Radiation influence on antioxidant capacity, bioactive compounds and extractability of coffee processing residues

Abstract

During the agro-industrial process, the complete reuse of waste is an important part of the process's sustainability. However, in most cases, these materials are inadequately discarded, bringing environmental, economic, and social implications. In this context, residue reuse represents an opportunity to develop by-products, in addition to adding value to the raw material. However, conventional treatment processes end up negatively altering the quantity and expressiveness of compounds and nutrients present in this residue. Therefore, ionizing radiation has stood out as a promising technique among the current resources available for residue reuse and microbial load reduction. Thus, the objective of this work is to apply ionizing radiation to coffee processing residues, such as husk and straw, with the aim of preserving and improving the compounds and antioxidant activity. For this purpose, doses of 5 kGy were used on husk and straw residue. The samples were subjected to extraction through physical and chemical processes to obtain an extract from the residue. The extracts were analyzed to identify total phenolic content (TPC), antioxidant activity (ABTS, FRAP, and ORAC), extraction efficiency (EE), and cytotoxicity assays. An improvement in TPC of 26.0% for husk and 19.5% for straw was observed. For antioxidant capacity, an improvement of 14.1%, 16.1%, and 33.3% for husk was observed in ABTS, FRAP, and ORAC analyses, respectively. The 5 kGy dose provided an increase in compound extractability of 26.7% (straw) and 191.9% (husk). In cytotoxicity tests, no significant differences were observed between the irradiated residue and the control. However, an effect related to extract concentration was observed. The irradiation process proved to be a promising technique for agro-industrial residue management. This technique, in addition to promoting already known microbiological benefits, also improved the quantity of compounds, antioxidant activity, and compound extractability. Thus, the present proposal highlights the application of nuclear energy as a viable solution and technological innovation for the reuse of agro-industrial residue.