The effects of drying methods on chemical profiles and antioxidant activities of two cultivars of Psidium guajava fruits

Freeze drying (FD), vacuum drying (VD) and hot-air oven drying (OD) were applied to investigate the effects of drying methods on the chemical compositions and antioxidant activities in the white and red guava fruits. 24 compounds were identified, and 10 of them were reported for the first time in guava fruits. The total polyphenols and antioxidant activity in the red guava powder were higher than those in the white guava powder dried under the same condition. Principle component analysis was performed to understand the difference in chemistry composition and the results indicated that the phytochemical composition in different guava powder were mainly influenced by the cultivar but not the drying methods. Quercetin, phloretin, hesperetin and oleanic acid were found to be the main compounds affecting the antioxidant activities in two cultivars. This study also demonstrated that VD induced the release of polyphenols from the matrix, with the additional advantage of reduced processing time and polyphenol oxidation, compared to the other analyzed methods. Our results suggest that vacuum-dried guava powder may be used as a nutritional and functional ingredient.