PERMEABILITY ESTIMATION OF A MODIFIED ATMOSPHERE PACKAGE FOR "HASS" AVOCADO STORAGE

Refrigeration and modified atmosphere packaging (MAP) are useful technologies to preserve and extend the shelf life of fruit and vegetables. The packaging industry aims to permanently develop technologies that provide suitable conditions for the commercialization of fruit and vegetables. Due to the market demands, packages were developed to protect fresh products from quality loss and to prolong shelf life. MAP is not always used for horticultural products in Mexico. There are few cases where packages are designed for a specific fruit. Sometimes, the same package is used for different fruit; therefore, there is no adequate control of the gas concentration during storage, causing a faster deterioration. The objective of this research was to simulate the O-2 and CO2 concentrations of "Hass" avocado (Persea americana Mill.) stored in a MAP with different O-2 and CO2 permeabilities, based on the non-stationary state mass balances for the gas concentrations and the enzymatic kinetics for O-2 consumption and CO2 production rates. A closed system and inhibition models were used to determine the respiratory behavior, and the correspondent kinetic parameters were obtained through a regression analysis. The O-2 and CO2 concentrations inside a MAP in function of time were satisfactorily (R-2>0.97) simulated at 8 +/- 1 degrees C using a competitive inhibition model. Through simulation, different permeabilities were tested to ensure lower O-2 and higher CO2 concentrations levels inside the MAP. With the estimated O-2 (2.9x10(-5) mL cm cm(-2) h(-1) cmHg(-1)) and CO2 (4.1x10(-5) mL cm cm(-2) h(-1) cmHg(-1)) permeabilities, the gas concentrations inside the package were simulated for the system to reach stable concentrations of 10.0 and 9.5 mol% for O-2 and CO2 after 240 h of storage. These permeabilities could improve the internal atmosphere and extend the "Hass" avocado shelf life when stored under MAP at 8 +/- 1 degrees C.