Modelling oxidative and fermentative carbon dioxide production of fruits and vegetables

Two models have been developed to describe carbon dioxide (CO2) production of fruits and vegetables in response to oxygen (O-2) and CO2 concentrations. The models describe a combination of oxidative and fermentative processes. In both cases the ATP production rate, representing ATP concentration, functions as an inhibitor of fermentative CO2 production. The difference between the models is that ATP production is calculated by using oxidative processes only or by a combination of oxidative and fermentative processes. The models are compared with two published ones which use the O-2 concentration as an inhibitor of fermentative CO2 production. The comparison is made using gas exchange data of apples, asparagus, broccoli, mungbean sprouts and cut chicory. All four models allow for increased CO2 production at low O-2 concentrations. However, high percentages of accountable variance were found only for one published model and the new one which uses oxidative ATP. The performance of the other two models is considerably poorer. The results do not clarify whether increased fermentation rates can be attributed to decreased O-2 levels or energy fluxes. The approach used, however, enables the calculation of CO2 production rates of different types of commodities stored under various gas conditions. This facilitates a better prediction of CO2 conditions inside storage rooms and MA packages.