Effects of selected thermal treatments on the bioactive and textural properties in bell peppers

Because of the impact of high temperature, unprocessed plant raw materials acquire different bioactive properties and their organoleptic qualities, such as elasticity or hardness, are changed. The aim of the study was to investigate the effect of selected thermal methods such as cooking, steaming, microwave or grilling on the total antioxidant capacity (TAC) and the content of polyphenolic compounds in red, yellow and green bell peppers. The TAC was analysed for both fresh and treated thermal bell peppers. Thermal treatments were performed in standard times for individual methods in consumer use. In methanol extracts, the antioxidant potential was assessed using the DPPH, ABTS and FRAP methods, as well as the content of polyphenols using the Folin–Ciocalteau method. All methods of thermal treatment caused significant (p≤0.05) changes in the TAC and in the total polyphenol content in bell peppers. The TAC was reduced the most by microwaves and traditional cooking (hot water). The greater reduction of the total polyphenol content was observed in bell peppers, which has undergone traditional cooking. The smallest changes in the antioxidant activity and the content of polyphenolic compounds were observed in bell peppers subjected to steam cooking. All analysed bell pepper colour varieties were also texturally tested using the double bite test. The conducted analyses showed significant changes in the elasticity and hardness of the analysed bell peppers because of the use of appropriate methods of thermal treatment. Reducing the elasticity and hardness of the tested bell peppers was observed to the greatest extent because of the microwave process. On the other hand, the steam cooking process caused the smallest changes in the elasticity and hardness of the tested bell peppers.