Gas Exchange Modeling

CONTENTS 5.1 Introduction 93 5.2 Respiration 945.2.1 Factors Affecting Respiration 94 5.2.2 Model Approaches to Respiration 95 5.2.3 Michaelis-Menten Approach 95 5.2.4 Outlook: Metabolic Flux Models 975.3 Gas Transport 98 5.3.1 Lumped Gas Transport 985.3.1.1 Effusion or Efflux Method 98 5.3.1.2 Limitations 1005.3.2 Reaction-Diffusion 100 5.3.2.1 Model 101 5.3.2.2 Parameter Estimation 102 5.3.2.3 Numerical Solution 103 5.3.2.4 Case Study 1045.3.3 Outlook: Multiscale Analysis of Gas Exchange 105 5.4 Relating Metabolic Rate to Rate of Quality Change 106 5.5 Conclusions 107 5.6 Future Research Needs 107 Acknowledgments 108 References 108In a controlled atmosphere storage, the O2 partial pressure is typically reduced while that of CO2 is often increased. The purpose of this procedure is to lower the respiration rate and, consequently, slow down those associated metabolic pathways that negatively affect the quality of the stored product. The respiration rate is therefore a good indicator of the physiological stage of the fruit and its storage potential, and has been measured in the past for many fruit and vegetables at various storage temperatures and gas compositions. As the respiration rate depends on the species and even the cultivar, season, development stage, climate, and many more factors, it needs to be determined for every new cultivar before it is introduced in the market.