Using pinholes as tools to attain optimum modified atmospheres in packages of fresh produce

A mathematical model for the gas flow through a pinhole applying the Stephan–Maxwell laws was tested and used in estimating the atmospheric change in a cut onion package. The effects of pinhole variables such as length, number and diameter on the package atmosphere were then calculated from the model. Established mathematical model equations could well predict the changes in gas composition in packages by taking into consideration the end effect of pinholes. Modification of the package atmosphere was found to be strongly affected by the dimensions and number of pinholes in the packaging. Longer pinholes with smaller diameters accelerate modification of the package atmosphere to lower O₂ and higher CO₂ concentrations. The number of pinholes highly influences the degree the atmosphere is modified inside the package when their length is short, while increased pinhole length significantly decreased the dependence of the atmosphere on the number of pinholes. If the variables of pinhole dimension and number are combined with variety of permeable films it is possible to design a package for cut onions which, it is calculated, should create and maintain an optimum atmosphere in the range of 2–8% O₂ and 5–15% CO₂. © 1998 John Wiley & Sons, Ltd.