Impact of different pretreatments on drying kinetics and quality of button mushroom slices dried by hot-air or electrohydrodynamic drying

Study on the quality characteristics of jujube slices under different pretreatment and drying methods

This study investigates the effects of different pretreatment methods, cold plasma (CP) and ultrasound (US), as well as different drying techniques, including vacuum freeze-drying (FD), hot air drying (HAD), and microwave coupled with pulsed vacuum drying (MPVD), on the quality characteristics of winter jujube slices. The physical, chemical, and functional properties were analyzed, encompassing farinograph attributes, particle size, cation exchange capacity, total phenolic and flavonoid content, and flavor compounds were analyzed. In terms of physical properties, jujube slices subjected to MPVD demonstrate superior water-holding capacity at 2.93 g/g and enhanced fluidity, with a sliding angle of 34.98° and an angle of repose of 43.47°, compared to FD jujube slices. Additionally, it exhibits a rehydration capacity of 2.98 g/g and a bulk density of 0.49 g/mL. Regarding chemical composition, the cation exchange capacity of US-FD jujube slices is measured at 0.64 mmol/g, while the total phenolic content reaches 11.97 mg/g, and the flavonoid content in CP-MPVD jujube slices is 5.21 mg/g. Notably, the cation exchange capacity of MPVD jujube slices pretreated by CP and US is 0.46 and 0.55 mmol/g, respectively. Concerning volatile compounds and flavor, FD slices retain higher concentrations of aldehydes (11.39 %) and alkenes (16.88 %), whereas MPVD slices contain 21.20 % alkanes. HAD slices contain the highest aromatic hydrocarbon content at 34.97 %. In summary, the optimized combination of CP and MPVD can enhance the drying efficiency of jujube slices, increase the flavonoid content in jujube slices, and improve their quality characteristics.

Effects of ultrasound-assisted plasma-activated water pretreatment combined with electrohydrodynamics on drying characteristics, active ingredients and volatile components of yam (Dioscorea opposita)

This paper explores the effect of ultrasound (US) assisted plasma-activated water (PAW) or deionized water (DW) pretreatment combined with electrohydrodynamics (EHD) on the drying of yam. The activity characteristics of four pretreatments (plasma activated water combined with ultrasound (PAW + US), plasma activated water (PAW), deionized water combined with ultrasound (DW + US), and deionized water (DW) (control)) and their effects on drying characteristics, rehydration rate, color, reducing sugars, total phenols, infrared spectra, and volatile compositions of yam under EHD drying process were investigated. The results showed that the media pretreaded by ultrasound (US) combined with plasma-activated water (PAW) has lower media of pH (53.84 % lower than that of US + DW), higher nitrite ion concentration (311 times over US + DW), higher oxidation reduction potential (50.58 % higher than that of US + DW), and higher electrical conductivity (99.29 times over US + DW). And ultrasonic pretreatment (US) combined with plasma-activated water (PAW) drying resulted in faster drying, better rehydration rate, higher brightness L * (18.35 % higher than that of US + DW) and whiteness (1.1 % higher than that of US + DW), and retention of more reducing sugars (10.96 % higher than that of US + DW) and total phenols (14.04 % higher than that of US + DW), and a higher variety and content of volatile components. This provides an experimental and theoretical basis for the application of ultrasonic (US) combined with plasma-activated water (PAW) pretreatment to electrohydrodynamic drying.

Enhancing ultrasonic-assisted drying of low-porosity products through pulsed electric field (PEF) pretreatment: The case of butternut squash

Ultrasonic-assisted drying is an effective technique for accelerating drying processes, particularly for products with high porosity. The structural changes induced by pulsed electric field (PEF) treatment can make low-porosity products more susceptible to the effects of ultrasound during drying. This study aimed to investigate the influence of PEF treatment on the structure of low-porosity products, such as butternut squash, and to evaluate its effect on ultrasonic-assisted drying. PEF pretreatment altered the physicochemical and microstructural properties of butternut squash. Thus, the higher the energy input, the higher the cell disintegration rate, the lower the shearing force and the lower the water holding capacity. For the same energy input applied, no influence was observed from the different combinations of pulse number and electric field intensity used. The microstructural analysis also showed greater effects with increasing intensity of PEF treatments. All these changes affected the subsequent drying, increasing the drying rate of conventional drying. Moreover, PEF pretreatment enhanced the ultrasound effects when applied during drying, reducing drying time by up to 47% when moderate PEF intensity was used. Therefore, PEF pretreatment under the appropriate conditions could make ultrasound-assisted drying of low-porosity products, such as butternut squash, more feasible.

Influence of electrohydrodynamics on the drying characteristics, microstructure and volatile composition of apricot abalone mushroom (Pleurotus eryngii)

The study explored the use of current fluid dynamics drying technology for apricot abalone mushroom, examining how different output voltages (15, 25, and 35 kV) affected drying characteristics, microstructure, and volatile components. Comparisons were made with samples dried using hot air drying (HAD) and natural air drying (AD). Results revealed that HAD had the fastest drying rate at 0.29664(g·h-1). However, apricot abalone mushroom treated with electrohydrodynamic drying (EHD) maintained a color closer to fresh samples, exhibited a 21% increase in the ordered structure of protein secondary structure, a 12.5-fold increase in bound water content, and the most stable cell structure compared to HAD and AD treatments. A total of 83 volatile organic compounds were identified in the apricot abalone mushroom, with alcohols and aldehydes being the most prominent in terms of threshold and relative content, peaking in the 35 kV treatment group. These findings provide both experimental and theoretical insights into applying current fluid dynamics for drying apricot abalone mushroom.

The Impact of Drying Methods on the Quality of Blanched Yellow Mealworm (Tenebrio molitor L.) Larvae

The growing world population necessitates the implementation of appropriate processing technologies for edible insects. The objective of this study was to examine the impact of distinct drying techniques, including convective drying at 70 °C (70CD) and 90 °C (90CD) and freeze-drying (FD), on the drying kinetics, physical characteristics (water activity, color), chemical characteristics (chemical composition, amino acid profile, oil properties, total polyphenol content and antioxidant activity, mineral composition, FTIR), and presence of hazards (allergens, microorganisms) of blanched yellow mealworm larvae. The freeze-drying process results in greater lightness and reduced moisture content and water activity. The study demonstrated that the freeze-dried insects exhibited lower contents of protein and essential amino acids as compared to the convective-dried insects. The lowest content of total polyphenols was found in the freeze-dried yellow mealworm larvae; however, the highest antioxidant activity was determined for those insects. Although the oil isolated from the freeze-dried insects exhibited the lowest acid and peroxide values, it proved to have the lowest PUFA content and oxidative stability. All the samples met the microbiological criteria for dried insects. The results of the study demonstrate that a high temperature during the CD method does not result in the anticipated undesirable changes. It appears that freeze-drying is not the optimal method for preserving the nutritional value of insects, particularly with regard to the quality of protein and oil.

Revealing the mechanism of post-harvest processing on rose quality based on dynamic changes in water content, enzyme activity, volatile and non-volatile metabolites

Existing studies on post-harvest processing of edible roses have mainly focused on processing techniques and physicochemical properties of the final dried products, with limited studies on how changes in metabolites during processing affect the quality of these products. This study investigated changes in water content and status, enzyme activity, phenolic compounds, and volatile and non-volatile compounds during processing and revealed the mechanisms by which post-harvest processing (drying without blanching (WBD) and drying with blanching (BD)) affects the quality of dried roses by establishing their correlations. Results showed that the blanching reduced the relative content of free water and water activity, thus reducing the subsequent drying time and enzyme activity. The BD method caused higher levels of phenolic compounds than the WBD method in terms of gallic acid, ellagic acid, epicatechin, and quercetin. The OPLS-DA analysis identified 6 differential volatiles out of 72 detected volatiles, contributing to the unique aroma of dried roses by activating olfactory receptors through hydrogen bonding and hydrophobic interactions. 58 differential metabolites were screened from 964 non-volatile metabolites. KEGG pathway analysis revealed that the changes in volatile and non-volatile metabolites induced by different processing methods were due to the effect of blanching on glutathione and fatty acid metabolism. These findings provide a comprehensive understanding of how post-harvest processing affects the quality of dried roses.

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.

Optimum drying conditions for ginger (Zingiber officinale Roscoe) based on time, energy consumption and physicochemical quality

The effect of ultrasonic pre-treatment on moisture removal characteristics of ginger in a convective dryer was investigated. The slabs were dried by practicing sonication durations of 0, 15 and 30 min at different levels of the air temperature and velocity. Following increasing the sonication duration and air temperature, required time and energy to dehydrate the samples were decreased. The pre-treatment played important role in improving rehydration capability and surface color retention in the dried gingers. Content of the main volatile component (α-Zingiberene) was not influenced by the sonication. Mean values for the phenolic contents and antioxidant activity at sonication duration of 0, 15 and 30 min were determined to be 18.93, 18.15 and 17.49 GAE/g dry matter and 83.57, 78.33 and 74.58 %, respectively. The desired values for the temperature, velocity and sonication duration were revealed to be about 66 °C, 3 m/s and 20 min, respectively.

Effect of Pulsed Electric Field Technology on the Composition and Bioactive Compounds of Black Soldier Fly Larvae Dried with Convective and Infrared-Convective Methods

In recent years, an increasing interest has been shown in alternative food sources. Many studies are focused on the use of insects. The aim of this study was to investigate the changes in the chemical and thermal properties of black soldier fly larvae influenced by the pulsed electric field (PEF) and convective (CD) or infrared-convective (IR-CD) drying techniques. Examinations of the basic chemical composition, properties of extracted fat (fatty acid composition, acid and peroxide values, and oxidative stability), total polyphenol content, antioxidant activity, allergen content, and thermogravimetric analysis (TGA) were performed. Generally, the results showed that dried black soldier fly larvae are a good source of protein and fat, up to 33% and 44%, respectively. The fat extracted from the dried insects consisted mainly of saturated fatty acids (above 75%), in particular lauric acid (C12:0). A good oxidative stability of the fat was also observed, especially from samples dried with the IR-CD method. The convective drying technique allowed for better preservation of protein content compared to samples dried with the IR-CD method. Nevertheless, samples treated with PEF were characterized by significantly lower protein content. The samples after PEF pretreatment, with an intensity of 20 and 40 kJ/kg and dried with the IR-CD method, were represented by a significantly higher total polyphenol content and antioxidant activity. Furthermore, in most cases, the convectively dried samples were characterized by a higher allergen content, both crustaceans and mollusks. Taking into account all of the investigated properties, it can be stated that the samples without treatment and those that were PEF-treated with an intensity of 40 kJ/kg and dried with the infrared-convective method (IR-CD) were the most rewarding from the nutritional point of view.

Electrohydrodynamic drying of citrus (Citrus sinensis L.) peel: Comparative evaluation on the physiochemical quality and volatile profiles

Based on the concept of circular economy, citrus peel was considered a valuable source of bioactive compounds for high-value foods. Electrohydrodynamic (EHD) drying is a novel technology appropriated for the dehydration of heat-sensitive products such as citrus peel. In current work, EHD drying of citrus peel was performed based on alternating current (AC) or direct current (DC) sources at various voltage levels (9, 18, 27, 36, and 45 kV). The effect of EHD on drying characteristics, water retention capacity, enzyme inactivation, phytochemical contents (phenolic compounds and carotenoids), and volatile compounds of citrus peel were evaluated and compared. Results showed that the drying time in the AC electric field was shorter compared to DC electric field at the same applied voltages due to the polarization layer formed by unipolar charges. The applied voltage determined electric field strength as well as the degree of tissue collapse and cell membrane rupture. EHD elucidated the transformation and degradation of phytochemicals including phenolic compounds, carotenoids, and volatile composition in proportion to the applied voltage. The findings indicate that EHD drying with AC improves drying behaviors, inactivates enzymes, and retains the phytochemical properties of citrus peel.

Review of postharvest processing of edible wild-grown mushrooms

Edible wild-grown mushrooms, plentiful in resources, have excellent organoleptic properties, flavor, nutrition, and bioactive substances. However, fresh mushrooms, which have high water and enzymatic activity, are not protected by cuticles and are easily attacked by microorganisms. And wild-grown mushroom harvesting is seasonal the harvest of edible wild-grown mushrooms is subject to seasonality, so their market availability is challenging. Many processing methods have been used for postharvest mushroom processing, including sun drying, freezing, packaging, electron beam radiation, edible coating, ozone, and cooking, whose effects on the parameters and composition of the mushrooms are not entirely positive. This paper reviews the effect of processing methods on the quality of wild and some cultivated edible mushrooms. Drying and cooking, as thermal processes, reduce hardness, texture, and color browning, with the parallel that drying reduces the content of proteins, polysaccharides, and phenolics while cooking increases the chemical composition. Freezing, which allows mushrooms to retain better hardness, color, and higher chemical content, is a better processing method. Water washing and ozone help maintain color by inhibiting enzymatic browning. Edible coating facilitates the maintenance of hardness and total sugar content. Electrolytic water (EW) maintains total phenol levels and soluble protein content. Pulsed electric field and ultrasound (US) inhibit microbial growth. Frying maintains carbohydrates, lipids, phenolics, and proteins. And the mushrooms processed by these methods are safe. They are the focus of future research that combines different methods or develops new processing methods, molecular mechanisms of chemical composition changes, and exploring the application areas of wild mushrooms.

Influence of electrohydrodynamics on the drying characteristics and physicochemical properties of garlic

Electrohydrodynamic (EHD) drying, natural air drying (AD) and hot air drying (HAD) were used to comprehensively study the drying characteristics and physicochemical properties of garlic, and low-field nuclear magnetic resonance (NMR), infrared spectroscopy, scanning electron microscopy and other technologies were used as detection methods. In terms of drying characteristics, HAD has the largest effective diffusion coefficient of moisture and the shortest average drying time. EHD-treated garlic slices had the most attractive color, the highest rehydration rate, the most stable cell structure, the highest content of active ingredients, and the most stable protein secondary structure. Therefore, electrohydrodynamic drying is a promising garlic slice drying technology and provides an effective method for the large-scale production of high-quality garlic.

Qualitative, energy and environmental aspects of microwave drying of pre-treated apple slices

In the present research, response parameters such as specific energy consumption (SEC), thermal efficiency (TE), energy efficiency (EF), drying time (DT), greenhouse gas (GHG) emission (such as CO2 and NOx), and quality features (color variation and shrinkage) were modeled by response surface methodology (RSM) for apple slices dried in a microwave dryer under ultrasonication (30 ℃-10 min) and blanching (80 °C-2 min) pretreatments. Also, RSM was applied to optimize two independent parameters including microwave power and sample thickness in the levels 100, 200, and 300 W and 2, 4, and 6 mm, respectively. The results indicated the significant influence (P < 0.01) of the independent parameters on the response parameters. The vales of SEC, DT, GHG emission, shrinkage, and color difference were linearly decreased with the declining sample thickness and increasing microwave power, while the energy and thermal efficiencies were increased by a quadratic equation. The use of ultrasonication and blanching pretreatments decreased the SEC, GHG emissions, and DT; while improving the quality of the samples as compared to the non-treated slices. The optimization results showed the optimal drying times (31.55, 82.19, and 50.55 min), SEC (3.42, 10.07, and 4.37 MJ/kg), CO2 with natural gas (1539.75, 1518.75, and 4585 g), CO2 with gas oil (3662.53, 2099.25, 2721.25 g), NOx with natural gas (10.094, 9.956, and 12.906 g), and NOx with gas oil (12.934, 12.758, and 16.538 g) at a microwave power of 300 W and sample thickness of 2 mm with desirability of 0.921, 0.935, and 0.916 for control samples, ultrasonicated, and blanched, respectively.

Application of novel pretreatment technologies for intensification of drying performance and quality attributes of food commodities: a review

Drying is an energy-intensive process that can be reduced by the application of pretreatment prior to drying to enhance mass transfer and minimize energy consumption. This review summarizes the mechanistic aspects and applications of emerging pretreatment approaches, namely ohmic heating (OH), ultrasound (US), high pressure processing (HPP), and pulsed electric field (PEF), with emphasis on the enhancement of mass transfer and quality attributes of foods. Novel pretreatments significantly improved the drying efficiency by increasing mass transfer, cavitation, and microchannel formation within the cell structure. Various processing parameters have great influence on the drying performance and quality attributes of foods. Several studies have shown that novel pretreatments (individual and combined) can significantly save energy while improving the overall drying performance and retaining the quality attributes. This work would be useful for understanding the mechanisms of novel pretreatment technologies and their applications for future commercial research and development activities.

Effect of Ultrasound Pretreatment on the Moisture Migration and Quality of Cantharellus cibarius Following Hot Air Drying

The effect of different ultrasound pretreatment powers (0-500 W) before hot air drying on the moisture migration and quality of Cantharellus cibarius (C. cibarius) was investigated in this study. The results showed that the ultrasound pretreatment accelerated the drying rate. When the ultrasound power was 400 W, the drying time of C. cibarius was reduced by 18.90% compared with the control group. The low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) results showed that the ultrasound pretreatment increased the water mobility in C. cibarius. The scanning electron microscopy (SEM) results revealed that the ultrasound pretreatment promoted the expansion of intercellular pores. In addition, the rehydration capacity and quality characteristics of the ultrasound-pretreated dried C. cibarius were better than those of the control group. Overall, this study concluded that ultrasound pretreatment is a promising pretreatment method for the hot air drying of C. cibarius products to reduce the total drying time significantly and improve the retention rate of the total phenolics and flavonoids of dried C. cibarius.

New preservation and detection technologies for edible mushrooms: A review

Edible mushrooms are nutritious, tasty, and have medicinal value, which makes them very popular. Fresh mushrooms have a high water content and a crisp texture. They demonstrate strong metabolic activity after harvesting. However, they are prone to textural changes, microbial infestation, and nutritional and flavor loss, and they therefore require appropriate post-harvest processing and preservation. Important factors affecting safety and quality during their processing and storage include their quality, source, microbial contamination, physical damage, and chemical residues. Thus, these aspects should be tested carefully to ensure safety. In recent years, many new techniques have been used to preserve mushrooms, including electrofluidic drying and cold plasma treatment, as well as new packaging and coating technologies. In terms of detection, many new detection techniques, such as nuclear magnetic resonance (NMR), imaging technology, and spectroscopy can be used as rapid and effective means of detection. This paper reviews the new technological methods for processing and detecting the quality of mainstream edible mushrooms. It mainly introduces their working principles and application, and highlights the future direction of preservation, processing, and quality detection technologies for edible mushrooms. Adopting appropriate post-harvest processing and preservation techniques can maintain the organoleptic properties, nutrition, and flavor of mushrooms effectively. The use of rapid, accurate, and non-destructive testing methods can provide a strong assurance of food safety. At present, these new processing, preservation and testing methods have achieved good results but at the same time there are certain shortcomings. So it is recommended that they also be continuously researched and improved, for example through the use of new technologies and combinations of different technologies. © 2023 Society of Chemical Industry.

Effect of Electrohydrodynamic (EHD) on Drying Kinetics and Quality Characteristics of Shiitake Mushroom

The effect of an electrohydrodynamic (EHD) drying system on the drying kinetics, microstructure and nutritional composition of shiitake mushrooms was studied. Shiitake mushroom slices were dried at 0, 18, 22, 26, 30 and 34 kV. The results showed that the drying rate, effective moisture diffusion coefficient and shrinkage of the EHD treatment group were significantly higher than those of the control group. The 34 kV treatment group had the highest drying rate (0.24 g W/g DM × h) and the highest effective moisture diffusion coefficient (1.45 × 10−6 m2/s), which were 6.75 and 7.41 times higher than those of the control group, respectively. The control group had the highest rehydration ratio (7.72) and showed unsatisfactory color performance. The scanning electron microscopy (SEM) results showed that compared with the control group, the surface of samples dried by EHD exhibited different degrees of encrustation, and the area of encrustation increased with increasing voltage. After analysis by Fourier transform infrared (FTIR) spectroscopy, it was found that the samples of both the EHD-treated and control groups had similar absorption peak positions, but the intensity of the absorption peak of the EHD-dried samples was greater. Compared with the control group, the shiitake mushroom slices dried by EHD had a higher protein content and polysaccharide content. The polysaccharide content in 22 kV treatment group was the highest (4.67 g/100 g), and the protein content in 26 kV and 34 kV treatment groups was the highest (17.0 g/100 g). This study provides an experimental and theoretical basis for an in-depth study of the drying kinetics of shiitake mushrooms and provides theoretical guidance and clues for the wider application of EHD drying technology.