Farid Chemat

Applications of ultrasound in food technology: Processing, preservation and extraction.

Ultrasound is well known to have a significant effect on the rate of various processes in the food industry. Using ultrasound, full reproducible food processes can now be completed in seconds or minutes with high reproducibility, reducing the processing cost, simplifying manipulation and work-up, giving higher purity of the final product, eliminating post-treatment of waste water and consuming only a fraction of the time and energy normally needed for conventional processes. Several processes such as freezing, cutting, drying, tempering, bleaching, sterilization, and extraction have been applied efficiently in the food industry. The advantages of using ultrasound for food processing, includes: more effective mixing and micro-mixing, faster energy and mass transfer, reduced thermal and concentration gradients, reduced temperature, selective extraction, reduced equipment size, faster response to process extraction control, faster start-up, increased production, and elimination of process steps. Food processes performed under the action of ultrasound are believed to be affected in part by cavitation phenomena and mass transfer enhancement. This review presents a complete picture of current knowledge on application of ultrasound in food technology including processing, preservation and extraction. It provides the necessary theoretical background and some details about ultrasound the technology, the technique, and safety precautions. We will also discuss some of the factors which make the combination of food processing and ultrasound one of the most promising research areas in the field of modern food engineering.

Green Extraction of Natural Products: Concept and Principles

The design of green and sustainable extraction methods of natural products is currently a hot research topic in the multidisciplinary area of applied chemistry, biology and technology. Herein we aimed to introduce the six principles of green-extraction, describing a multifaceted strategy to apply this concept at research and industrial level. The mainstay of this working protocol are new and innovative technologies, process intensification, agro-solvents and energy saving. The concept, principles and examples of green extraction here discussed, offer an updated glimpse of the huge technological effort that is being made and the diverse applications that are being developed.

Ultrasound assisted extraction of food and natural products. Mechanisms, techniques, combinations, protocols and applications. A review

This review presents a complete picture of current knowledge on ultrasound-assisted extraction (UAE) in food ingredients and products, nutraceutics, cosmetic, pharmaceutical and bioenergy applications. It provides the necessary theoretical background and some details about extraction by ultrasound, the techniques and their combinations, the mechanisms (fragmentation, erosion, capillarity, detexturation, and sonoporation), applications from laboratory to industry, security, and environmental impacts. In addition, the ultrasound extraction procedures and the important parameters influencing its performance are also included, together with the advantages and the drawbacks of each UAE techniques. Ultrasound-assisted extraction is a research topic, which affects several fields of modern plant-based chemistry. All the reported applications have shown that ultrasound-assisted extraction is a green and economically viable alternative to conventional techniques for food and natural products. The main benefits are decrease of extraction and processing time, the amount of energy and solvents used, unit operations, and CO2 emissions.

The Extraction of Natural Products using Ultrasound or Microwaves

Over the centuries mankind has benefited from the natural materials that occur in plants. In earlier times the whole plant or an extract was used in cooking or as a medicine but nowadays the active constituents of plant extracts provide targets for the synthetic chem- ist. In this review we will explore the advantages that accrue from the incorporation of either ultrasound or microwaves in the extraction process. The two techniques offer different approaches in that ultrasound is generally used to improve conventional solvent extraction whereas microwaves are known for their ability to remove constituents via heating without solvents.

Solvent-free ultrasound-assisted extraction of lipids from fresh microalgae cells: a green, clean and scalable process.

In order to comply with criteria of green chemistry concepts and sustainability, a new procedure has been performed for solvent-free ultrasound-assisted extraction (UAE) to extract lipids from fresh Nannochloropsis oculata biomass. Through response surface methodology (RSM) parameters affecting the oil recovery were optimized. Optimum conditions for oil extraction were estimated as follows: (i) 1000 W ultrasonic power, (ii) 30 min extraction time and (iii) biomass dry weight content at 5%. Yields were calculated by the total fatty acids methyl esters amounts analyzed by GC-FID-MS. The maximum oil recovery was around 0.21%. This value was compared with the one obtained with the conventional extraction method (Bligh and Dyer). Furthermore, effect of temperature on the yield was also investigated. The overall results show an innovative and effective extraction method adapted for microalgae oil recovery, without using solvent and with an enable scaling up.

Towards the industrial production of antioxidants from food processing by-products with ultrasound-assisted extraction

Apple pomace, a by-product of the cider production, has been studied as a potential source of polyphenols, compounds of great interest for the industry. Ultrasound has been used to improve extraction efficiency in terms of time needed and total polyphenol content. A preliminary study has been first investigated to optimize ethanol proportion of aqueous extractant (50%, v/v) and solid/liquid ratio (<15%, w/v). A response surface methodology has then been used to maximize total polyphenol content of extracts and investigate influence of parameters involved in extraction procedures for both total polyphenols content and composition of extracts. Optimal settings reached from a central composite design were applied for ultrasound-assisted extraction and were compared to conventional procedure: yields were increased by more than 20%. Ultrasound-assisted polyphenols extraction from apple pomace appears to be a relevant, rapid, sustainable alternative to conventional procedure, and that scale up of the process is possible.

Microwave hydrodiffusion and gravity, a new technique for extraction of essential oils

A new process design and operation for the extraction of essential oils was developed. Microwave hydrodiffusion and gravity (MHG) is a combination of microwaves for hydrodiffusion of essential oils from the inside to the exterior of biological material and earth gravity to collect and separate. MHG is performed at atmospheric pressure without adding any solvent or water. MHG has been compared with a conventional technique, hydrodistillation (HD), for the extraction of essential oil from two aromatic herbs: spearmint (Mentha spicata L.) and pennyroyal (Mentha pulegium L.) belonging to the Labiatae family. The essential oils extracted by MHG for 15 min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by conventional hydrodistillation for 90 min. MHG also prevents pollution through potential 90% of energy saved which can lead to greenhouse gas emission benefits.

Solvent-free microwave extraction of essential oil from aromatic herbs: from laboratory to pilot and industrial scale.

Solvent-free microwave extraction (SFME) has been proposed as a green method for the extraction of essential oil from aromatic herbs that are extensively used in the food industry. This technique is a combination of microwave heating and dry distillation performed at atmospheric pressure without any added solvent or water. The isolation and concentration of volatile compounds is performed in a single stage. In this work, SFME and a conventional technique, hydro-distillation HD (Clevenger apparatus), are used for the extraction of essential oil from rosemary (Rosmarinus officinalis L.) and are compared. This preliminary laboratory study shows that essential oils extracted by SFME in 30min were quantitatively (yield and kinetics profile) and qualitatively (aromatic profile) similar to those obtained using conventional hydro-distillation in 2h. Experiments performed in a 75L pilot microwave reactor prove the feasibility of SFME up scaling and potential industrial applications.

Green ultrasound-assisted extraction of carotenoids based on the bio-refinery concept using sunflower oil as an alternative solvent.

A green, inexpensive and easy-to-use method for carotenoids extraction from fresh carrots assisted by ultrasound was designed in this work. Sunflower oil was applied as a substitute to organic solvents in this green ultrasound-assisted extraction (UAE): a process which is in line with green extraction and bio-refinery concepts. The processing procedure of this original UAE was first compared with conventional solvent extraction (CSE) using hexane as solvent. Moreover, the UAE optimal conditions for the subsequent comparison were optimized using response surface methodology (RSM) and ultra performance liquid chromatography--diode array detector--mass spectroscopy (UPLC-DAD-MS). The results showed that the UAE using sunflower as solvent has obtained its highest β-carotene yield (334.75 mg/l) in 20 min only, while CSE using hexane as solvent obtained a similar yield (321.35 mg/l) in 60 min. The green UAE performed under optimal extraction conditions (carrot to oil ratio of 2:10, ultrasonic intensity of 22.5 W cm(-2), temperature of 40 °C and sonication time of 20 min) gave the best yield of β-carotene.

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.