Microenvironment and Quality Preservation of Broccoli under Active Modified Atmosphere Packaging

To improve the shelf quality and extend the shelf life of broccoli, this study involved analysis and modeling of the postharvest respiration process and gas exchange process in active modified atmosphere packaging (MAP). Additionally, it determined the microenvironment packaging parameters and conducted experimental validation to identify optimal microenvironment conditions for maximizing the shelf life of broccoli. ‘Naihan Youxiu’ broccoli was selected for this study. Seven respiration rate models, namely empirical, competitive, non-competitive, uncompetitive, and mixed competitive-noncompetitive enzyme kinetic models, Langmuir adsorption model, and chemical kinetic model, were established. The results showed that the empirical model had a coefficient of determination greater than 0.90 at all tested temperatures (0, 5, 10, 15, and 20 ℃), and its accuracy was validated through experiments conducted at 12 ℃, demonstrating its suitability for characterizing the respiration process of broccoli. Furthermore, the empirical model was combined with a model of gas exchange between the inside and outside of the active MAP to establish a mathematical model for broccoli preservation under active modified atmosphere conditions. Utilizing this model, the microenvironment packaging parameters for broccoli were determined as follows: at a storage temperature of 10 ℃, each package, 0.3 m × 0.3 m in size with a single-sided thickness of 4 × 10^-5 m, contained 0.5 kg of broccoli. The suitable CO₂ permeability coefficient of the packaging film was calculated as 47.692 mL·m/(m²·h·0.1 MPa). This study compared changes in five representative quality indicators of broccoli such as total glucosinolates and total chlorophyll during storage in packaging materials with appropriate and inappropriate CO₂ permeability coefficients. The results indicated that compared with packaging materials with an inappropriate permeability coefficient, those with an appropriate permeability coefficient significantly better maintained the nutritional quality of broccoli, such as total glucosinolates, sulforaphane, and ascorbic acid contents. They also inhibited chlorophyll degradation, inactivated magnesium chelatase activity, and effectively extended the shelf life at 10 ℃ from 3-4 to 12 days. This further validates the excellent packaging parameter predictive performance of the established mathematical model for broccoli preservation under active modified atmosphere conditions.