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

Abstract

ABSTRACTThe respiratory behavior of fresh‐cut spinach under different temperatures and gas conditions was evaluated to develop an integrated respiration model taking into account the temperature dependence of enzyme kinetics parameters. The dependence of respiration rate on the O2 and CO2 concentrations has been described assuming the enzyme kinetics model for combined type of inhibition caused by CO2. The respiration model parameters under the specified environmental conditions of 10, 15, 20C and 75% relative humidity were estimated using non‐linear regression technique and were utilized to predict the rates of respiration for O2 consumption and CO2 evolution. Mixed type of inhibition was observed at all the temperatures, but changed from predominantly competitive at 10 and 15C to predominantly uncompetitive at 20C. The enzyme kinetics parameters were analyzed according to Arrhenius law, as well as simple linear and polynomial equations to determine relationships for describing their temperature dependence. The final integrated model encompassed the effect of headspace gaseous concentrations, CO2 inhibition, surrounding temperature, and can be utilized for respiratory and shelf‐life studies of different fruits and vegetables.PRACTICAL APPLICATIONSFresh‐cut spinach leaves have an enormous market around the world owing to their high nutritive value. Shelf life and quality of fresh‐cut produce may be greatly reduced due to high rates of respiration. Traditional packaging, handling, storage and transportation techniques reduce the shelf life and various nutritional and phytochemical components of fresh‐cut produce. Temperature control and atmospheric modifications (low O2: 1–5% and high CO2: 5–10%) help to maintain produce quality by reducing respiration rate and enhance shelf‐life by minimizing the adverse effects of cutting in fruits and vegetables. This research has focused on determination of respiratory behavior of fresh‐cut spinach leaves at temperatures commonly encountered during transportation and retail distribution i.e., 10–15C. The results of the study show the potential of use of modified atmosphere packaging for packaging of fresh‐cut spinach leaves. Utilization of the results of this research would be of immense help in developing a user friendly program for simulating in‐pack gaseous conditions by varying the experimental parameters and in proper designing of modified atmosphere packages for storage and transportation to retail markets.