Effects of pre-treatment on physicochemical properties of capsicum annum l. when drying by vacuum tray dryer and storage at room temperature

Currently, the physicochemical quality of dried chillies is becoming a characteristic of consumer choice. A study was conducted to investigate the quality of physicochemical properties of dried chillies drying by vacuum tray dryer (VTD) when compared with sun drying (SD) and freeze-drying (FD). The highest capsaicin content with the lowest moisture content was achieved when drying by the VTD technique. However, the total phenolic content and antioxidant activity are highest in dried chillies drying by FD followed by VTD. Furthermore, the physiochemical properties of dried chillies that dry under VTD technique in combination with different pre-treatment techniques were investigated to study the quality of the dried red chillies during processing and storage. The fresh chillies pretreated by hot blanching(B) gave a higher capsaicin content almost 102.9% when compared with the non-treated sample. The blanched chillies samples either by B followed by soaking in citric acid solution(B+CA) showed the lowest L* indicating richness of dark red colour of dried chillies after drying by VTD. Soaking fresh chillies in citric acid solution (CA) showed an increase of a* value (redness) to 29.00 near fresh chillies' red colour. The highest retention of capsaicin content was only for 3 months of storage when chillies were soaked in CA solution and then start to deteriorate. The combination of different pretreatment techniques of fresh chillies drying by VTD is a potential drying method due to the retention of high-bioactive contents.