MODELING OXIDATIVE AND FERMENTATIVE CARBON-DIOXIDE PRODUCTION OF FRUITS AND VEGETABLES

Two models have been developed to describe carbon dioxide (CO2) produc tion of fruits and vegetables in response to oxygen (O-2) and CO2 conc entrations. The models describe a combination of oxidative and ferment ative processes. In both cases the ATP production rate, representing A TP concentration, functions as an inhibitor of fermentative CO2 produc tion. The difference between the models is that ATP production is calc ulated by using oxidative processes only or by a combination of oxidat ive and fermentative processes. The models are compared with two publi shed ones which use the O-2 concentration as an inhibitor of fermentat ive CO2 production. The comparison is made using gas exchange data of apples, asparagus, broccoli, mungbean sprouts and cut chicory. All fou r 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 per formance of the other two models is considerably poorer. The results d o not clarify whether increased fermentation rates can be attributed t o decreased O-2 levels or energy fluxes. The approach used, however, e nables the calculation of CO2 production rates of different types of c ommodities stored under various gas conditions. This facilitates a bet ter prediction of CO2 conditions inside storage rooms and MA packages.