Effect of Type of In-Package Sulfur Dioxide Generator and Packaging Materials on Quality of Stored Table Grapes

Abstract

Storage tests were held to determine the effect of the kind and thickness of the plastic film of inpackage SO₂ generators on the release rate of SO₂ and amounts of SO₂ and water vapor retained within unvented containers of table grapes. An emulsion of NaHSO₃ with plastic polymers extruded as a thin layer on kraft paper was as effective for a firststage generator as was a two-ply tea-bag stock generator with pouches containing NaHSO₃ powder, and is cheaper to manufacture. As a first-stage generator, however, neither extruded strips of the emulsion on kraft paper nor perforated polyethylene film pouches containing NaHSO₃ powder generated SO₂ soon enough. Further, emulsion strips heat-sealed between polyethylene-coated paper sheets generated SO₂ only long enough to be satisfactory for a month as second-stage generators. The thickness of polyethylene film around the pouches of NaHSO₃ was more significant in rate of release of SO₂ than was the dose of NaHSO₃ up to 10 weeks of storage. Thereafter dose of the NaHSO₃ was marked in effect. Cellulose acetate showed considerable promise as a film regulating release of SO₂ for storage periods of three months. Polyethylene-coated curtains in wood lugs were more effective than kraft curtains in retaining SO₂ and water vapor in the unvented container.