Measuring dielectric properties for microwave-assisted extraction of essential oils using single-mode and multimode reactors

Parizotto, Carlos Adriano; Dall’Oglio, Evandro Luiz; Vasconcelos, Leonardo Gomes de; Sousa, Paulo Teixeira de; Filho, Eduardo G. R. Taques; Kuhnen, Carlos Alberto

doi:10.1039/c8ra08727j

Cited by 8 publications

(3 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Literature studies on the behavior of plants, including the aromatic ones, such as Cymbopogon nardus (L.) Rendle, Eucalyptus spp., Piper aduncum L., Piper hispidinervum C. DC., Cupressus sempervirens L. and Cistus spp., show how their dielectric properties, even if they are not high such as pure water medium, allow rapid heating due to the presence of a mixture of ions, non-polar long chains and large polar molecules, typical chemical constituents of branches, leaves and inflorescences, that activate dissipative energy mechanisms [ 30 , 31 ]. In particular, water and salt content play a fundamental role: the greater the quantity of water present (and saline content) in the plant, the better the response to the applied electric field will be and, consequently, the faster the heating and the removal of moisture.…”

Section: Resultsmentioning

confidence: 99%

Postharvest Microwave Drying of Basil (Ocimum basilicum L.): The Influence of Treatments on the Quality of Dried Products

Martino

Caputo

Amato

et al. 2022

Foods

View full text Add to dashboard Cite

Edible herbs are widely used in the human diet due to their pleasant flavors and countless health benefits associated with their components having, mainly, antioxidant and anti-inflammatory therapeutic functions. Since herbs are highly perishable materials because of their high water content, to guarantee products are safe and stable over time, it is necessary that they undergo stabilization operations. The application of microwave-assisted drying, a promising technique in terms of process sustainability, for the stabilization of the aromatic herb, Ocimum basilicum L., was investigated. The activities were carried out by applying different operating conditions in order to evaluate the impact of the time/temperature combination on the final quality of dried basil. The latter was investigated via the chemical characterization of extracted essential oils and tissue damages. Conventional convective processes were also applied to perform comparisons between dried basil products both under production and the quality preservation points of view. Results showed that microwave heating is suitable as a drying method, as expected, due to the well-known interaction between vegetable tissue (rich in water) and the electromagnetic field; and that drying methods have a different influence on the chemical composition of the essential oils extracted from dried products, in terms of the number (ranging from 41 to 18 components in different dried samples) and percentage (until 67% in linalool and 21% in α-trans-bergamotene in different dried samples) of its’ constituents.

show abstract

Section: Resultsmentioning

confidence: 99%

Postharvest Microwave Drying of Basil (Ocimum basilicum L.): The Influence of Treatments on the Quality of Dried Products

Martino

Caputo

Amato

et al. 2022

Foods

View full text Add to dashboard Cite

show abstract

“…In oregano batches treated by microwave heating at 2300 W—10 min (MW1), 1150 W—15 min (MW2), and 460 W—35 min (MW3), the water contents were 8.6, 7.5 and 12.3%, respectively. Short treatment times (minutes not hours) are related to the ability of the fresh product, rich in water, to interact with microwaves 16 , 25 .…”

Section: Resultsmentioning

confidence: 99%

Impact of drying methods on the yield and chemistry of Origanum vulgare L. essential oil

Caputo

Amato

Bartolomeis

et al. 2022

Sci Rep

View full text Add to dashboard Cite

Oregano (Origanum vulgare L.) is mainly cultivated, both as fresh and dried herb, for several purposes, such as ailments, drugs, and spices. To evaluate the influence of some drying methods on the chemical composition of the essential oil of oregano, its aerial parts were dehydrated by convective drying techniques (shade, static oven), microwave-assisted heating (three different treatments) and osmotic treatment. The oils were analyzed by GC-FID and GC–MS. The highest essential oil yield was achieved from microwave and shade drying methods. In total, 39 components were found, with carvacrol (ranging from 56.2 to 81.4%) being the main constituent; other compounds present in lower amounts were p-cymene (1.6–17.7%), γ-terpinene (0.8–14.2%), α-pinene (0.1–2.1%), thymol methyl ether (0.4–1.8%) and thimoquinone (0.5–3.5%). The essential oil yields varied among the different treatments as well as the relative compositions. The percentages of p-cymene, γ-terpinene and α-pinene decreased significantly in the dried sample compared with the fresh sample; on the other hand, carvacrol, isoborneol and linalool increased significantly in the dried materials. The choice of the drying method for obtaining the essential oil therefore appears crucial not only in relation to the higher yield but also and above all in reference to the percentage presence of components that can direct the essential oil toward an appropriate use.

show abstract

“…Vegetables/herbs and, more generally, plant matter/water mixtures are suitable materials for microwave heating technology due to their water contents and composition (free water, presence of ions with low polarity, non-polar long-chain hydrocarbons, large polar molecules [47,48]. In particular, dipolar polarization is the most significant loss mechanism; the conductivity mechanism improves the dissipation capacity (measurements (or estimation methods) of dielectric properties of plants and herbs can be found in [29,30,49,50]). The different effect of temperature on loss mechanisms guarantees a continuous efficient heating.…”

Section: Dielectric Heating: Physical Issuesmentioning

confidence: 99%

Natural Food Resource Valorization by Microwave Technology: Purslane Stabilization by Dielectric Heating

Apicella,

Amato,

de Bartolomeis

et al. 2023

Foods

View full text Add to dashboard Cite

The application of microwave-assisted drying is a promising technique due to the features of process sustainability that are usable for responsible productions. It is largely applied for the stabilization of food products, especially in the agro-food sector. In this study, the weed Portulaca oleracea L. (purslane), with its richness in antioxidant components in addition to its recognized pharmacological properties, has been considered due to its potential to be a natural, well-accepted future food. Attention was focused on the role of the heat and mass transfer rates involved in the drying processes on the nutritional profile of the dried products. For this purpose, different drying protocols (convective, microwave irradiation, microwave-vacuum irradiation) were applied to different parts of purslane herb (apical, twigs, entire structures) and chemical characterizations were performed by a GC/MS analysis of the extracts of the dried products. The results show that microwave treatments can assure a better preservation of fatty acids such as SFAs, MUFAs, and PUFAs (which constitute over 90% of the total components in the apical part, 65% in twigs, and 85% in microwave-vacuum-dried entire purslane samples) and phytosterols (their highest preservation was found in microwave-dried twigs) compared with convective treatments. The chemical composition variability as well as treatment times depend on the drying rates (in microwave treatments, the times are on a minute scale and the rates are up to three orders of magnitude greater than convective ones), which in turn depend on the heating transport phenomena. This variability can lead towards products that are diversified by properties that transform a weed into a valorized food source.

show abstract

Measuring dielectric properties for microwave-assisted extraction of essential oils using single-mode and multimode reactors

Abstract: Dielectric properties of plants/water mixtures enables the design of single mode cavities for microwave assisted extraction of essentials oils.

Cited by 8 publications

References 34 publications

Postharvest Microwave Drying of Basil (Ocimum basilicum L.): The Influence of Treatments on the Quality of Dried Products

Postharvest Microwave Drying of Basil (Ocimum basilicum L.): The Influence of Treatments on the Quality of Dried Products

Impact of drying methods on the yield and chemistry of Origanum vulgare L. essential oil

Natural Food Resource Valorization by Microwave Technology: Purslane Stabilization by Dielectric Heating

Contact Info

Product

Resources

About