Effect of high-humidity hot air impingement blanching (HHAIB) on drying and quality of red pepper (Capsicum annuum L.)

- HHAIB efficiently denatures PPO of red pepper.
- Over-blanching negatively influences drying rate, red pigment content and texture.
- Micro-cracks occur in surface of red pepper and by thus enhance drying rate.
- The first-order fraction model describes PPO inactivation well.

Effects of high-humidity hot air impingement blanching (HHAIB) under different times (30, 60, 90, 120, 150, 180, 210, and 240 s) on drying characteristics and quality attributes of red peppers in terms of surface colour, red pigment content, microstructure and texture were investigated. Results showed that polyphenol oxidase (PPO) residual activity of the samples decreased with increasing blanching time; it was decreased to 7% after 120 s. A first-order fraction model described PPO inactivation well. Suitable HHAIB time can reduce drying time extensively. Pepper surface colour was influenced by different treatments. In terms of red pigment content, there was no significant difference for blanching time under 120 s, whereas over blanching (blanching time ⩾150 s) can significantly reduce the red pigment content. Microstructure observations indicate that superficial micro-cracks occur, which explain, why HHAIB enhances drying rate. The firmness, hardness, and gumminess of the samples decreased with increase of HHAIB time.