Drying kinetics and quality characteristics of green apple peel ( Mallus communis L. var. “Granny Smith”) used in herbal tea production

Nutrient and Bioactive Fraction Content of Olea europaea L. Leaves: Assessing the Impact of Drying Methods in a Comprehensive Study of Prominent Cultivars in Morocco

This study explores the potential of olive leaves, long integral to Mediterranean traditional medicine, as a rich source of valuable compounds. The challenge lies in their considerable water content, hindering these compounds' full valorization. Four drying methods (air-drying, oven-drying, freeze-drying and solar-drying) were investigated for their impact on nutrient and bioactive compound content in the leaves of four olive varieties ("Arbequina", "Koroneiki", "Menara" and "Picholine Marocaine") cultivated in Morocco. In their fresh state, "Picholine Marocaine" exhibited the highest protein levels (6.11%), "Arbequina" had the highest phenolic content (20.18 mg gallic acid equivalents/g fresh weight (FW)), and "Koroneiki" and "Menara" were highest in flavonoids (3.28 mg quercetin equivalents/g FW). Specific drying methods proved optimal for different varieties. Oven-drying at 60 °C and 70 °C effectively preserved protein, while phenolic content varied with drying conditions. Air-drying and freeze-drying demonstrated effectiveness for flavonoids. In addition, an analytical approach using high-performance liquid chromatography and diode array detection (HPLC-DAD) was applied to investigate the effects of the different drying methods on the bioactive fraction of the analyzed samples. The results showed qualitative and quantitative differences depending on both the variety and the drying method used. A total of 11 phenolic compounds were tentatively identified, with oleuropein being the most abundant in all the samples analyzed. The freeze-dried samples showed the highest content of oleuropein in the varieties "Arbequina" and "Picholine Marocaine" compared to the other methods analyzed. In contrast, "Koroneiki" and "Menara" had higher oleuropein content when air dried. Overall, the obtained results highlight the importance of tailored drying techniques for the preservation of nutrients and bioactive compounds in olive leaves.

Asparagus (Asparagus racemosus L.) roots: nutritional profile, medicinal profile, preservation, and value addition

Asparagus (Asparagus racemosus L.) is one of the most significant traditional medicinal plants, containing phytochemicals that are non-nutritive but beneficial to health. It contains bioactive metabolites such as fructo-oligosaccharides, polysaccharides, asparosides, shatavarins, sapogenins, racemosols, isoflavones, glycosides, mucilage, and fatty acids, while saponin is one of the main active constituents of asparagus roots. Asparagus helps in fertility promotion, stress management, and hormone modulation. It also treats stomach ulcers, kidney disorders, and Alzheimer's disease. Substitution of asparagus powder or extract for value addition of food products (such as beverages, bakery, and milk) enhances the nutritional and functional properties. Currently, the plant is considered endangered in its natural habitat because of its destructive harvesting, habitat destruction, and deforestation. As it is a highly perishable commodity, it needs proper handling, preservation, and storage. This review will outline the medicinal properties, uses, value addition, and preservation techniques of asparagus roots. The study found that, till now, the only preservation techniques used to increase the shelf life of asparagus roots are drying and irradiation. © 2022 Society of Chemical Industry.

Drying and rehydration kinetics of peeled and unpeeled green apple slices (Granny Smith cv)

In this work, the kinetics of drying and rehydration of green apple slices peeled and unpeeled (Granny Smith cv) were studied. The apple slices were dried at 50, 60, and 70 °C, and after that, rehydrated at ambient (T_a) and boiling temperature (T_b). The drying kinetics were adjusted with the Dincer and Dost model, giving a good fit. Effective diffusivity (D_eff) and the convective mass transfer coefficient (h_m) were also determined, both coefficients increase with drying temperature, being 1.25 × 10^-9 m² s^-1 and 9.53 × 10^-7 m² s^-1 the highest values obtained for the peeled apple slices respectively. Peleg and Weibull models were adjusted to the rehydration experimental data obtaining a good fit (R² > 0.99). D_eff values increase significantly with rehydration temperature but take similar values between peeled and unpeeled samples. Acidity, pH, moisture content, solid soluble content, and equivalent diameter were determined to compare the fresh apple slices with those after dehydration and the post-rehydration process. The apple slices rehydrated at boiling temperature better preserved the characteristics of fresh samples due to the short immersion times in water, no significant differences were observed between peeled and unpeeled apples. According to the results, it is convenient to dry the apple slices unpeeled at 70 °C and rehydrate them at T_b.

Utilizing of the Common Dehydrating Techniques to obtain maximum benefit from the Protein and mineral Composition of rosemary leaves for Spice and Herbal Tea Production

In the study, we examined in detail the effect of dehydrating using natural drying in the shade, convection drying, and microwave drying, which are the most widely used techniques, especially for tea and spices, both in practice and in theory, on the protein, and mineral composition of rosemary leaves. Also, we determined the color parameters, which are the reason for the selection because it creates the allure for spices. In microwave drying at 600 W, we obtained results close to fresh rosemary in all color parameters, especially brightness and greenness. Although natural drying, which does not have any energy and investment costs, is the second-best method in terms of color, 50 °C, which is the most common drying technique in the market, caused significant color losses affecting the commercial value of the product. We reached the closest protein and P, Ca, Mg, Fe, Zn, Mn, and contents to fresh products in dried ones at 600 W. In contrast, in K only, the highest measurement was at 200 W. Strikingly, we observed dramatic losses reducing the benefit obtained from the product regarding protein and almost all nutrients in both convective and natural drying techniques, the most common methods in practice.

Microwave and convective drying kinetics and thermal properties of orange slices and effect of drying on some phytochemical parameters

We dried the orange slices massed 100 ± 0.10 g from the initial moisture content of 6.97 ± 0.02 kg _water kg_DM ^-1 to the final moisture ones of 0.12 ± 0.01 kg _water kg_DM ^-1 using two different drying methods defined as convective drying at 50, 75, 100, and 125 °C along with microwave drying at eight output power between 90 and 1000 W. In the study, we measured the drying methods' energy consumption and observed that the microwave drying method's energy consumption was very low at high and low powers. Also, we modeled the results using twenty-one different thin-layer drying equations and obtained results closest to experimental data with the modified Henderson and Pabis equation for all powers in microwave drying and all temperatures in convective drying. We calculated both effective moisture diffusivities and activation energy using the drying data. Some thermal properties such as specific heat, thermal conductivity, thermal diffusivity, and thermal effusivity were calculated and recorded to be decreasing in all thermal properties with drying. Also, we measured the color parameters known as L, a, b, C, α°, and ΔE, browning index (BI), whitening index (WI), and vitamin C (ascorbic acid) in the study. We concluded that the most suitable drying method is microwave drying at medium powers of 350 and 500 W by considering both drying and quality parameters.

The effect of different drying techniques on color parameters, ascorbic acid content, anthocyanin and antioxidant capacities of cornelian cherry

Cornelian cherry was dehydrated using different drying techniques: namely natural, microwave, convective, and combined drying. The moisture content of cornelian cherry was reduced from 72.56% to 10.27%. The color parameters closest to the fresh samples were measured at 50 °C, 70 °C, 90 °C, and at 100 and 300 W. Both fresh and dried cornelian cherries show high antioxidant capacity and comprise of various polyphenolic compounds. TEAC_CUPRAC is the most suitable method for determining the total antioxidant capacity of cornelian cherry. We measured the total anthocyanin content closest to the fresh cornelian cherry with 2.62 and 2.11 mg (CDE) g^-1 (dw) at 70 °C and 300 W. Also, we found the closest vitamin C to the fresh ones with values of 25.02 and 20.08 mg 100 g^-1 (fw) at 300 and 500 W. Generally, the suitable drying technique in terms of physical parameters and phytochemical compounds was the microwave drying at 300 W.

Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients

Apple concentrate juice industry generates a flavored coproduct (apple aroma) recovered in the evaporation process, which is poorly valuated due to the lack of chemical characterization and standardization. In this study, industry apple aroma was characterized, allowing for the identification of 37 compounds, the majority esters (20), alcohols (7), and aldehydes (4). The storage temperature did not affect its volatile composition. Five key compounds were selected and monitored for 10 months of storage, and also compared with other three productions of another season allowing for observation of the same Aroma Index. Apple pomace was also used to produce a hydrodistillate. Contrary to the apple aroma, apple pomace hydrodistillate was unpleasant, reflected in a different volatile composition. Although no additional aroma fraction could be obtained from this wet byproduct, when dried, apple pomace presented 15 volatile compounds with toasted, caramel, sweet, and green notes. The infusions prepared with the dried apple pomace exhibited 25 volatile compounds with a very pleasant (fruity, apple-like, citrus, and spicy notes) and intense aroma. The addition of sugar changed the volatile profile, providing a less intense flavor, with almond, caramel, and sweet notes. These results show that apple aroma and pomace are high-quality flavoring agents with high potential of valuation as food ingredients.