Valorisation of Zingiber officinale Roscoe postharvest residues as byproducts with antioxidant capacity

Abstract

During the postharvest phase of ginger, 2.6%–5% by weight of ginger rhizome residues are generated, which are disposed in landfills and constitute a continuous source of organic contamination causing serious environmental problems. The objective of this study was to valorise ginger postharvest residues (shoot, finger, slice, trunk, root, and rootles) from district Pichanaki (Peru) as dry powdered byproducts with an antioxidant capacity similar to that of rhizome. The nutrition composition, phenolic compounds, such as total phenolic content, total flavonoid content, 6-gingerol content, and 6-shogaol content, antioxidant capacity expressed by ferric reducing antioxidant power and IC50 of 2,2-diphenyl-1-picrylhydrazyl radical, surface changes, and structural morphology were evaluated. In addition, the dependent variables were correlated using the Pearson's matrix and principal component analysis (PCA). The results for shoot, finger, slice, and trunk residues showed similar phenolic compound contents and antioxidant capacities to those of rhizome, but similar results were not obtained for root and rootlet residues. These results were corroborated by analyses of surface and structural morphologies. The Pearson's matrix showed that the content of phenolic compounds correlated with the antioxidant capacity and carbohydrate content for the rhizome and residues, except for the root. The PCAshowed that residues that exhibited higher contents of starch grains with reserve functions such as shoot, finger, slice, and trunk were correlated with higher contents of phenolic compounds with antioxidant capacity, while residues with higher contents of crude fibre and ash with a support function exhibited a low antioxidant capacity. Thus, the shoot, finger, slice, and trunk residues, from district Pichanaki (Peru), can be valorised and reincorporated as byproducts in the ginger value chain. They are important for the food, cosmetic, and pharmaceutical industries.