Implications of inappropriate storage temperatures in harvested green coffee (robusta sp.) beans to antioxidant properties and polyphenol oxidase activity

The effects of various storage temperatures on antioxidant properties and enzyme activity of green coffee beans were evaluated during storage. The green coffee beans were harvested and stored at different storage temperatures of 35 ?C, 26 ?C and 9 ?C. Lower storage temperature (9 ?C) greatly preserved the reduction of phenolics and antioxidant capacity detected using FRAP (Ferric Reducing Antioxidant Power) which was 38.20 mg TE/g, total phenolic content (TPC) which was 38.20 mg GAE/g and DPPH (Radical Scavenging Effect) which was 82.56%. Temperature 9 ?C also retained the moisture of the green coffee beans up to 54.31% at day 5. For enzyme activity of polyphenol oxidase (PPO), the lower temperature inactivated the enzyme which resulted in lower activity of the enzyme stored at temperature 9 ?C which was 0.82 U/g followed by 0.90 U/g and 1.03 U/g for 26 ?C and 35 ?C at day 1 of storage. However, green coffee beans stored at 9 ?C showed some external chilling injury symptoms starting from day 7 of the storage. The phenolics and antioxidants activity in green coffee beans during storage decreased with increase of storage temperature starting from 9 ?C, 26 ?C and 35 ?C. While the PPO activity increased with increase of storage temperature