Comparative evaluation of drying techniques on quality attributes, phytochemicals, and antioxidant capacity of Coffea arabica var. typica pulp

This study investigated the effects of different drying methods, including freeze drying (FD), sun drying (SD), hot air drying at 60 °C and 70 °C (HA60, HA70), and vacuum drying at 60 °C and 70 °C (VC60, VC70), on the microbiological safety, physicochemical properties, bioactive compounds, antioxidant capacity, and 5-hydroxymethylfurfural (HMF) content of dried coffee pulp. FD preserved the highest levels of chlorogenic acid, caffeine, proanthocyanidins, total phenolic content (557 mg GAE/100 g DW), total flavonoid content (203 mg CE/100 g DW), and antioxidant activity (DPPH, FRAP, and ORAC assays), while also maintaining superior color quality and undetectable HMF levels. However, FD-samples exhibited microbial counts within acceptable limits, whereas all thermal drying methods effectively eliminated detectable microorganisms. HA at 70 °C led to the greatest degradation of bioactive compounds and highest HMF formation (42 mg/kg DW). Vacuum drying, particularly at 70 °C, emerged as a promising alternative, providing a balance between microbial safety, retention of phytochemicals, antioxidant activity, and lower HMF accumulation. These findings suggested that VC70 as a practical and efficient method for producing microbiologically safe, bioactive-rich coffee pulp powder suitable for functional food applications.