Drying Rate and Product Quality Evaluation of Roselle (Hibiscus sabdariffa L.) Calyces Extract Dried with Foaming Agent under Different Temperatures

Integrated drying model of lychee as a function of temperature and relative humidity

Drying is a universal method applied for food preservation. To date, several models have been developed to evaluate drying kinetics. In this study, lychee was dried employing a hot air dryer, and the drying kinetics was evaluated by comparing the Newtonian model, Henderson and Pabis model, Page model, and Logarithmic model. However, temperature and relative humidity, the key driving forces for drying kinetics, are not considered by these models. Thus, an integrated drying model, as a function of temperature and relative humidity, was developed to predict the hot air-drying kinetics and mass transfer phenomena of lychee followed by the calibration and validation of the model with independent experimental datasets. The model validation consisted of Nash- Sutcliffe model coefficient (E ), coefficient of determination ( R 2 ) and index of agreement ( d ) and all of them were found close to 1 indicating perfect model fit. Besides, the developed model was applied for process optimization and scenario analysis. The drying rate constant was found as a function of temperature and relative humidity that was high at high temperature and low relative humidity. Interestingly, temperature showed a higher effect on the drying rate constant compared to relative humidity. Overall, the present study will open a new window to developing further drying model of lychee to optimize quality its quality parameters.

Impact of Processing and Physicochemical Parameter on Hibiscus sabdariffa Calyxes Biomolecules and Antioxidant Activity: From Powder Production to Reconstitution

Hibiscus sabdariffa is a tropical plant with red calyxes whose anthocyanins, phenols, and antioxidant activity make it attractive to consumers both from a nutritional and medicinal standpoint. Its seasonality, perishability, and anthocyanin instability, led to the setup of stabilization methods comprising drying and powdering. However, its properties can often be altered during these stabilization processes. Treatments such as dehumidified-air-drying, infrared drying, and oven-drying, and their combination showed better quality preservation. Moreover, powder production enables superior biomolecule extractability which can be linked to a higher bioaccessibility. However, the required temperatures for powder production increase the bioactive molecules degradation leading to their antioxidant activity loss. To overcome this issue, ambient or cryogenic grinding could be an excellent method to improve the biomolecule bioavailability and accessibility if the processing steps are well mastered. To be sure to benefit from the final nutritional quality of the powder, such as the antioxidant activity of biomolecules, powders have to offer excellent reconstitutability which is linked to powder physicochemical properties and the reconstitution media. Typically, the finest powder granulometry and using an agitated low-temperature reconstitution media allow for improving anthocyanin extractability and stability. In this review, the relevant physicochemical and processing parameters influencing plant powder features from processing transformation to reconstitution will be presented with a focus on bioactive molecules and antioxidant activity preservation.

Green Synthesis of FexOy Nanoparticles with Potential Antioxidant Properties

Iron oxide nanoparticles (Fe_xO_y-NPs) are currently being applied in numerous high-tech sectors, such as in chemical sectors for catalysis and in the medical sector for drug delivery systems and antimicrobial purposes, due to their specific, unique and magnetic properties. Nevertheless, their synthesis is under continuous investigation, as physicochemical methods are considered expensive and require toxic solvents. Thus, green nanotechnology has shown considerable promise in the eco-biogenesis of nanoparticles. In the current study, Fe_xO_y-NPs were synthesized by two different methods: via green synthesis through the use of polyphenols, which were extracted from Phoenix dactylifera L.; and via chemical synthesis, in which the reducing agent was a chemical (NaOH), and iron chloride was used as a precursor. Thus, polyphenol extraction and its ability to produce nanoparticles were evaluated based on the drying temperature used during the Phoenix dactylifera L. recollection, as well as the extraction solvent used. The results highlight the potential of polyphenols present in Phoenix dactylifera L. for the sustainable manufacture of Fe_xO_y-NPs. Finally, green and chemical syntheses were compared on the basis of physicochemical characteristics and functional properties.

A stability-indicating HPLC-UV method for the quantification of anthocyanin in Roselle (Hibiscus Sabdariffa L.) spray-dried extract, oral powder, and lozenges

Hibiscus sabdariffa L. (H.S.) plant and its calyces have received much attention from researchers because of their potential medicinal and nutritional values. Calyces are the major source of anthocyanin in this plant. Therefore, a well-developed, efficient, and accurate analytical method is needed to assure proper standardization and control the quality of H.S. plant herbal and nutraceutical products. The objective of this work is to develop a simple, rapid, stability-indicating HPLC-UV method for the quantitative determination of anthocyanin in spray-dried aqueous extract (SDE), oral powder, and compressible lozenges formulations using Delphinidin-3-O-sambubioside (Dp3S) as a marker compound. The chromatographic conditions were optimized using Eclipse plus® C18 column. The mobile phase comprised water acidified with 0.2% formic acid (FA) and acetonitrile (ACN) (90:10, v/v) using a gradient system at a flow rate of 0.8 mL/min. The detection wavelength was 525 nm. The column was maintained at 45 °C, and the injection volume was 15 μL. The developed method was validated according to the international conference of harmonization (ICH) guidelines for linearity, detection and quantitation limits, accuracy, precision, specificity, and robustness. Forced degradation studies under acid, base, oxidation, heat, and U.V light, were performed on the pure compound, extract, and the H.S. developed formulations. Significant degradation of the compound was observed under all tested conditions except U.V. light, where degradation was minimum. There was no interference from impurities, degradation products, or excipients at the retention time of Dp3S 3.2 min indicating the specificity of the method. The developed method was statistically confirmed to be accurate, precise, and reproducible. This simple, rapid, and specific method can be employed efficiently to determine anthocyanin in H.S. plant extract and nutraceutical products.

Impact of Foam-Mat Drying on Plant-Based Foods Bioactive Compounds: a Review

Plant-based foods are recognized by their remarkable content of bioactive compounds. In an attempt to increase plant-based foods shelf-life, technologies like drying can be used. Foam-mat drying is a mild drying technology that removes water, usually by using hot air, from a foam obtained by the whipping of a liquid or semi-liquid food added with a foaming agent. There are several reports on the use of foam-mat drying for extending plant-based foods shelf-life, including reports on the effect of drying on their bioactive compounds. Therefore, this study aimed at reviewing the literature on the impact of foam-mat drying on plant-based foods bioactive compounds published in the last 10 years. Results show that short foam-mat drying time is beneficial to bioactive compounds retention. In addition, hot air temperature between 40-65 °C, foam thickness between 0.2 and 1 cm and the use of egg white as one of the foaming agents leads to high bioactive retention. Egg white is also the most used foaming agent. Regarding the mathematical models used for fitting the foam-mat drying kinetics, the Page model was shown as the most proper model. Foaming agent concentration is a delicate parameter, as its increase in foam formulation may beneficially enhance drying rates but, at the same time, it dilutes bioactive compounds and may cause their loss by oxidation. In conclusion, foam-mat drying stands out as a suitable technology for producing food powders with high bioactive retention.

Technical Parameters Affecting the Spray Drying of Roselle (Hibiscus Sabdariffa) Powder

Roselle (Hibiscus sabdariffa) was a member of Malvaceae family. Its calyxes had bright red color due to presence of anthocyanin with an excellent antioxidant property. Raw roselle (Hibiscus sabdariffa L.) calyx was highly perishable due to its high moisture content. In order to diversify products from this plant, this research evaluated the possibility of spray drying for roselle extract into dried powder for long-term consumption. We focused on the effect of sugar alcohols (mannitol, sorbitol, isomalt, xylitol, erythritol) at 8%, carrier agents (maltodextrin, gum arabic, glutinous starch, whey protein concentrate, carboxymethyl cellulose) at 12%, operating parameters of spray dryer (inlet/outlet air temperature, feed rate) on physicochemical quality (bulk density, solubility, total phenolic content, total flavonoid content, anthocyanin content) of rosselle powder. Results showed that the optimal spray drying variables for rosselle powder should be 8% isomalt, 12% whey protein concentrate, inlet/ outlet air temperature 140/85oC/oC, feed rate 12 ml/min. Based on these optimal conditions, the highest physicochemical attributes of the dried roselle calyx powder would be obtained.

Effects of drying temperature and relative humidity on the quality of dried onion slice

Onion, a very common season ingredient, is useful as an antioxidant and optimal conditions are required for its drying while ensuring the best quality is retained. This study evaluated the effect of drying temperatures and relative humidity on both drying rate and onion quality. Onions with an average diameter of 20.125 ± 0.025 mm were peeled and sliced into a thickness of 1.233 ± 0.029 mm. They were then dried for 120 min under various temperatures ranging from 40 to 70 °C. Both moisture content and total phenolic compounds were measured and analyzed as responses, and the data obtained were used for estimating the kinetic parameters of drying rate and total phenolic compounds degradation. The results show that the drying kinetics followed Fick's model. Moreover, the total phenolic compounds degradation can be properly expressed using a first-order reaction model, and the optimization using response surface method revealed that the optimum conditions of onion slice drying were achieved at 49.6 °C and relative humidity of 0.65%. These conditions can significantly reduce drying time with phenolic compounds retention of up to 96%.