NONLINEAR ESTIMATION OF RESPIRATORY DYNAMICS OF FRESH-CUT SPINACH (SPINACIA OLERACEA) BASED ON ENZYME KINETICS

摘要

The respiratory behavior of fresh-cut spinach under different temperaturesnand gas conditions was evaluated to develop an integrated respirationnmodel taking into account the temperature dependence of enzyme kineticsnparameters. The dependence of respiration rate on the O2 and CO2 concentrationsnhas been described assuming the enzyme kinetics model for combinedntype of inhibition caused by CO2. The respiration model parameters under thenspecified environmental conditions of 10, 15, 20C and 75% relative humiditynwere estimated using non-linear regression technique and were utilized tonpredict the rates of respiration for O2 consumption and CO2 evolution. Mixedntype of inhibition was observed at all the temperatures, but changed fromnpredominantly competitive at 10 and 15C to predominantly uncompetitive atn20C. The enzyme kinetics parameters were analyzed according to Arrheniusnlaw, as well as simple linear and polynomial equations to determine relationshipsnfor describing their temperature dependence. The final integrated modelnencompassed the effect of headspace gaseous concentrations, CO2 inhibition,nsurrounding temperature, and can be utilized for respiratory and shelf-lifenstudies of different fruits and vegetables.