Quality characteristics of dried onion and garlic slices according to thermal and nonthermal treatment methods

In the present study, the application of suitable thermal and nonthermal pretreatment methods was explored to develop a dried products comprising onion and garlic slices. Pretreatment was performed via blanching for 30 sec, steaming for 1 min, dipping in warm water (45℃) for 30 min, and dipping in cold water (8℃) for 1 hr. Furthermore, physicochemical and microbiological analyses were performed in conjunction with sensory evaluations. The group subjected to pretreatment via cold-water dipping exhibited the lowest moisture content and water activity with a negligible redness, yellowness, and browning index. Furthermore, the results of sensory evaluation revealed that this group exhibited relatively high color and overall acceptability. The group subjected to pretreatment via blanching presented severe browning and shape distortion. The samples in the group subjected to pretreatment via cold-water dipping did not exhibit a significant difference in pH; furthermore, the number of microorganisms during storage was lower than that in the control group. It was concluded that the hot-air drying of onion and garlic slices after cold-water dipping resulted in an increase in drying efficiency and the suppression of browning, without inducing major component changes. The facile technique demonstrated in the present study is expected to be fast and cost-effective, thereby facilitating practical application in farms.