Estimation of pressure and volume changes for packages of kimchi, a Korean fermented vegetable

Abstract

Kimchi, a vegetable containing lactic acid bacteria, produces CO2 gas because of its continued fermentation during storage, resulting in a pressure build-up and extensive expansion of its containers. This pressure build-up and volume expansion occurring in packaged kimchi constitute a serious problem, since it makes the product unattractive and difficult to market. As an attempt to solve this problem, a kinetic model for CO2 production in kimchi during storage was established as a function of salt content and temperature to monitor the pressure and volume variations of the packages. The concentrations of CO2 in headspace and CO2 dissolved in brine were related by Henry's law, which allowed easy determination of CO2 production from fermentation and offered a useful estimate of the CO2 partial pressure in the packages. The CO2 production in kimchi consisted of two stages of constant rate and could be described for both stages as R CO 2 ,i =Ki exp(−Eai/RT), where Ki is a function of salt content. In the model, the pressure and volume of the packages were presumed to be the sum of contributions of the CO2 produced during the fermentation as well as O2 and N2 from entrapped air. Variations of pressure and volume due to temperature change were assumed to be governed by the ideal gas law. Measurements of pressure and volume for te kimchi packages stored both at constant and changing temperatures were in good agreement with the predicted values, thus confirming the validity of the proposed model. © 1997 John Wiley & Sons, Ltd.