Effects of catalytic infrared drying in combination with hot air drying and freeze drying on the drying characteristics and product quality of chives

Vacuum freeze drying combined with catalytic infrared drying to improve the aroma quality of chives: Potential mechanisms of their formation

This study aimed to investigate the effect of vacuum freeze drying combined with catalytic infrared drying (FD-CIRD) process on aromas, free amino acids, reducing sugars and free fatty acids in chive leaves and stems. Gas chromatography-mass spectrometry combined with multivariate data analysis revealed that dipropyl disulfide was the key aroma that distinguished the differences between chive leaves and stems. The key aromas benzeneacetaldehyde, decanal and 1-octen-3-ol enhanced FD-CIRD chive leaves and stems aromas. The free amino acid content was highest at FD-CIRD stage in all samples except for the control (FD), while the reducing sugar content was lowest. The content of unsaturated fatty acids gradually decreased at FD stage and increased at FD-CIRD stage. Additionally, correlation analysis revealed that phenylalanine was a potential precursor of benzacetenealdehyde, oleic and linolenic acids were potential precursors of decanal and 1-octen-3-ol. Therefore, FD-CIRD technique helps to improve the sensory profile of dried chives.

A recent update on the connection between dietary phytochemicals and skin cancer: emerging understanding of the molecular mechanism

Constant exposure to harmful substances from both inside and outside the body can mess up the body's natural ways of keeping itself in balance. This can cause severe skin damage, including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. However, plant-derived compounds found in fruits and vegetables have been shown to protect against skin cancer-causing free radicals and other harmful substances. It has been determined that these dietary phytochemicals are effective in preventing skin cancer and are widely available, inexpensive, and well-tolerated. Studies have shown that these phytochemicals possess anti-inflammatory, antioxidant, and antiangiogenic properties that can aid in the prevention of skin cancers. In addition, they influence crucial cellular processes such as angiogenesis and cell cycle control, which can halt the progression of skin cancer. The present paper discusses the benefits of specific dietary phytochemicals found in fruits and vegetables, as well as the signaling pathways they regulate, the molecular mechanisms involved in the prevention of skin cancer, and their drawbacks.

Impact of Ultrasound Pre-Treatment on the Drying Kinetics and Quality of Chicken Breast-A Comparative Study of Convective and Freeze-Drying Methods

Fresh meat has a limited shelf life and is prone to spoilage. Drying serves as a common method for food preservation. Non-thermal techniques such as ultrasound treatment (US) can positively affect the drying processes and alter the final product. The study aimed to evaluate the impact of US pre-treatment on the hot air (HA) and freeze-drying (FD) of chicken breast meat and the quality of the dried products. US pre-treatment had a varied impact depending on the drying method used. The contact US method extended the HA drying time (about 50%) but improved water removal during FD (about 30%) compared to the untreated samples. Both methods resulted in low water content (<8.3%) and low water activity (<0.44). While rehydration properties (RR) and hygroscopicity (H) were not significantly affected by US pre-treatment in HA drying (about 1.35% and about 1.1, respectively), FD noticed differences due to shrinkage and porosity variations (RR: 2.4-3.2%, H: 1.19-1.25). The HA-dried samples exhibited notably greater tissue shrinkage and a darker surface color than the FD meat. Ultrasonic processing holds substantial potential in creating dried meat products with tailored characteristics. Hence, meticulous consideration of processing methods and parameters is of utmost importance.

Evolution of volatile compounds of baked dried tofu during catalytic infrared baking process and their correlation with relevant physicochemical properties

BACKGROUND

Energy-saving and low-carbon baking processes, as well as the need to determine the flavor-forming mechanisms of baked dried tofu, are becoming increasingly necessary. The application of emerging catalytic infrared radiation (CIR) technology in baking of dried tofu is considered of high interest due to the low energy consumption and high baking efficiency compared to traditional baking methods. Hence, this study aimed to investigate the evolution of aroma compounds in baked dried tofu during the CIR baking process and reveal relevant relationships between physical qualities, potential flavor precursors and key volatile compounds.

RESULTS

The results showed that the surface color of dried tofu gradually turned an appetizing golden yellow color during the rapid heating process, caused by the uniform infrared radiation from the radiant emitters. Meanwhile, the moisture of dried tofu experienced minimal reduction and the hardness of dried tofu gradually increased with the formation of crust on the surface. In addition, 49 volatile compounds were identified by headspace solid-phase microextraction-gas chromatography-mass spectrometry and 13 substances - 1-hexanol, 1-octen-3-ol, 1-pentanol, heptanal, nonanal, hexanal, (E,E)-2,4-decadienal, (E,Z)-2,4-decadienal, octanal, (E)-2-octenal, (E)-2-nonenal, 2-heptanone and 2-pentylfuran - were confirmed as key aroma compounds. Moreover, the amino acids aspartic acid, glutamic acid, isoleucine, lysine and arginine, and the fatty acids butyric, caprylic, capric, tridecanoic, stearic, oleic and linolenic were responsible for the unique flavor of CIR-baked dried tofu.

CONCLUSION

Consequently, the findings can provide a scientific basis for manufacturers to achieve precise quality control and large-scale production of CIR-baked dried tofu products. © 2024 Society of Chemical Industry.

Quality and Process Optimization of Infrared Combined Hot Air Drying of Yam Slices Based on BP Neural Network and Gray Wolf Algorithm

In this paper, the effects on drying time (Y1), the color difference (Y2), unit energy consumption (Y3), polysaccharide content (Y4), rehydration ratio (Y5), and allantoin content (Y6) of yam slices were investigated under different drying temperatures (50-70 °C), slice thicknesses (2-10 mm), and radiation distances (80-160 mm). The optimal drying conditions were determined by applying the BP neural network wolf algorithm (GWO) model based on response surface methodology (RMS). All the above indices were significantly affected by drying conditions (p < 0.05). The drying rate and effective water diffusion coefficient of yam slices accelerated with increasing temperature and decreasing slice thickness and radiation distance. The selection of lower temperature and slice thickness helped reduce the energy consumption and color difference. The polysaccharide content increased and then decreased with drying temperature, slice thickness, and radiation distance, and it was highest at 60 °C, 6 mm, and 120 mm. At 60 °C, lower slice thickness and radiation distance favored the retention of allantoin content. Under the given constraints (minimization of drying time, unit energy consumption, color difference, and maximization of rehydration ratio, polysaccharide content, and allantoin content), BP-GWO was found to have higher coefficients of determination (R2 = 0.9919 to 0.9983) and lower RMSEs (reduced by 61.34% to 80.03%) than RMS. Multi-objective optimization of BP-GWO was carried out to obtain the optimal drying conditions, as follows: temperature 63.57 °C, slice thickness 4.27 mm, radiation distance 91.39 mm, corresponding to the optimal indices, as follows: Y1 = 133.71 min, Y2 = 7.26, Y3 = 8.54 kJ·h·kg-1, Y4 = 20.73 mg/g, Y5 = 2.84 kg/kg, and Y6 = 3.69 μg/g. In the experimental verification of the prediction results, the relative error between the actual and predicted values was less than 5%, proving the model's reliability for other materials in the drying technology process research to provide a reference.

Research progress in the application of catalytic infrared technology in fruit and vegetable processing

Fruit and vegetable processing can effectively maintain the quality and safety of fruit and vegetable-based products while extending the shelf life of products and saving transportation costs. Infrared (IR) technology has been widely used in many operating units of fruit and vegetable processing because of its versatility of uniform heating, high heat transfer efficiency, and minimized damage to fruit and vegetable tissues. Catalytic IR (CIR), compared to traditional electric IR, is powered by natural gas or liquefied gas, which can improve thermal efficiency while significantly saving energy. However, there is no comprehensive overview discussing and summarizing the utilization and application of the CIR technology in fruit and vegetable processing. Therefore, this review aims to highlight recent advances in the application of CIR technology in fruit and vegetable processing. Specifically, a comprehensive discussion of the physicochemical properties and underlying mechanisms of CIR is provided, and its applications as a single method or in combination with other technologies in fruit and vegetable processes, such as blanching, peeling, microbial population reduction, and drying, are also presented. Besides, the currently used laboratory and pilot-scale equipment of CIR has also been summarized.

Influence of electrohydrodynamics on the drying characteristics and volatile components of iron stick yam

The drying characteristics, rehydration capacity, color, infrared spectra and volatile components of iron stick yam slices were investigated under different alternating current (AC) voltages (13, 17, 21 kV), hot air drying (HAD) (60 °C) and natural drying (AD) by electrohydrodynamic (EHD) drying and HAD experimental devices. The results showed that slices of iron stick yam dried the quickest with HAD, which also had the fastest drying rate; while drying the slices of iron stick yam with EHD led to a better rehydration capacity, higher brightness L* and whiteness, a more stable protein secondary structure, and a greater variety and content of volatile components compared with AD and HAD. These finding indicated that EHD is a more promising method for drying iron stick yam.

Heat source replacement strategy using catalytic infrared: A future for energy saving drying of fruits and vegetables

Drying is an important process for fruits and vegetables, which requires a lot of heat and the heat sources are mainly coal, electricity, natural gas, and solar energy. Most of the heat is usually wasted due to the long drying process and poor transfer efficiency. The use of coal also pollutes the environment. The national electricity curtailment policy regulates the drying industry. Therefore, the fruits and vegetables drying industry is facing new challenges due to its own development needs and external factors. Catalytic infrared drying (CIR) technology brings solutions to these problems. Compared with other drying technologies, CIR has a high drying efficiency and can effectively reduce the use of electric energy, avoid waste, and minimize pollution of water. However, improper processing conditions still cause quality deficits such as severe browning, and the drying is difficult due to weak infrared penetration. Although CIR has shortcomings, it is still expected to establish an energy-saving and efficient fruit and vegetable drying system.

Novel Efficient Physical Technologies for Enhancing Freeze Drying of Fruits and Vegetables: A Review

Drying is the main technical means of fruit and vegetable processing and storage; freeze drying is one of the best dehydration processes for fruit and vegetables, and the quality of the final product obtained is the highest. The process is carried out under vacuum and at low temperatures, which inhibits enzymatic activity and the growth and multiplication of micro-organisms, and better preserves the nutrient content and flavor of the product. Despite its many advantages, freeze drying consumes approximately four to ten times more energy than hot-air drying, and is more costly, so freeze drying can be assisted by means of highly efficient physical fields. This paper reviews the definition, principles and steps of freeze drying, and introduces the application mechanisms of several efficient physical fields such as ultrasonic, microwave, infrared radiation and pulsed electric fields, as well as the application of efficient physical fields in the freeze drying of fruits and vegetables. The application of high efficiency physical fields with freeze drying can improve drying kinetics, increase drying rates and maintain maximum product quality, providing benefits in terms of energy, time and cost. Efficient physical field and freeze drying technologies can be well linked to sustainable deep processing of fruit and vegetables and have a wide range of development prospects.

Effects of multi-frequency ultrasonic assisted sodium hypochlorite on the cleaning effect and quality of fresh-cut scallion stems

This study aimed to evaluate the feasibility of multi-frequency ultrasound-assisted sodium hypochlorite (NaClO) on fresh-cut scallion stem (FCS) cleaning. Ultrasonic cleaning parameters (frequency mode, frequency amplitude, and the sample to water ratios) were optimized against cleanliness and microbial biomass as evaluation indexes. Under the optimum conditions, the free chlorine residues and quality attributes of FCS were also investigated. The results showed that the cleanliness of FCS improved significantly (p < 0.05) and the total number of microorganisms, especially Escherichia coli, decreased dramatically under the optimized cleaning condition with the simultaneous ultrasound (US) at the sweep frequency (SF) combination of 20 + 28 kHz, the ultrasonic density of 60 W/L, pulse time of 10 s, which indicated that the shelf life of FCS would be extended. Compared to FCS after the 250 ppm NaClO cleaning, the retention of ascorbic acid (AA), color, and texture structure of FCS had no significant difference after ultrasound-assisted NaClO treatment. Meanwhile, the content of allicin increased by 52.5% under ultrasound-assisted cleaning. The integration of US into the cleaning process resulted in a notably reduction of 68% in NaClO concentration, as well as the weight loss and respiration rate (RR) of the scallion stems. Therefore, ultrasound-assisted NaClO cleaning was regarded as a promising and effective approach for cleaning fresh-cut vegetables.

Recent Developments in the Hybridization of the Freeze-Drying Technique in Food Dehydration: A Review on Chemical and Sensory Qualities

Freeze-drying is an excellent method for dehydration due to its benefits, including increased shelf-life, unique texture, and, in particular, good nutritive quality. However, the applicability of traditional freeze-drying systems in the food industry is still challenging owing to their prolonged drying duration, extraordinary energy usage, and high process cost. Therefore, the need to upgrade or develop conventional freeze-dryers for common or sophisticated food structures is ever-increasing. Enhancements to the freeze-drying process can significantly speed up drying and reduce energy consumption while maintaining phytochemicals, physical quality, and sensory attributes in final products. To overcome the downsides of conventional freeze-drying, hybrid freeze-drying methods were introduced with a great potential to provide food products at shorter drying durations, lower costs, and environmental friendliness while resulting in the same nutritive and sensory qualities as that of conventional freeze-drying in special circumstances. An overview of the most current improvements, adaptations, and applications of hybrid freeze-drying in food dehydration is given here. In this review, comparative studies are offered to characterize the drying process from the standpoint of chemical quality and sensory attributes. All the reviewed studies confirmed that the nutritional and sensory qualities of the end product can be retained using hybrid freeze-drying almost to the same extent as using single freeze-drying. It was also inferred that hybrid freeze-drying can surpass conventional freeze-drying and allow for obtaining dried products with characteristics typical of raw material if operating parameters are optimized based on product quality and energy usage.

Effect of Combined Infrared Hot Air Drying on Yam Slices: Drying Kinetics, Energy Consumption, Microstructure, and Nutrient Composition

Using hot air drying (HAD) and combined infrared hot air drying (IR-HAD) test devices, the drying kinetics, unit energy consumption, color difference values, rehydration rate, microstructure, and changes in polysaccharide and allantoin contents of yam slices were examined at various temperatures (50 °C, 55 °C, 60 °C, 65 °C, and 70 °C). The findings demonstrated that each of the aforementioned parameters was significantly impacted by the drying temperature. IR-HAD dries quicker and takes less time to dry than HAD. The Deff of IR-HAD is higher than that of HAD at the same temperature and increases with the increase in temperature. The activation energy required for IR-HAD (26.35 kJ/mol) is lower than that required for HAD (32.53 kJ/mol). HAD uses more energy per unit than IR-HAD by a factor of greater than 1.3. Yam slices treated with IR-HAD had higher microscopic porosity, better rehydration, lower color difference values, and higher polysaccharide and allantoin levels than HAD-treated yam slices. The IR-HAD at 60 °C had the greatest comprehensive rating after a thorough analysis of the dried yam slices using the coefficient of variation method. Three statistical indicators were used to evaluate six thin-layer drying models, and the Weibull model was most applicable to describe the variation of drying characteristics of yam slices.

The Optimization of Hybrid (Microwave-Conventional) Drying of Sweet Potato Using Response Surface Methodology (RSM)

Hybrid microwave-hot air (MW-HA) drying of sweet potatoes was optimized using a face-centered central composite design (FCCCD) with response surface methodology through the desirability function. The independent variables were drying temperature (50-70 °C) and microwave power (0-180 W), while the investigated responses were the drying time (Dt), the rehydration ratio (RR), the water-holding capacity (WHC), the antioxidant activity change (AA-PC), the total phenolic content change (TPC-PC), and the beta-carotene content change (BC-PC). The main criteria for the optimization of hybrid drying of sweet potatoes was to produce dried potatoes in the shortest drying time with a maximum RR and WHC and with minimum bioactive content (AA, TPC, and BC) loss. The optimum conditions were found to be a drying temperature of 54.36 °C with a microwave power of 101.97 W. At this optimum point, the Dt, RR, WHC, AA-PC, TPC-PC, and BC-PC were 61.76 min, 3.29, 36.56, 31.03%, -30.50%, and -79.64%, respectively. The results of this study provide new information about the effect of the hybrid drying method (MW-HA) on the rehydration ability and bioactive compounds of sweet potatoes, as well as the optimum values of the process.

Effects of roasting on the chemical compositions, color, aroma, microstructure, and the kinetics of changes in coffee pulp

Roasting is a critical process that affects the quality attributes of coffee beans; however, how roasting conditions affect the physical, chemical, biological, and organoleptic changes of coffee pulp needs more research. In the present study, we investigated the effects of roasting temperatures and times on chemical compositions and quality attributes of coffee pulp. The results showed that the contents of total soluble sugar (TSS) and free amino acid (FAA) followed a temporal pattern of first increasing and then decreasing under the roasting temperatures between 100 and 160°C. Total phenolic content (TPC) and antioxidant activity of coffee pulp significantly (p < 0.05) increased after roasting, reaching the maximum values of 83.09 mg gallic acid equivalent (GAE) /g and 360.45 µM 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) /g, respectively, when coffee pulp was roasted at 160°C for 18 min. Drying rates of coffee pulp fitted the Logarithmic kinetic model, while color (L*, a*, and b*) changes and 5-caffeoylquinic acid degradation followed the first-order kinetic model. Electronic nose analysis showed that the main aroma compounds of the coffee pulp are sulfur-containing organics that were reduced with the extended roasting time. Scanning electronic microscopy analysis presented the loosened, shrunk, and cracked microstructure on the surface of the roasted coffee pulp, which might contribute to the increased TSS, FAA, TPC, and antioxidant activity of coffee pulp roasted under specific conditions. In conclusion, our research provides valuable information for preparing high-quality coffee pulp tea. PRACTICAL APPLICATION: This article investigates the effects of roasting on the chemical composition, color, flavor, microstructure, and the kinetics of changes in the moisture, color, and 5-caffeoylquinic acid (5-CQA) of the coffee pulp. We have found that high-temperature and short-time roasting helps retain the total phenolic contents, antioxidant activity, and aroma. The drying kinetic fits the Logarithmic model, and the changes in color and 5-CQA fit the first-order kinetic model. This study provides meaningful information for preparing coffee pulp tea with high-quality attributes and antioxidant activity.

Novel sequential and simultaneous infrared-accelerated drying technologies for the food industry: Principles, applications and challenges

Infrared drying (IRD) is considered an innovative drying solution for the food industry with advantages of energy-saving potentials, reduced drying time and production cost-effectiveness. However, IRD also suffers from drawbacks such as weak penetrative ability, and product overheating and burning. Therefore, over the years, significant progress has been made to overcome these shortcomings by developing infrared-accelerated drying (IRAD) technology based on the combination of IRD with other drying technologies. Although several reviews have been published on IRD, no review focusing on IRAD is yet available. The current review presents up-to-date knowledge and findings on the applications of IRAD technologies for enhancing the quality and safety of food. The fundamental principles and characteristics of IRAD, energy-saving potentials, simulation and optimization approaches for enhancing efficiency, and developments in various acceleration approaches by combining with other drying techniques for achieving better end-products are discussed, and challenges and future work for developing the novel accelerated drying technology are also presented. Due to the synergistic effects of sequential or simultaneous combined drying methods, the total drying time and energy required are drastically lowered with most IRAD technologies, and consequently there are significant improvements in the sensory, nutritional, and safety attributes of dried food products with better appearance and quality. The development of multi-wavelength IRAD systems based on infrared absorption bands, and the incorporation of novel sensing techniques for real-time monitoring during drying will further enhance process efficiency and food quality and safety.