Evaluation of Models for Spinach Respiratory Metabolism Under Low Oxygen Atmospheres

Anaerobic respiration is a major problem that causes the deterioration of fresh produce packaged under low O-2 atmospheres. The problem becomes more severe and causes high losses in the packages handling at ambient conditions, especially in developing countries. In designing modified atmosphere packaging, the risk of anaerobic development greatly depends upon the accuracy of respiration rate prediction; therefore, the respiration rate model for a particular produce has to be identified. In this study, different atmospheric storage conditions in a closed system were realized to examine the adaptability of respiration rate models for spinach storage under low O-2 at an expected ambient temperature of 25 A degrees C. Six models were applied and it was found that, for aerobic conditions, the respiration rate could be described with a constant respiratory quotient by three models, viz., (a) Michaelis-Menten model without inhibition, (b) Michaelis-Menten model with uncompetitive inhibition, and (c) Langmuir adsorption model, whereas three other models, viz. (d) Michaelis-Menten model with competitive inhibition, (e) Michaelis-Menten model with noncompetitive inhibition, and (f) Michaelis-Menten with mixed inhibition could not be fitted. Among the three successful models, the Michaelis-Menten with uncompetitive inhibition was found to be the most suitable model for practical applications in developing countries where cold-chain systems are lacking. This model can be applied for the prediction of gas composition and optimize the packages, particularly to ensure the aerobic respiration.