Process stability of Capsicum annuum pectin methylesterase in model systems, pepper puree and intact pepper tissue

Fresh-Cut Bell Peppers in Modified Atmosphere Packaging: Improving Shelf Life to Answer Food Security Concerns

The influence of modified atmosphere packaging (MAP, 10% O₂ and 45% CO₂) on the quality characteristics of fresh-cut green, red and yellow bell peppers (Capsicum annuum L. var annuum) was investigated. Packaging film bags (Krehalon MLF40-PA/PE) with fresh-cut bell peppers were stored for up to 17 days at 5 °C. The in-package O₂ level ranged between 10 and 15%, respecting the current recommendations for fresh-cut vegetable products. Initial CO₂ levels were higher than commonly used (from 5 to 10%), decreasing progressively over time due to the permeability of the selected polyethylene film. At the end of the storage period, they stabilized between 2 and 5%. A small variation in texture, moisture, titratable acidity, pH and microbial growth was observed during the storage period, as well as a good color retention and sensory properties maintenance. Negligible losses in the antioxidant activity and bioactive compounds (total phenol, flavonoid, anthocyanin and carotenoid content) were noted at the end of the study. Sensory analysis showed that panelists could not detect significant differences among sampling periods. A PCA with predictive biplots confirmed the existence of significant correlations. The products retain their initial characteristics without severe loss of quality until at least the 17th storage day. Given the current commercial shelf life of fresh-cut bell peppers, ranging from 9 to 14 days, the described treatment enabled an increase of at least 3 days (20%) of the products shelf life, reducing food waste and contributing to food security.

New evidence on pectin-related instantaneous pressure softening mechanism of asparagus lettuce under high pressure processing

Evidence on mechanism of instantaneous pressure softening of asparagus lettuce under high pressure processing was explored with respect to pectin methylesterase activity, degree of methylation of pectin, degree of methylation patterns of pectin fractions, and pectin distribution in cell wall matrix. Instantaneous pressure softening was observed at 300 MPa, while texture recovery was obtained at 500 MPa. Pectin methylesterase activity was not significantly affected at 100 and 300 MPa, but dramatically activated at 500 MPa (p < 0.05). Correspondingly, the degree of methylation of pectin decreased as pressure rose. Results of in situ immuno-dot blotting and immunolabeling based on specific bindings of antipectin antibodies showed a significant reduction of chelator-soluble pectin at 300 MPa, in contrast to a remarkable increase at 500 MPa. High pressure processing-induced demethoxylation was further verified by the enhanced fluorescence intensity of LM19 (an antihomogalacturonan antibody specifically binds to nonmethoxylated pectin) immunolabeled pectin, which was mainly located in tricellular junctions at 300 MPa, but covered the full cell surface at 500 MPa. In conclusion, instantaneous pressure softening of asparagus lettuce is strongly associated with loss of chelator-soluble pectin at 300 MPa.

Effects of high pressure processing on activity and structure of soluble acid invertase in mango pulp, crude extract, purified form and model systems

The effects of high pressure processing (HPP) on the activity of soluble acid invertase (SAI) in mango pulp, crude extract, purified SAI and purified SAI in model systems (pectin, bovine serum albumin (BSA), sugars and pH 3-7) were investigated. The activity of SAI in mango pulp was increased after HPP, and that in crude extract stayed unchanged. The activity of purified SAI was decreased after HPP at 45 and 50°C. Pectin exhibited a concentration-dependent protection for purified SAI against HPP at 50°C/600MPa for 30min. Pectin that had an esterification degree (DE) of 85% exhibited a greater protection than pectin that had a DE of 20-34%. BSA, acidic pH (3-6) and sucrose also exhibited protection for purified SAI against HPP. HPP at 50°C/600MPa for 30min disrupted the secondary structure and tertiary structure of purified SAI, but no aggregation of purified SAI was observed after HPP.