyto-histochemistry, stereomicroscopic analysis, Scanning Electron Microscopy (SEM)) have been used to understand the complexity of plant structures and to highlight ultrasound-induced impacts especially on metabolites storage structures, with a neat comparison with conventional "silent" extraction procedure. The main results indicate that spatial UAE impacts are strongly related to plant structures' properties (morphology, thickness, etc.) and particularly to the nature and the chemical constitution of their storage specialized structures. From a temporal point of view, for all studied leaves, observed mechanisms followed a special order according to structures and their mechanical resistance level to ultrasound (US) treatment. Microscopic mapping of metabolites and structures should be considered as a decision tool during UAE to target intensification process.

Histo-cytochemistry and scanning electron microscopy for studying spatial and temporal extraction of metabolites induced by ultrasound. Towards chain detexturation mechanism.

There are more than 1300 articles in scientific literature dealing with positive impacts of Ultrasound-Assisted Extraction (UAE) such as reduction of extraction time, diminution of solvent and energy used, enhancement in yield and even selectivity, intensification of diffusion, and eliminating wastes. This present study aims to understand what are the mechanism(s) behind these positive impacts which will help to design a decision tool for UAE of natural products. Different microscopic observations (Scanning Electron Microscopy (SEM), Environmental Scanning Electron Microscopy (e-SEM), Cyto-histochemistry) have been used for spacial and temporal localization of metabolites in rosemary leaves, which is one of the most studied and most important plant for its antioxidant metabolites used in food industry, during conventional and ultrasound extraction. The study permits to highlight that ultrasound impacted rosemary leaves not by a single or different mechanisms in function of ultrasound power, as described by previous studies, but by a chain detexturation mechanism in a special order: local erosion, shear forces, sonoporation, fragmentation, capillary effect, and detexturation. These detexturation impacts followed a special order during ultrasound treatment leading at the end to the total detexturation of rosemary leaves. These mechanisms and detexturation impacts were identified in glandular trichomes, non-glandular-trichomes and the layer adaxial and abaxial cuticle. Modelling metabolites diffusion phenomenon during conventional and ultrasound extraction with the second Fick's law allowed the estimation of diffusivities and solvent penetration into the inner tissues and in meantime to accelerate the release of valuable metabolites.

Manothermosonication as a useful tool for lipid extraction from oleaginous microorganisms.

Manothermonication is a recognized and efficient method used for sterilization in food preservation. The synergistic effect of sonication combined with pressure and temperature allows enhancing the cavitation activity. Never employed for extraction, this study is about the transposition of this process as a tool of extraction. In this study, Rhodosporidium toruloides yeast was submitted to extraction by four modes of sonication, with a temperature ranged from 20 to 55°C and a pressure between 1 to 2bars. The lipids extraction yields were compared to the conventional maceration. Microbial oils obtained from both processes were analyzed and quantified by HPTLC (High Performance Thin-Layer Chromatography) and GC-FID (Gas Chromatography with flame ionization detector) after transesterification of lipids. Manothermosonication (30min, 2bars, 55°C) permits to enhance of approximately 20% the extraction yield of lipids to compared to conventional maceration. The fatty acid profiles of each pretreatment and extraction by US, MS, TS and MTS do not affect the fatty acid profiles of yeast (majority of oleic acid (C18:1n9), linoleic acid (C18:2n6) and palmitic acid (C16:0)). Manothermosonication technique shows a great potential for lipid extraction from oleaginous microorganisms.

Impact of ultrasound on solid-liquid extraction of phenolic compounds from maritime pine sawdust waste. Kinetics, optimization and large scale experiments.

Maritime pine sawdust, a by-product from industry of wood transformation, has been investigated as a potential source of polyphenols which were extracted by ultrasound-assisted maceration (UAM). UAM was optimized for enhancing extraction efficiency of polyphenols and reducing time-consuming. In a first time, a preliminary study was carried out to optimize the solid/liquid ratio (6g of dry material per mL) and the particle size (0.26 cm(2)) by conventional maceration (CVM). Under these conditions, the optimum conditions for polyphenols extraction by UAM, obtained by response surface methodology, were 0.67 W/cm(2) for the ultrasonic intensity (UI), 40°C for the processing temperature (T) and 43 min for the sonication time (t). UAM was compared with CVM, the results showed that the quantity of polyphenols was improved by 40% (342.4 and 233.5mg of catechin equivalent per 100g of dry basis, respectively for UAM and CVM). A multistage cross-current extraction procedure allowed evaluating the real impact of UAM on the solid-liquid extraction enhancement. The potential industrialization of this procedure was implemented through a transition from a lab sonicated reactor (3 L) to a large scale one with 30 L volume.

Ultrasound versus microwave as green processes for extraction of rosmarinic, carnosic and ursolic acids from rosemary.

Ultrasound and microwave as green processes are investigated in this study, focusing on the extraction selectivity towards antioxidant extraction from rosemary leaves. Due to its richness in valuable compounds such as rosmarinic, carnosic and ursolic acids, rosemary is a reference matrix for extraction study. In this work, six alternative processes are compared: ultrasound (bath, reactor and probe), microwave (reflux under microwave, microwave under nitrogen pressure and microwave under vapor pressure). The main result of this study is that selective extraction can be achieved according to extraction techniques and therefore to the extraction process.

Relative characterization of rosemary samples according to their geographical origins using microwave-accelerated distillation, solid-phase microextraction and Kohonen self-organizing maps.

For centuries, rosemary (Rosmarinus officinalis L.) has been used to prepare essential oils which, even now, are highly valued due to their various biological activities. Nevertheless, it has been noted that these activities often depend on the origin of the rosemary plant and the method of extraction. Since both of these quality parameters can greatly influence the chemical composition of rosemary oil, an original analytical method was developed where "dry distillation" was coupled to headspace solid-phase microextraction (HS-SPME) and then a data mining technique using the Kohonen self-organizing map algorithm was applied to the data obtained. This original approach uses the newly described microwave-accelerated distillation technique (MAD) and HS-SPME; neither of these techniques require external solvent and so this approach provides a novel "green" chemistry sampling method in the field of biological matrix analysis. The large data set obtained was then treated with a rarely used chemometric technique based on nonclassical statistics. Applied to 32 rosemary samples collected at the same time from 12 different sites in the north of Algeria, this method highlighted a strong correlation between the volatile chemical compositions of the samples and their origins, and it therefore allowed the samples to be grouped according to geographical distribution. Moreover, the method allowed us to identify the constituents that exerted the most influence during classification.

High power ultrasound effects on lipid oxidation of refined sunflower oil.

The effects of high power ultrasound treatment (20 kHz) on some components of refined sunflower oil were studied in order to verify if and to what extent modifications in the lipidic fraction can occur. Traditional parameters including free acidity, total polar compounds, peroxide value, and conjugated dienes concentration were determined in refined sunflower oil samples before, immediately after the ultrasonic treatment and during storage. Differences between treated and untreated samples were detected only for peroxide values (PV). The PV increased from 5.38 meq. O2/kg oil for untreated oil to 6.33 meq. O2/kg oil for sunflower oil sonicated (20 kHz; 150 W; 2 min). The fatty acid composition was obtained by high resolution gas chromatography. No significant changes were observed regarding the decrease in fatty acid composition before and immediately after the treatment. Regarding the volatile fraction, some off-flavour compounds for example hexanal and limonene resulting from the ultrasonic degradation of sunflower oil were identified by gas chromatography coupled to mass spectrometry (GC-MS).

Deterioration of edible oils during food processing by ultrasound.

During food emulsification and processing of sunflower oil (most used edible oil), a metallic and rancid odour has been detected only for insonated oil and foods. Some off-flavour compounds (hexanal and hept-2-enal) resulting from the sono-degradation of sunflower oil have been identified. A wide variety of analytical techniques (GC determination of fatty acids, UV spectroscopy, free fatty acids and GC/MS) were used to follow the quality of insonated sunflower oil and emulsion. Different edible oils (olive, sunflower, soybean, em leader ) show significant changes in their composition (chemical and flavour) due to ultrasound treatment.

Sono-oxidation treatment of humic substances in drinking water.

Currently humic substances are removed from the raw water prior to chlorination by the conventional coagulation and filtration method using aluminium sulphate. Application of high-intensity (> 10 W/cm2) ultrasonic irradiation in conjunction with oxidative process using commercial oxidants H2O2 was investigated as an alternative. Sono-oxidation and sonodegradation of natural and synthetic humic substances have been followed over time by measuring total organic carbon (TOC) and absorbance by ultraviolet spectrometer (UV-VIS). It took approximately 60 min to reduce TOC by half and to have a complete degradation of humic acid.