Utilization of Cumbeba (Tacinga inamoena) Residue: Drying Kinetics and Effect of Process Conditions on Antioxidant Bioactive Compounds

Mathematical Modelling of Convective Drying of Orange By-Product and Its Influence on Phenolic Compounds and Ascorbic Acid Content, and Its Antioxidant Activity

Orange peel is one of the main by-products from juice processing, and is considered as a promising source of phenolic compounds with anti-carcinogenic, anti-inflammatory, anti-microbial and antioxidant properties. The drying is an essential step to ensure the storage of this by-product at an industrial level, in order to use it as a functional ingredient or as a nutraceutical. Thus, this research focuses on the evaluation of the effect of the convective air-drying process in orange by-products at three different temperatures (40, 60 and 80 °C) and air flows (0, 0.8 and 1.6 m/s) on the phenolic content (measured by HPLC-MS), the antioxidant activity (measured by DPPH, ABTS and FRAP), and the vitamin C content (measured by HPLC-UV/VIS). Moreover, the mathematical modelling of its drying kinetics was carried out to examine the orange by-product behavior. Among the tested mathematical models, the Page model reported the highest fit and the best drying conditions, which showed the lowest reductions were at 60 °C with an air flow of 1.6 m/s and taking 315 min.

Exploring drying kinetics and fate of nutrients in thermal digestion of solid organic waste

Thermal digestion has emerged as a novel technique for the rapid treatment of solid organic waste (SOW). Dehydration mechanism and fate of nutrients during the thermal digestion of the SOW were explored. A series of experiments were carried out in a specially designed laboratory-scale dehydrator to determine its drying kinetics. The statistical analysis revealed that the diffusion model predicted the dehydration profile most accurately than other models. The effective moisture diffusivity coefficient depended on the temperature and varied from 2.81 × 10^-08 m²/s to 8.68 × 10^-08 m²/s at the tested temperature range. The activation energy required for complete dehydration was found to be 26.56 kJ/mol. The artificial neural network (ANN) model was found highly efficient (R² - 0.983) in predicting the total drying time required for attaining equilibrium moisture content. The total N decreased from 2.2% to 1.81% due to evaporation of ammonical nitrogen, while the availability of P and K was increased from 0.38% to 0.43% and 1.47% to 1.75%, respectively when the temperature was increased from 110 °C to 170 °C. The thermal dehydration technique was found effective in digesting the organics and improving the bioavailability of the nutrients, which favours for its re-utilization in agriculture.

Mathematical Models to Describe the Foam Mat Drying Process of Cumbeba Pulp (Tacinga inamoena) and Product Quality

The present study investigated the mathematical modeling foam-mat drying kinetics of cumbeba pulp and the effect of drying conditions on the color and contents of ascorbic acid, flavonoids, and phenolic compounds of the powder pulps obtained. Foam-mat drying was carried out in a forced air circulation oven at temperatures of 50, 60, and 70 °C, testing foam-mat thicknesses of 0.5, 1.0, and 1.5 cm. The increase in the water removal rate is a result of the increase in air temperature and the decrease in the thickness of the foam layer. Among the empirical and semi-empirical mathematical models, the Midilli model was the one that best represented the drying curves in all conditions evaluated. Effective water diffusivity ranged from 1.037 × 10⁻⁹ to 6.103 × 10⁻⁹ m² s⁻¹, with activation energy of 25.212, 33.397, and 36.609 kJ mol⁻¹ for foam thicknesses of 0.5, 1.0, and 1.5 cm, respectively. Cumbeba powders showed light orangish colors and, as the drying temperature increased from 50 to 70 °C, for all thicknesses, the lightness value (L*) decreased and the values of redness (+a*) and yellowness (+b*) increased. Foam-mat drying at higher temperatures (60 and 70 °C) improved the retention of ascorbic acid and flavonoids, but reduced the content of phenolic compounds, while the increase in thickness, especially for flavonoids and phenolic compounds, caused reduction in their contents. The foam-mat drying method allowed obtaining a good-quality cumbeba pulp powder.

Foaming characteristics and impact of ethanol pretreatment in drying behavior and physical characteristics for avocado pulp powder obtained by foam mat drying

The objective of this study was to optimize the production of powdered avocado using foam mat drying. In order to achieve this, the effect of Emustab^® (4, 6, and 8% w/w), goat's milk (10, 15, and 20% w/w), and whipping time (15, 20, and 25 min) on the foam physical properties of avocado pulp were evaluated. In addition, the influence of ethanol pretreatment on the drying kinetics, thermodynamic properties, and physicochemical characteristics of the powders was also assessed. An experimental design 2³ with three central points was used in this study and optimized foam conditions were dried at 50, 60, and 70°C, with a fixed air speed of 1.5 m/s. Empirical and diffusive models (boundary conditions of the third type) were adjusted to the experimental data to describe the drying kinetics and to determine the process activation energy and thermodynamic properties. The final products were characterized regarding their physical properties. Optimized foam mat drying conditions were achieved when avocado pulp was whipped for 15 min and 8% of Emustab^® and 20% of powdered goat milk were used as foaming agents. The use of an ethanol pretreatment and higher drying temperature (70°C) resulted in higher drying rate (1.6 × 10² /min) and shorter processing time (270 min). The ethanol pretreatment reduced the activation energy and Biot number and led to more uniform moisture distribution. The physical properties, such as water content, water activity, bulk, and tapped densities decreased with an increase in drying temperature and pretreatment with ethanol, whereas water absorption capacity increased. PRACTICAL APPLICATION: In this work, new information about the drying kinetics and mass transfer of the foam mat avocado pulp using ethanol as pretreatment is obtained. The results will contribute to the optimization production avocado foaming and powder. Ethanol pretreatment can represent an alternative to minimize the negative impacts on drying process and can be surely suggested as an industrial application.

Short- and Medium-Wave Infrared Drying of Cantaloupe (Cucumis melon L.) Slices: Drying Kinetics and Process Parameter Optimization

The main objective of the present work was to study the drying kinetics and obtain the optimum process parameters of cantaloupe slices using short-and medium-wave infrared radiation (SMIR) drying technology. The effect of three independent variables of infrared radiation temperature (55–65 °C), slice thickness (5–9 mm) and radiation distance (80–160 mm) on the L value, color difference (∆E), hardness and vitamin C content were investigated by using the Response Surface Methodology (RSM). The results showed that the Page model can adequately predict the moisture content between 55 and 65 °C (R2 > 0.99). The effective moisture diffusivity (Deff) varied from 5.26 × 10−10 to 2.09 × 10−9 m2/s and the activation energy (Ea) of the SMIR drying was 31.84 kJ/mol. Infrared radiation temperature and slice thickness exerted extremely significant effects on L value and color difference (ΔE) (p < 0.01), with higher infrared radiation temperature and thin slice thickness leading to a decrease in the L value and an increase in ΔE. Hardness and vitamin C content were significantly affected by infrared radiation temperature, slice thickness and radiation distance, of which the slice thickness was the most distinct factor affecting the hardness value. Higher infrared radiation temperature and larger slice thickness and radiation distance resulted in higher vitamin C degradation. For the given constraints (maximized vitamin C content and L value, minimized ΔE and hardness value), the optimum drying parameters were infrared radiation temperature 58.2 °C, slice thickness 6 mm and radiation distance 90 mm. Under the optimum drying combination conditions, the experimental values were 65.58 (L value), 8.57 (∆E), 10.49 N (hardness) and 106.58 mg/100 g (vitamin C content), respectively. This study is beneficial to the development of the cantaloupe food processing industry and provides more insights for the application of SMIR drying technology to improve the drying rate and product quality of cantaloupe.

Aloe vera Gel Drying by Refractance Window®: Drying Kinetics and High-Quality Retention

In most cases, conventional drying produces inferior quality products and requires higher drying times. A continuous pilot Refractance Window^® equipment was used to dry Aloe vera gel slabs of 5 and 10 mm thick at 60, 70, 80, and 90 °C, seeking a dry product with high-quality retention. Based on five empirical models, drying kinetics, diffusion coefficient, and activation energy were analyzed. Midilli–Kuck was the best predicting model. Short drying times (55–270 min) were needed to reach 0.10 g water/g solid. In addition, the technique yielded samples with high rehydration capacity (24–29 g water/g solid); high retention of color (∆E, 3.74–4.39); relatively low losses of vitamin C (37–59%) and vitamin E (28–37%). Regardless of the condition of temperature and sample thickness, a high-quality dried Aloe vera gel could be obtained. Compared with other methods, Refractance Window^® drying of Aloe vera achieved shorter drying times with higher quality retention in terms of color, vitamins C and E, and rehydration. Finally, the dried Aloe vera gel could be reconstituted to a gel close to its fresh state by rehydration.

Mathematical Modelling of Conveyor-Belt Dryers with Tangential Flow for Food Drying up to Final Moisture Content below the Critical Value

This work presents the mathematical modeling of the conveyor-belt dryer with tangential flow operating in co-current, which has the advantage of improving the preservation of the organoleptic and nutritional qualities of the dried food. On the one hand, it is a more cumbersome dryer than the perforated cross flow belt dryer but, on the other hand, it has a low air temperature in the final section where the product has a low moisture content and, therefore, it is more heat sensitive. The results of the mathematical modeling allowed a series of guidelines to be developed for a rational design of the conveyor-belt dryer with tangential flow for the specific case of the moisture content of the final product XF lower than the critical one XC (XF < XC). In fact, this work follows a precedent in which a mathematical model was developed through the differentiation of the drying rate equation along the dryer belt with the hypothesis that the final moisture content XF of the product was higher than the critical one XC. The relationships between the extensive quantities (air flow rate and product flow rate), the intensive quantities (temperatures, moisture content and enthalpies) and the dimensional ones (length and width of the belt) were then obtained. Finally, based on these relationships, the rules for an optimized design for XF < XC were obtained.