Search Results (16)

This study investigated the effect of the water content of large yellow croaker fillets on their quality characteristics after roasting. The large yellow croaker fillets were randomly divided into groups, namely, the fresh group (BMC-77), the 3% salt-cured group (BMC-70), and groups cured with 3% salt followed by hot air drying to obtain different moisture contents (BMC-65, BMC-60, and BMC-55). Then, the fillets were roasted at 220 °C for 20 min. There were four replicates for each group. Various indicators, including color, texture, thiobarbituric acid-reactive substance (TBARS) content, total volatile basic nitrogen (TVB-N) content, water distribution, volatile components, and myofibrillar proteins were determined, and a sensory evaluation was carried out. The results showed that as the water content decreased, the lightness (L*) of the roasted fillets significantly decreased (p < 0.05), while the redness (a*) and yellowness (b*) increased. The hardness, shear force, TBARS, and TVB-N values all increased significantly (p < 0.05). The proportion of immobile water decreased, while the proportions of tightly bound water, free water, and loosely bound water increased. The electronic nose, electronic tongue, and GC-MS analyses revealed that there were significant differences in odor, taste, and volatile components among fillets with different water contents. A comprehensive analysis of all the indicators demonstrated that the fillets with an initial water content of 65% (BMC-65) achieved the best sensory qualities after roasting in terms of taste and flavor. An appropriate reduction in the initial water content helped to improve the texture and appearance of the fillets while delaying the degradation of proteins and lipids. This study provides a theoretical foundation for optimizing the roasting process of large yellow croaker fillets. Future research could explore the synergistic effects of the roasting conditions and water content to achieve more accurate quality control. Full article

In this study, the drying properties of new-mown oat grass were investigated using three methods: high-voltage discharge plasma drying (HVDP), hot-air drying (HAD), and natural air drying (AD). The HVDP process mainly generates discharge plasma between needle electrodes and a dielectric plate by changing the discharge voltage. HVDP, which is a new type of non-thermal drying technology, uses the energy exchange associated with the action of plasma and the non-uniform electric field force to accelerate the evaporation of water. The results show that HVDP has obvious advantages in terms of the drying rate and drying time, as well as reducing energy consumption while retaining nutrients. In particular, under the condition of 35 kV, HVDP not only effectively shortened the drying time and reduced the energy consumption but also selectively degraded the nutrient-reducing substances (e.g., lignin) and retained the substances positively correlated with the nutrient quality, significantly improving the nutrient content of the treated oat grass. In conclusion, as an innovative non-thermal drying technology, HVDP has great potential to improve the drying efficiency and reduce nutrient degradation in oat grass, providing an innovative solution to improve its quality and utilisation. Full article

Shrimp is one of the most popular and widely consumed seafood products worldwide. It is highly perishable due to its high moisture content. Thus, dehydration is commonly used to extend its shelf life, mostly via air drying, leading to a temperature increase, moisture removal, and matrix shrinkage. In this study, a mathematical model was developed to describe the changes in moisture and temperature distribution in shrimp during hot-air drying. The model considered the heat and mass transfer in an irregular-shaped computational domain and was solved using the finite element method. Convective heat and mass transfer coefficients (57.0–62.9 W/m²∙K and 0.007–0.008 m/s, respectively) and the moisture effective diffusion coefficient (6.5 × 10⁻¹⁰–8.5 × 10⁻¹⁰ m²/s) were determined experimentally and numerically. The shrimp temperature and moisture numerical solution were validated using a cabinet dryer with a forced air circulation at 60 and 70 °C. The model predictions demonstrated close agreement with the experimental data ($R^2\ge$ 0.95 for all conditions) and revealed three distinct drying stages: initial warming up, constant drying rate, and falling drying rate at the end. Initially, the shrimp temperature increased from 25 °C to around 46 °C and 53 °C for the process at 60 °C and 70 °C. Thus, it presented a constant drying rate, around 0.04 kg/kg min at 60 °C and 0.05 kg/kg min at 70 °C. During this stage, the process is controlled by the heat transferred from the surroundings. Subsequently, the internal resistance to mass transfer becomes the dominant factor, leading to a decrease in the drying rate and an increase in temperatures. A numerical analysis indicated that considering the irregular shape of the shrimp provides more realistic moisture and temperature profiles compared to the simplified finite cylinder geometry. Furthermore, a sensitivity analysis was performed using the validated model to assess the impact of the mass and heat transfer parameters and relative humidity inside the cavity on the drying process. The proposed model accurately described the drying, allowing the further evaluation of the quality and safety aspects and optimizing the process. Full article

In this study, the hot-air drying of caraway seeds was enhanced using two nonthermal physical field technologies: cold plasma (CP) and ultrasonic waves (US). Air drying temperatures of 35, 45, and 55 °C with CP pretreatment exposure times (CP_t) of 25 and 50 s were used. When convective drying was accompanied by US, power levels (US_p) of 60, 120, and 180 W were applied. Experimentally, the most effective contribution was found by using both CP pretreatment (25 s) and US (180 W), in which the maximum decreases of 31% and 39% were estimated for the drying period and specific energy consumption, respectively. The total color change, the rupture force, TPC, TFC, and antioxidant capacity were also estimated for evaluating the quality of dried products. In a CP-US-assisted drying program (25 s, 180 W), the minimum change in color and the rupture force were found to be 6.40 N and 20.21 N, respectively. Compared to the pure air drying, the combined application of CP and US resulted in a mean increase of 53.2, 43.6, and 24.01% in TPC, TFC, and antioxidant capacity of extracts at the temperature of 35 °C. Based on the response surface methodology (RSM) approach and obtained experimental data, accurate mathematical predictive models were developed for finding the optimal drying condition. The optimization process revealed that 39 °C, 180 W, and 23 s resulted in a desirability of 0.78 for drying caraway seeds. Full article

To extend the application of cost-effective high-yield pulps in packaging, strength and barrier properties are improved by advanced-strength additives or by hot-pressing. The aim of this study is to assess the synergic effects between the two approaches by using nanocellulose as a bulk additive, and by hot-pressing technology. Due to the synergic effect, dry strength increases by 118% while individual improvements are 31% by nanocellulose and 92% by hot-pressing. This effect is higher for mechanical fibrillated cellulose. After hot-pressing, all papers retain more than 22% of their dry strength. Hot-pressing greatly increases the paper’s ability to withstand compressive forces applied in short periods of time by 84%, with a further 30% increase due to the synergic effect of the fibrillated nanocellulose. Hot-pressing and the fibrillated cellulose greatly decrease air permeability (80% and 68%, respectively) for refining pretreated samples, due to the increased fiber flexibility, which increase up to 90% using the combined effect. The tear index increases with the addition of nanocellulose, but this effect is lost after hot-pressing. In general, fibrillation degree has a small effect which means that low- cost nanocellulose could be used in hot-pressed papers, providing products with a good strength and barrier capacity. Full article

This research was conducted to determine the influences of biopolymer dip-coating pretreatments as a non-thermal green technology on the drying behavior, retention of bioactive compounds, and quality properties of pears. The fresh pears were washed, peeled, and diced into cubes of 5 × 5 mm with a 2 mm thickness and were dipped into 0.3% (w/v) solutions of sodium alginate (SA), pectin (PC), xanthan gum (XG), Arabic gum (AG), and gelatin (GE) before hot air drying (70 °C, 2.0 m/s). The weight loss of samples during drying was recorded online, and the moisture ratio (MR) and drying rate were plotted against drying time. Biopolymers significantly decreased the drying time (maximum 33.33% by SA) compared with uncoated samples except for XG. Moisture diffusion coefficients were determined according to Fick’s second law of diffusion by plotting LnMR against drying time, and a linear regression analysis was applied to the data for the determination of moisture diffusion coefficients which ranged from 2.332 to 3.256 × 10⁻⁹ m²/s. The molecular transport of momentum, heat, and mass were determined from Newton’s law of viscosity, Fourier’s law, and Fick’s law, respectively. The results indicated that the friction drag force, convective heat, and mass transfer coefficients were 6.104 × 10⁻⁶ N, 76.55 W/m²·K, and 0.0636 m/s, respectively. Mathematical modeling showed the suitability of the Midilli and Kucuk and the Peleg models for the prediction of drying and rehydration processes, respectively. Thermal conductivity, specific heat, and density of coated samples ranged from 0.559–0.579 (W/m·K), 3735–3859 (J/kg·K), and 850.90–883.26 (Kg/m³), respectively. The porosity was reduced due to the penetration of biopolymers into the cellular matrix of samples. The highest total polyphenol content and antioxidant activity belonged to the AG samples. The biopolymers covering the surface of samples produced a protection layer against the loss of bioactive compounds. Biopolymers can be successfully used as a non-thermal green process for improving the drying and quality characteristics of pears at the industrial level. Full article

Numerical simulations were carried out for moist, porous media, intermittent microwave convective drying (IMCD) using a multiphase flow model in porous media subdomains coupled with a forced-convection heat-transfer model in an external hot air subdomain. The models were solved by using COMSOL Multiphysics was applied at the pulse ratio (PR) of 3. Based on drying characteristics of porous media and the distribution of the evaporation interface, IMCD was compared with convection drying (CD). Drying uniformity K, velocity difference, temperature difference, and humidity difference were introduced to evaluate the performance of three models with different inlets and outlet wall curvature. The numerical results show that as the moisture content of slices was reduced to 3 kg/kg, the drying rate in IMCD was 0.0166–0.02 m/s higher than that in CD, and the total drying time of the former was 81.35% shorter than that of the latter. In the late drying stage of IMCD, the core of the sample still had a high vapor concentration and temperature, which led to the evaporation interface remaining on the surface. The vapor evaporated from the slices can diffuse rapidly to the outside, which is why IMCD is superior to traditional convection drying. Through the comprehensive analysis of the models with different inlet and outlet wall curvatures, the drying uniformity K of the type III was the highest, reaching 89.28%. Optimizing flow-field distribution can improve uniform of airflow distribution. Full article

Considering the solar radiation status in Oman, a low-cost, indirect, stand-alone, forced-convective solar dryer was developed to dry medicinal herbs, which are sensitive to direct sun. The hot air flow was obtained using a solar-panel-powered blower and air passing through a black-body solar collector. This drying process could extend the shelf life of herbs while preserving their medicinal and nutritional (physicochemical) properties and adhering to food safety and hygiene practices. This study investigated the benefits of an indirect solar drying technique on the retention of quality attributes of mint and basil used in medicinal applications. Herbs used during drying could be subjected to changes in their physicochemical properties such as color, water activity (Aw), total soluble solids (TSS), phenol content, antioxidant capacity, and moisture content (MC), and, thus, results were compared with fresh herb samples. The dryer chamber-maintained temperature and relative humidity regimes of 30–50 °C and 21–95% and the expected final moisture content (wet basis) was 10%. The dryer showed improved physicochemical quality parameters and the retention of green color with parameter ranges of Aw 0.44–0.63, phenol content (increase) 1705–8994 mg/100 g DM, and antioxidant capacity (increase) 0.61–0.67 µmol/g DM, respectively. This study showed the ability of developed solar dryers to preserve the physicochemical properties of medicinal herbs during drying and can extend to other food products. Full article

Drying involves removing moisture from food. Therefore, to preserve the phenolic and bioactive compounds such as curcumin, dimethoxy curcumin and bisdemethoxi curcumin, etc., an efficient drying method is considered necessary. The primary drying methods are sun drying, hot air oven drying and fluidized bed drying. Traditional drying methods result in the loss of volatile oil (up to 25%) by evaporation and destruction of some light-sensitive oil constituents. Three methods of drying Turmeric with pretreatments boiled/unboiled and whole/sliced (2.5 cm long) were compared on physical and quality parameters. Texture analysis from sundry sliced boiled rhizomes achieved maximum peak force (45.40 kg), which was an indication of maximum uniform drying. Moisture content was strongly and significantly associated with drying time in different drying methods. Out of the three drying methods, in general, the sun drying showed a declining trend of L*, a* and b* values with drying time. Whereas a slower rate of decrease in L*, a* and b* values was predominant in the oven dry method. Interestingly, in the case of the fluidized method, almost static L*, a* and b* values were measured at 3 h of drying onwards after a declining trend of those values. In the case of sun and oven drying, the hue angle reached its peak at the fourth hour of drying, then gradually declined up to final drying. However, for fluidized bed drying, it had a continuous declining trend for other parameters such as chroma and total color change; there was a sharp decreasing trend for all throughout. Turmeric whole boiled dried in the sun produced the maximum curcumin (5.82%) and the sliced boiled ones produced the maximum oleoresin (8.10%), indicating good quality powdered product among all other drying treatments. Considering all the aspects, it is recommended that sun drying should be followed in post-harvest operations, as it produces a quality powder with comparatively more curcumin, despite its longer drying time. Full article

This work reports the results obtained with an innovative configuration of a closed-static solar greenhouse for sludge drying. The novelty of the solar greenhouse configuration consisted in using a forced ventilation system to provide hot air for sludge drying and the utilization of solar irradiation for energy supply. Wet sewage sludge (97% humidity) was successfully dried up to a residual humidity close to 5% after 25 days during wintertime. The increase of the airflow rate supplied under the sludge bed improved the sludge drying rate. Moreover, the fraction of volatile suspended solids decreased from 70% to 41% after 13 days, indicating that air supply promoted the simultaneous stabilization of the sludge as a side-effect to the drying process. Overall, the specific energy consumption per ton of evaporated water was estimated to approximately 450 kWh/t, resulting in about 55% of energy demand lower than a conventional thermal drying system, while using only free solar energy. The achieved high weight reduction of up to 99% implies a noticeable reduction of the excess sludge handling costs, indicating that solar greenhouse drying is a highly interesting opportunity for sludge drying in medium-small sized WWTPs. Full article

Since late 2019 many people all over the world have become infected and have died due to coronavirus. There have been many general studies about the spread of the virus. In this study, new and accumulated confirmed cases (NCC and ACC), new and accumulated recovered cases (NRC and ARC), and new and accumulated deaths (ND and AD) were evaluated by geographical properties, meteorological parameters and air particulate matters between 3 April 2020 and 11 June 2020 within 15 provinces in Iran. Meteorological parameters, air particulate matters and COVID-19 data were collected from Iran Meteorological Organization, the Environmental Protection Agency and Aftabnews website, respectively. The results of the study show that provinces in dry lands (i.e., Kerman and South Khorasan) not only had low admission of NCC, ACC, ARC and AD but also presented lower rates of NCC, ACC and AD per 10⁵ population. Air temperature showed positive and significant correlation with the number of COVID-19 cases. This is because of hot outdoor air especially in costal and equatorial regions that forces people to stay in closed environments with no ventilation and with closed-cycle air conditioners. Maximum air pressure was found to be the most frequent (66%) and significant parameter correlating with health outcomes associated with COVID-19. The most engaged province in this study was Khuzestan, while provinces in dry lands (i.e., Kerman and South Khorasan) showed low number of health endpoints associated with COVID-19. The highest rate of accumulated and new recovered cases per 10⁵ population were also found in Khuzestan and Kerman provinces. North Khorasan also showed the worst rate of N&ARC/10⁵ population. Therefore, air temperature, dry lands and population were the most important factors for the control of coronavirus spread. Full article

Among food crops, rice has the largest planting area, the highest yield per unit area and the largest total yield in China. However, cleaning performance is reduced by the high moisture content of rice during the harvesting process. In order to decrease the adhesion among wet rice threshed mixtures and improve the cleaning performance, the method of hot airflow cleaning was proposed. Firstly, the fluidization characteristics of wet sticky rice under the action of hot air were compared with those of dry particles. In this work, the minimum suspension velocity and the fastest suspension time were used and quantified to characterize the fluidization characteristics. It was found that the minimum suspension velocity and the fastest suspension time of the wet rice threshed mixture are both higher than those of dry particles due to the liquid bridge force. Moreover, the dispersion degree of the wet rice threshed mixture can be improved by the hot airflow due to the decrease in the surface water content of impurities. Secondly, the influence of the temperature and vibration frequency in the air-and-screen cleaning device on the dispersion characteristics of the wet rice threshed mixture were investigated. The accumulation mass was measured to quantify the dispersion degree. It was found that the increase in vibration frequency has little effect on the dispersion of the wet rice threshed mixture. The accumulation mass on the front of the sieve decreases slightly with the increase in the gas temperature range from ambient temperature to 30 °C. Then, the dispersion degree increases rapidly when the temperature exceeds 40 °C. The dispersion effect is the best when the temperature is 50 °C and the vibration frequency is 5 Hz. These results provide a basis for the cleaning of the wet rice threshed mixture in a combine harvester. Full article

The dry-hot wind climate is one of the major agro-meteorological disasters associated with high temperature, low humidity, and specific wind forces, which seriously affects the yield of wheat in the North China Plain. A field experiment was conducted to investigate the field microclimate, net photosynthetic rate, chlorophyll content of flag leaves, grain filling rate, and wheat yield after sprinkler misting under the condition of a dry-hot wind climate in the 2018 and 2019 seasons. Two travel speeds, full and half speed, and the corresponding irrigation amounts of 2.5 and 5 mm were used by a center pivot irrigation system during dry-hot wind conditions. A treatment without irrigation was applied as a control. The results showed that the air temperature and relative air humidity were greatly improved within 60 min after irrigation, especially in the upper part of the canopy. The net photosynthetic rate of flag leaves under 5 mm irrigation was higher than that under 2.5 mm irrigation during the middle and late grain filling periods. The adverse effects of dry-hot wind on the chlorophyll content of the flag leaves were mainly concentrated in the late grain filling stage. In the two years of the experiment, the average 1000-grain weights of 5 and 2.5 mm of irrigation treatments were 4.3 and 2.8% higher, and the grain yields were 5.8 and 3.3% higher, respectively, than those of the non-irrigated yields. Overall, applying a small amount of water between 12:00–14:00 with a center pivot before the occurrence of dry-hot wind is an effective means to regulate the field microclimate and produce more yield in the North China Plain. Full article

Moisture content and water activity play important roles in extending the shelf life of dried meat products, such as jerky. However, the commonly used hot air drying process is time-consuming, costly, and adversely affects the quality of dried meat products, warranting the development of an advanced and economical drying method. This study investigated the effect of super-heated steam (SHS) drying on the quality characteristics of semi-dried restructured jerky as a measure to prevent the excessive quality deterioration of meat products during drying. The control sample was dried using hot air, and the treatment samples were dried using SHS at different temperatures (200, 250, and 300 °C) and for different durations (90, 105, and 120 min). With increasing SHS temperature and duration, the moisture content, water activity, and residual nitrite content of the jerky were reduced. The shear force values for treatments at 200 and 250 °C were lower than those for the control. With a non-significant difference in lipid oxidation compared with the control, the overall acceptability score was the highest for the treatment at 250 °C for 120 min. In conclusion, SHS (250 °C for 120 min) drying has a potential industrial value to replace the hot air drying method. Full article

Hot air drying (HAD) at temperatures below the spontaneous evaporation temperature could be combined with microwave (MW) radiation as a thermal energy source in order to reduce the drying time. A photon flux in the microwave range interacts with dipolar molecules (water) through orientation and induction, producing electrical energy storage and thermal energy accumulation and generating an increase in the internal energy of food. The different mechanisms involved in water transport could change when the microwave penetration depth exceeds the sample characteristic dimension of mass transport. The aim of this paper is to determine the effect of MW in the combined HAD-MW drying of raw potato in order to obtain the real driving forces and mechanisms involved in the water transport, with the purpose of optimizing the MW power used. For this purpose, combined drying was carried out on potato samples (0, 4 and 6 W/g). The sample surface temperature was monitored by infrared thermography, and the sample mass was measured continuously through a precision balance. In parallel with continuous drying, another drying treatment was performed at different times (20, 40, 60, 90, 120, 180, 420 min) and conditions (0, 4 and 6 W/g) to analyze the dielectric properties, mass, moisture, volume and water activity. The results show that it is possible to monitor combined drying by infrared thermography, and it can be concluded that the convection heating is mostly transformed into surface water evaporation, with negligible thermal conduction from the surface, and microwave radiation is mostly transformed into an increase in the potato’s internal energy. Full article