Evandro de Castro Melo

Coffee husks (Coffea arabica) are abundant agro-industrial by-products with potential for value-added applications, making the optimization of drying conditions essential for preserving their quality. This study evaluated the effects of drying temperature on the drying kinetics, thermodynamic properties, and volatile profile of coffee husks from organic and conventional production systems. Samples were dried in a convective fixed-bed dryer at 30, 40, and 50 °C. Drying kinetics were described using fifteen mathematical models, while thermodynamic parameters (ΔH, ΔS, and ΔG), volatile compounds (HS-SPME/GC–MS), water activity (Aw), and texture were evaluated. The Modified Henderson and Pabis model provided the best fit to the drying data (R² > 0.99). A total of 505 volatile compounds were identified, and samples dried at 40 °C retained the highest number of sensory-relevant compounds. Organic coffee husks exhibited a distinct volatile profile compared with conventional husks, possibly due to differences in postharvest processing. Drying reduced water activity to values below 0.60, which are generally considered unfavorable for the growth of most microorganisms during storage. Overall, the results suggest that drying at 40 °C provides a suitable balance between drying performance and volatile compound preservation in coffee husks.

The aim of this study was to evaluate the influence of pretreatment (ultrasound + etanol), associated with different drying air temperatures, on the yield and quality of the essential oil of ripe fruits of Schinus terebinthifolius Raddi and to adjust previously described mathematical models in the specialized literature in order to obtain graphical representation of the drying kinetics. The experiments were conducted according to a Central Composite Design considering two factors with the following ranges: pre-treatment duration (ultrasound+ethanol) from 0 to 12 minutes and drying air temperature from 40 to 80 ºC. Four mathematical models, namely: Lewis, Page, Midilli, and Henderson & Pabis, were fitted to the experimental data. The essential oil was extracted by hydrodistillation and its constituents were identified by gas chromatography coupled with mass spectrometry (GC–MS). The Midilli model best represented the drying kinetics of ripe fruits of S. terebinthifolius pretreated with ultrasound + ethanol. The drying time of S. terebinthifolius fruits was influenced both by the pretreatment duration (with linear effect) and by the drying air temperature (linear and quadratic effects). None of the evaluated factors showed significance on the essential oil yield. It was not possible to adjust a model that simultaneously optimized the drying time and the yield of the essential oil of ripe and dried fruits of S. terebinthifolius, previously treated with ultrasound + ethanol.

Drying is an important step, as it extends plant durability and delays the development of undesirable microorganisms. However, depending on the drying method, conditions involved and plant species, changes can occur in the plants, which can improve or reduce their medicinal properties. Ultrasonic pretreatment has the advantage of facilitating water migration into the cells, improving the drying rate. In this context, the objective of this study was to evaluate the influence of different drying temperatures associated with ultrasonic pretreatment, on the chemical composition of the essential oil from Cyperus rotundus L. tubers. The assays were conducted according to a Central Composite Rotational Design (CCRD), considering two factors with the following ranges: duration of the ultrasonic bath from 0 to 40 minutes, drying air temperature from 40 to 70 ºC. The essential oil was extracted by hydrodistillation and its constituents were identified by gas chromatography coupled to mass spectrometry (GC–MS). Twenty-four compounds were identified in C. rotundus essential oil, corresponding to more than 70% of the total peak areas resulting from the chromatographic reading. In the twelve drying treatments evaluated, the compounds 3,4-dimethyl-3-cyclohexen-1-carboxaldehyde, caryophyllene oxide and α-cyperone were found at higher concentrations (between 17.85-25.38%; 17.27-25.26%; 4.95-11.34%, respectively) in eleven; in treatment 11, the major compounds were caryophyllene oxide (23.40%), 3,4-dimethyl-3-cyclohexen-1-carboxaldehyde (21.5%) and humulene (8.41%). At high temperatures and long ultrasonic times, a lower quality of C. rotundus essential oil was observed. The best results were obtained at intermediate ultrasonic bath temperatures and times, where there was an improvement in quality compared to fresh tubers (control).

The aim of this study was to evaluate the influence of different drying temperatures associated with ultrasound+ethanol pre-treatment on the chemical composition of the essential oil from ripe fruits of S. terebinthifolius. The experiments were conducted using a Central Composite Design, considering two factors within the following ranges: duration of ultrasound+ethanol pre-treatment from 0 to 12 minutes, drying air temperature from 40 to 80 °C. The essential oil was extracted by hydrodistillation, and its constituents were identified by gas chromatography-mass spectrometry (GC-MS). In the essential oil of S. terebinthifolius, five compounds were identified, accounting for over 80% of the total peak areas from the chromatographic analysis. Applying different pre-treatment times combining ultrasound and ethanol, along with different drying temperatures, resulted in qualitative changes in the chemical composition of the essential oil of S. terebinthifolius. The most satisfactory results were achieved at drying air temperatures of 50 °C and 70 °C, with shorter ultrasound+ethanol pre-treatment times. Additionally, it was observed that longer ultrasound+ethanol pre-treatment times (12 minutes) led to a reduction in the quality of the essential oil of S. terebinthifolius.

Despite the broad therapeutic action of plant species with bioactive compounds and drying being the most recommended operation for maintaining the quality of various plant materials, the fact that these materials differ in terms of moisture content, chemical composition, and morphology makes the optimization of drying methods and parameters for each species essential tools for obtaining dried plant biomass of high commercial value. The use of ethanol as a pre-treatment for drying, through immersion, allows for the modification of the product's natural structure and improves moisture transfer, consequently increasing the drying rate (KOMPANY et al., 1990). Ultrasonic waves can increase the availability of energy and accelerate mass transfer processes in the product, preserving its main qualitative attributes without significantly raising the drying air temperature (O’DONNEL et al., 2010). Therefore, this review aimed to elucidate the use of ultrasound and/or ethanol pre-treatment in the drying of various medicinal plant species, exploring their mechanisms of action and addressing their main effects on the desorption process and the chemical composition of these materials.

This study investigated the effect of intermittent drying on the specific energy consumption, plant extract yield, content of phenolic compounds, flavonoids, and antioxidant activity of L. origanoides leaves. Drying tests were carried out at the Postharvest Laboratory of Medicinal, Aromatic and Spice Plants of the Agricultural Engineering Department of the Federal University of Viçosa, Viçosa, MG, Brazil (20 ° 46 '13, 5 ”S; 42 ° 52 ' 23.3 ”W, and 645 m altitude) in June 2019. The experiment was conducted using a 3 × 4 factorial scheme matching three drying temperatures (50, 60 and 70 °C), with two drying methods: drying continuous and intermittent drying (with three intermittent ratios between drying and resting in minutes: 10/20, 15/15 and 20/10). The design used was completely randomized and with three replications. Drying with a 10/20 intermittency ratio reduced the specific energy consumption during the drying of L. origanoides leaves at 50 and 70 °C. The application of the 10/20 intermittency ratio maximized the yield of plant extract during the drying of the leaves of L. origanoides at 60 and 70 °C. Drying with a 10/20 intermittency ratio maximized the content of total phenolic compounds and total flavonoids at all evaluated drying air temperatures. Intermittent drying did not significantly affect the antioxidant activity of the plant extract of L. origanoides leaves.

Eugenol (C₁₀H₁₂O₂) presents various therapeutic properties. Due to this fact, it arises interest into the pharmaceutic industry and it has a commercial value. However, there is still a low offer of this product in the market. The aim of this work was to evaluate the Eugenol concentration in the essential oil from dried leaves of O. gratissimum L., and to determine whether this species bares promising characteristics as a source of eugenol. Fresh leaves of Ocimum gratissimum L. were used to extract the essential oil by hydrodistillation, and after the distillation of the essential oil a chromatographic analysis was performed. The essential oil (1.66% to 6,29%) was subjected to descriptive analysis and it has been observed that: the essential oil samples presented eugenol concentration of 82.40% after extraction. The storage has yielded a raise in eugenol concentration and about of this observation the essential oil of O. gratissimum L. presented potential as a eugenol source.

O reconhecimento das propriedades terapêuticas é tão antigo quanto a ocorrência dos humanos na Terra. Independentemente da finalidade do uso de plantas medicinais, não há dúvida de que tem havido um aumento na demanda por métodos naturais, representando um grande desafio para produtores e pesquisadores, no que diz respeito à padronização e controle de qualidade da matéria-prima, para garantir a qualidade das espécies oferecidas aos consumidores e à indústria farmacêutica. Apesar do aumento do consumo e consequente expansão do mercado de plantas medicinais, poucos são os estudos específicos envolvendo a utilização de técnicas de embalagem e armazenamento para esse tipo de produto. Diante do exposto, este estudo levantou conceitos envolvendo embalagens, bem como características de alguns polímeros comumente utilizados no armazenamento de produtos de origem vegetal, técnicas e equipamentos utilizados na embalagem de produtos alimentícios e trabalhos envolvendo o uso de atmosfera modificada na área de armazenamento de plantas medicinais.