Polyphenol oxidase inactivation from apple juice by Al-based metal–organic frameworks: New anti-browning strategy in fruits and vegetables

Abstract

Polyphenol oxidase (PPO) is critical due to enzymatic browning in fruits and vegetables, developing economic impact in fruits industry. Metal-Organic Frameworks (MOF) have shown interesting characteristics such as water stability, low toxicity, and good adsorption yield, making them good candidates for PPO inactivation. Al-based-MOFs, MIL-53(Al), DUT-5, and MIL-110 were tested as PPO inactivators in apple juice by enzyme-MOF interactions at r.t. through two possible mechanisms, i) substrate scavengers (substrates:catechol and 4-methylcatechol) or ii) enzyme activity modifiers. The scavenging behavior of Al-based-MOFs was moderate, in the same magnitude, being catechol adsorption better than 4-methylcatechol. PPO activity was reduced by at least 70% by MIL-53(Al)/DUT-5 in 10/30 min respectively, and MIL-110 inactivated PPO in 50 min with some structural modifications. Enzyme-MOF interactions are major responsible for PPO inactivation. This could be a new applicability of MOFs, as an alternate PPO inactivation process, easily included in juice processing, retaining sensorial/nutritional properties, developed at r.t thus energy-cost-effective.