Proximate composition and profiles of free amino acids, fatty acids, minerals and aroma compounds in Citrus natsudaidai peel

•The results indicate that C. natsudaidai peel can be utilized as natural food additives.•C. natsudaidai peel showed high carbohydrate and potassium content when compared to the pulp itself.•Free amino acids present in hydrophilic extracts of C. natsudaidai peel did not influence the taste.•Hydrophobic extracts of C. natsudaidai peel contain aroma compounds with a citrusy smell. Bulky hard peel of Citrus natsudaidai is discarded and not utilized enough in Japan. In this study, the nutritional composition and volatile components of three cultivars of C. natsudaidai peel were determined. Considering the proximate composition and minerals, C. natsudaidai peels showed good carbohydrate and potassium content. The peel color varied probably due to the difference of cultivars. C. natsudaidai peels were extracted and analyzed for free amino acids and for fatty acids and volatile compounds. The amount of free amino acids in the extracts was not enough to affect the taste of extracts. The proportion of individual fatty acid was not comparable to other plant oils, however, typical aroma compounds with citrusy smell were identified. C. natsudaidai extracts could contribute for the utilization as flavoring additives without affecting taste.