Effects of various blanching methods on weight loss, enzymes inactivation, phytochemical contents, antioxidant capacity, ultrastructure and drying kinetics of red bell pepper (Capsicum annuum L.)

- Comparative quantitative evaluation of HWB, MWB, IRB, and HHAIB was performed.
- Except HWB, the other blanching methods enhanced antioxidant activity of blanched peppers.
- MWB and IRB treatment yielded lower weight loss than HWB and HHAIB.
- Ultrastructure analysis verified the difference phytochemical contents among four treatments.
- All four blanching treatments accelerated the drying kinetics relative to unblanched peppers.

The effects of hot water blanching (HWB), microwave blanching (MWB), infrared blanching (IRB) and high-humidity hot air impingement blanching (HHAIB) on weight loss, enzyme inactivation (peroxidase, POD and polyphenol oxidase, PPO), characteristic bioactive component contents (red pigments and ascorbic acid), antioxidant capacity (total antioxidant activity and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity), ultrastructure and drying kinetics of red bell peppers under different blanching conditions were investiaged. Results showed that the MWB and IRB treatment yielded lower weight loss than HWB and HHAIB. The inactivation of both PPO and POD enzymes was strongly dependent on blanching temperature and duration and microwave power for microwave blanching. The peppers treated by MWB, IRB, and HHAIB obtained higher red pigments and ascorbic acid retention, total antioxidant activity and DPPH values compared with the samples blanched by HWB. Ultrastructure analysis verified the difference phytochemical contents among four treatments. All four blanching treatments enhanced the drying kinetics relative to unblanched peppers. The Weibull distribution model was employed to calculate the moisture effective diffusivity (Deff), which ranged from 1.2688 × 10−10 to 2.8754 × 10−10 m2/s. The current findings not only contribute to a better understanding of different blanching methods but also provide more data and information for selecting blanching technologies.