Based on quality, energy consumption selecting optimal drying methods of mango slices and kinetics modelling

Drying kinetic, thermodynamic and quality analyses of infrared drying of truffle slices

Kinetic and thermodynamic parameters are the most important part for making a suitable tool for drying agricultural products. Moreover, calculation of the energy required for the drying of product, the properties of the rehydration ratio, the food appearance changes, and the evaluation of the microstructure of food are crucial. Since the thermodynamic properties of truffle slices have not yet been reported, this study aims to establish a mathematical model to describe drying process of agriculture product, evaluate the effective moisture diffusion coefficient (Deff), determining the activation energy (Ea) to elucidate the thermodynamic characteristics, measure color characteristics, and rehydration ratio (RR) during the drying process of truffle slices. Truffle slices were dried in an infrared (IR) dryer at four temperatures of 50-80°C and two thicknesses of 0.5 and 1 cm. The best model to describe the drying process of truffle slices was Midilli et al.'s model. The value of Deff, SEC, and RR were in the range of 3.06 × 10-8 to 2.48 × 10-7 m2/s, 79.68-191.271 kWh/kg, and 5.99-7.49, respectively. The Deff of truffle slices increased with the above-mentioned parameters of the samples. The Ea obtained was 26.62-27.43 kJ/mol. The results indicated that enthalpy and entropy decreased with increasing drying temperature, while Gibbs free energy improved. The enthalpy, entropy, and Gibbs free energy values changed between 24.48-25.28 kJ/mol, -130.47 to -122.63 J/mol °K, and 63.97-70.17 kJ/mol, respectively. In addition, the results of color attributes decreased with increasing temperature, while chroma oppositely increased.

Optimization of the pulsed vacuum drying process of green walnut husk through temperature adaptive regulation

This study aimed to optimize the temperature adaptive conditions of pulsed vacuum drying (PVD) for green walnut husk (GWH) to tackle the issues of severe environmental pollution and limited utilization of GWH. The results of the single-factor experiment revealed that the optimal drying temperature for PVD of GWH was 65°C, with a pulsed ratio of 9 min: 3 min. The drying time decreased from 10.87 to 6.32 h with increasing drying temperature and from 8.83 to 6.23 kW·h/kg with increasing pulsed ratio. Energy consumption also decreased with shorter drying time and shorter vacuum time. Under this optimal variable temperature drying condition, GWH exhibited the highest total active substance content, with respective values of 9.43 mg/g for total triterpenes, 35.68 mg/g for flavonoids, 9.51 mg/g for polyphenols, and 9.55 mg/g for quinones. The experimental drying data of GWH were best fitted by a logarithmic model, with R2 values ranging from 0.9927 to 0.9943. Furthermore, the observed microstructure of GWH corresponded to the variations in total active substance content. This study provided valuable theoretical guidance for addressing environmental pollution associated with GWH and facilitating the industrialization and refinement of GWH drying processes. PRACTICAL APPLICATION: There is a growing interest in harnessing the potential value of agricultural waste to transform low-cost raw materials into high-value products while mitigating environmental pollution. In this study, for the first time, the effects of variable temperature pulsed vacuum drying on the content of active substances, drying time, and energy consumption of green walnut husk (GWH) were investigated. The findings serve as a theoretical foundation for addressing environmental pollution issues associated with GWH and enabling the industrialization and precision drying of GWH.

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.