Bioprocess of robusta cherry coffee with polyphenol oxidase and quality enhancement.

Flavor plays an important role in consumer
satisfaction and influences further consumption of foods.
Robusta coffee is rich in caffeine and phenolics and is
undesirable for coffee connoisseurs compared to arabica
coffee. The exogenous polyphenol oxidase (4,000 U/ml)
was extracted from the fruiting bodies of Pleurotus florida
otherwise referred as the oyster mushroom. The polyphenol
oxidase (PPO) was partially purified by ammonium sulfate
precipitation followed with DEAE-cellulose with a recovery
yield of 51.2 %. It appeared as a single band on SDSPAGE
gel with a molecular mass of approximately 60 kDa.
The PPO with specific activity of 125 U/mg proteins was
active at pH 5–7 and 30–60 °C temperature. The robusta
cherry coffee was treated with PPO at different intervals of
time and the changes induced were evaluated. Insignificant
changes were observed with respect to the visual properties
of the treated beans. However, the PPO-induced biochemical
reactions that resulted in the reduction of bitterness of
robusta cherry coffee and also decline in caffeine and chlorogenic
compositions were compared to untreated. The
nonvolatile components such as phenolics of the treated
samples were found to have reduced from 6.50 to 4.05 %
(30 min) and 3.96 % (60 min) in the treated samples leading
to elevated sensory attributes with overall rating of
8–8.5 in hedonic scale. This is the first implication of PPO
on robusta cherry coffee to enhance the quality profile and
are viable compared with physical and chemical methods.