Abstract
We investigated the effects of different drying methods (room temperature drying, heat pump drying, freeze drying, microwave vacuum drying [MVD], and combined microwave power vacuum drying) on the active ingredients of green coffee beans. We specifically focused on eleven phenolic acids, total phenolic content (TPC), total flavonoid content, antioxidant activity, polyphenol oxidase (PPO), the inhibition of linoleic acid peroxidation (LPO), and enzyme activity, and the bio‐accessibility in vitro and bioavailability of phenolics and antioxidant activities were also evaluated. MVD‐treated beans had the lowest PPO activity and the highest contents of 5‐caffeoylquinic acid (1.39 g/100 g DW), 3‐feruloylquinic acid (0.25 g/100 g DW), 4‐feruloylquinic acid (0.25 g/100 g DW), 5‐feruloylquinic acid (1.52 g/100 g DW), and TPC (5.98 g GAE/100 g DW), and the highest antioxidant activity. MVD was the least time‐consuming (0.63 hr/kg) and energy‐consuming (1.88 kwh/kg) method. Moreover, the strongest inhibition of LPO and α‐glucosidase was observed in MVD‐treated beans. Thus, MVD is suggested to be the most suitable drying technique for the preservation of phenolic compounds and bioactivities of green coffee beans.
Highlights
Coffee is a shrub that belongs to the family Rubiaceae, genus Coffea
The relative phenolics bioavailability index (RBV), which is an indication of potential bioavailability of phenolic compounds, was calculated as follows: RBV = CAE∕CBE
The phenolics bioavailability index (PBV), which is an indication of the bioavailability of phenolic compounds, was calculated as follows: PBV = CAE∕CGE, (7)
Summary
Coffee is a shrub that belongs to the family Rubiaceae, genus Coffea. It is widely cultured in tropical areas, and in China, it is mainly distributed in the Hainan and Yunnan provinces (Dong, Tan, Zhao, Hu, & Lu, 2015). Robusta) and Arabica (Coffea arabica) are the two varieties dominating the international market. The global production of coffee cherry has been estimated at 8 million metric tons per year, which shows its economic importance (Battista, Fino, & Mancini, 2016). Critical epidemiological and intervention studies have shown that moderate daily consumption of coffee has various positive effects on the human body (O'Keefe et al, 2013). Coffee beans are rich in antioxidants and nutrients (Fukushima et al, 2009)
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