Respiratory parameters of huitlacoche (Ustilago maydis) under modified atmosphere conditions
2018
Valle-Guadarrama, S. | Espinosa-Solares, T. | Lopez-Cruz, I. L. | Sanchez-Flores, R.
Huitlacoche (Ustilago maydis) is an edible fungus that develops from the cob of corn (Zea mays). This fungus is consumed fresh, but is highly perishable. The modified atmosphere packaging (MAP) technology has been suggested as an alternative that could enlarge shelf life. The objective of the work was to characterize the respiratory activity of huitlacoche under O2 and CO2 concentrations that differ from those of normal air storage, in order to improve handling in MAP. Galls of huitlacoche grown in Tulancingo, Hidalgo, Mexico were used. Batches of 150 g of product were placed in containers with walls impermeable to gases, where changes of O2 and CO2 concentrations were monitored during 15 h at 20°C or during 30 h at 3°C, with relative humidity higher than 95%, and atmospheric pressure of 77.993 kPa. The procedure was repeated in presence of lime to remove CO2 from containers, in order to assess its effect on respiration. A transient mass balance was carried out to describe the concentration change as a function of O2 consumption rate, and this was represented through the Michaelis-Menten (M-M) enzymatic kinetic theory. Equations were programmed in the MatLab® environment and parameters of M-M were calibrated using the nonlinear least square algorithm (lsqnonlin.m function) of the Optimization Toolbox of MatLab®. Temperature affected the maximum oxygen consumption rate, which had values of 27.1×10(-9) kg kg-1 s-1 at 20°C and 4.5×10(-9) kg kg-1 s-1 at 3°C. However, the thermal condition did not affect the M-M constant, which had values of 11.44 kPa (14.67%) and 12.93 kPa (16.58%), respectively. Besides, CO2 did not exert an inhibitory effect on respiration within the limits tested, which was verified through analysis of variance applied to parameters obtained from a Michaelis-Menten model without inhibition and from an uncompetitive model.
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