Influence of drying temperature on quality attributes of bell pepper ( Capsicum annuum L .): Drying kinetics and modeling, rehydration, color, and antioxidant analysis

Enhanced osmotic dehydration of watermelon rind using honey-sucrose solutions: A study on pre-treatment efficacy and mass transfer kinetics

This study investigates the osmotic dehydration process of watermelon rind using a solution composed of honey and sucrose. The impact of the ratio of rind-to-solution and temperature on the process is illustrated. Pre-treatments such as blanching, microwaves, and ultrasonication were utilized. Ultrasonication reduces the time needed for osmosis in a sample, resulting in increased fluid loss and solute uptake; therefore, it was selected as the method to investigate the kinetics and modelling of mass transfer. The effective diffusivities for water loss (ranging from 3.02 × 10-5 to 4.21 × 10-4 m2 s-1) and solid gain (ranging from 1.94 × 10-6 to 3.21 × 10-6 m2 s-1) were shown to increase with process variables such as temperature and the rind-to-solution ratio. The activation energy decreased as the process temperature increased, ranging from 3.723 to 0.928 kJ mol-1 for water loss and from 1.733 to 0.903 kJ mol-1 for solid gain, respectively. The sample treated with microwaves exhibited the maximum dehydration coefficient, rendering it appropriate for producing dehydrated products. Five empirical models were utilized, with the power law model (R 2 = 0.983) and the Magee model (R 2 = 0.950) being the most suitable for water loss data and solid gain, respectively.

Influence of a double-stage solar tunnel dryer on the preservation of quality characteristics and the Modelling of colour variations in red chili peppers

In this work, the influence of two-stage solar tunnel drying on the preservation of quality attributes of both chili pepper varieties, Mareko Fana (MF) and Bako Local (BL), was studied. Both varieties were dried in different drying modalities, i.e. solar tunnel and open sun drying. The quality attributes were evaluated during the drying process using FTIR and spectrophotometry techniques. Different colour evolution models were implemented and a suitable model was selected. The results showed that after drying of the Mareko Fana chili variety, the lightness retention was found in the range of 81 %-89 %, the redness retention between 25 % and 42 % and the yellowness retention between 14 % and 38 %. For the Bako Local variety, the values were in the range of 78 %-82 %, 42 %-60 % and 36 %-55 %, respectively. The first order model gave a higher correlation coefficient (R2 > 0.96), which indicated the suitability of the model for predicting the color variation for both varieties. The volatile aromatic compounds in the chili peppers were greatly lost during open sun drying, while solar tunnel drying maintained these compounds for both varieties. However, during the solar tunnel drying process, a significant amount of alkyl halides or alkyl-chlorides were lost. The amount of dihydrocapsaicin and capsaicin from the chili peppers ranged from 10,172 μg/kg to 16,313 μg/kg and 16,676 μg/kg to 27,189 μg/kg for both dihydrocapsaicin and capsaicin, respectively. In tunnel, open-air, and uncontrolled open-air solar drying, the MF chili variety lost copsaicinoid content by 3.4 %, 14.8 %, and 38.3 %, respectively; in the BL variety, comparable losses were 1.8 %, 4.4 %, and 13.6 %. A minimum loss of ascorbic acids was recorded during solar tunnel drying. The results showed that well-designed double stage solar tunnel dryers are important for effective drying processes that preserve quality attributes of the chili pepper.

Comparative evaluation of drying methods for struvite produced from electrocoagulated source-separated urine: Implications for quality, energy and cost-effectiveness

Struvite precipitation from source-separated urine is crucial for waste utilization and sustainability. However, after precipitation, the high moisture content of struvite necessitates an additional drying process that can be costly and inefficient. In the present study, the performance of different drying methods-open sun drying, air drying, conventional drying (20-100 °C), and microwave drying (180-720 W) on the quality of struvite obtained from source-separated urine through electrocoagulation using Mg-Mg electrodes were evaluated. It was found that higher temperatures and power in the convective oven and microwave resulted in higher diffusivity (10-9-10-7 m2s-1), leading to reduced drying times. Different models were employed to comprehend the drying mechanism, and the one with the highest correlation coefficient (R2 = 0.99) and the lowest statistical values was selected. The key findings indicated that higher power and temperature levels were more cost-effective. However, characterization of the dried struvite using X-ray diffraction and Fourier-transformed infrared spectroscopy, disintegration of struvite crystals at temperatures above 60 °C in the conventional oven and 180 W in the microwave oven was observed. Based on the results, we conclude that sun drying is a cost-effective and environmentally friendly alternative for drying struvite without compromising its quality.

Influence of Ultrasonic and Chemical Pretreatments on Quality Attributes of Dried Pepper (Capsicum annuum)

This study investigates the effects of ultrasound, in combination with chemical pretreatments, on the quality attributes (total phenolic and carotenoid content, antioxidant activity (2,2-Diphenyl-1-picrylhydrazyl assay (DPPH)), ferric-reducing ability (FRAP), CIE L* a* b* color, non-enzymatic browning, rehydration ratio, textural and morphological properties) of red pepper subjected to drying (hot air drying or freeze drying). The fractional factorial design was used to assess the impact of factors. The global Derringer desirability function was used to determine the optimal conditions for the best quality attributes of dried pepper. The drying method influenced total phenolic content, a* (redness), and initial rehydration ratio; pretreatment time significantly affected FRAP antiradical activity, a*, chroma and non-browning index, while pH-value had a significant effect on the texture of dried pepper. Non-enzymatic browning was reduced to 72.6%, while the DPPH antioxidant capacity of freeze-dried peppers was enhanced from 4.2% to 71.9%. Ultrasonic pretreatment led to changes in the pepper morphology, while potassium metabisulfite (KMS) was a more effective additive than citric acid.

Development of highly reusable, mechanically stablecorn starch-based aerogel using glycerol for potential application in the storage of fresh spinach leaves

Impact of glycerol on the physico-functional, morphological, mechanical, and rehydration properties ofcorn starch-based aerogel has been investigated. The aerogel was prepared from hydrogel (sol-gel method) using solvent exchange and supercritical CO₂ drying. Glycerol-infused aerogel had a more connected, denser structure (0.38-0.45 g/cm³), enhanced hygroscopic behavior, and was reusable up to eight times in terms of its capacity to absorb water after being drawn from the soaked sample. However, the inclusion of glycerol reduced the aerogel's porosity (75.89-69.91 %) and water absorption rate (WAR; 118.53-84.64 %) but enhanced its percentage shrinkage (75.03-77.99 %) and compressive strength (26.01-295.06 N). The most effective models for describing the rehydration behavior of aerogel were determined to be the Page, Weibull, and Modified Peleg models. Glycerol addition improved the internal strength of the aerogel so could be recycled without significant change in the physical characteristics of the aerogel. By effectively eliminating the condensed moisture that was developed inside the packing owing to the transpiration of fresh spinach leaves, the aerogel extended the storage life of the leaves by up to eight days. The glycerol-based aerogel has the potential to be employed as a carrier matrix for various chemicals and a moisture scavenger.

Analysis of Volatiles of Rose Pepper Fruits by GC/MS: Drying Kinetics, Essential Oil Yield, and External Color Analysis

Condiments and culinary supplements are subjected to long-term storage and may undergo physical, chemical, and biological changes that can influence their quality. Thus, the objective of the present study was to analyze the drying kinetics of rose pepper (Schinus terebinthifolius Raddi) fruits in an oven with forced air circulation at different temperatures, namely, 45, 55, 65, and 75°C, and determine the effective diffusion coefficient and activation energy using different mathematical models. Furthermore, the effects of the different drying temperatures were analyzed for external color parameters and yield of essential oil contents by gas chromatography coupled to a mass spectrometer. Of the ten models used for fitting, Thompson’s model was one with the best fitting to represent the drying of rose pepper fruits. The diffusion coefficient increases with the elevation of drying air temperature, described by the Arrhenius equation, with activation energy of 53.579 kJ·mol−1. The color of the fruits decreased in lightness (L ${}^{\ast }$ ) with the increase in temperature. Of the thirty-eight terpenes identified, α-pinene and cis-ocimene were the most abundant, with the overall highest yield being found at a drying temperature of 45°C.