Beyond High-Pressure Processing: Enzymatic Browning and Oxidative Instability in Refrigerated Guacamole A critical review and multi-hurdle framework for clean-label control

High-pressure processing (HPP) has become a preferred preservation technology for refrigerated avocado products because it can deliver strong microbial control while retaining a fresh sensory profile. Yet HPP does not sterilize avocado biochemistry. Polyphenol oxidase (PPO) and lipoxygenase (LOX) are unusually pressure-resistant in avocado matrices, substantial residual activity can remain after commercially relevant treatments, and both enzymes may recover activity during refrigerated storage. Consequently, colour stability in guacamole cannot be understood as a simple function of initial PPO inactivation. This critical review integrates avocado-specific evidence on enzymatic browning, lipid oxidation, HPP-induced tissue disruption, antioxidant interventions, oxygen management and post-opening exposure. We argue that refrigerated guacamole behaves as a coupled aqueous–lipid oxidative system in which visual browning, loss of greenness, volatile oxidation products and sensory deterioration emerge from the balance between residual oxidative pressure and remaining defence capacity. This balance is formalized here as an “oxidative stability budget”: a conceptual framework that considers residual or reactivated PPO/LOX, oxygen availability, phenolic and unsaturated-lipid substrates, reducing reserve, pH/chelating capacity, lipid-phase antioxidants, packaging barrier and temperature. The review also highlights an underappreciated paradox: a botanical extract may perform well in radical-scavenging assays yet worsen avocado browning if its phenolics serve as PPO substrates. Therefore, the term antioxidant should not be treated as synonymous with anti-browning. A translational multi-hurdle strategy is proposed, combining HPP with controlled acidification/chelation, a measurable reducing reserve, targeted PPO inhibition, lipid-phase protection and oxygen management. The most informative industrial endpoint may not be colour immediately after processing, but colour kinetics after opening late in shelf life, when oxygen is reintroduced and the reducing reserve may be depleted. A staged validation framework is provided to convert ingredient screening into mechanism-based formulation decisions for refrigerated guacamole and related avocado products.