A method for determination of emission rates from SO2 sheets for storage of grapes

Introduction Table grapes are very susceptible to decay caused by Botrytis cinerea during storage, and one of the common means to control decay is by packaging the fruit with a SO2-generating sheet. Typically, the sheets contain sodium metabisulphite in a granulated form that releases SO2 upon absorption of water in two phases: a fast-release phase of high SO2 level and a slow, continual release of a low level of SO2. Objective Currently, there is no published method to compare or validate the performance of different SO2 sheets. This paper describes a simple analytical method to quantify the rate of SO2 release from the sheets which does not require setting up storage experiments with grapes. Results The method was used to test the total amount of SO2, which was released under the experimental conditions. However, most of the study was focused on a relative measurement that can help with comparing different SO2 sheets or the same sheets from different production dates. Conclusion The method revealed significant differences in SO2 release pattern between different types of SO2 sheets or the same sheets from different years of production. The method can allow grape growers to have better tools that will ensure successful control of decay during storage.