Enzymatic Activity and Its Relationships with the Total Phenolic Content and Color Change in the High Hydrostatic Pressure-Assisted Curing of Vanilla Bean (Vanilla planifolia)

Abstract

Diverse enzymatic reactions taking place after the killing of green vanilla beans are involved in the flavor and color development of the cured beans. The effects of high hydrostatic pressure (HHP) at 50–400 MPa/5 min and blanching as vanilla killing methods were evaluated on the total phenolic content (TPC), polyphenoloxidase (PPO), and peroxidase (POD) activity and the color change at different curing cycles of sweating–drying (C0–C20) of vanilla beans. The rate constants describing the above parameters during the curing cycles were also obtained. The TPC increased from C1 to C6 compared with the untreated green beans after which it started to decrease. The 400 MPa samples showed the highest rate of phenolic increase. Immediately after the killing (C0), the highest increase in PPO activity was observed at 50 MPa (46%), whereas for POD it was at 400 MPa (25%). Both enzymes showed the maximum activity at C1, after which the activity started to decrease. As expected, the L* color parameter decreased during the entire curing for all treatments. An inverse relationship between the rate of TPC decrease and enzymatic activity loss was found, but the relationship with L* was unclear. HHP appears to be an alternative vanilla killing method; nevertheless, more studies are needed to establish its clear advantages over blanching.

Microstructural Changes in Vanilla planifolia Beans after Using High-Hydrostatic-Pressure Treatment in the Curing Process

“…The mature green vanilla beans were prepared as described by Buitimea-Cantúa et al [9], washed with tap water, and organized into groups of 50 beans for each treatment. As a control treatment, each group of 50 green beans was scalded by immersion in 4 L of tap boiling (94 • C) water for 8 s. For HHP treatment, the samples were placed in 11 × 8 cm 2 polyethylene bags, vacuum-sealed, and treated in a Hiperbaric H135 unit (Burgos, Spain) at 100, 200, 300, and 400 MPa for 5 min, using water at 7 • C as the pressure transmitting medium [21].…”

“…Once the 20 drying-sweating cycles were complete, the vanilla beans were conditioned within cellophane bags in an incubator at 25 • C and 50% RH for 30 days. Throughout this vanilla curing process, beans were sampled as follows: cycle 0 (C 0 ), cycle 1 (C 1 ), cycle 3 (C 3 ), cycle 5 (C 5 ), cycle 7 (C 7 ), cycle 10 (C 10 ), cycle 14 (C 14 ), cycle 16 (C 16 ), cycle 20 (C 20 ); additionally, green beans (GB) were used as reference [21].…”