Chrysanthemum (Chrysanthemum morifolium Ramat.) is a seasonal plant with high medicinal and aesthetic value, and drying is an effective practice to enhance its storability after harvesting. The effects of hot air drying (HAD), combined infrared and hot air drying (IR-HAD), and sequential IR-HAD and HAD (IR-HAD + HAD) on the drying behavior, color, shrinkage, aroma profiles, phenolic compounds, and microstructure of chrysanthemum cakes were studied. Results showed that the increasing temperature resulted in a decrease in drying time and an increase in drying rate and moisture diffusivity. The Logarithmic and Page models exhibited superior fit in describing the dehydration process. Among the three drying strategies, IR-HAD was more effective in reducing energy consumption, improving shrinkage, water holding capacity, water binding capacity and cellular microstructure, while IR-HAD + HAD showed better inhibitory effect on color deterioration. Furthermore, gas chromatography–mass spectrometry (GC-MS) analysis revealed that different drying strategies dramatically influenced the aroma profiles in samples, and IR-HAD obtained the highest concentration of volatiles. The results of ultra-performance liquid chromatography (UPLC) indicated that the introduction of infrared radiation contributed to increasing the contents of chlorogenic acid, luteolin, total phenolic and flavonoid. These suggested that IR-HAD was a promising technique for drying medicinal chrysanthemum.

This work aimed to discuss effects of pulsed vacuum drying (PVD) at different temperatures (45°C, 50°C, 55°C and 60°C), vacuum durations (5 min, 10 min and 15 min) and multi-stage heating on drying kinetics, colour attributes, phenolic compounds and antioxidant capacity of chrysanthemum (Imperial chrysanthemum). Results indicated that successive temperature increase reduced the drying time and enhanced the drying rate and moisture diffusivity. Lower temperature (45°C) and the multi-stage (35°C-55°C-60°C) drying presented the superiority in the protection of color, preservation of phytochemical composition (chlorogenic acid, luteolin, total phenolic and total flavonoid content) and improvement of antioxidant capacity (DPPH and FRAP) of chrysanthemum, which was attributed to the low-oxygen drying environment and reduction of thermal degradation losses. Based on the results of drying efficiency and drying quality, the multi-stage heating (35°C-55°C-60°C) has the excellent potential to produce high-quality dried chrysanthemum on a commercial scale. Keywords: pulsed vacuum drying, drying kinetics, chlorogenic acid, luteolin, antioxidant capacity DOI: 10.25165/j.ijabe.20221504.7359 Citation: Xu H H, Wu M, Zhang T, Gao F, Zheng Z A, Li Y. Effects of different pulsed vacuum drying strategies on drying kinetics, phenolic composition, and antioxidant capacity of chrysanthemum (Imperial chrysanthemum). Int J Agric & Biol Eng, 2022; 15(4): 236–242.

Mixed extrusion of animal and plant proteins has great potential in meat substitution studies. In this study, we analyzed the mechanism of change in the reorganization of animal and plant proteins during extrusion by exploring the changes in physicochemical properties with different percentages of silkworm chrysalis protein (SCP) additions (3%, 6%, 9%, 12%, 15%) mixed with pea protein isolate (PPI). The results showed that the moderate addition of SCP (12%) reduced the stiffness and denseness of the protein structure of the extrudates, and increased the total amino acid content of the extrudates, up to 74.83. Meanwhile, the addition of SCP changed the rearrangement of the proteins to form new chemical cross-linking bonds with higher bonding energies. Enthalpy of the sample up to 252.6 J/g, enhancing the denaturation energy requirement of the sample. Notably, the addition of SCP weakened the textural properties of the product, resulting in a minimum fibrous degree of 0.88, and improved the overall color of the sample, resulting in an L* value of up to 114.61. Such a change makes the product more suitable for further processing. Scanning electron microscopy (SEM) revealed that the addition of SCP changed the microstructure of the product, resulting in a looser, more porous sample overall. These results systematically elucidate the microscopic mechanisms of SCP and PPI restructuring during high-moisture extrusion.