Tamara Allaf

Instant controlled pressure drop technology and ultrasound assisted extraction for sequential extraction of essential oil and antioxidants

The instant controlled pressure drop (DIC) technology enabled both the extraction of essential oil and the expansion of the matrix itself which improved solvent extraction. The sequential use of DIC and Ultrasound Assisted Extraction (UAE) triggered complementary actions materialized by supplementary effects. We visualized these combination impacts by comparing them to standard techniques: Hydrodistillation (HD) and Solvent Extraction (SE). First, the extraction of orange peel Essential Oils (EO) was achieved by HD during 4h and DIC process (after optimization) during 2 min; EO yields was 1.97 mg/g dry material (dm) with HD compared to 16.57 mg/g d m with DIC. Second, the solid residue was recovered to extract antioxidant compounds (naringin and hesperidin) by SE and UAE. Scanning electron microscope showed that after HD the recovered solid shriveled as opposite to DIC treatment which expanded the product structure. HPLC analyses showed that the best kinetics and yields of naringin and hesperidin extraction was when DIC and UAE are combined. Indeed, after 1h of extraction, DIC treated orange peels with UAE were 0.825 ± 1.6 × 10(-2)g/g of dry material (dm) for hesperidin and 6.45 × 10(-2) ± 2.3 × 10(-4)g/g d m for naringin compared to 0.64 ± 2.7 × 10(-2)g/g of dry material (dm) and 5.7 × 10(-2) ± 1.6 × 10(-3)g/g d m, respectively with SE. By combining DIC to UAE, it was possible to enhance kinetics and yields of antioxidant extraction.

Instant Controlled Pressure Drop (DIC) Texturing of Heat-Sensitive Spray-Dried Powders: Phenomenological Modeling and Optimization

Powders of expanded granules generally get high functional characteristics due to porous structure of such granules. The present study aimed at comparing the two ways of high-pressure air or steam alternatively used in détente instantanée contrôlée (DIC; French for instant controlled pressure drop) to achieve the modified three-stage spray-drying operation. Both operations were studied in terms of the process performance and functional/structural powder quality in the case of skim milk. The initial water content, the temperature levels, and the initial and final pressures contribute together to define the amount of expanding air or vapor thus generated. This is an important texturing parameter strictly combined with rheological and glass transition to define the texturing phenomenon. Response surface methodology—design of experiments (RSM-DoE) was achieved with DIC pressure, treatment time, and water content as independent variables for both operation ways. The analyses of the technological, physical, and structural properties of untreated and DIC textured powders were carried out and considered as response dependent variables. The results illustrated that whatever the type of DIC, the optimized DIC treatment implied a controlled increase in porosity, interstitial air volume, and compressibility, as well as specific surface area and reconstitution aptitude.

Solvent-Free Extraction: Myth or Reality?

One of the many environmental challenges faced by Extraction field is the widespread use of organic solvents. With a solvent based extraction the solvent necessarily has to be separated from the final extract. A large number of these solvents are toxic that pose a risk to workers and community members and virtually all of them are classified as volatile organic compounds (VOCs) that contribute to smog. In this context, the development of solvent-free extraction processes is of great interest in order to modernize classical processes making them cleaner, safer and easier to perform. This chapter presents a picture of current knowledge on innovative solvent-free methods of natural products extraction. It provides the necessary theoretical background and some details about extraction using the most innovative, rapid and green techniques such as microwaves, instant controlled pressure drop (DIC) process and Pulsed Electric Field (PEF): the technique, the mechanism and some applications.

DIC Texturing for Solvent Extraction

Because of the natural structure of plants, which oppose resistance to penetration by any liquid, solvent extraction is very slow. The kinetics involves multiple serial steps and internal diffusion is generally the limiting process. Moreover, during the extraction of bioactive molecules from a natural product, volatile compounds are also extracted and consequently this lowers the final quality of the extract, rendering deodorization a necessity.

Extraction of Essential Oils and Volatile Molecules

Fundamental studies of the transfer processes in steam extraction (steam distillation) have identified a paradoxical situation in which gradients of temperature and essential oil vapor pressure are both directed towards the core, resulting in a flow in the opposite direction to that required for an extraction operation. Steam distillation is thus a front progression operation. In order to intensify essential oil (EO) extraction and improve the quality of both extract and residue, instant controlled pressure drop (DIC) treatment was defined and used as a direct extraction–texturing treatment. With DIC treatment, volatile molecules can be removed by autovaporization, followed by a total pressure gradient (Darcy-type law) which substantially reduces extraction time. Thus, the processing time of DIC-EO extraction is about 4 min compared to several hours (or even days) with hydro- or steam distillation. This is obviously linked to low heat energy consumption. The final essential oil that is extracted meets the various quality requirements in terms of the absence of thermal degradation. In addition, DIC treatment can also be used to expand the compact plant and to enhance its technological aptitude for a second operation such as drying, solvent extraction, and press extraction.

Coupling DIC and Ultrasound in Solvent Extraction Processes

Solvent extraction can be achieved in two steps: the first stage of solute dissolution in the solvent is carried out at the surface of the product (illustrated by the starting accessibility) and a second stage of diffusion phenomena, of the both, solvent towards the core of the solid matrix and the solute within the filled-with-solvent pores.