Drying Time Research Articles

Fast-airflow tumble clothes dryer with small thermoelectric heat pump: Experimental evaluation

Residential clothes drying accounts for about 5 % of the total residential-sector energy consumption in the United States. Most dryers use electric resistance heaters to dry clothes and have low efficiencies. Higher-efficiency dryers that use vapor compression heat pumps are expensive and complex and have not gained a large market share in the United States. A novel tumble clothes dryer using a small thermoelectric heat pump with faster airflow than typical dryers is presented in this work. The benchtop performance of the thermoelectric heat pump and high-speed blower are presented, and the development of the prototype dryer is described. The dryer was tested for efficiency and dry time for a range of airflow rates and applied currents to the thermoelectric heat pump. The combined efficiency factor was 5.09–6.29 lbBDW/kWh (specific moisture extraction rate of 1.23–1.53 kgw/kWh) with 100–138 min dry times for these tests. The measured efficiency was 36 %–68 % greater than the minimum efficiency standard in the United States, and compared with vapor compression heat pump–based clothes dryers, the prototype dryer had less expensive, less complex components and did not use refrigerants. The performance of this small thermoelectric heat pump clothes dryer is also compared with previous iterations of the thermoelectric tumble clothes dryer described in the literature.

Controlling Drying Conditions in Vacuum for Uniform Film Formation in Inkjet-Printed OLEDs.

The drying process of inkjet-printed organic light-emitting diodes (OLEDs) is influenced by both ink properties and external environmental factors, which ultimately affect the film profile. First, we conducted a detailed investigation of the drying time based on changes in the boiling point (BP) of mixed solvents and analyzed the correlation with the film profile. Under atmospheric drying conditions in a nitrogen (N2) atmosphere, the increased drying time under capillary-driven flow leads to greater particle movement toward the edges, significantly increasing the coffee-ring effect. Additionally, using a high-boiling-point solvent mixture of ethyl 4-methylbenzoate (EMB) and 2-ethylhexyl benzoate (EHB), we produced uniform thin films both between and within pixels (inter and intrapixel uniformity) through a vacuum drying process. In particular, we proposed a drying process model that divides the drying of inkjet pixels into a microfluidic phase and a gelation phase. Through five gelation phase-controlled vacuum drying experiments, the morphology within the pixels was precisely investigated. By sufficiently removing residual solvents after the microfluidic phase and then proceeding with heating, we produced uniform thin films. Furthermore, we fabricated OLED devices using this gelation phase-controlled vacuum drying process, achieving uniform pixel emission and improved device performance.

Impact of olive oil and potassium carbonate pretreatment on physico-chemical properties of sun-dried Sundar Khani raisins (Vitis vinifera L.)

Sundar Khani is native grape variety of Pakistan which has long berry length and significantly rich in taste and sweetness. There is limited literature on pretreatment and drying data for this valuable variety of Grapes. Current study was conducted to investigate the physio-chemical indices of potassium carbonate (K2CO3) and olive oil combined treatments followed by natural sun drying method. The effects of 2 % K2CO3 pretreatments alone and in combination with various amounts of pure olive oil (1 %, 2 %, and 3 %) were studied. The results showed that, physical attributes like raisin length, width, volume, weight and total replication weight increased under distilled water treatment, while, combination of 2 % K2CO3 + 3 % Olive oil significantly reduced the drying time, 2 % K2CO3 + 1 % Olive oil gave higher final yield, rehydration ratio was highest under dH2O treatment and greater decay loss was observed at 2 %K2CO3 + 2 % olive oil. Further, 2 % K2CO3 displayed higher ratios of total soluble solids, sugars and peroxidase enzyme activity as well as titratable acidity, anthocyanins, total phenols, flavonoids were maximum at 2 % K2CO3 + 2 % Olive oil pretreatment. In addition, 2 % K2CO3 + 3 % Olive oil increased the Catalase enzyme activity as well as achieved higher scores in the evaluation of sensory attributes particularly morphological form, color and overall acceptance. This study aimed to investigate the physicochemical indices of Sundar Khani grapes under different pretreatment and sun-drying conditions using K2CO3 and olive oil and it could be suggested that raisin production of Sundar Khani by using above mentioned treatments along with sun drying could have future scope both in export and industrial markets due to its incredible reduction in drying and processing time.

Optimizing insect repellence in open sun drying of fish through the combined influence of salt, turmeric, pepper and the bacteriocin nisin under tropical conditions

AbstractBackgroundSun drying of fish in open air is an age‐old traditional practice in Asia and some other parts of the world. This study aims to suggest optimal field doses of turmeric, pepper, salt and the bacteriocin nisin (food additive, E234) for open‐sun‐dried silver jewfish (Johnius argentatus) under a tropical environment. Investigations were carried out on the blowfly infestation, proximate composition, water reconstitution properties and organoleptic and microbial quality of open‐air‐dried fish samples.ResultsA direct relationship between moisture reduction and drying period was observed with salt‐treated samples demonstrating accelerated moisture reduction, reaching as low as 14.1% after 34 h. Turmeric and pepper treatments provided some protection against weight loss but ultimately extended the drying time to 38 h. Botanical pesticides like turmeric or pepper exhibited significant efficacy against blowfly adult and larval infestation with similar efficacy observed in 15% and 25% salt‐treated samples. Proximate composition analysis revealed that salt‐treated samples had lower moisture ranging from 14.1% to 16.0% but higher protein of 58.2%–62.1%, while the lipid and ash content did not vary significantly (p > 0.05). The water reconstitution properties of salt‐treated samples exhibited superior rehydration rates, with the highest in nisin (Niseen S) + 15% salt‐treated samples at 60°C, while organoleptic evaluations revealed salt‐treated samples to possess favourable attributes with minimal insect infestation and broken pieces. Finally, microbial analysis demonstrated the lowest aerobic plate count in dried fish samples treated with nisin (Niseen S) alone or in combination with 15% salt and/or 3% turmeric ranging from 3.97 ± 0.20 to 4.33 ± 0.07 log cfu/g.ConclusionIt is concluded that 200 ppm nisin (Niseen S)‐treated samples in combination with 3% turmeric and/or 15% salt are a viable option for producing high‐quality dried fish in traditional open‐air sun‐drying practices.

Short-Cycle Autoclave Sterilization of Instruments in Same-Day Ophthalmic Surgeries

What Is the Issue? The volume of ophthalmic surgeries is increasingly high, with cataract surgery being 1 of the most performed surgeries in Canada. Infections following ophthalmic surgeries, while rare, can cause severe complications that may lead to irreversible vision loss. Reducing postsurgery infections is a high priority in clinical practice. Running a full wrapped, terminal steam sterilization cycle for ophthalmic instruments in autoclaves may be inefficient for ophthalmic surgeries and may cause unnecessary heavy economic and environmental burdens due to high surgical volumes. Using instruments sterilized on a short cycle between sequential same-day ophthalmic surgeries may help improve efficiency and reduce resources used. These instruments are generally processed using autoclaves (i.e., steam sterilizers); the effectiveness of a shorter-cycle method of sterilization is unclear. What Did We Do? To inform decisions regarding the use of autoclaves for short-cycle sterilization for sequential same-day instrument use in ophthalmic surgery, we sought to identify and summarize evidence comparing this method to full-cycle sterilization of wrapped instruments and identify any relevant recommendations. We searched key resources, including journal citation databases, and conducted a focused internet search for relevant evidence published since 2012. One reviewer screened articles for inclusion based on predefined criteria. What Did We Find? In a laboratory setting to simulate sequential same-day procedures, short-cycle sterilization with interrupted dry time for unwrapped ophthalmic instruments is feasibly as effective as full-cycle sterilization for wrapped instruments using the STATIM autoclave. Similarly, short-cycle sterilization with interrupted dry time for contained ophthalmic instruments is feasibly as effective as full-cycle sterilization for contained instruments using the AMSCO autoclave. For sequential same-day ophthalmic procedures, wet instruments sterilized by a short-cycle process with an interrupted dry time can remain sterile for at least 3 minutes if kept in a covered sterilizer containment device. One guideline recommends that wrapped or unwrapped ophthalmic instruments sterilized by a short-cycle process without full drying should be stored in a covered containment device until retrieved by staff wearing sterile gloves and gowns in the operating room for the subsequent surgery after a short delay. Phaco handpieces should be immediately primed with a balanced salt solution and remain wet as they sit on the sterile instrument table. We did not identify any clinical setting evidence from studies or autoclave manufacturers. It is unclear if clinical outcomes differ between patients undergoing sequential same-day ophthalmic surgeries using short-cycle sterilized instruments and those undergoing surgery using full-cycle sterilized instruments. What Does This Mean? Preliminary laboratory evidence and guideline recommendations supporting the use of autoclaves for short-cycle sterilization of instruments for sequential same-day ophthalmic surgeries are available. However, there is no clinical effectiveness evidence available on this process in patient settings. Future research is necessary to understand the clinical safety of using instruments sterilized by short cycles for sequential same-day use for patients undergoing ophthalmic surgeries. In addition to the evidence and recommendations identified, other factors, such as environmental influence, may be useful considerations when making decisions about short-cycle sterilization for sequential same-day instrument use for ophthalmic surgery.

Enhancing moisture transfer and quality attributes of tomato slices through synergistic cold plasma and Osmodehydration pretreatments during infrared-assisted pulsed vacuum drying

The present study examines the impacts of combined cold plasma treated water (PW) and osmodehydration (OD) pretreatment (PO), and operation parameters like PW duration and voltage of treatment on the dehydration, functional and sensory characteristics of sliced tomato fruits subjected to simultaneous infrared-assisted pulsed vacuum drying (IR-PVD). From the results, PO pretreatment modified the surface structures by the formation of microchannels and cavities through impingements from the reactive species (RS), and was improved due to increased treatment duration and voltage, and resulted in accelerating the transfer of moisture from the slices to the surroundings during the dehydration process. Consequently, PO pretreatment achieved an enhancement in the moisture diffusivity by up to 64.83%, shortened the total drying time by up to 40%, and presented substantial improvements in the physicochemical properties including vitamin C, lycopene, colour, total soluble solids, phenolic and flavonoid contents, and overall human acceptability. However, significant decreases in rehydration and hardness properties were shown compared with control, and higher rehydration by up to 21.66% at higher treatment duration and voltage when compared with OD pretreatment. Overall, PO pretreatment incited an effective moisture removal and retention of vital physicochemical and bioactive constituents in the slices due to the activities of plasma injected RS. This study provides an empirical basis for the application of PO during IR-PVD of fruits and vegetables and demonstrated as a suitable energy-saving alternative for improving the conventional OD of foods in the industry.

Optimization of microwave-assisted drying of scallions (Allium fistulosum L.): A comprehensive study on drying kinetics, energy consumption, CO2 emissions, and thermodynamic properties

This study explores the effectiveness of microwave-assisted drying for scallions (Allium fistulosum L.), focusing on drying kinetics, energy consumption, CO2 emissions, and thermodynamic properties. Scallion samples were subjected to different microwave power levels (136 W and 264 W) and varying sample masses (5 g, 10 g, and 20 g) to assess the drying process. The Page model was identified as the most suitable for describing the drying kinetics, providing a precise fit to the experimental data. The study revealed that higher microwave power levels significantly enhanced the drying efficiency by increasing moisture diffusivity, thereby reducing drying time. The thermodynamic analysis indicated that the drying process is endothermic, requiring external energy for moisture removal, with positive enthalpy and Gibbs free energy values confirming the non-spontaneous nature of the process. Entropy analysis suggested a decrease in molecular disorder during drying. In terms of energy consumption and CO2 emissions, the results highlighted that microwave-assisted drying offers a lower environmental impact, with specific energy consumption (SEC) values demonstrating efficient energy use during the drying process. This study supports the viability of microwave-assisted drying as a sustainable and efficient method for processing scallions. The findings provide valuable insights for optimizing drying processes in the food industry, emphasizing the potential for microwave drying technologies to improve energy efficiency and reduce environmental impact.

Application of artificial intelligence to predict energy consumption and thermal efficiency of hybrid convection-radiation dryer for garlic slices

This study aims to examine the energy-related aspects of a hybrid convection-radiation drying technique employed in the drying process of garlic slices. Several factors, including infrared radiation intensity (1500, 2000, and 3000 W/m2), air temperature (40, 50, and 60 °C), and airflow rates of the drying chamber (0.7, 1.0, and 1.5 m/s) were evaluated to optimize the responses of drying time (min), energy consumption (kJ), thermal efficiency (%), and specific energy consumption (MJ/kg). Furthermore, an Artificial Neural Network model was employed to predict the effects of the parameters above on the drying system's specific energy consumption, energy consumption, drying time, and thermal efficiency. The obtained data were analyzed using a self-organizing map and principal component analysis. Interestingly, the findings showed that increasing the air temperature and infrared radiation intensity led to shorter drying times, while higher airflow rates resulted in longer drying durations. Additionally, it was found that higher infrared intensity and air temperature, combined with lower airflow rates, improved the energy indices. Increasing the air velocity to 1.0 and 1.5 m/s at the same air temperature and radiation intensity resulted in a considerable increase in drying time by 9 and 22.7%, respectively. The lowest efficiency value of 10.1% was observed at 40 °C temperature and an air velocity of 1.5 m/s. The Artificial Neural Network model demonstrated high accuracy with a Root Mean Square Error of 0.05 and an overall accuracy of (95%) in predicting the drying parameters. Notably, the self-organizing map visualization revealed that higher air temperatures and radiation corresponded to lower drying times, energy consumption, and specific energy consumption. Conversely, higher airflow rates resulted in increased drying time and energy consumption. The present study suggested that 60 °C, 3000 W/m2 and 0.7 m/s are optimum conditions for efficiently drying garlic slices under the hybrid dryer. This investigation addresses the limitations and deficiencies of previous work on energy optimization and efficiency analysis of garlic under a hybrid dryer with infrared heating systems. Further studies on the economic feasibility of applying such a system for sample drying and the impact of drying on the thermal behaviors of the products need additional investigation.

A simplified but improved numerical approach to determine moisture balance for plastic shrinkage cracking in concrete

This paper introduces an improved numerical approach for evaluating moisture balance on concrete surface which can initiate plastic shrinkage cracking on the surface of fresh concrete in concrete slab. Because plastic shrinkage cracks occur when the tensile stress induced from the surface drying of concrete exceeds the tensile strength in the freshly placed concrete, moisture balance calculated by the introduced approach can be used as the primary indicator for plastic shrinkage cracking. The numerical approach introduced in this paper therefore emphasized an exact evaluation of bleeding and evaporation on the concrete surface. In determining bleeding, the approach introduced in the previous study was improved through the consideration of additional influencing factors of the accelerator and steel fiber and the supplementation of additional experimental data. For reliable prediction of evaporation, an empirical relation was newly introduced. The reduction of evaporation rate with time was taken into consideration, and the use of the weighed characteristic velocity rather than the direct application of the wind velocity was recommended. Determination of an exact distribution for the weighed characteristic wind velocity on the surface of a concrete slab was based on computational fluid dynamic (CFD) analyses. In particular, the effect of installing a windscreen along the sides of the concrete slab was intensively examined. Upon verification of the introduced numerical approach through correlation studies between experimental data and numerical results, additional parametric studies were also performed to numerically examine the relative contribution of each influencing factor in plastic shrinkage cracking. Moreover, the introduced approach can effectively be used for the on-site prediction of surface drying time of a concrete slab and for the preparation of a proper curing strategy to mitigate plastic shrinkage cracking.

Coating effect of polyurethane-layered double hydroxide nanocomposite on steel

The motivation behind this work is the preparation of polyurethane-magnesium aluminum layered double hydroxide (PU-LDH) nanocomposite and its application as a coating for steel protection. The coating was prepared with different doses of LDH, ranging from 0 to 2% of the coating weight. The effect of different concentrations on the mechanical, adhesion, and surface properties of PU coating is studied. Firstly, LDH was prepared via the coprecipitation process and then distributed in PU matrix. The nanocomposites were then crosslinked in the form of coating layers on steel. The preparation of the thermally stable crystalline LDH nanoparticles with 89 nm particle size was confirmed by FTIR, XRD, DLS, and TGA. SEM photos showed the dispersed and intercalated structure. The coating characteristics demonstrate that addition of LDH decreased the drying time and increased the dry film thickness of PU up to 1.5% due to the crosslinking between the large surface area nanofiller and polyurethane matrix. Furthermore, the prepared LDH nanofiller increased the adhesion strength, impact resistance, abrasion resistance, modulus, and flexibility of PU due to the strong polymeric network structure. The 2% nanocomposite coating shows poor properties due to the excess concentration and heterogeneous dispersion of nanoparticles within the PU polymer. The resistance to fire and some chemicals was supported by the thermally and physically stable LDH nanoclay. The former characterizations state that the proposed PU-LDH nanocomposite is an enhanced and applicable coating.

Rapid ambient pressure drying preparation of bulk ZrO2-SiO2 aerogels with high thermal stability

In this study, the sol-gel stage co-precursor method was used to hydrophobically modify the gel and increase the content of alkali catalyst in the gel, thereby reducing the capillary force generated during ambient pressure drying and enhancing the strength of the gel skeleton. This improvement makes the gel skeleton structure not easy to destroy during the rapid drying process, thus greatly reducing the preparation time of atmospheric pressure drying, which could be as short as 10 h. It is worth mentioning that this method does not require extensive use of modifiers and organic solvents, so it has low cost, high efficiency, and broad industrial production application prospects. The experimental results show that the DDS/ZSA aerogel exhibits the lowest thermal conductivity (0.035 W m−1 K−1) when the dilute ammonia content is 5 ml. However, it should be noted that too low or too high an amount of dilute ammonia will lead to a decrease in aerogel performance, so it needs to be controlled within the appropriate range. In addition, the prepared aerogel has excellent hydrophobic properties with a contact angle greater than 140° and excellent thermal stability at 1000 °C, which can be used in harsh, humid, and high-temperature environments.

Experimental investigation of dynamic drying in single pharmaceutical granules containing acetaminophen or carbamazepine using synchrotron X-ray micro computed tomography

Drying time, velocity, and temperature are important aspects of the drying process for pharmaceutical granules observed during tablet manufacturing. However, the drying mechanism of single granules is often limited to modelling and simulation, with the internal and physical changes difficult to quantify at an experimental level. In this study, in-situ synchrotron-based X-ray imaging techniques were used for the first time to investigate the dynamic drying of single pharmaceutical granules, quantifying internal changes occurring over the drying time. Two commonly used excipients (lactose monohydrate (LMH) and microcrystalline cellulose (MCC)) were used as pure components and binary mixtures with one of either two active pharmaceutical ingredients of differing hydrophilicity/hydrophobicity (acetaminophen (APAP) and carbamazepine (CBZ)). Water was used as a liquid binder to generate single granules of 25 % to 30 % moisture content. Results showed that for most samples, the drying time and composition significantly influences the pore volume evolution and the moisture ratio, with the velocity and temperature of the drying air possessing mixed significance on increasing the rate of pore connectivity and moisture removal depending on the sample composition. Effects of active ingredient loading resulted in minimal influence on the drying of CBZ and generated binary mixtures, with APAP and its respective mixtures’ drying behaviour dominated by the material’s hydrophilic nature.

Drying kinetics, energy, colour and FTIR spectroscopy analysis on indirect solar dryer with paraffin wax and glass pieces as thermal storage material

This research focuses on developing an innovative Indirect Solar Dryer (ISD) incorporating paraffin wax and glass pieces as Thermal Storage Material (TSM) within the solar collector towards sustainable food preservation for future usage. Experiments were conducted using three distinct configurations of solar dryers: one with glass pieces and paraffin wax, another with glass pieces only, and a third without TSM. Additionally, conventional Open Solar Drying (OSD) was examined for comparison. Comparative analyses were performed on drying kinetics and energy efficiency. Results from the drying kinetics demonstrated a significant decrease in the Moisture Content (MC) of turmeric, from 84.2 % (w.b.) to 8.3 % (w.b.) within 29 h employing the configuration incorporating paraffin wax and glass pieces as TSM. Furthermore, this same configuration exhibited the highest dryer efficiency of 68.3 %. In addition to drying kinetics, Moisture Ratio (MR) was forecasted using twelve drying mathematical models, with the logarithmic model producing the most accurate forecasts (χ2 = 0.0009843 and R2 = 0.9782). Colour and Fourier Transform Infrared (FTIR) analyses have been investigated to assess the quality of the dried turmeric specimens. The configuration utilizing glass pieces and paraffin wax as integrated TSM yielded the best colour quality. FTIR spectroscopy investigation discovered peaks of the C-H Stretch within the range of 2830–2900 cm−1 in the ISD configuration spectrum, whereas these peaks were absent in the OSD spectrum, indicative of uneven drying in OSD. Based on these experimental findings, the designed ISD configuration with integrated glass pieces and paraffin wax TSM demonstrates effective results in reduced drying time and improved food specimen quality. It suggests that the proposed ISD configuration could serve as a sustainable and preferable method for drying in various industries.

Preparation and Properties of Waterborne Acrylic-Modified Epoxy Phosphate Resin and Its Coating

An acrylic acid-modified epoxy phosphate resin coating was synthesized by a four-step method marked “A-B-C-D”, and it was used as an efficient protective layer for steel structures. The coating exhibited good properties, mainly including water resistance (≥240 h), salt spray resistance (≥300 h), surface drying time (≤1 h), and adhesion (≥6.5 MPa).

Physicochemical properties and volatile compounds of Rosa roxburghii fruit using different drying methods

To enhance the drying quality of Rosa roxburghii fruit, this study examined the effects of four methods: Natural Drying (ND), Hot Air Drying (AD), Heat Pump Drying (PD), and Vacuum Freezing Drying (FD). Fresh R. roxburghii fruit was used to assess drying characteristics, color, microstructure, active ingredient content, antioxidant activity, and volatile substances. Drying times for ND, AD, PD, and FD were 28, 7, 6, and 21 h, respectively, with the rate order PD > AD > FD > ND. AD samples showed superior water-binding capacity, solubility, and highest levels of flavonoids and polyphenols, enhancing antioxidant activity. FD samples had the best color performance and retained more intact cell structures and higher Vitamin C and polysaccharide levels. Volatile compounds were analyzed, revealing 45, 60, 61, and 50 compounds for ND, AD, PD, and FD, respectively. AD proved to be the most efficient method, providing optimal drying time, color, active ingredient content, antioxidant activity, and volatile components. This finding offers valuable guidance for selecting a drying method that preserves the quality of dried R. roxburghii fruit and suits industrial production.

The Use of Beetroot Juice as an Impregnating Solution to Change Volatile Compounds, Physical Properties and Influence the Kinetics of the Celery Drying Process.

The effect of different methods of drying celery root enriched with beet juice by vacuum impregnation (VI) was studied. The process of convection drying, vacuum drying and freeze drying was carried out. Compared to dried indigenous celery, dry impregnated tissue was characterized by lower values of dry matter, L* and b* color parameters, as well as higher values of water activity, density and a* color parameter. In addition, VI reduced the drying time. Forty Volatile Organic Compounds (VOCs) were found in celery, while fifty-one VOCs were found in the profile of celery with beetroot juice. The innovative method of vacuum impregnation made it possible to produce a new type of product with changed properties and a variable VOCs profile. The best fit of the drying process kinetics was achieved by using the logistic model. Increasing the temperature during convection drying resulted in shorter drying time, increased values of dry matter, reduced the water activity value and altered VOCs.

Physicochemical Characterisation of White Pepper: A Comparative Study Between Traditional Sun Drying and Convective Rotary Drum Drying Methods

Drying is a crucial process in preserving the physicochemical qualities of white pepper. This study investigates the impact of two drying processes, namely traditional sun drying (TSD) and rotary drum drying (RDD), on the quality of white pepper. TSD requires three consecutive sunny days for drying, whereas RDD achieves the target moisture content of 12% within a rapid drying time of 120 min. The research employs thermo-gravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy analysis, and scanning electron microscopy (SEM) to analyse the dimensions, thermo-physical profiles, chemical constituents, and microstructure of the pepper samples. RDD, with a drying temperature of 55°C and centrifugation force of 129.7 × g, ensures fast and uniform drying while preserving the physicochemical qualities of white pepper. In terms of physical characteristics, RDD results in larger dried pepper dimensions, measuring 4.56 mm on average, compared to TSD, which measures 4.35 mm. SEM observations reveal varying pore sizes and cracks in both drying methods. Additionally, quality validation conducted by the Malaysian Pepper Board demonstrates that RDD exhibits superior quality compared to TSD. The RDD samples show moisture content, piperine, volatile, and ash percentages of 11.83, 8.18, 2.53, and 0.82, respectively, while the TSD samples show 10.37, 7.16, 2.43, and 0.74. All samples complied with Standard Malaysian White Pepper No. 1 and International Pepper Community Grade 1. Future studies should focus on enhancing different drying methods to achieve efficient white pepper drying while preserving its quality.

Effects of freeze–thaw pre‐treatment with different freezing methods on the microwave freeze drying of carrots

SummaryThree freeze–thaw (FT) pre‐treatments using different freezing methods that freezing at −80 °C (FT‐80), freezing at −25 °C (FT‐25) and vacuum freezing (VFT) were used for carrot slices, the effects and mechanisms of FT pre‐treatment on the drying characteristics and product quality of carrots during microwave freeze drying (MFD) were studied. The results showed that FT pre‐treatment under different freezing methods affected the water state of carrots, resulting in varying degrees of moisture loss and shortening drying time by 14.3% to 42.8%. VFT treatment caused the greatest water loss (35.33%) during FT and significantly increased the effective moisture diffusivity in the MFD process. FT treatments did not cause any significant degradation in the colour of the carrots. The VFT and FT‐80 treatments resulted in an elevated rehydration ratio, increased crispiness of MFD carrots and products with a porous microstructure and higher porosity. In contrast, the FT‐25 treatment led to a decrease in porosity due to destructive damage to the carrot cell structure. However, this damage favoured the extractability of carotenoids, resulting in a higher carotenoid content than the other treatments. This study provides a theoretical foundation for the practical implementation of FT pre‐treatment using various freezing methods on fresh foods prior to drying. It is recommended to employ VFT pre‐treatment before MFD due to its efficiency and effectiveness.

Studies on the drying behaviour of red chilli and it’s effect on quality

Processing of chilli is an important aspect in the production of good quality chilli. Harvested chilli has moisture content about 80% (w.b) which has to be properly dried to keep away from aflatoxin infestation. Open yard sun drying is the conventional method being practised which takes long time for drying. Pre-treatment like destalking could reduce the drying time considerably resulting in uniformly dried product. The present work was aimed to find the effect of drying on the quality of chilli. Red chilli (variety: Sannam) was dried with stalk and without stalk under open sun and solar tunnel dryer. The drying behaviour of chilli was studied. The influence of drying on the quality parameters viz., vitamin C content, colour (L*, a*, b* values), shrinkage and ASTA colour was found. Drying studies resulted in reduction in moisture content from 323% (d.b) to 8% (d.b). The time taken for drying under open sun drying and solar drying was 33 and 17 hours respectively for chilli dried with stalk. Similarly, the time taken for drying chilli without stalk under open sun drying and solar drying was 29 and 16 hours respectively. Quality analysis of dried samples showed higher vit.C (13 mg/100g) and ASTA colour value (67.4) for solar dried chilli without stalk.

Combination of contact ultrasound and infrared radiation for improving the quality and flavor of air-dried beef during hot air drying

Air-dried beef, a traditional dry fermented meat product in China, whose quality is largely influenced by processing conditions. In this study, contact ultrasound (CU) and infrared radiation (IR) were employed to enhance hot air drying (HAD), with an investigation into the mechanisms underlying improvements in quality and flavor. Samples subjected to CU and IR treatments during HAD (CU-IRD) demonstrated superior color (L* = 42.68, a* = 5.05, b* = −3.86) and tenderness (140.59 N) than HAD group, primarily attributed to reduced drying times and alterations in ultrastructure. Analyses utilizing SDS-PAGE and total volatile basic nitrogen (TVB-N) revealed that HAD and CU-HAD resulted in significant protein oxidation (197.85 mg TVB-N/kg and 202.23 mg TVB-N/kg, respectively), while IR treatments were associated with increased thermal degradation of proteins, producing lower molecular weight peptides. Compared with HAD group, the activities of certain lipases and proteases were enhanced by ultrasound and infrared treatments, leading to the release of greater amounts of free fatty acids and flavor amino acids. Furthermore, the thermal effects of infrared and the cavitation effects of ultrasound contributed to increased fat oxidation, amino acid Strecker degradation, and esterification reactions, thereby augmenting the diversity and concentration of volatile flavor compounds, including alkanes, ketones, aldehydes, and esters. These findings indicate that the synergistic application of CU and IR represents a promising strategy for enhancing the quality of air-dried beef.