Effect of hot‐air drying on flavour compounds of bell peppers (Capsicum annuum)

The influence of hot‐air drying on the composition of both volatile and non‐volatile flavour compounds of different Dutch bell pepper cultivars was investigated. Contents of glucose, fructose, ascorbic, citric, and oxalic acid decreased significantly after drying, while the levels of sucrose, malic, fumaric, and cis‐aconitic acid increased. Glucose, fructose and ascorbic acid probably participate in Maillard reactions during heating. Different effects of drying could be distinguished on the composition of volatile compounds. The majority of these compounds evaporated during drying. Some compounds were partly retained in the dried bell peppers, whereas others disappeared completely. Gas chromatography‐sniffing port analysis revealed that compounds with mainly “fresh” odour notes like lettuce/grassy/green bell pepper ((Z‐2‐3‐hexenal), fruity/almond ((E)‐2‐hexenal), fruity (octanal), lettuce/green bell pepper ((Z)‐3‐hexenol), and grassy/green bell pepper ((Z)‐2‐hexenal) decreased or disappeared after drying. Another group of compounds increased or were formed during drying, like 4‐octen‐3‐one, (E)‐2‐heptenal, (E)‐2‐octenal, (E,Z)‐ and (E,E)‐2,4‐heptadienal, decanal, and (E)‐2‐nonenal; most are known as autoxidation products of unsatu‐rated fatty acids. The increased levels of 2‐methylpropionic and 2‐ and 3‐methylbutyric acid, 2‐metlhylpropanal, and 2‐ and 3‐methylbutanal seemed to be due to Strecker degradation. Gas chromatography‐sniffing port analysis showed that the latter three compounds had distinct cacao, sweaty, and spicy odour characteristics.