Effects of blanching and storage on capsaicinoid stability and peroxidase activity of hot chili peppers (Capsicum frutescens L.)

Comprising the major pungent principles capsaicin, dihydrocapsaicin and nordihydrocapsaicin, changes in capsaicinoid contents of chili powders after thermal treatment and during storage experiments were monitored. For this purpose, freshly harvested chili pods and chili pastes were immediately pasteurized at 80 °C, 90 °C and 100 °C for 5 and 10 min, respectively, and finally lyophilized. Heating and drying resulted in a 21.7% to 28.3% degradation of the initial capsaicinoid content, the three major capsaicinoids showing similar heat susceptibility. During storage at ambient temperature over 6 months with and without illumination, further degradation of the pungent principles by 6.8–11.9% was observed. Since residual enzyme activities were assumed to cause capsaicinoid losses, soluble peroxidase (POD) activity was investigated. It was shown that immediate thermal treatment of the plant material did not result in a complete POD inactivation even under rigorous temperature–time regimes. In contrast, a regeneration of about 30% of initial POD activity was found in those samples which were first blanched at 80 °C for 5 and 10 min and then minced. However, no correlation between POD activity and capsaicinoid losses could be established.Industrial relevanceBesides microbial contamination and color properties, the pungent principles called capsaicinoids are the major quality parameters of hot chili peppers and might be influenced by peroxidase activity. The present contribution demonstrated that heating of fresh chili pods slightly diminishes capsaicinoids, which were further reduced during storage at ambient temperature irrespective of soluble peroxidase activity. The production of high quality spices characterized by low microbial load and bright color requires thermal treatment of the raw material; however, a slight decrease in capsaicinoid concentration cannot be excluded.