Ultrafiltration for the separation of polyphenol oxidase and peroxidase and its effect on physicochemical and antioxidant properties of coconut (Cocos nucifera l.) water

Abstract

Coconut water is a nutritious, natural, and refreshing drink. However, a challenge for the coconut water industry is its fast deterioration caused by naturally occurring enzymes mainly polyphenol oxidase (PPO) and peroxidase (POD). This study aimed to separate the PPO and POD using ultrafiltration and to evaluate its effect on the physicochemical properties and antioxidant attributes of tender and mature coconut water. The membrane used was polyethersulfone (PES) with two molecular weight cut-offs, namely 30 kDa (PES 30) and 50 kDa (PES 50) and conducted in a vacuum filter unit. The results showed that ultrafiltration with PES 30 completely separated the POD activity of both tender and mature coconut water. The ultrafiltration was also able to separate 86.07% PPO activity of tender coconut water and 100% separation on mature coconut water. While PES 50 could separate 49.60% PPO activity in tender coconut water. The ultrafiltration process also increased the clarity of mature coconut water and maintained the total sugar, sodium, and potassium contents in both maturities. However, ultrafiltration using these membrane types reduced total phenolic content and radical scavenging activity. In conclusion, this study revealed that ultrafiltration can remove the oxidative enzymes to extend the shelf life against oxidation deterioration. Further studies should be conducted to investigate the separation of enzymes without high significance loss of polyphenols, antioxidants, and nutritional properties.