Spatial distribution of gas concentrations and RQ in a controlled atmosphere storage container with pear fruit in very low oxygen conditions

• Published in: Postharvest biology and technology 2019-10, Vol.156, p.110903, Article 110903
• Main Authors: Delele, M.A., Bessemans, N., Gruyters, W., Rogge, S., Janssen, S., Verlinden, B.E., Smeets, B., Ramon, H., Verboven, P., Nicolai, B.M.
• Format: Article
• Language: English
• Subjects: Aerodynamics; Air circulation; Airspace; Atmosphere; Carbon dioxide; Computational fluid dynamics; Computer applications; Computer simulation; Containers; Discrete element method; Disorders; Dynamic response; Flavors; Fluid dynamics; Fruits; Gas exchange; Gases; Hydrodynamics; Hypoxia; Mathematical models; Oxygen; Quotients; Respiration; Respiratory quotient; Spatial distribution; Transport; Velocity
• ISSN: 0925-5214; 1873-2356
• DOI: 10.1016/j.postharvbio.2019.05.004

Fruit that is stored in sub-optimal controlled atmosphere (CA) condition is susceptible to internal disorders and off-flavours. Understanding spatial variation in fruit respiration and gas exchange in the storage environment may aid in developing more robust and dynamic storage protocols that prevent unfavourable conditions. A computational fluid dynamics (CFD) model of transport of respiratory gases (O2 and CO2) in a CA storage container with pear fruit was constructed and validated using measured air velocity and gas concentration profiles, and respiratory quotient (RQ) values. The model incorporated the actual pear fruit (cv. 'Conference') geometry using a statistical shape model, and filling of the fruit inside the ventilated box was done using discrete element simulations. The model calculates air circulation, fruit respiration kinetics and transport of the respiratory gases in and between the surrounding air and the fruit. The dynamic response of the gas concentrations inside the CA storage system was predicted as a consequence of fruit respiration and air circulation. Air circulation greatly improved the uniformity of the respiratory gas distribution inside the CA storage system. There was a good agreement between the measured and predicted air velocity with an average relative error of 18.61%. The overall average relative error of the predicted O2 and CO2 distribution in the surrounding free air region was 1.90% and 0.63%, respectively. The model revealed that the volumetric average gas concentration and values of RQ inside the pear internal air space and pear cells were different from those measured in the surrounding air of the container. O2 and CO2 concentrations in the fruit were affected by fruit size. Larger fruits showed relatively lower O2 and higher CO2 at the fruit mass centres. During very low oxygen storage (0.22 kPa) with an average RQ = 3.04 in the surrounding air but 5.08 in the cells, the cellular oxygen concentration of the fruits was below the critical concentration for ATP imbalance (0.043 kPa), thereby increasing susceptibility to hypoxia related disorders.