Comparison and quality testing of polymer non-woven postharvest preservation sheets using X-ray tomography

Sulphur dioxide (SO₂) gas is routinely used in the table grape industry as a chemical preservative. A balance between enough gas for decay control and a low enough dose to prevent a phytotoxic effect on the grapes is required. Engineering SO₂ generating pads that emit a suitable concentration of gas is therefore of the utmost importance for the table grape industry. The aim of this paper is to demonstrate the development of a novel method through which the quality of SO₂ generating pads and the amount of gas it releases can be monitored. The aim of this paper is therefore to demonstrate a high-resolution X-ray tomography methodology designed particularly for the quantitative analysis of polymeric non-woven layered materials used in the production of SO₂ generating pads. The quality and structure of the non-woven materials is of interest since it may influence the rate at which the concentration of SO₂ is released from the pads. The scanning procedure for this sample type is described in addition to specialized image processing steps, which allow quantitative analysis of various parameters of interest for quality comparison. A quantitative comparison of three commercially available products is included and this demonstrates the potential use of this method in quality control and comparison of different suppliers or competitors. This method could be applied to any low-density fibrous material where fibres have a diameter of more than approximately 6 microns.