HighHydrostaticPressure-Assisted Curing of Vanilla planifolia: Effects on Moisture Loss, Phenolic Content, Enzyme...

Vanilla planifolia curing is a critical process for developing vanillin and other aroma compounds; however, conventional thermal scalding (CTS) used during the killing stage may reduce the enzymatic activity required for phenolic compound formation during subsequent curing stages. This study evaluated the effect of high hydrostatic pressure (HHP) as a non-thermal killing method. Green vanilla pods were subjected to HHP treatments at 20-600 MPa for either 5 s or 5 min and compared with CTS. Moisture content, β-glucosidase and phenylalanine ammonia-lyase activities, total phenolic content, glucovanillin, vanillin, and antioxidant capacity were monitored throughout 20 sweating-drying cycles. Initial moisture content was 92%, but after 20 curing cycles, most HHP and CTS treatments reached final contents of 19.7-27.8%, except 20 MPa/5 min, which retained 60.4%, indicating delayed dehydration. Selected HHP treatments produced up to a fivefold higher initial apparent β-glucosidase activity than scalding and maintained higher activity during some early curing cycles, promoting glucovanillin conversion to vanillin. PAL activity increased immediately after the killing treatments, reaching 32.43 µmol min^-1 kg^-1 db for CTS and comparable values in specific HHP treatments (20 MPa/5 s, 50 MPa/5 s, and 100 MPa/5 min), demonstrating that PAL activity is affected by the pressure treatments. Selected HHP treatments also exhibited significantly higher TPC and antioxidant capacity than CTS samples at specific curing stages. Furthermore, an inverse relationship between glucovanillin depletion and vanillin formation was observed, resulting in greater vanillin accumulation and lower losses during curing. These findings indicate that HHP is a promising non-thermal alternative to conventional scalding for improving vanilla bean quality and potentially shortening the curing process.