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

The effects of hot air drying (HAD), freeze drying (FD), and catalytic infrared drying in combination with hot air drying (CIRD-HAD) and freeze drying (CIRD-FD) on the drying characteristics and product quality of chives were studied. The intermediate moisture contents for CIRD-HAD and CIRD-FD were 70%, 75%, 80% and 85%. The relationships among moisture content, drying rate, colour, structure, odour and nutrient retention were analysed. The results showed that, on the premise of the moisture content of the final product being lower than 8%, compared with HAD, CIRD-HAD significantly shortened the drying time by 23–77.5 min for the various intermediate moisture contents, and better preserved the nutrients (chlorophyll, allicin, vitamin c and volatile components) in the dried products; compared with FD, CIRD-FD significantly shortened the drying time by 1.1–3.8 h for the various intermediate moisture contents while the qualities were comparable. Overall, catalytic infrared combined drying is a promising method for obtaining high-quality dried chives. Among various drying conditions, intermediate moisture contents of 75%–80% for CIRD-HAD and 80%–85% for CIRD-FD are recommended as the most suitable for chives in terms of drying time and quality of the final product.