Effect of drying techniques and treatment with blanching on the physicochemical analysis of bitter-gourd and capsicum

•Highest moisture was removed from solar dried bitter-gourd and capsicum.•The maximum functional components were retained in solar dried vegetables.•Solar dried vegetables attained the highest score of sensory acceptability.•Solar drying proved to be a potent technique over hot air and open sun drying.

Solar drying increases the quality and shelf life of the food product. In this study, three drying methods (solar, hot air, and sun drying) were used to evaluate the physicochemical properties of dried green colored vegetables (bitter-gourd and capsicum). In addition, drying treatment was coupled with blanching (hot water and steam) as pre-treatment. It was found that the maximum functional compounds (flavonoid and polyphenol) were retained in solar dried bitter gourd (0.43 ± 0.02 RE mg/g; 0.12 ± 0.01 GAE mg/100 g) and capsicum (1.15 ± 0.11 RE mg/g; 1.29 ± 0.01 GAE mg/100 g), respectively. Moreover, nutritional quality (vitamin A & C) was higher in solar dried (1.50 ± 0.10 I.U., 3.95 ± 0.01 I.U.; 33.2 ± 0.3 mg/100 g, 49.8 ± 0.1 mg/100 g) in comparison to hot air and open sun dried vegetables. However, hot water blanched vegetables showed significant less degradation of polyphenols, flavonoids, and chlorophyll (p > 0.05) in relation to steam blanched vegetables in combination with solar drying. Also, solar dried vegetables attained the highest score of sensory acceptability. Therefore, it can be concluded that solar drying could be an effective technique over hot air and open sun drying for retaining better quality of dried vegetables.

Graphical abstractDownload high-res image (320KB)Download full-size image