Bioactive Compounds and Industrial Peeling Applications of Inner and Outer Shells of Chestnuts (Castanea spp.)

Abstract

The aim of this review is to provide information concerning the types of chestnut shells (inner and outer), their compositions and bioactive compounds, as well as to mention industrial peeling applications. These shells are comprised of high-valued natural active compounds, such as polyphenols (phenolic acids, flavonoids, tannins, hydroxycoumarins -scopoletin, scoparone-), pigments (melanin) and minor compounds (minerals, dietary fiber, vitamin C and E, essential amino acids and fatty acids). The total phenolic acids and flavonoid content of C. sativa shell were ranged between 119.17-223.62 mg/kg db and 330 – 503 mg CE/g. It is also a good source of vitamin C with reported levels of 15.57 and 28.97 mg AA/100 mg db in water and ethanol extracts, respectively. The shells are used as food additives due to their colorant, antioxidant and antimicrobial properties. The shells are exposed by the peeling process applied to obtain the fruit without the shell which is mainly used. The most frequently used technique in chestnut peeling is the Brulage peeling method. However, in this technique, used peeling mechanism is insufficient to obtain both inner and outer shells separately at the same time. Moreover, further research is needed to obtain the shells individually, to analyse each shell in detail, and to increase the industrial use of shells.