Mathematical modeling of pickling of bamboo shoot strips and their sulfur dioxide removal during cooking

Sulfur dioxide (SO2) is a commonly used preservative in pickled food; however, excessive SO2 in food is a severe safety issue. Removing SO2 by cooking in water is a complex process including several physical and chemical phenomena. This study develops a mathematical model to characterize the heat and mass transfer and chemical reactions involved in (i) soaking of bamboo shoot strips (BSS) in SO2 solutions of 300-800 ppm at pH 4.5-9.0, and (ii) SO2 removal from pickled BSS during cooking at 60-95 degrees C. Simulations based on finite element method were conducted to characterize the SO2 concentration, pH and temperature of BSS during the processes. Inverse problem method was used to estimate process parameters. The predicted results were well validated by a series of soaking and cooking experiments conducted under different conditions. The mathematical model developed is proven to be a useful tool to guide how to produce safe pickled foods.